Patent Description:
Flat shape batteries which are called coin-type batteries or button batteries have been known. In a battery of this type, an electrode body configured such that a separator is sandwiched between a positive electrode and a negative electrode is housed in a battery case with an electrolyte. The battery case includes an exterior can which has a bottom portion and a peripheral wall portion and in which an opening portion is provided in the peripheral wall portion, a sealing can which has a flat portion and a side wall portion and in which an opening portion and a shoulder portion are formed in the side wall portion, and a gasket that is arranged between the exterior can and the sealing can. The peripheral wall portion of the exterior can and the side wall portion of the sealing can are fitted together.

For batteries which have the above described structure, in order to increase an internal volume and thus increase capacity while efficiently applying a pressure to the gasket to seal in fitting of the exterior can and the sealing can, various examinations have been conducted for sealing structures of the exterior can and the sealing can.

As one of the sealing structures, it has been proposed to make a cross-sectional shape of the gasket into an L shape without providing a fold portion in the side wall portion of the sealing can (Patent Document <NUM>). Using the above described sealing structure, an internal volume of the side wall portion can be increased, as compared to a structure in which the side wall portion of the sealing can is folded. Thus, the capacity of the battery can be increased.

It has been also proposed to increase adhesion of an edge portion of the side wall portion of the sealing can and the gasket by making curvature radius of an inner circumference side portion of an edge of the side wall portion of the sealing can smaller than curvature radius of an outer circumference side portion and bending the opening portion of the side wall portion of the sealing can toward a center of the battery, in order to increase leakage resistance in a case in which a fold portion is not provided in the side wall portion of the sealing can (Patent Documents <NUM> and <NUM>). Accordingly, it is possible to improve sealing properties, and thus, suppress the occurrence of leakage.

However, even in the case of making the cross-sectional shape of the gasket into the L shape as described above, reduction of the thickness of the gasket has a limitation. Thus, the internal volume of a battery cannot be increased by a certain amount or more. For this reason, even in a case where the cross-sectional shape of the gasket is devised, the capacity of the battery can be increased only within a limited range.

On the other hand, the use of a material except for the gasket described above as a sealing member has been studied. Patent Document <NUM>, for example, discloses a button battery using a sealing member of a thermoplastic resin (e.g., polyamide or polyether ether ketone) having a thickness of about <NUM>. Patent Document <NUM>, for example, discloses a coin-type battery having gasket, at least a portion of which is disposed between a peripheral wall portion of an exterior can and a side wall portion of a sealing can. Patent Document <NUM>, for example, discloses a button type alkaline battery having a gasket which is formed in a shape so that, in the state the negative electrode case is incorporated into the gasket, the lower face of the terminal part of the negative electrode case and the upper face of the gasket bottom part are in contact each other, the outer face of the periphery part of the negative electrode case and the inner face of the gasket are in contact each other, and the first bending part of the negative electrode case and the projection part of the gasket are in contact each other.

In the case of sealing using a thin resin sealing member as disclosed in Patent Document <NUM>, however, it is difficult to obtain sealing properties more excellent than those in the case of performing sealing with a gasket. Thus, there has been required a reliable battery whose capacity is increased without impairing sealing properties by enlarging a housing space in which an electrode body is housed.

It is an object of the present invention to increase a capacity without impairing the sealing properties by enlarging a housing space in which an electrode body is housed and to provide a coin-type battery with excellent reliability and a manufacturing method thereof.

A coin-type battery according to an embodiment of the present invention is a coin-type battery that includes an exterior can including a bottom portion and a peripheral wall portion and having an opening on an opposite side to the bottom portion in a thickness direction, a sealing can which includes a flat portion and a side wall portion and has an opening on an opposite side to the flat portion in the thickness direction and of which a stepped shoulder portion that is located between the flat portion and the opening and expands in a radial direction is provided in the side wall portion, a resin film at least a portion of which is arranged between the peripheral wall portion of the exterior can and the side wall portion of the sealing can, and a power generation element arranged in a housing space formed by the exterior can and the sealing can. The resin film includes a film peripheral wall portion formed to have a cylindrical shape and arranged between the peripheral wall portion of the exterior can and the side wall portion of the sealing can, and a film bottom portion arranged between the bottom portion of the exterior can and an open end portion of the side wall portion of the sealing can, and is an annular body, and when it is assumed that an external diameter of the bottom portion of the exterior can is d1 (mm), an inner diameter of the open end portion in the peripheral wall portion of the exterior can is d2 (mm), an external diameter of the flat portion of the sealing can is d3 (mm), and an external diameter of the open end portion in the side wall portion of the sealing can is d4 (mm), <NUM> ≤ d3/d1 ≤ <NUM> and <NUM> ≤ d2/d4 ≤ <NUM> are satisfied, and a sealant is preferably disposed at at least one of a position between the peripheral wall portion of the exterior can and the resin film or a position between the side wall portion of the sealing can and the resin film (first configuration).

With this configuration, the housing space of the electrode body in the coin-type battery can be made larger than that of a conventional structure, and thus, the capacity of the battery can be increased. That is, the sealing member disposed between the peripheral wall portion of the exterior can and the side wall portion of the sealing can can be constituted by the thin resin film so that the distance between the peripheral wall portion of the exterior can and the side wall portion of the sealing can can be made smaller than that of the conventional structure using a gasket as the sealing member. Accordingly, the housing space of the electrode body in the sealing can can be made larger than that of the conventional structure.

In addition, since an empty space where the sealing member is not disposed is formed inside the side wall portion of the sealing can, the housing space of the electrode body in the sealing can can be made larger.

Furthermore, the external diameter d3 of the flat portion of the sealing can and the external diameter d1 of the bottom portion of the exterior can satisfy the relationship of <NUM> ≤ d3/d1 ≤ <NUM> so that a space inside the sealing can can be made larger with respect to external dimensions of the battery.

The relationship between the inner diameter d2 of the open end portion in the peripheral wall portion of the exterior can and the external diameter d4 of the open end portion in the side wall portion of the sealing can varies depending on a fitting structure of the peripheral wall portion of the exterior can to the side wall portion of the sealing can. That is, in the conventional structure in which the peripheral wall portion of the exterior can is caulked to the shoulder portion of the side wall portion of the sealing can and in which sealing is performed by pressing the sealing member between the open end portion of the side wall portion of the sealing can and the bottom portion of the exterior can, d2/d4 is a small value of about <NUM>.

On the other hand, as in the configuration described above, the relationship between the inner diameter d2 of the open end portion in the peripheral wall portion of the exterior can and the external diameter d4 of the open end portion in the side wall portion of the sealing can satisfies <NUM> ≤ d2/d4 ≤ <NUM> so that sealing performance similar to that in the conventional structure can be obtained in a configuration fitted to the side wall portion of the sealing can in the radial direction. That is, the value of d2/d4 is set within the range described above so that the peripheral wall portion of the exterior can presses the thin sealing member in the radial direction with an appropriate force. Accordingly, it is possible to enhance sealing performance of the sealing member disposed between the peripheral wall portion of the exterior can and the side wall portion of the sealing can.

Thus, by setting d2/d4 in the above range, the sealing structure can be made compact. Accordingly, it is possible to reduce the size of the coin-type battery while increasing a housing space for housing an electrode body.

As a result, with the configuration described above, a compact coin-type battery capable of increasing the housing space for housing the electrode body can be obtained without impairing sealing properties. That is, the configuration described above can obtain a reliable coin-type battery having a large capacity.

In the first configuration, it is preferable to satisfy d3/d4 ≥ <NUM> (second configuration). The value of d3/d4 is set at <NUM> or more so that the projection dimension of the shoulder portion in the side wall portion of the sealing can can be reduced in the radial direction of the battery. Thus, since a dead space except for a space necessary for housing the electrode body can be reduced, a small-size coin-type battery having a larger capacity can be obtained. The value of d3/d4 is preferably <NUM> or more, and especially preferably <NUM> or more.

To ensure a certain degree of sealing properties between the film bottom portion and the bottom portion of the exterior can by setting the projection dimension of the shoulder portion at a predetermined dimension or more to generate a force with which open end portion of the side wall portion of the sealing can presses the film bottom portion against the bottom portion of the exterior can, the value of d3/d4 is preferably <NUM> or less.

In the first or second configuration, the resin film is preferably formed of a heat-resistant resin with a melting point or a decomposition temperature of which is <NUM> or more (third configuration). This configuration can obtain good sealing properties between the side wall portion of the sealing can and the peripheral wall portion of the exterior can even at high temperatures.

In the third configuration, the heat-resistant resin is preferably polyphenylene sulfide (fourth configuration). This configuration can reduce transmission of moisture in the resin film. As a result, durability of the battery can be enhanced.

In any one of the first through fourth configurations, a thickness of the resin film is preferably <NUM> to <NUM> (fifth configuration). With this configuration, a compact coin-type battery capable of increasing a housing space for housing the electrode body can be obtained.

Thickness variations and surface asperities of the resin film reduce adhesion between the peripheral wall portion of the exterior can and the resin film or reduce adhesion between the side wall portion of the sealing can and the resin film, and thus, moisture easily enters the battery. Thus, durability of the battery might decrease. On the other hand, the presence of the sealant at at least one of a position between the peripheral wall portion of the exterior can and the resin film or a position between the side wall portion of the sealing can and the resin film can reduce entering of moisture into the battery due to thickness variations and surface asperities of the resin film. As a result, durability of the battery can be enhanced.

A method for manufacturing a coin-type battery is a method for manufacturing a coin-type battery including: an exterior can including a bottom portion and a peripheral wall portion and having an opening on an opposite side to the bottom portion in a thickness direction; a sealing can which includes a flat portion and a side wall portion and has an opening on an opposite side to the flat portion in the thickness direction and of which a stepped shoulder portion that is located between the flat portion and the opening and expands in a radial direction is provided in the side wall portion; a resin film at least a portion of which is arranged between the peripheral wall portion of the exterior can and the side wall portion of the sealing can; and a power generation element arranged in a housing space formed by the exterior can and the sealing can. The resin film is a heat-shrinkable cylindrical member. The method includes the steps of: applying the sealant (<NUM>) at least either between the peripheral wall portion (<NUM>) of the exterior can (<NUM>) and the resin film (<NUM>) or between the side wall portion (<NUM>) of the sealing can (<NUM>) and the resin film (<NUM>); covering an outer peripheral surface of the side wall portion of the sealing can with the resin film such that an end portion of the resin film projects from the side wall portion of the sealing can; performing a heat treatment on the resin film and shrinking the resin film to thereby integrate the resin film with the side wall portion of the sealing can while covering an open end portion of the side wall portion of the sealing can with the resin film; disposing the side wall portion of the sealing can integrated with the resin film inside the peripheral wall portion of the exterior can to thereby locate the resin film between the peripheral wall portion of the exterior can and the side wall portion of the sealing can and between the bottom portion of the exterior can and the side wall portion of the sealing can; and displacing the peripheral wall portion of the exterior can in a radial direction relative to the side wall portion of the sealing can to thereby fit the peripheral wall portion of the exterior can and the side wall portion of the sealing can to each other and, in a state before the peripheral wall portion of the exterior can and the side wall portion of the sealing can are fitted together, when it is assumed that a height of the sealing can is h1 (mm), in the side wall portion of the sealing can, an external diameter of the open end portion is d5 (mm), an external diameter and a can thickness at a position of <NUM>/<NUM> of h1 from a tip of the open end portion toward the flat portion are d6 (mm) and t1 (mm), respectively, and a can thickness at a position of <NUM>/<NUM> of t1 from the tip of the open end portion toward the flat portion is t2 (mm), -<NUM> ≤ d5-d6 ≤ <NUM> and t2/t1 ≥ <NUM> are preferably satisfied (first method).

This method can easily obtain a coin-type battery in which at least part of the resin film is disposed between the peripheral wall portion of the exterior can and the side wall portion of the sealing can.

That is, the resin film as a heat-shrinkable cylindrical member is subjected to a heat treatment to be contracted while projecting from the side wall portion of the sealing can and covering the outer peripheral surface of the side wall portion so that the resin film shrinks in the radial direction and is changed into a shape conforming to the side wall portion of the sealing can and part of the resin film projecting from the side wall portion of the sealing can is bent inward in the radial direction. Accordingly, while the resin film covers the open end portion of the side wall portion of the sealing can, the resin film can be integrated with the side wall portion of the sealing can. In addition, in a state where the side wall portion of the sealing can integrated with the resin film is disposed inside the peripheral wall portion of the exterior can, the peripheral wall portion of the exterior can is displaced from the side wall portion of the sealing can in the radial direction so that the peripheral wall portion of the exterior can and the side wall portion of the sealing can can be fitted to each other. This method can obtain a coin-type battery in which at least part of the resin film is disposed between the peripheral wall portion of the exterior can and the side wall portion of the sealing can.

In the first method, a temperature at which the heat treatment is performed on the resin film is preferably higher than a temperature of a glass transition point of the resin film (second method). With this method, heat contraction of the resin film is promoted so that the resin film and the side wall portion of the sealing can can be more firmly integrated.

In the first or second method, in the step of covering the outer peripheral surface of the side wall portion of the sealing can with the resin film, the resin film covering the outer peripheral surface of the side wall portion of the sealing can is preferably caused to project from the open end portion of the side wall portion of the sealing can to a range of <NUM> to <NUM> (third method).

That is, in a case where the width of the resin film projecting from the open end portion of the side wall portion of the sealing can is <NUM> or more, the open end portion of the side wall portion of the sealing can can be more easily covered with the resin film during the heat treatment on the resin film. On the other hand, in a case where the width of the resin film projecting from the open end portion of the side wall portion of the sealing can is <NUM> or less, the width of the film bottom portion formed in the heat treatment on the resin film can be adjusted in a suitable range.

In any one of the first through third methods, in the step of integrating the resin film with the side wall portion of the sealing can by performing the heat treatment on the resin film and shrinking the resin film, a portion of the resin film projecting from the open end portion of the side wall portion of the sealing can is preferably deformed inward in the side wall portion relative to the open end portion and, thereby, the resin film projects inward in the side wall portion from the open end portion to a range of <NUM> to <NUM> (fourth method).

In a case where the width of the resin film projecting inward from the open end portion of the side wall portion of the sealing can is <NUM> or more, it is further ensured to cover the open end portion of the side wall portion of the sealing with the resin film. Accordingly, in the coin-type battery, it is further ensured to dispose the resin film between the bottom portion of the exterior can and the open end portion of the side wall portion of the sealing can. Thus, it is possible to ensure electrical insulation between the bottom portion of the exterior can and the open end portion of the side wall portion of the sealing can.

On the other hand, in a case where the width of the resin film projecting inward in the side wall portion from the open end portion of the side wall portion of the sealing can is <NUM> or less, a redundant volume of the resin film disposed in the battery can be reduced. As a result, a decrease in an effective volume of the housing space of the electrode body in the battery can be prevented.

By using a coin-type battery according to an embodiment of the present invention and a manufacturing method thereof, a coin-type battery a capacity of which has been increased by increasing a housing space in which an electrode body is housed and which has excellent reliability can be achieved without impairing sealing properties.

Embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same or corresponding parts are denoted by the same reference sign and the description of the parts is not repeated.

<FIG> is a cross-sectional view illustrating an outline structure of an embodiment of a coin-type battery that is formed by a manufacturing method of a coin-type battery according to the present invention. This coin-type battery <NUM> includes a positive electrode can <NUM> as an exterior can having a closed end cylindrical shape, a negative electrode can <NUM> as a sealing can that covers an opening of the positive electrode can <NUM>, a resin film <NUM> that is sandwiched between the positive electrode can <NUM> and the negative electrode can <NUM>, and an electrode body <NUM> (a power generation element) that is housed in a housing space S formed by the positive electrode can <NUM> and the negative electrode can <NUM>. Therefore, the coin-type battery <NUM> is made into a flat coin shape in which a dimension in a radial direction is larger than a dimension in a height direction by fitting the positive electrode can <NUM> and the negative electrode can <NUM> together. In the housing space S that is formed by the positive electrode can <NUM> and the negative electrode can <NUM> of the coin-type battery <NUM>, in addition to the electrode body <NUM>, a non-aqueous electrolyte (not illustrated) is also sealed. Note that the reference sign P in <FIG> denotes an axis of the coin-type battery <NUM>. In the following description, in the coin-type battery <NUM>, an axial direction is the height direction and a direction that is orthogonal to the axial direction is the radial direction.

The positive electrode can <NUM> is made of a metallic material, such as stainless (for example, SUS316 or the like). Ni-plating can be applied to an outer surface of the positive electrode can <NUM> and the positive electrode can <NUM> is formed to have a closed end cylindrical shape by press-forming. The positive electrode can <NUM> includes a circular bottom portion <NUM> and a cylindrical peripheral wall portion <NUM> formed continuously from an outer periphery of the bottom portion <NUM>. The peripheral wall portion <NUM> is provided so as to extend from an outer peripheral end of the bottom portion <NUM> in the height direction of the coin-type battery <NUM> in a longitudinal-sectional view (a state illustrated in <FIG>). That is, the peripheral wall portion <NUM> extends from the bottom portion <NUM> in the axial direction. Also, the positive electrode can <NUM> has an opening on an opposite side to the bottom portion <NUM> in the axial direction.

As will be described later, in a state in which the resin film <NUM> is sandwiched between the positive electrode can <NUM> and the negative electrode can <NUM>, an open end portion <NUM> (an end portion of the peripheral wall portion <NUM>, which is located closer to the opening) of the peripheral wall portion <NUM> is deformed so as to tilt inwardly in a radial direction of the positive electrode can <NUM>, and thereby, the positive electrode can <NUM> is caulked to the negative electrode can <NUM>.

The negative electrode can <NUM> is also made of a metallic material, such as stainless (for example, NAS64 or the like). Ni-plating can be applied to an outer surface of the negative electrode can <NUM> and the negative electrode can <NUM> is formed to have a closed-end cylindrical shape by press-forming. The negative electrode can <NUM> includes a substantially cylindrical side wall portion <NUM> an external diameter of which is smaller than that of the peripheral wall portion <NUM> of the positive electrode can <NUM> and a circular flat portion <NUM> that closes one of openings of the side wall portion <NUM>. Similar to the positive electrode can <NUM>, the side wall portion <NUM> is provided so as to extend from an outer peripheral end of the flat portion <NUM> in the height direction of the coin-type battery <NUM> in the longitudinal-sectional view. That is, the side wall portion <NUM> extends from the flat portion <NUM> in the axial direction. Also, the negative electrode can <NUM> has an opening on an opposite side to the flat portion <NUM> in the axial direction.

Note that the side wall portion <NUM> extends in the axial direction without being folded in an edge portion. That is, the negative electrode can <NUM> is a so-called straight can without a fold portion in the edge portion of the side wall portion <NUM>.

A diameter expansion portion 22b a diameter of which is larger than that of a base end portion 22a that is located closer to the flat portion <NUM> is formed in the side wall portion <NUM>. That is, in the side wall portion <NUM>, a stepped shoulder portion 22c that expands in the radial direction is formed between the base end portion 22a and the diameter expansion portion 22b. In the structure of this embodiment, the peripheral wall portion <NUM> of the positive electrode can <NUM> is pressed against the side wall portion <NUM> in the radial direction in a state in which the resin film <NUM>, which will be described later, is sandwiched therebetween.

Note that, in the peripheral wall portion <NUM> of the positive electrode can <NUM>, the open end portion <NUM> is largely displaced in the radial direction, as compared to the other portions of the peripheral wall portion <NUM>, and thereby, a portion of a pressing force by the peripheral wall portion <NUM> of the positive electrode can <NUM> can be also applied to the shoulder portion 22c of the negative electrode can <NUM>. Therefore, an open end portion <NUM> (an end portion of the side wall portion <NUM>, which is located closer to the opening) of the side wall portion <NUM> of the negative electrode can <NUM> sandwiches a film bottom portion <NUM> of the resin film <NUM>, which will be described later, with the bottom portion <NUM> of the positive electrode can <NUM>.

Next, embodiments that are considered suitable for realizing an increased capacity and excellent sealing properties in a coin-type battery <NUM> that is formed by a manufacturing method of a coin-type battery according to the present invention will be specifically described below.

An external diameter d1 of the bottom portion <NUM> of the positive electrode can <NUM> and an external diameter d3 of the flat portion <NUM> of the negative electrode can <NUM> preferably satisfy <NUM> ≤ d3/d1 ≤ <NUM>.

In this embodiment, the external diameter d1 of the bottom portion <NUM> of the positive electrode can <NUM> is substantially equal to an external diameter of the coin-type battery <NUM>. Therefore, a ratio of an internal space of the negative electrode can <NUM> to an actual volume (a volume that is calculated from external dimensions of the coin-type battery <NUM>) of the coin-type battery <NUM> can be increased by making the external diameter d3 of the flat portion <NUM> of the negative electrode can <NUM> to be <NUM>% or more of the external diameter d1 of the bottom portion <NUM> of the positive electrode can <NUM>. That is, a ratio of the housing space S of the electrode body <NUM> to the actual volume of the coin-type battery <NUM> can be made large by causing d3/d1 ≥ <NUM> to be satisfied. Thus, a battery capacity of the coin-type battery <NUM> can be increased.

On the other hand, the external diameter d3 of the flat portion <NUM> of the negative electrode can <NUM> is preferably <NUM>% or less of the external diameter d1 of the bottom portion <NUM> of the positive electrode can <NUM> and is more preferably <NUM>% or less. Thus, the open end portion <NUM> of the peripheral wall portion <NUM> of the positive electrode can <NUM> can be displaced by a certain amount or more in the radial direction and thus be caulked to the side wall portion <NUM> of the negative electrode can <NUM>. Therefore, in the coin-type battery <NUM>, good sealing properties can be ensured.

An external diameter d4 of the open end portion <NUM> in the side wall portion <NUM> of the negative electrode can <NUM> and an inner diameter d2 of the open end portion <NUM> in the peripheral wall portion <NUM> of the positive electrode can <NUM> that is in a state of being caulked to the negative electrode can <NUM> with the resin film <NUM> sandwiched therebetween preferably satisfy <NUM> ≤ d2/d4 ≤ <NUM>.

A relation between the external diameter d4 of the open end portion <NUM> in the side wall portion <NUM> of the negative electrode can <NUM> and the inner diameter d2 of the open end portion <NUM> in the peripheral wall portion <NUM> of the positive electrode can <NUM> varies depending on a fitting structure of the peripheral wall portion <NUM> of the positive electrode can <NUM> with respect to the side wall portion <NUM> of the negative electrode can <NUM>. For example, in a structure of a known coil-type battery in which a peripheral wall portion of a positive electrode can is caulked to a shoulder portion of a side wall portion of a negative electrode can and a gasket is pressed between an open end portion of a side wall portion of a sealing can and a bottom portion of an exterior can, thereby sealing the battery, a value of d2/d4 is a small value, that is, about <NUM>.

In contrast, in this embodiment, the peripheral wall portion <NUM> of the positive electrode can <NUM> is displaced in the radial direction, and thereby, the peripheral wall portion <NUM> of the positive electrode can <NUM> is pressed against the side wall portion <NUM> of the negative electrode can <NUM>. That is, the peripheral wall portion <NUM> of the positive electrode can <NUM> is fitted to the side wall portion <NUM> of the negative electrode can <NUM> in the radial direction.

In the above described fitting structure, the relation between the inner diameter d2 of the open end portion <NUM> in the peripheral wall portion <NUM> of the positive electrode can <NUM> and the external diameter d4 of the open end portion <NUM> in the side wall portion <NUM> of the negative electrode can <NUM> is made to satisfy <NUM> ≤ d2/d4 ≤ <NUM>, and thereby, the peripheral wall portion <NUM> of the positive electrode can <NUM> presses the resin film <NUM> in the radial direction with the appropriate force. Thus, sealing properties of the resin film <NUM> arranged between the peripheral wall portion <NUM> of the positive electrode can <NUM> and the side wall portion <NUM> of the negative electrode can <NUM> can be improved.

When the value of d2/d4 is smaller than <NUM>, a pressing force is concentrated on a portion such as the open end portion <NUM> of the side wall portion <NUM> of the negative electrode can <NUM>. Thus, a force with which the peripheral wall portion <NUM> of the positive electrode can <NUM> presses the resin film <NUM> in the radial direction decreases so that sealing performance of the entire battery decreases, whereas in a case where a force with which the open end portion <NUM> of the negative electrode can <NUM> presses the resin film <NUM> in the axial direction is large, the open end portion <NUM> of the negative electrode can <NUM> might touch the bottom portion <NUM> of the positive electrode can <NUM> by breaking the resin film <NUM> to thereby cause a short circuit.

On the other hand, when the value of d2/d4 is larger than <NUM>, caulking between the peripheral wall portion <NUM> of the positive electrode can <NUM> and the side wall portion <NUM> of the negative electrode can <NUM> is insufficient. Therefore, also in this case, there is a probability that the sealing properties of the entire battery are reduced.

Furthermore, the external diameter d3 of the flat portion <NUM> of the negative electrode can <NUM> and the external diameter d4 of the open end portion <NUM> in the side wall portion <NUM> of the negative electrode can <NUM> preferably satisfy d3/d4 ≥ <NUM>.

Also, a relation between the external diameter d3 of the flat portion <NUM> of the negative electrode can <NUM> and the external diameter d4 of the open end portion <NUM> in the side wall portion <NUM> of the negative electrode can <NUM> varies depending on the fitting structure of the peripheral wall portion <NUM> of the positive electrode can <NUM> with respect to the side wall portion <NUM> of the negative electrode can <NUM>. For example, in a structure of a known coin-type battery in which a peripheral wall portion of a positive electrode can is caulked to a shoulder portion of a side wall portion of a negative electrode can, the shoulder portion is designed to have a certain width dimension or more. In the known coin-type battery, the value of d3/d4 in is about <NUM>.

In contrast, in this embodiment, as described above, the peripheral wall portion <NUM> of the positive electrode can <NUM> is fitted to the side wall portion <NUM> of the negative electrode can <NUM> in the radial direction. Therefore, in the radial direction of the coin-type battery <NUM>, a projection dimension of the shoulder portion 22c in the side wall portion <NUM> of the negative electrode can <NUM> can be made small, as compared to a known structure, a dead space other than a necessary space used for housing the electrode body <NUM> can be reduced, and the capacity of the battery can be increased. From the above described viewpoint, the value of d3/d4 is more preferably <NUM> or more and, particularly, is preferably <NUM> or more.

However, the shoulder portion 22c the projection dimension of which is made to be a predetermined dimension or more causes the open end portion <NUM> of the side wall portion <NUM> of the negative electrode can <NUM> to generate a force that presses a film bottom portion <NUM>, which will be described later, against the bottom portion <NUM> of the positive electrode can <NUM>, and therefore, in order to ensure constant sealing properties between the film bottom portion <NUM> and the bottom portion <NUM> of the positive electrode can <NUM>, the value of d3/d4 is preferably <NUM> or less.

As described above, the fitting structure in the coin-type battery <NUM> can be downsized by making the projection dimension of the shoulder portion 22c in the side wall portion <NUM> of the negative electrode can <NUM> smaller in the radial direction of the coin-type battery <NUM>. Therefore, it is possible to realize downsizing of the coin-type battery <NUM> while increasing the housing space S in which the electrode body <NUM> is housed.

Note that, in this embodiment, the term "external diameter" means a diameter of a target portion in an outermost circumference position in a radial direction. The term "inner diameter" means a diameter of a target portion in an innermost position in the radial direction. In <FIG>, the dimensions of d1 to d4 are specifically illustrated.

In order to increase the ratio of the housing space S of the electrode body <NUM> to the actual volume of the coin-type battery <NUM>, a value of d3/d1 is more preferably <NUM> or more and, particularly, is preferably <NUM> or more. On the other hand, in order to provide better caulking of the open end portion <NUM> in the peripheral wall portion <NUM> of the positive electrode can <NUM> and thereby improve sealing properties, the value of d3/d1 is more preferably <NUM> or less, particularly, is preferably <NUM> or less, and is most preferably <NUM> or less.

Also, in order to provide a better pressing force by the peripheral wall portion <NUM> of the positive electrode can <NUM> in the radial direction, the value of d2/d4 is more preferably <NUM> or more and, particularly, is preferably <NUM> or more. On the other hand, in order to ensure a necessary caulking amount, the value of d2/d4 is more preferably <NUM> or less and, particularly, is preferably <NUM> or less.

The resin film <NUM> can be formed of, for example, polyphenylene sulfide (PPS), poly ether ether ketone (PEEK), tetrafluoroethylene-perfluoroalkoxy-ethylene copolymer (PFA), polypropylene (PP), or the like. The resin film <NUM> is preferably formed of a heat-resistant resin, such as PPS, with a melting point or a decomposition temperature of which is <NUM> or more to prevent reduction in sealing properties at high temperature.

The resin film <NUM> is a heat-shrinkable cylindrical resin member. The resin film <NUM> has a thickness of about <NUM>, for example. To ensure good sealing properties, the thickness of the resin film <NUM> is preferably <NUM> or more, for example. To increase the volume of the housing space S of the electrode body <NUM>, the thickness of the resin film <NUM> is preferably <NUM> or less, for example.

The resin film <NUM> may be a commercially available heat-shrinkable film made of the resin described above. That is, the resin film <NUM> is preferably a cylindrical heat-shrinkable tube, for example.

The resin film <NUM> is integrated with the outer surface of the side wall portion <NUM> of the negative electrode can <NUM> by a heat treatment, which will be described later. The resin film <NUM> after the heat treatment includes a film peripheral wall portion <NUM> located on the outer surface of the side wall portion <NUM> of the negative electrode can <NUM>, and a film bottom portion <NUM> located on the open end portion <NUM> of the side wall portion <NUM> of the negative electrode can <NUM>. The shape of the resin film <NUM> before the heat treatment may be any shape except for the cylindrical shape as long as the resin film <NUM> can be integrated with the outer surface of the side wall portion <NUM> of the negative electrode can <NUM>.

As illustrated in <FIG>, the resin film <NUM> is located outside the side wall portion <NUM> of the negative electrode can <NUM> in a state in which the resin film <NUM> is sandwiched between the positive electrode can <NUM> and the negative electrode can <NUM>. The film peripheral wall portion <NUM> is formed to have a cylindrical shape that extends in the axial direction, along the outer surface of the side wall portion <NUM> of the negative electrode can <NUM>. The film peripheral wall portion <NUM> is arranged between the peripheral wall portion <NUM> of the positive electrode can <NUM> and the side wall portion <NUM> of the negative electrode can <NUM>. The film bottom portion <NUM> is formed to have an annular shape that extends from one of end portions of the film peripheral wall portion <NUM> in the axial direction toward inside of the film peripheral wall portion <NUM>. That is, the resin film <NUM> has a hole 30a surrounded by the film bottom portion <NUM>. Thus, the resin film <NUM> is formed as an annular body which has a hook-shaped cross section. The film bottom portion <NUM> is sandwiched between the open end portion <NUM> in the side wall portion <NUM> of the negative electrode can <NUM> and the bottom portion <NUM> of the positive electrode can <NUM>.

Although not specifically shown, sealants are disposed between the resin film <NUM> and the peripheral wall portion <NUM> of the positive electrode can <NUM>, and between the resin film <NUM> and the side wall portion <NUM> of the negative electrode can <NUM>. A material for each sealant is not specifically limited as long as the material has resistance to an electrolyte and has a low moisture permeability. A commercially available sealant may be various products used as moisture-proof coating agents and including, for example, "ELEP COAT" (registered trademark) produced by Nitto Shinko Corporation, "HumiSeal" (registered trademark) produced by AIRBROWN Co. , "Hayacoat" (registered trademark) produced by Sunhayato Corp. , and "Fluorosurf" (registered trademark) produced by FluoroTechnology Co.

In the resin film <NUM>, thickness variations and surface asperities tend to occur in a heat treatment, and thus, adhesion cannot be sufficiently obtained between the peripheral wall portion <NUM> of the positive electrode can <NUM> and the resin film <NUM> or between the side wall portion <NUM> of the negative electrode can <NUM> and the resin film <NUM> in some cases. For this reason, as compared to the case of using a resin gasket as a sealing member, sealing properties easily degrade, and durability of the battery easily decreases because of entering of moisture.

On the other hand, those problems derived from the resin film <NUM> can be solved by disposing the sealant at least one of, and preferably both, a position between the resin film <NUM> and the peripheral wall portion <NUM> of the positive electrode can <NUM> and a position between the resin film <NUM> and the side wall portion <NUM> of the negative electrode can <NUM>. Thus, entering of moisture into the battery can be reduced so that durability of the battery can be enhanced.

As illustrated also in <FIG>, the electrode body <NUM> is formed by alternately stacking a substantially disk-shaped positive electrode <NUM> which is housed in a bag-shaped separator <NUM> and a substantially disk-shaped negative electrode <NUM> in the height direction of the coin-type battery <NUM>. Thus, the electrode body <NUM> as a whole has a substantially columnar shape that extends in the axial direction. Also, the electrode body <NUM> is formed by stacking the positive electrodes <NUM> and the negative electrodes <NUM> such that both end surfaces of the electrode body <NUM> in the axial direction are negative electrodes.

As illustrated in <FIG>, the positive electrode <NUM> is a member in which a positive electrode active material layer <NUM> containing a positive electrode active material, such as, for example, lithium cobalt oxide or the like, is formed on both sides of a positive electrode current collector <NUM> made of a metal foil, such as aluminum or the like.

As illustrated in <FIG>, the negative electrode <NUM> is a member in which a negative electrode active material layer <NUM> containing a negative electrode active material, such as graphite or the like, is formed on both sides of a negative electrode current collector <NUM> made of a metal foil, such as copper or the like. However, each of the negative electrodes that are located in both of end portions of the substantially columnar electrode body <NUM> in an axial direction has the negative electrode active material layer <NUM> on only one surface side of the negative electrode current collector <NUM> such that the negative electrode current collectors <NUM>, <NUM> are located in the end portions of the electrode body <NUM> in the axial direction. That is, the negative electrode current collectors <NUM>, <NUM> are exposed at both ends of the substantially columnar electrode body <NUM>. One of the negative electrode current collectors <NUM> of the electrode body <NUM> is positioned on the bottom portion <NUM> of the positive electrode can <NUM> via the positive electrode current collector <NUM> and an insulation sheet <NUM> (see <FIG> and <FIG>). The other negative electrode current collector <NUM> of the electrode body <NUM> contacts on the flat portion <NUM> of the negative electrode can <NUM> in a state in which the electrode body <NUM> is arranged between the positive electrode can <NUM> and the negative electrode can <NUM> (see <FIG>).

The separator <NUM> is a bag-shaped member that is formed to have a substantially circular shape in a plan view and is formed to have a size with which the separator <NUM> can house the substantially disk-shaped positive electrode <NUM>. The separator <NUM> is formed of a microporous thin film made of polyethylene that is excellent in electrical insulation properties. As described above, the separator <NUM> is formed of a microporous thin film, and thus, lithium ions can permeate the separator <NUM>. The separator <NUM> is formed by bonding peripheral portions of the two substantially circular microporous thin films by heat welding or the like.

As illustrated in <FIG> and <FIG>, in the positive electrode current collector <NUM> of the positive electrode <NUM>, a conductive positive electrode lead <NUM> that extends toward the outside of the positive electrode current collector <NUM> in a plan view is integrally formed therewith. A portion of the positive electrode lead <NUM>, which is located closer to the positive electrode current collector <NUM>, is also covered by the separator <NUM>. Note that the positive electrode current collector <NUM> in which the positive electrode active material layer <NUM> is not provided is arranged between the insulation sheet <NUM> and the bottom portion <NUM> of the positive electrode can <NUM>. That is, the positive electrode current collector <NUM> electrically contacts the bottom portion <NUM> of the positive electrode can <NUM>.

In the negative electrode current collector <NUM> of the negative electrode <NUM>, a conductive negative electrode lead <NUM> that extends toward the outside of the negative electrode current collector <NUM> in a plan view is integrally formed therewith.

As illustrated in <FIG> and <FIG>, the positive electrodes <NUM> and the negative electrodes <NUM> are stacked such that the positive electrode lead <NUM> of each of the positive electrodes <NUM> is located in one side and the negative electrode lead <NUM> of each of the negative electrodes <NUM> is located on an opposite side to the positive electrode lead <NUM>.

As described above, in a state in which the plurality of positive electrodes <NUM> and negative electrodes <NUM> is stacked in the height direction of the coin-type battery <NUM>, the plurality of positive electrode leads <NUM> is connected to one another by ultrasonic welding or the like, in a state in which edge sides thereof are superposed on one another in the height direction. Thus, the plurality of positive electrodes <NUM> is electrically connected to one another via the plurality of positive electrode lead <NUM> and each of the positive electrodes <NUM> and the positive electrode can <NUM> are electrically connected to one another. On the other hand, the plurality of negative electrode leads <NUM> is connected to one another by ultrasonic welding or the like, in a state in which edge sides thereof are superposed on one another in the height direction. Thus, the plurality of negative electrodes <NUM> is electrically connected to one another via the plurality of negative electrode leads <NUM> and each of the negative electrodes <NUM> and the negative electrode can <NUM> are electrically connected to one another.

Next, a manufacturing method of the coin-type battery <NUM> according to the present invention, which is performed for manufacturing the coin-type battery <NUM> that has the above described structure, will be described.

<FIG> is a cross-sectional view illustrating an outline structure of a sealing can (a negative electrode can) that is used for assembling a battery. <FIG> and <FIG> are enlarged partial cross-sectional views each illustrating an enlarged cross section of an enlarged diameter portion of a side wall portion of the sealing can. <FIG> is an enlarged cross-sectional view illustrating an embodiment of a side wall portion of a sealing can that is used in a manufacturing method of a coin-type battery according to the present invention and <FIG> is an enlarged partial cross-sectional view illustrating an example of a side wall portion of a known sealing can.

As described above, the sealing can includes the substantially cylindrical side wall portion <NUM> and the circular flat portion <NUM> that closes one of openings of the side wall portion <NUM>. The side wall portion <NUM> is provided so as to extend from an outer peripheral end of the flat portion <NUM> in a direction (a height direction) which is orthogonal to the flat portion <NUM> in a longitudinal-sectional view. That is, the side wall portion <NUM> extends from the flat portion <NUM> in the height direction. The sealing can has an opening on an opposite side to the flat portion <NUM> in the height direction. Note that the reference sign P in <FIG> denotes an axis that extends in the height direction of the sealing can.

Also, as described above, the side wall portion <NUM> includes the base end portion 22a that is located closer to the flat portion <NUM>, the diameter expansion portion 22b that is located closer to the open end portion <NUM>, and the shoulder portion 22c that is formed therebetween. A position in which the shoulder portion 22c is formed is preferably a position that is as close to the flat portion <NUM> as possible in order to increase the internal volume of the battery. That is, the diameter expansion portion 22b is preferably made as large as possible in the height direction. Specifically, when the height of the sealing can is h1 (mm), the diameter expansion portion 22b may be formed in a position higher than <NUM>/<NUM> of h1. That is, when, in the side wall portion <NUM> of the sealing can, the external diameter of the open end portion <NUM> is d5 (mm) and the external diameter in a position located at <NUM>/<NUM> of h1 from an edge 23a of the open end portion <NUM> toward the flat portion <NUM> is d6 (mm), the position of the shoulder portion 22c in the height direction is preferably a position in which d5 and d6 are the same. Note that, in reality, considering a manufacture tolerance, the diameter expansion portion 22b may be formed such that -<NUM> ≤ d5 - d6 ≤ <NUM> is satisfied.

On the other hand, when the position of the shoulder portion 22c is too close to the flat portion <NUM>, sealing by the exterior can is difficult. Therefore, in the side wall portion <NUM>, a portion located at <NUM>/<NUM> of h1 from the edge 23a of the open end portion <NUM> toward the flat portion <NUM> is preferably the base end portion 22a.

As illustrated in <FIG>, a case where a tip 123a of the open end portion <NUM> has an acute shape tends to have problems such as damage of the inner side of the peripheral wall portion <NUM> of the positive electrode can <NUM> by the tip 123a of the open end portion <NUM> that interrupts the resin film <NUM> in fitting, into the peripheral wall portion <NUM> of the positive electrode can <NUM>, the side wall portion <NUM> of the sealing can integrated with the resin film <NUM>, and breakage in the resin film <NUM> in pressing the film bottom portion <NUM> by the tip 123a of the open end portion <NUM>. Thus, a leakage easily occurs in an assembled battery. In view of this, as illustrated in <FIG>, the tip of the side wall portion of the sealing can preferably has a cross-sectional shape whose outer shape is curved in a vertical cross section. Character Q in <FIG> and <FIG> indicates a center line representing a center position of the thickness of the diameter expansion portion 22b or 122b in the radial direction.

In order not to make the shape of the edge 23a of the open end portion <NUM> with a sharp angle as much as possible, the sealing can may be formed such that, when a can thickness of the sealing can in a position at <NUM>/<NUM> of h1 from the edge 23a of the open end portion <NUM> toward the flat portion <NUM> is t1 (mm), the can thickness is maintained up to a position that is as close to the edge 23a of the open end portion <NUM> as possible.

Specifically, the edge 23a may be formed such that, when the can thickness in a position at <NUM>/<NUM> of t1 from the edge 23a of the open end portion <NUM> toward the flat portion <NUM> is t2 (mm), t2/t1 ≥ <NUM> is satisfied. In general, an upper limit of a value of t2/tl is <NUM> but, considering the manufacture tolerance or the like, the value of t2/t1 may be a value that is slightly larger than <NUM>.

The above described problems are less likely to occur when the edge 23a of the open end portion <NUM> is located in a position closer to the inner circumferential side in the radial direction than the central line Q, as illustrated in <FIG>, than when the edge 23a of the open end portion <NUM> is located in a position closer to the outer circumferential side in the radial direction than the central line Q, as illustrated in <FIG>. Therefore, the edge 23a of the open end portion <NUM> is preferably formed in a position closer to the inner circumferential side in the radial direction than the central line Q in the radial direction.

Furthermore, as illustrated in <FIG>, R is provided in an outer circumference side prat 23b of the open end portion <NUM>, and thereby, the generation of above described problems can be further suppressed. The curvature radius of R of the open end portion <NUM> is not particularly limited but, considering processability as well, it is considered that the curvature radius may be about <NUM> to <NUM>.

The sealing can that has the above described shape can be obtained by press-forming by adjusting well-known conditions when press-forming is performed.

As illustrated in <FIG>, the resin film <NUM> for use in assembly of a battery is a heat-shrinkable cylindrical resin member.

<FIG> illustrates a state where the side wall portion <NUM> of the sealing can is covered with the resin film <NUM> before a heat treatment in assembly of a battery. <FIG> illustrates a state where the cylindrical resin film <NUM> is subjected to a heat treatment to be integrated with the side wall portion <NUM> of the sealing can in assembly of a battery.

As illustrated in <FIG>, the cylindrical resin film <NUM> before the heat treatment is disposed to cover the side wall portion <NUM> of the sealing can. This process corresponds to the step of covering the outer peripheral surface of the side wall portion <NUM> of the sealing can with the resin film. The inner diameter of the resin film <NUM> is adjusted to establish d7 > d5 where d7 (mm) is an inner diameter of the cylindrical resin film <NUM> before the heat treatment. That is, the inner diameter of the resin film <NUM> is larger than the external diameter of the open end portion <NUM> of the side wall portion <NUM> of the sealing can. To increase adhesion of the resin film <NUM> to the side wall portion <NUM> of the sealing can in the heat treatment, the difference between d7 and d5 is preferably <NUM> or less.

As illustrated in <FIG>, in covering the side wall portion <NUM> of the sealing can with the cylindrical resin film <NUM> before the heat treatment, the resin film <NUM> is disposed to the side wall portion <NUM> of the sealing can such that one end of the resin film <NUM> in the cylinder axis direction projects from the open end portion <NUM> of the side wall portion <NUM> of the sealing can (where the projection length is indicated by L in <FIG>). At this time, the resin film <NUM> may be cut at a predetermined position in the cylinder axis direction such that one end of the resin film <NUM> in the cylinder axis direction projects from open end portion <NUM> of the side wall portion <NUM> of the sealing can. In the heat treatment on the resin film <NUM>, the projecting portion of the resin film <NUM> is contracted by heat and bent inward in the radial direction to thereby cover the open end portion <NUM> of the side wall portion <NUM> of the sealing can. To cover the open end portion <NUM> with the resin film <NUM> more sufficiently, the projection length L is preferably <NUM> or more, and more preferably <NUM> or more. On the other hand, to prevent an excessive increase in the width of a film bottom portion formed by the heat treatment, the projection length L is preferably <NUM> or less, more preferably <NUM> or less, and especially preferably <NUM> or less.

The resin film <NUM> is disposed to the side wall portion <NUM> of the sealing can such that the other end portion of the resin film <NUM> in the cylinder axis direction is located at the same position as the flat portion <NUM> of the sealing can in the cylinder axis direction, for example. At this time, the resin film <NUM> may be cut at a predetermined position in the cylinder axis direction such that the other end portion in the cylinder axis direction is located at the same position as the flat portion <NUM> of the sealing can in the cylinder axis direction. It is sufficient that after sealing by caulking the peripheral wall portion of the exterior can (positive electrode can <NUM>) to the side wall portion <NUM> of the sealing can, the resin film <NUM> is present between the open end portion of the peripheral wall portion of the exterior can and the sealing can so that electrical insulation can be obtained. Thus, the position of the other end portion of the resin film <NUM> in the cylinder axis direction can be appropriately adjusted as necessary.

To enhance sealing properties after the sealing, a sealant <NUM> is preferably applied to the inner peripheral surface of the resin film <NUM> before the side wall portion <NUM> of the sealing can is covered with the resin film <NUM>. The sealant <NUM> may be previously applied to at least one of the inner peripheral surface or the outer peripheral surface of the resin film <NUM>. The sealant <NUM> may be applied to the outer peripheral surface of the side wall portion <NUM> of the sealing can. The sealant <NUM> may be applied to the inner peripheral surface of the peripheral wall portion of the exterior can.

The width to which the sealant <NUM> is applied (indicated by X in <FIG>) is not specifically limited as long as the advantage of enhancement of sealing properties (suppression of moisture entering) can be obtained, but in general, the width is preferably <NUM> or more, and more preferably <NUM> or more. The sealant <NUM> may be applied to the entire surface of a portion of the resin film <NUM> that touches the side wall portion <NUM> of the sealing can or the peripheral wall portion of the exterior can.

After the side wall portion <NUM> of the sealing can has been covered with the cylindrical resin film <NUM> before the heat treatment as illustrated in <FIG>, the resin film <NUM> is subjected to the heat treatment, and as a result, the resin film <NUM> is integrated with the outer peripheral surface of the side wall portion <NUM> of the sealing can as illustrated in <FIG>. This process corresponds to the step of integrating the resin film <NUM> with the side wall portion <NUM> of the sealing can while covering the open end portion <NUM> of the side wall portion <NUM> of the sealing can with the resin film <NUM> by contracting the resin film <NUM> under the heat treatment. The heat treatment temperature of the resin film <NUM> is not limited to a specific treatment, but if the heat treatment temperature is higher than the temperature of the glass transition point of the resin film <NUM>, heat contraction of the resin film <NUM> is promoted, and the resin film <NUM> is more suitably integrated with the side wall portion <NUM> of the sealing can. A period of the heat treatment may be appropriately adjusted in accordance with progress of heat contraction of the resin film <NUM>.

In this manner, a part of the resin film <NUM> constitutes the film peripheral wall portion <NUM> conforming to the outer peripheral surface of the side wall portion <NUM> of the sealing can, and another part of the resin film <NUM> constitutes the film bottom portion <NUM> located on the open end portion <NUM> of the side wall portion <NUM> of the sealing can. That is, with the heat treatment on the resin film <NUM> as described above, the film peripheral wall portion <NUM> covering the base end portion 22a, the shoulder portion 22c, and the diameter expansion portion 22b of the side wall portion <NUM> of the sealing can are formed. In addition, with the heat treatment on the resin film <NUM> as described above, the film bottom portion <NUM> is formed to extend inward in the film peripheral wall portion <NUM> from one end portion of the film peripheral wall portion <NUM> in the axial direction. That is, the portion of the resin film <NUM> projecting from the open end portion <NUM> of the side wall portion <NUM> of the sealing can is deformed inward in the side wall portion <NUM> relative to the open end portion <NUM> so that the film bottom portion <NUM> (whose projection length is indicated by M in <FIG>) in which the resin film <NUM> projects inward in the side wall portion <NUM> from the open end portion <NUM> is thereby formed. This film bottom portion <NUM> covers the open end portion <NUM> of the side wall portion <NUM> of the sealing can.

To further ensure electrical insulation between the open end portion <NUM> of the side wall portion <NUM> of the sealing can and the bottom portion of the exterior can by the resin film <NUM>, the projection length M of the film bottom portion <NUM> is preferably <NUM> or more, and more preferably <NUM> or more. On the other hand, to reduce a redundant volume of the film bottom portion <NUM> disposed in the battery, the projection length M is preferably <NUM> or less, more preferably <NUM> or less, and especially preferably <NUM> or less.

The portion projecting inward from the side wall portion <NUM> of the film bottom portion <NUM> may have a structure that is bent toward the flat portion of the sealing can.

Steps of manufacturing a coin-type battery using the sealing can (the negative electrode can) in which the resin film <NUM> is integrated will be described. Note that, as the exterior can (the positive electrode can), a general exterior can that includes a circular bottom portion and a cylindrical peripheral wall portion that is formed continuously from the bottom portion on an outer circumference and extends in the axial direction, and has an opening on an opposite side to the bottom portion may be used.

First, the plurality of plate-like positive electrodes <NUM> each of which is covered by the separator <NUM> and the plurality of plate-like negative electrodes <NUM> are stacked in the height direction to form a substantially columnar electrode body <NUM> illustrated in <FIG>. The electrode body <NUM> is manufactured by a similar method to a known method, and therefore, description of a detailed manufacturing method will be omitted.

The electrode body <NUM> is disposed in the exterior can (hereinafter referred to as the positive electrode can <NUM>) together with an insulation sheet <NUM>, for example, and the positive electrode current collector <NUM> is either welded to, or electrically brought into contact with, the inner surface of the positive electrode can <NUM>. Next, a non-aqueous electrolyte is injected into a sealing can (hereinafter referred to as a negative electrode can <NUM>) in which the resin film <NUM> is attached onto the outer peripheral surface of the side wall portion <NUM> as described above, and the positive electrode can <NUM> housing the electrode body <NUM> is disposed to cover an opening of the negative electrode can <NUM>. In this state, the peripheral wall portion <NUM> of the positive electrode can <NUM> is pushed radially inward against the side wall portion <NUM> of the negative electrode can <NUM> and caulked thereto.

At this time, the peripheral wall portion <NUM> of the positive electrode can <NUM> and the side wall portion <NUM> of the negative electrode can <NUM> are fitted together by displacing the peripheral wall portion <NUM> of the positive electrode can <NUM> with respect to the side wall portion <NUM> of the negative electrode can <NUM> in the radial direction in a state in which the resin film <NUM> is arranged between the negative electrode can <NUM> and the positive electrode can <NUM> such that the film peripheral wall portion <NUM> is sandwiched between the side wall portion <NUM> of the negative electrode can <NUM> and the peripheral wall portion <NUM> of the positive electrode can <NUM> and the film bottom portion <NUM> is sandwiched between the open end portion <NUM> in the side wall portion <NUM> of the negative electrode can <NUM> and the bottom portion <NUM> of the positive electrode can <NUM>.

In the foregoing manner, the coin-type battery <NUM> having the configuration described above is obtained. To further enhance sealing properties of the battery, the sealant <NUM> is preferably provided not only between the resin film <NUM> and the side wall portion <NUM> of the negative electrode can <NUM> but also between the resin film <NUM> and the peripheral wall portion <NUM> and the bottom portion <NUM> of the of the positive electrode can <NUM>, before assembly of the battery. The sealant <NUM> may be previously applied to at least one of the inner peripheral surface or the outer peripheral surface of the resin film <NUM> or may be previously applied to at least a portion of the side wall portion <NUM> of the negative electrode can <NUM> and the peripheral wall portion <NUM> and the bottom portion <NUM> of the positive electrode can <NUM>.

As described above, the coin-type battery <NUM> that is formed through the above described steps is preferably designed such that the external diameter d1 of the peripheral wall portion <NUM> of the positive electrode can <NUM> and the external diameter d3 of the flat portion <NUM> of the negative electrode can <NUM> satisfy <NUM> ≤ d3/d1 ≤ <NUM>. Also, the coin-type battery <NUM> is preferably designed such that, in a state where the positive electrode can <NUM> is caulked to the negative electrode can <NUM> with the resin film <NUM> sandwiched therebetween, the inner diameter d2 of the open end portion <NUM> in the peripheral wall portion <NUM> of the positive electrode can <NUM> and the external diameter d4 of the open end portion <NUM> in the side wall portion <NUM> of the negative electrode can <NUM> satisfy <NUM> ≤ d2/d4 ≤ <NUM>.

Thus, the housing space S in the coin-type battery <NUM> can be made large, as compared to a known structure, and the capacity of the coin-type battery <NUM> can be increased. That is, a space inside of the negative electrode can <NUM> can be made large relative to external dimensions of the battery by causing a relation between the external diameter d3 of the flat portion <NUM> of the negative electrode can <NUM> and the external diameter d1 of the bottom portion <NUM> of the positive electrode can <NUM> to satisfy <NUM> ≤ d3/d1 ≤ <NUM>.

Also, the sealing properties can be increased in a battery structure in which the ratio of the internal space of the negative electrode can <NUM> to the actual volume of the battery is made large by causing the relation between the external diameter d4 of the open end portion <NUM> in the side wall portion <NUM> of the negative electrode can <NUM> and the inner diameter d2 of the open end portion <NUM> in the peripheral wall portion <NUM> of the positive electrode can <NUM> to be <NUM> ≤ d2/d4 ≤ <NUM>. Therefore, a compact sealing structure can be realized, and accordingly, the battery capacity can be increased without enlarging the coin-type battery <NUM>.

Note that, in the coin-type battery <NUM>, an amount by which the peripheral wall portion <NUM> of the positive electrode can <NUM> is displaced due to being caulked is relatively small, and therefore, the shape of the negative electrode can <NUM> is kept such that an original shape of the sealing can is maintained. Therefore, the external diameter d5 of the side wall portion <NUM> in the open end portion <NUM> in the original sealing can and the external diameter d4 of the side wall portion <NUM> in the open end portion <NUM> in the negative electrode can <NUM> of the coin-type battery <NUM> which has been assembled are substantially the same. Also, in order to cause a ratio (d3/d4) between the external diameters d3 and d4 of the flat portion <NUM> of the negative electrode can to be in a range of <NUM> or more and <NUM> or less, a ratio between the external diameter of the flat portion <NUM> in the original sealing can and d5 may be set to be substantially in a range of <NUM> or more and <NUM> or less.

Next, a manufacturing method of the coin-type battery <NUM> according to the present invention will be more specifically described using working examples and comparative examples below.

Using LiCoO<NUM> as a positive electrode active material, carbon black as a conduction assisting agent, and PVDF as a binder, a positive electrode is formed in a manner described below.

First, <NUM> parts by mass of LiCoO<NUM> and <NUM> parts by mass of carbon black are mixed and a mixture obtained thereby and a binder solution in which <NUM> parts by mass of PVDF has been dissolved in NMP (N-methyl-<NUM>-pyrrolidone) in advance are mixed, thereby preparing a positive electrode mixture paste. The obtained positive electrode mixture paste is applied to both surfaces of a positive electrode current collector made of an aluminum foil having a thickness of <NUM> by an applicator. Note that the positive electrode mixture paste is applied onto the positive electrode current collector such that a coated portion and an uncoated portion are alternately arranged and also that a portion a front surface of which is a coated portion has a back surface that is also a coated portion. Subsequently, the applied positive electrode mixture paste is dried to form a positive electrode active material layer, roll press is performed thereon, and thereafter, the positive electrode current collector is cut into pieces each having a predetermined size, thereby obtaining strip positive sheets. Note that the positive electrode sheets are formed such that a portion of each of the positive electrode sheets on which the positive electrode active material layer is formed has an entire thickness of <NUM>.

The strip positive electrode sheet is punched such that the portion on which the positive electrode active material layer is formed serves as a body portion (a diameter of an arc portion: <NUM>) and a portion on which the positive electrode active material layer is not formed serves as a positive electrode tab portion (a width: <NUM>), thereby obtaining a positive electrode. In <FIG>, a plan view schematically illustrating a positive electrode after being punched is illustrated. The positive electrode <NUM> includes a body portion 41a in which the positive electrode active material layer <NUM> is formed on each of both surfaces of the positive electrode current collector <NUM> and a positive electrode tab portion 41b that protrudes from the body portion 41a and has a narrower width than that of the body portion 41a.

Using graphite as a negative electrode active material and PVDF as a binder, a negative electrode is formed in a manner described below.

First, <NUM> parts by mass of graphite and a binder solution in which <NUM> parts by mass of PVDF has been dissolved in NMP in advance are mixed to prepare a negative electrode mixture paste. The obtained negative electrode mixture paste is applied to one surface or both surfaces of a negative electrode current collector made of a copper foil having a thickness of <NUM> by an applicator. Note that the negative electrode mixture paste is applied onto the negative electrode current collector such that a coated portion and an uncoated portion are alternatively arranged and that, if the negative electrode mixture paste is applied to both surfaces of the current collector, a portion a front surface of which is a coated portion has a back surface that is also a coated portion. Subsequently, the applied negative electrode mixture paste is dried to form a negative electrode active material layer, roll press is performed thereon, and thereafter, the negative electrode current collector is cut into pieces each having a predetermined size, thereby obtaining strip negative sheets. Note that the negative sheets are formed such that a portion of the negative electrode sheet on which the negative electrode active material layer is formed has an entire thickness of <NUM> if the negative electrode active material layer is formed on both surfaces of the current collector and <NUM> if the negative electrode active material layer is formed on one surface of the current collector.

The strip negative electrode sheet is punched such that the portion on which the negative electrode active material layer is formed serves as a body portion (a diameter of an arc portion: <NUM>) and a portion on which the negative electrode active material layer is not formed serves as a negative electrode tab portion, thereby obtaining each of a negative electrode that includes a negative electrode active material layer on one surface of a current collector and a negative electrode that includes a negative electrode active material layer on both surfaces of the current collector. Note that a negative electrode of negative electrodes that have a negative electrode active material layer on one surface of a current collector, which is arranged on a side closer to an external can, is punched after a PET film (an insulation sheet) which has a thickness of <NUM> is bonded to an exposed surface of the strip negative electrode sheet in which the current collector is exposed. In <FIG>, a plan view schematically illustrating the negative electrode after being punched is illustrated. The negative electrode <NUM> includes a body portion 46a in which the negative electrode active material layer <NUM> is formed on both surfaces or one surface of the negative electrode current collector <NUM> and a negative electrode tab portion 46b that protrudes from the body portion 46a and has a narrower width than that of the body portion 46a.

A non-aqueous electrolyte was prepared by dissolving LiPF<NUM> into a mixed solvent in which a volume ratio between ethylene carbonate and methylethyl carbonate is <NUM>:<NUM> in a concentration of <NUM> mol/l.

In <FIG>, a separator that was used in this working example is schematically illustrated. A microporous film (a thickness of <NUM>) made of polyethylene having the shape illustrated in <FIG> is arranged on each of both surfaces of the positive electrode <NUM> formed in the above described manner and a portion of a peripheral portion of a main body portion 44a of each of both of the separators <NUM> and a portion of an extending portion 44b are welded by hot pressing (a temperature of <NUM>, a press time of <NUM> seconds) to form a joint portion in the portion of the peripheral portion of the main body portion 44a in each of the two separators <NUM> and the portion of the peripheral portion of the extending portion 44b, and thereby, the positive electrode <NUM> and the separator <NUM> are integrated.

<FIG> illustrates an electrode body in which the positive electrode <NUM>, the negative electrode <NUM>, and the separator <NUM> are stacked. In <FIG>, the positive electrode <NUM> that is arranged under the separator <NUM> is indicted by a dotted line, the negative electrode tab portion 46b of the negative electrode <NUM>, which is arranged further under them, is indicated by a long dashed short dashed line, and a binding tape <NUM> that restrains displacement of each component element of the electrode body is indicated by a long dashed double-short dashed line. The positive electrode <NUM> illustrated in <FIG> is stacked on the negative electrode <NUM> via one of a pair of separators <NUM> integrated with the positive electrode <NUM> sandwiched therebetween in the thickness direction in the electrode body. Note that, although not particularly illustrated in <FIG>, the negative electrode is arranged under the separator <NUM> (a back side of a plane of <FIG>).

The separator <NUM> illustrated in <FIG> includes a joint portion 44c (indicated by a lattice pattern in <FIG>) welded to another separator <NUM> arranged thereunder (the back side of the plane of <FIG>) with the positive electrode <NUM> (indicated by the dotted line in <FIG>) sandwiched therebetween in the thickness direction thereof in the peripheral portion. That is, the pair of separators <NUM> arranged with the positive electrode <NUM> sandwiched therebetween in the thickness direction is welded with one another in the peripheral portion to have a bag shape, the positive electrode <NUM> is housed inside thereof, and thereby, the positive electrode <NUM> and the separators <NUM> are integrated.

Note that the separator <NUM> illustrated in <FIG> includes the main body portion 44a (that is, the main body portion 44a that has a larger area in a plan view than that of the body portion 41a of the positive electrode <NUM>) which covers an entire surface of the body portion 41a of the positive electrode <NUM> and the extending portion 44b that protrudes from the main body portion 44a and covers a boundary portion between the body portion 41a and the positive electrode tab portion 41b of the positive electrode <NUM>. Then, the joint portion 44c in which the pair of separators <NUM> arranged on the both surfaces of the positive electrode <NUM> is welded with one another is provided in at least portions of peripheral portions of the main body portion 44a and the extending portion 44b of the separators <NUM>. A non-welding portion 44d in which the separators <NUM> are not welded with one another is provided in a portion of the peripheral portion of the main body portion 44a.

Note that, in this working example, the width of the joint portion 44c that is provided in each of the main body portion 44a and the extending portion 44b of the separator <NUM> is <NUM> and the length of the extending portion 44b from the main body portion 44a in the peripheral portion in a protruding direction is <NUM>. A portion of an outer edge of the main body portion 44a of the separator <NUM> that has a length of <NUM>% of the entire length of the outer edge is the joint portion.

Using eleven positive electrodes integrated with the above described separators, ten negative electrodes each in which a negative electrode active material layer was formed on each of both surfaces of a negative electrode current collector, and two negative electrodes (one of which was a negative electrode in which a PET film was bonded to an exposed surface in which a current collector was exposed) each in which a negative electrode active material layer was formed on one surface of a negative electrode current collector, the positive electrodes and the negative electrodes were alternately stacked such that the negative electrodes each in which the negative electrode active material layer was formed on one surface of a negative electrode current collector were located in most outer portions, and the entire electrodes were fastened by a binding tape, thereby an electrode body was obtained.

Next, a positive electrode tab portion of each of the positive electrodes, which protruded toward one side of the electrode body, and a negative electrode tab portion of each of the negative electrodes, which protruded in an opposite direction to a direction of protrusion of the positive electrode tab portion, were integrated by welding the tab portions in a state in which the positive electrode tab portions and the negative electrode tab portions were separately put together.

As an exterior can, a metal can including a circular bottom portion and a cylindrical peripheral wall portion formed to extend from an outer peripheral end of the bottom portion in a direction (the height direction) orthogonal to the bottom portion and having an opening on an opposite side to the bottom portion was formed by press-forming a plate formed of SUS316 and having a thickness of <NUM>. Note that Ni plating was performed on an outer surface of the exterior can. An external diameter of the bottom portion of the exterior can was <NUM>.

As a sealing can, the metal can illustrated in <FIG> including a circular flat portion and a side wall portion formed to extend from an outer peripheral end of the flat portion in a direction (the height direction) orthogonal to the flat portion and having an opening on an opposite side to the flat portion was formed by press-forming a plate formed of NAS64 and having a thickness of <NUM>. Note that Ni plating was performed on an outer surface of the sealing can. The height h1 of the sealing can was <NUM> and the external diameter of the flat portion thereof was <NUM>. A shoulder portion was formed in a position located at <NUM> (<NUM>/<NUM> of h1) from an edge of an open end portion toward the flat portion. The external diameter d5 of the side wall portion in the open end portion was <NUM>, the external diameter d6 and the can thickness t1 of the side wall portion in a position located at <NUM>/<NUM> of h1 from the edge of the open end portion toward the flat portion were <NUM> and <NUM>, respectively, and the can thickness t2 of the side wall portion in a position at <NUM>/<NUM> of t1 from the edge of the open end portion toward the flat portion was <NUM>. That is, a diameter expansion portion 22b of the side wall portion was formed such that d5 - d6 = <NUM> and t2/t1 =<NUM> were satisfied.

Note that the edge of the open end portion was located in a position closer to an inner circumferential side in the radial direction than a central line of a thickness of the diameter expansion portion in the radial direction.

As a sealing member between the exterior can and the sealing can, a resin film (heat-shrinkable film) having a cylindrical shape illustrated in <FIG> and made of polyphenylene sulfide whose glass transition point is about <NUM> was used.

The cylindrical resin film was placed onto the sealing can such that the side wall portion of the sealing can was covered with the resin film and one end portion of the resin film in the cylinder axis direction was located at the same position as the flat portion of the sealing can, and then, the other end portion of the resin film in the cylinder axis direction was cut such that the projection length L from the sealing can was <NUM>. Thereafter, the sealing can be covered with the resin film was subjected to a heat treatment while being held in an electric heating furnace at <NUM> for <NUM> minutes so that the resin film was thereby integrated with the outer peripheral surface of the side wall portion of the sealing can. At this time, the projection length M of the resin film projecting inward from the open end portion of the sealing can was <NUM>.

Next, in the external can, the PET film of the negative electrode of the electrode body was arranged so as to face an inner surface of the exterior can, and the positive electrode tabs of the positive electrodes which were integrated were welded to the inner surface of the exterior can.

Furthermore, after the non-aqueous electrolyte was injected into the sealing can integrated with the resin film, sealing was performed by putting the exterior can in which the electrode body was housed over the sealing can and caulking the peripheral wall portion of the exterior can to the side wall portion of the sealing can. Thus, a coin-type non-aqueous secondary battery having a similar structure to that of the battery illustrated in <FIG> and having an external diameter of <NUM> and a height of <NUM> was obtained.

An "ELEP COAT (registered trademark) LSS-520MH (product name)" produced by Nitto Shinko Corporation was previously applied to a width of <NUM> over the inner peripheral surface of the resin film and the inner surface of the peripheral wall portion of the exterior can, and sealing was performed such that the sealant was interposed between the entire opposed surfaces of the resin film and the sealing can and the entire opposed surfaces of the resin film and the exterior can after assembly of a battery.

The external diameter d1 of the bottom portion of the exterior can in the battery thus obtained was <NUM> (mm). The inner diameter d2 of the open end portion in the peripheral wall portion of the exterior can was <NUM> (mm). The external diameter d3 of the flat portion of the sealing can was <NUM> (mm). The external diameter d4 of the open end portion in the side wall portion of the sealing can was <NUM> (mm). Therefore, in the battery, d3/d1 = <NUM>, d2/d4 = <NUM>, and d3/d4 = <NUM> were satisfied.

A coin-type non-aqueous secondary battery was fabricated by using, as a sealing member, a ring-shaped polyphenylene sulfide gasket <NUM> having the cross-sectional shape illustrated in <FIG>, instead of the resin film. <FIG> is an end view in a case where the ring-shaped gasket <NUM> is cut in a plane including an axis P.

In the gasket <NUM>, a thickness t3 in the radial direction of a portion located between the peripheral wall portion of the exterior can and the side wall portion of the sealing can and a thickness t4 in the axial direction of a portion located between the side wall portion of the sealing can and the bottom portion of the exterior can were <NUM> and about <NUM>, respectively, before assembly of the battery.

In the battery of the first comparative example, since the gasket <NUM> was used as a sealing member instead of the resin film, the diameters of the sealing can and the electrode body, for example, were changed in accordance with an increase in the thickness of the sealing member.

Specifically, a positive electrode in which a curved portion of a body portion including the positive electrode active material layer has a diameter of <NUM> was formed from a strip positive electrode sheet, and a negative electrode in which a curved portion of a body portion including a negative electrode active material layer has a diameter of <NUM> was formed from a strip negative electrode sheet. The positive electrode and the negative electrode were used to form an electrode body to thereby fabricate a battery.

The external diameter d1 of the bottom portion of the exterior can in the battery was <NUM> (mm). The inner diameter d2 of the open end portion in the peripheral wall portion of the exterior can was <NUM> (mm). The external diameter d3 of the flat portion of the sealing can was <NUM> (mm). The external diameter d4 of the open end portion in the side wall portion of the sealing can was <NUM> (mm).

Therefore, in the battery of the first comparative example, d3/d1 = <NUM>, d2/d4 = <NUM>, and d3/d4 = <NUM> were satisfied.

Using a sealing can having a known structure in which a side wall portion was folded back in an open end portion, an annular gasket having a U-shaped longitudinal section corresponding to the side wall portion of the sealing can, and the same exterior can as that of the first working example, a coin-type battery was formed.

Note that, in the batteries of the second comparative example, a housing space in which an electrode body was housed was reduced as compared to the batteries of the first comparative example, and therefore, the external diameter of the electrode body was reduced accordingly.

For each of the batteries of the first working embodiment, the first comparative example and the second comparative example, when a theoretical capacity of a positive electrode was <NUM> C (mAh), charging at a constant voltage of <NUM> V was conducted after charging at a constant current of <NUM> C (mA) was conducted up to <NUM> V, and the charging was terminated at a time when a current value reduced to reach <NUM> C. Each of the charged batteries was discharged with a constant current of <NUM> C (mA) and a discharge capacity until the voltage of the battery reached <NUM> V was measured. Measurement results are illustrated in Table <NUM>.

As shown in Table <NUM>, the coin-type battery of the first working example has an increased discharge capacity larger by <NUM>% than that of the battery of the second comparative example having the conventional structure. As compared to the battery of the first comparative example whose internal volume was increased by reducing the thickness of the gasket, the coin-type battery of the first working example increased the discharge capacity by <NUM>%.

The capacity difference described above becomes conspicuous as the external diameter of the battery decreases. Thus, for batteries whose external diameters are <NUM> or less, advantages of the present invention are more remarkable.

To measure a content of moisture entering from a sealed portion into the battery in high-temperature storage in the batteries of the first working example and the first comparative example, an evaluation battery was fabricated in the following manner.

First, <NUM> of electrolytic manganese dioxide powder was compressed under a pressing pressure of <NUM> to thereby form a disk-shaped formed body having a diameter of <NUM> and a height of <NUM> was produced, and then, the formed body was held in a dry air atmosphere at <NUM> for <NUM> hours or more and dried.

Next, in the same manner as that of the first working example except that the dried formed body was used instead of the electrode body of the battery of the first working example and a non-aqueous electrolyte was not injected, an evaluation battery A (having the same sealing structure as that of the first working example) enclosing the formed body was produced.

For the battery of the first comparative example, an evaluation battery B (having the same sealing structure as that of the first comparative example) was produced in a manner similar to the evaluation battery A.

Each evaluation battery fabricated as described above was held in an atmosphere at <NUM> at a relative humidity of <NUM>% for <NUM> days, and then, a formed body was taken from the evaluation battery so that a moisture content of the formed body was measured with a Karl-Fisher moisture meter (produced by Kyoto Electronics Manufacturing Co. , "MKC-510N" (device name)).

In addition, the moisture content of the formed body in each evaluation battery before high-temperature storage as described above was previously measured, and a difference between a measurement result of the moisture content before the high-temperature storage and a measurement result of a moisture content after the high-temperature storage (i.e., the degree of increase of moisture content) was obtained. In this manner, sealing performances (moisture permeabilities in high-temperature storage) of the batteries of the first working example and the first comparative example were evaluated.

Table <NUM> shows the moisture content difference.

As shown in Table <NUM>, since the battery of the first working example used the polyphenylene sulfide resin film as a sealing member, entering of moisture into the battery in high-temperature storage was significantly reduced, as compared to the battery of the first comparative example using the gasket of the same material as a sealing member. Thus, the battery showing good sealing properties was obtained.

Next, in order to check electrical insulation properties and sealing properties of batteries using the "hook-shaped gasket", the third to sixth comparative examples were formed in a manner described below.

Similar to the first working example, a coin-type non-aqueous secondary battery was formed, except that the external diameter d3 of a flat portion of a sealing can was <NUM> (d3/d1 = <NUM>).

Similar to the first working example, a coin-type non-aqueous secondary battery was formed, except that the external diameter d3 of the flat portion of the sealing can was <NUM> (d3/d1 = <NUM>) and the inner diameter d2 of the open end portion in the peripheral wall portion of the exterior can was <NUM> (d2/d4 = <NUM>) in accordance with an increase in the external diameter d3.

Similar to the first working example, a coin-type non-aqueous secondary battery was formed, except that the external diameter d3 of the flat portion of the sealing can was <NUM> (d3/d1 = <NUM>) and the inner diameter d2 of the open end portion in the peripheral wall portion of the exterior can was <NUM> (d2/d4 = <NUM>).

Similar to the first working example, a coin-type non-aqueous secondary battery was formed, except that the inner diameter d2 of an open end portion in a peripheral wall portion of an exterior can was <NUM> (d2/d4 = <NUM>).

In each of the batteries of the first working example and the third to sixth comparative examples, charging and discharging were performed under the same conditions as those of the above described battery capacity measurement to measure an internal resistance of each of the batteries after being discharged, and thereby, presence or absence of a short circuit in each of the batteries was checked.

Also, charging was performed under the same conditions as those of the above described battery capacity measurement, the batteries after being charged were stored in an environment of <NUM> and a relative humidity of <NUM>% for <NUM> days, and thereafter, presence or absence of a fluid leakage in the batteries was checked.

Results of the above described check are illustrated in Table <NUM>. Note that, in Table <NUM>, each of batteries in which a short circuit and a fluid leakage did not occur is indicated by a circle and each of batteries in which a short circuit and a fluid leakage occurred is indicated by ×.

As is understood from Table <NUM>, in the battery of the first working example in which the values of d3/d1 and d2/d4 were in a range of <NUM> ≤ d3/d1 ≤ <NUM> and in a range of <NUM> ≤ d2/d4 ≤ <NUM>, respectively, a short circuit and a fluid leakage did not occur.

On the other hand, in the battery of the third comparative example, as compared to the battery of the first working example, a ratio of a housing space of an electrode body was small, and therefore, a short circuit occurred.

Further, in the batteries of the fourth to sixth comparative examples, a fluid leakage occurred due to reduction in sealing properties. In particular, in the battery of the fifth comparative example in which the value of d2/d4 was small, the open end portion of the side wall portion of the sealing can presses the resin film in the axial direction with a large pressing force, and thus, a short circuit occurred because of contact between the open end portion of the side wall portion of the sealing can and the bottom portion of the exterior can.

As is clear from the foregoing, according to the constitution of the present invention, a capacity of a small coin-type battery can be increased while maintaining sealing properties.

In the above described embodiment, the electrode body <NUM> has a structure in which the plurality of positive electrodes <NUM> and the plurality of negative electrodes <NUM> are alternately stacked, but a structure of an electrode body may be a structure other than the above described structure.

In the above described embodiment, the positive electrode <NUM> includes a positive electrode active material layer containing a positive electrode active material, such as lithium cobalt oxide or the like, and the negative electrode <NUM> includes the negative electrode active material layer <NUM> containing a negative electrode active material, such as graphite or the like. However, a structure of a positive electrode and a negative electrode may be a structure other than the above described structure.

Although, in the above described embodiment, the positive electrode can <NUM> is an exterior can and the negative electrode can <NUM> is a sealing can, reversely, a positive electrode can may be a sealing can and a negative electrode can may be an exterior can.

Claim 1:
A coin-type battery (<NUM>) comprising:
an exterior can (<NUM>) including a bottom portion (<NUM>) and a peripheral wall portion (<NUM>) and having an opening on an opposite side to the bottom portion (<NUM>) in a thickness direction;
a sealing can (<NUM>) which includes a flat portion (<NUM>) and a side wall portion (<NUM>) and has an opening on an opposite side to the flat portion (<NUM>) in the thickness direction and of which a stepped shoulder portion (22c) that is located between the flat portion (<NUM>) and the opening and expands in a radial direction is provided in the side wall portion (<NUM>);
a resin film (<NUM>) at least a portion of which is arranged between the peripheral wall portion (<NUM>) of the exterior can (<NUM>) and the side wall portion (<NUM>) of the sealing can (<NUM>); and
a power generation element (<NUM>) arranged in a housing space formed by the exterior can (<NUM>) and the sealing can (<NUM>),
wherein the resin film (<NUM>) includes
a film peripheral wall portion (<NUM>) formed to have a cylindrical shape and arranged between the peripheral wall portion (<NUM>) of the exterior can (<NUM>) and the side wall portion (<NUM>) of the sealing can (<NUM>), and
a film bottom portion (<NUM>) arranged between the bottom portion (<NUM>) of the exterior can (<NUM>) and an open end portion (<NUM>) of the side wall portion (<NUM>) of the sealing can (<NUM>), and
is an annular body, and
when it is assumed that an external diameter of the bottom portion (<NUM>) of the exterior can (<NUM>) is d1 (mm), an inner diameter of the open end portion (<NUM>) in the peripheral wall portion (<NUM>) of the exterior can (<NUM>) is d2 (mm), an external diameter of the flat portion (<NUM>) of the sealing can (<NUM>) is d3 (mm), and an external diameter of the open end portion (<NUM>) in the side wall portion (<NUM>) of the sealing can (<NUM>) is d4 (mm), <NUM> ≤ d3/d1 ≤ <NUM> and <NUM> ≤ d2/d4 ≤ <NUM> are satisfied, and
a sealant (<NUM>) is disposed at at least one of a position between the peripheral wall portion (<NUM>) of the exterior can (<NUM>) and the resin film (<NUM>) or a position between the side wall portion (<NUM>) of the sealing can (<NUM>) and the resin film (<NUM>).