Patent Description:
The present invention relates to an electrode assembly embedded in a secondary battery, and more particularly, to an electrode having advantages of a lamination & stacking method with a relatively stable structure and advantages of a Z-folding method with a relatively small allowable tolerance.

Thus, recently, many studies on rechargeable batteries are being carried out. As technology development and demands for mobile devices increase, the demands for rechargeable batteries as energy sources are rapidly increasing.

Such a secondary battery is configured so that an electrode assembly is built in a battery case (for example, a pouch, a can, and the like). The electrode assembly built in the battery case is repeatedly chargeable and dischargeable because of a structure in which a positive electrode/a separator/a negative electrode are stacked.

<FIG> is a side view illustrating a process of manufacturing a unit cell <NUM> to be stacked in an electrode assembly through a lamination & stacking process among electrode assemblies according to the related art, and <FIG> is a side view illustrating a state in which the plurality of unit cells <NUM> manufactured in <FIG> are stacked.

Referring to the drawings, in the lamination & stacking manner, the positive electrode <NUM>, the separator <NUM>, the negative electrode <NUM>, and the separator <NUM> are continuously unwound to be supplied in a state of being wound in the form of a roll. Here, each of the positive electrode <NUM> and the negative electrode <NUM> is cut by a predetermined size and moved together with separators <NUM> that are continuously supplied, to pass through a laminating device. Here, the positive electrode <NUM> has a structure in which a positive electrode active material is applied to a surface of a positive electrode collector, and the negative electrode <NUM> has a structure in which a negative electrode active material is applied to a surface of a negative electrode collector.

While passing through the laminating device, heat and a pressure may be applied between the positive electrode <NUM>, the separator <NUM>, the negative electrode <NUM>, and the separator <NUM> to bond the positive electrode <NUM>, the separator <NUM>, the negative electrode <NUM>, and the separator <NUM> to each other. In the bonded state, the positive electrode <NUM> and the positive electrode <NUM>, which are adjacent to each other (the negative electrode <NUM> and the negative electrode <NUM>, which are adjacent to each other), are cut therebetween to continuously manufacture one unit cell <NUM> in which the positive electrode <NUM>, the separator <NUM>, the negative electrode, and the separator <NUM> are sequentially stacked downward. The unit cells <NUM> are stacked in a predetermined number to manufacture an electrode assembly.

Also, the electrode assembly according to the related art may also be manufactured through a Z-folding method. The electrode assembly manufactured through the Z-folding method has a structure in which a positive electrode and a negative electrode alternately inserted at both sides while a continuously supplied separator is provided at a center and then folded in a zigzag shape. Z-folding has been disclosed in <CIT>, <CIT>.

In the lamination & stacking method as described above, since layers to be stacked are bonded to each other, the electrode assembly may have superior durability against an external impact and be stable compared to other manufacturing methods. On the other hand, since the processes are performed in order of stacking of the electrodes and the separator, lamination, cutting, and stacking of the unit cells, the number of processes is greater than that of other processes. On the other hand, in the case of the Z-folding method, a process period is shorter, resulting in higher production rate when compared to the lamination & stacking method.

Furthermore, when the number of processes increases, allowable tolerances for each process may be accumulated. For example, an allowable tolerance in the lamination & stacking method is determined in consideration of, when the electrodes and the separator are stacked, an allowable tolerance when cutting the positive electrode and the negative electrode and an allowable tolerance when cut into the unit cells. As a result, the allowable tolerance in the electrode assembly manufactured through the lamination & stacking method may be reduced. Thus, there is a problem that the size of the positive electrode relative to the negative electrode increases. On the other hand, when the electrode assembly is manufactured in the Z-folding manner, since the number of processes is small, the positive electrode may have a size greater than that of the negative electrode.

That is, since the capacity of the electrode assembly increases as the size of the positive electrode is greater than that of the negative electrode, it is preferable that the size of the positive electrode increases as much as possible. However, the size of the positive electrode is limited to a certain limit to reduce possibility of degradation of the positive electrode and an occurrence of short circuit. Here, the size of the positive electrode is more reduced by the allowable tolerance during the production, but the size of the positive electrode is more limited in the lamination & stacking manner because the number of processes increases (due to the large allowable tolerance). <CIT>, <CIT>, <CIT>, <CIT>, and <CIT> disclose an electrode assembly formed by stacking the electrode units.

Therefore, a main object of the present invention is to provide an electrode assembly having an advantage of an electrode assembly using a Z-folding method (increasing in size of the positive electrode compared to a negative electrode due to reduction of an allowable tolerance) and an advantage of an electrode assembly using a lamination & stacking method (a negative electrode, a separator, and a positive electrode, which constitute a unit cell, are bonded to improve stability).

An electrode assembly of the present invention for achieving the above object is defined in the appended set of claims. The present invention comprises the electrode assembly in which a positive electrode and a negative electrode are alternately stacked, and a separator is disposed between the positive electrode and the negative electrode, the electrode assembly comprising: a folding unit a negative electrode unit and a positive electrode unit are alternately inserted between layers of the separator of which one side and the other side are alternately folded in a zigzag shape in a direction perpendicular to a direction in which the positive electrode and the negative electrode are stacked; and a stacking unit in which the positive electrode, the separator, and the negative electrode, each of which is cut by a predetermined size, are sequentially stacked, wherein the negative electrode is disposed at the outermost layer of the negative electrode unit, and the positive electrode is disposed at the outermost layer of the positive electrode unit, and the stacking unit is stacked on each of the uppermost layer and the lowermost layer of the folding unit.

Also, the positive electrode, the separator, and the negative electrode, which are stacked in the stacking unit, may be bonded to each other at contact surfaces therebetween. The bonding in the stacking unit may be performed by applying heat and a pressure.

When the stacking unit is stacked on the folding unit, the positive electrode or the negative electrode, which is disposed at the outermost layer of the stacking unit, may be a single-sided electrode in which an active material is applied to only one surface of a collector.

Here, in the single-sided electrode, the active material may be applied to a surface contacting the separator. That is, a positive electrode collector or the negative electrode collector may be disposed at the outermost layer.

In a first embodiment of the present invention, the negative electrode unit is one negative electrode, and the positive electrode unit is one positive electrode. Also, the negative electrode or the positive electrode may be stacked at the outermost layer of the folding unit, and the separator may be stacked on a layer of the stacking unit, which contacts the folding unit.

In this embodiment, the stacking unit may be a monocell in which one positive electrode, one negative electrode, and two separators are stacked, wherein one of the separators may be stacked between the positive electrode and the negative electrode, and the other one may be stacked at a position contacting the outermost layer of the folding unit.

In a second embodiment, the separator may be stacked on the outermost layer of the folding unit, and the stacking unit may be a monocell in which one positive electrode, one negative electrode, and one separator are stacked, wherein the separator may be stacked between the positive electrode and the negative electrode.

In a third embodiment, the negative electrode or the positive electrode may be stacked at one of the outermost layers of the folding unit, and the separator may be stacked at the other one of the outermost layers, the stacking unit stacked on one of the outermost layers, at which the positive electrode or the negative electrode is stacked, may be a monocell in which one positive electrode, one negative electrode, and two separators are stacked, wherein one of the separators may be stacked between the positive electrode and the negative electrode, and the other one may be stacked at a position contacting the outermost layer of the folding unit, and the stacking unit stacked on one of the outermost layers, at which the separator is stacked, may be a monocell in which one positive electrode, one negative electrode, and one separator are stacked, wherein the separator may be stacked between the positive electrode and the negative electrode.

In the foregoing embodiments, the separator stacked between the negative electrode unit and the positive electrode unit in the folding unit has a thickness different from that of the separator stacked within the stacking unit.

Furthermore, in the present disclosure, the negative electrode unit may be a bicell in which the negative electrode is stacked at each of both the outermost layers, and one or more positive electrodes are stacked between the negative electrodes, and the positive electrode unit may be a bicell in which the positive electrode is stacked at each of both the outermost layers, and one or more negative electrode are stacked between the positive electrodes. In more detail, the negative electrode unit may be a bicell in which the negative electrode/the separator/the positive electrode/the separator/the negative electrode are stacked sequentially from the outermost layer, and the positive electrode unit may be a bicell in which the positive electrode/the separator/the negative electrode/ the separator/the positive electrode are stacked sequentially from the outermost layer. Here, the positive electrode, the separator, the negative electrode, which are stacked to constitute each of the negative electrode unit and the positive electrode unit, may be bonded to each other at contact surfaces therebetween.

Also, the separator stacked between the negative electrode unit and the positive electrode unit in the folding unit may have a thickness different from that of the separator stacked within the negative electrode unit and the positive electrode unit.

Also, in the stacking unit, the separator may be stacked at the outermost layer at an opposite side of a direction in which the stacking unit faces the folding unit.

Furthermore, a stacking unit in which the positive electrode, the separator, the negative electrode, each of which is cut by a predetermined size, may be sequentially stacked is additionally stacked on an outer surface of the stacking unit. In the stacking unit, the stacking units disposed at the upper and lower portions of the folding unit may have the same stacking structure, and more or fewer electrodes are stacked according to specification of the electrode assembly.

Also, as necessary, two or more folding units may be continuously stacked between the stacking units disposed at the uppermost layer and the lowermost layer. Here, the stacking unit in which the positive electrode, the separator, the negative electrode, each of which is cut by a predetermined size, may be sequentially stacked is inserted between the two folding units that are continuously stacked. The stacking unit <NUM> may be a bicell in which the uppermost layer and the lowermost layer have the same polarity or a monocell in which the uppermost layer and the lowermost layer have polarities different from each other and may have the same structure as the stacking unit disposed each of the upper and lower portions of the folding unit.

Furthermore, the negative electrode unit stacked on the folding unit is one negative electrode, and the positive electrode unit is one positive electrode, the negative electrode may have an area greater than that of the positive electrode, and a gap (d) between a point at which the separator is folded and the negative electrode may be less than that between the point at which the separator is folded and the positive electrode.

Also, in the folding unit, an end of the separator may comprise an extension part extending by a predetermined length, and the extension part may surround the folding unit and the stacking units after the stacking units are stacked on upper and lower portions of the folding unit, and an end of the extension part may be bonded to be fixed to a surface of the folding unit or the stacking unit.

Furthermore, as the electrode assembly having the above technical features is provided, the present invention may additionally provide a secondary battery in which the electrode assembly according to the present invention is embedded in the pouch and a secondary battery module in which a plurality of secondary batteries are electrically connected to each other.

According to the present invention having the above-described configuration, the folding unit having the Z-folding structure (having a structure of the electrode assembly manufactured in the Z-folding manner) and the stacking unit having a lamination & stacking structure (having a structure of the electrode assembly manufactured in the lamination &stacking method) may be bonded to each other. Thus, the positive electrode may increase in area relative to the negative electrode in the folding unit to increase in capacity, and the stacking unit may be disposed on the outermost layer of the folding unit to improve stability.

Furthermore, the positive electrode or the negative electrode, which is disposed at the outermost layer of the stacking unit, may be provided as the single-sided electrode in which the active material is applied to only one surface of the collector to reduce the degradation due to the precipitation of the active material and also reduce the possibility of occurrence of the short circuit due to the external impact.

Also, the separator stacked between the negative electrode unit and the positive electrode unit in the folding unit has a thickness different from that of the separator stacked within the stacking unit to minimize the volume.

The present invention may provide the structure in which the separator is stacked at the outermost layer at an opposite side of a direction in which the stacking unit faces the folding unit and the structure in which the plurality of stacking units are additionally stacked to provide the various structures according to the required specification of the secondary battery.

Two or more folding units may be continuously stacked. That is, when the stacking number of folding unit increases, the cumulative tolerance may increase. Thus, two folding units, each of which has less stacking number, may be stacked to reduce the cumulative tolerance, and also, the stacking number may increase to increase in capacity.

Also, in the folding unit, the end of the separator may comprise the extension part extending by a predetermined length, and the extension part may surround the folding unit and the stacking units after the stacking units are stacked on the upper and lower portions of the folding unit, and the end of the extension part may be bonded to be fixed to the surface of the folding unit or the stacking unit, thereby preventing the shaking of the folding unit and the stacking unit and improving the durability against the external impact.

Furthermore, the present invention may additionally provide a secondary battery in which the electrode assembly according to the present invention is embedded in the pouch and a secondary battery module in which a plurality of secondary batteries are electrically connected to each other.

The present invention relates to an electrode assembly in which a positive electrode <NUM> and a negative electrode <NUM> are alternately stacked, and separators <NUM> and <NUM> are disposed between the positive electrode <NUM> and the negative electrode <NUM>. The electrode assembly has a structure in which a stacking unit <NUM> manufactured in the lamination & stacking manner is stacked on each of both sides (upper and lower sides) of a folding unit <NUM> manufactured in a Z-folding manner.

That is, in the folding unit <NUM>, a positive electrode unit and a negative electrode unit are alternately inserted between layers of a separator <NUM> of which one side and the other side are folded in a zigzag shape in a direction (a horizontal direction in <FIG>) perpendicular to a direction (a vertical direction in <FIG>) in which the positive electrode <NUM> and the negative electrode <NUM> are stacked.

Here, the negative electrode unit in which the negative electrode is disposed at each of the outermost layers (the uppermost layer and the lowermost layer) and the positive electrode unit in which the positive electrode is disposed at each of the outermost layers are cells that constitutes individual electrodes or individual units.

Also, the stacking unit has a structure in which the positive electrode <NUM>, the separator <NUM>, and the negative electrode <NUM>, each of which is cut to a predetermined size, are sequentially stacked. The positive electrode <NUM>, the separator <NUM>, and the negative electrode <NUM>, which are stacked in the stacking unit, are bonded to each other at contact surfaces therebetween by heat and a pressure. The stacking unit has a structure in which one separator <NUM> is further added when the negative electrode <NUM> and the positive electrode <NUM> are disposed at the outermost layers of the folding unit <NUM>.

Furthermore, when the stacking unit <NUM> is stacked on each of the upper and lower layers of the folding unit <NUM>, the positive electrode or the negative electrode, which is disposed at the outermost layer of the stacking unit <NUM>, is a single-sided electrode in which an active material is applied to only one surface of a collector. The single-sided electrode disposed at the outermost layer is disposed so that the active material is applied to a surface contacting the separator (so that a positive electrode collector or a negative electrode collector is disposed at the outermost layer).

Hereinafter, embodiments according to the present invention will be described with reference to the accompanying drawings.

<FIG> is a front view illustrating a process of manufacturing an electrode assembly according to a first embodiment of the present invention. As illustrated in the drawing, in a folding unit according to this embodiment, a negative electrode is one individual negative electrode <NUM>, and a positive unit is one individual positive electrode <NUM>.

Also, a stacking unit is a monocell in which one positive electrode <NUM>, one negative electrode <NUM>, and two separators <NUM> are stacked. In the stacking unit, one of the separators <NUM> is stacked between the positive electrode <NUM> and the negative electrode <NUM>, and the other one is stacked at a position contacting the positive electrode <NUM> disposed at the outermost layer of the folding unit <NUM>. That is, in the stacking unit, the positive electrode <NUM>/the separator <NUM>/the negative electrode <NUM>/the separator <NUM> are stacked sequentially from the outermost layer.

In this embodiment, although the positive electrode <NUM> is stacked at the outermost layer of the folding unit <NUM> and the outermost layer of the stacking unit <NUM>, the present invention is not limited thereto. For example, the negative electrode <NUM> may be stacked at the outermost layer of the folding unit <NUM> and the outermost layer of the stacking unit <NUM>.

The folding unit <NUM> has a structure in which n electrodes (the sum of the number of stacked positive and negative electrodes) are stacked, where n is a natural number greater than at least <NUM>. In this embodiment, the stacking unit <NUM> is stacked on each of upper and lower layers of the folding unit <NUM> in which the positive electrode <NUM> is disposed at each of the uppermost and lowermost layers. Here, the stacking unit <NUM> is stacked so that a surface thereof, on which the separator is disposed, contacts the outermost positive electrode <NUM> of the folding unit <NUM>.

This embodiment is an embodiment having the most basic stacking structure in the present invention. Thus, second to third embodiments to be described later may have structures in which the structure according to the first embodiment is modified, but have the same technical idea as the first embodiment in that the stacking unit <NUM> is additionally stacked on both sides of the folding unit <NUM>.

<FIG> is a front view illustrating a process of manufacturing an electrode assembly according to a second embodiment of the present invention. In this embodiment, a separator <NUM> is stacked at the outermost layer of a folding unit <NUM> (unlike the first embodiment, an electrode is not stacked at the uppermost layer when a positive electrode and a negative electrode are alternately inserted to both sides of a separator of a folding unit).

Also, a stacking unit <NUM> additionally stacked on each of upper and lower layers of the folding unit <NUM> is provided as a monocell in which one positive electrode <NUM>, one negative electrode <NUM>, and one separator <NUM> are stacked.

As illustrated in the drawing, since the electrode disposed at the outermost layer of the folding unit <NUM> is the positive electrode <NUM>, the stacking unit <NUM> is stacked in a direction in which the negative electrode <NUM> faces the folding unit <NUM>.

<FIG> is a front view illustrating a process of manufacturing an electrode assembly according to a third embodiment of the present invention. In this embodiment, a positive electrode <NUM> is stacked at the uppermost layer of outermost layers of a folding unit <NUM>, and a separator <NUM> is disposed at the lowermost layer.

Also, a stacking unit <NUM> stacked on an upper side of the folding unit <NUM> has a monocell structure in which a positive electrode <NUM>/a separator <NUM>/a negative electrode <NUM>/a separator <NUM> are stacked sequentially from the outermost layer (uppermost layer), like the first embodiment. Also, the stacking unit <NUM> stacked on a lower side of the folding unit <NUM> is provided as a monocell in which one positive electrode <NUM>, one separator <NUM>, and one negative electrode <NUM> are stacked, like the second embodiment. Here, the negative electrode <NUM> faces an upper side.

<FIG> is a front view illustrating a process of manufacturing an electrode assembly according to the present disclosure.

In the disclosure, each of a positive electrode unit and a negative electrode unit is provided as a bicell C (a C type bicell in which a positive electrode is disposed at an intermediate layer) in which a plurality of electrodes are stacked instead of individual electrodes. That is, the negative electrode unit is a bicell C in which a negative electrode <NUM> is tacked on both the outermost layers, and one or more positive electrodes <NUM> are stacked between the negative electrodes <NUM>, and the positive electrode unit is a bicell A (an A type bicell in which the negative electrode is stacked at an intermediate layer) in which the positive electrode <NUM> is stacked on both the outermost layer, and one or more negative electrodes <NUM> are stacked between the positive electrodes <NUM>.

In more detail, as illustrated in the drawing, the positive electrode unit is the A type bicell in which the positive electrode <NUM>/the separator <NUM>/the negative electrode <NUM>/the separator <NUM>/the positive electrode <NUM> are stacked sequentially from the outermost layer, and the negative electrode unit is the C type bicell in which the negative electrode <NUM>/the separator <NUM>/the positive electrode <NUM>/the separator <NUM>/the negative electrode <NUM> are stacked sequentially from the outermost layer.

Here, the positive electrode <NUM>, the separator <NUM>, the negative electrode <NUM>, which are stacked to constitute each of the negative electrode unit and the positive electrode unit, are bonded to each other at contact surfaces therebetween. Each of the negative electrode unit and the positive electrode unit is configured so that three electrodes are stacked, but the present invention is not limited thereto. For example, five, seven or more electrodes may be stacked.

The folding unit <NUM> is configured so that the separator <NUM> is disposed at the uppermost layer and the lowermost layer. Also, the stacking unit <NUM> stacked on each of the upper side and the lower side of the folding unit <NUM> is provided as the bicell (more specifically, the A type bicell). That is, in the bicells stacked at the outermost layer of the folding unit <NUM>, the negative electrode <NUM> is disposed at the outermost layer. Also, the stacking unit <NUM> has the bicell structure in which the positive electrode <NUM> is disposed on the surface contacting the folding unit <NUM>. Here, in the stacking unit <NUM>, although three electrodes are stacked in the drawing, the present invention is not limited thereto. For example, five, seven or more electrodes may be stacked.

Furthermore, <FIG> illustrates a state in which a difference in area between the separator and the negative electrode is not generated or is small in the electrode assembly according to the present disclosure. Referring to the drawings, in each of the bicell A constituting the negative electrode unit and the bicell A constituting the positive electrode unit, which are illustrated in <FIG>, the separator <NUM> has the widest area, followed by the negative electrode <NUM> having the widest area, and the positive electrode <NUM> has the smallest area. On the other hand, in the bicell C and the bicell A, which are illustrated in <FIG>, the negative electrode <NUM> has an area equal to or slightly less than that of the separator <NUM> (in more detail, a difference 'd' in length between the negative electrode and the separator, which are illustrated in <FIG>, corresponds to about <NUM> to <NUM>% of the length of the separator).

As described above, if the difference in area between the negative electrode <NUM> and the separator <NUM> is not generated or is reduced, the area of the negative electrode <NUM> may more increase compared to the structure in which the separator has an area greater than that of the negative electrode as illustrated in <FIG>, under the condition in which the electrode assembly have the same volume. As a result, the positive electrode <NUM> may also increase in area to increase in charging and discharging capacity. Also, since measurement accuracy of a sensor (vision sensor) is improved during the production process (because there is no portion covered by the separator having a length greater than that of the negative electrode), a size and relative position of the negative electrode <NUM> may be more accurately grasped to reduce a production tolerance. When the tolerance is reduced as described above, the negative electrode may increase in size.

Although the positive electrode unit and the negative electrode unit are provided as the C type bicell and the A type bicell in the present disclosure, it is not limited thereto. For example, each of the positive electrode and the negative electrode may be provided as a monocell in which the uppermost electrode and the lowermost electrode are different from each other (for example, a cell in which a positive electrode/a separator/a negative electrode/a separator, a positive electrode/a separator/a negative electrode/a separator/a positive electrode/a separator/a negative electrode, a negative electrode/a separator/a positive electrode, a negative electrode/a separator/a positive electrode/a separator/a negative electrode/a separator/a positive electrode, or the like are stacked sequentially downward. Also, even though provided as the monocell, it is preferable that a difference in area between the separator <NUM> and the negative electrode <NUM> is minimally generated as possible due to the above-described reason. That is, the negative electrode may have a size of <NUM>% to <NUM>% of the size of the separator.

Although the coupling structure of the folding unit <NUM> and the stacking unit <NUM> has been described according to the first to third embodiments of the present invention and the preceding disclosure, if the coupling structure has a structure in which the negative electrode unit and the positive electrode unit are inserted into the separator <NUM> while the separator <NUM> is folded in the zigzag shape, the structure may be applied to the folding unit <NUM> of the present invention, and if the coupling structure has a structure in which the electrodes <NUM> and <NUM> and the separator <NUM> are sequentially stacked, the structure may be applied to the stacking unit <NUM> of the present invention. In addition to the foregoing embodiments, more various combinations may be possible.

For reference, the electrode assemblies according to the first to third embodiments and the preceding disclosure may be manufactured by a plurality of applicable manufacturing methods. Here, it is preferable that the stacking unit <NUM> is stacked on each of the upper and lower layers of the folding unit <NUM>, and then, heat and a pressure are applied between the folding unit <NUM> and the stacking unit <NUM> to generate predetermined bonding force. That is, the bonding force between the folding unit <NUM> and the stacking unit <NUM> may prevent the folding unit <NUM> and the stacking unit <NUM> from being separated from each other when the electrode assembly is embedded in a pouch as well as wen an external impact is applied in the pouch. Such the bonding may be generated by thermocompression of the separator when predetermined heat and pressure are applied in the vertical direction (the stacking direction) after the folding unit <NUM> and the stacking unit <NUM> are completely stacked.

One of the reasons in which the stacking unit <NUM> is stacked on the outer surface of the folding unit <NUM> in the present invention is because the single-sided electrode is easily disposed on the outermost layer in the electrode assembly. That is, in order that the single-sided electrode is disposed at the outermost layer of the folding unit <NUM> without the additional stacking of the stacking unit <NUM>, a device for separately inserting the single-side electrode in addition to a device for sequentially inserting the negative electrode unit and the positive electrode unit from left and right sides is required. However, the device for separately inserting the single-sided electrode may interfere with the device for inserting the negative electrode unit and the positive electrode unit, and a production time may increase because the single-sided electrode is separately inserted. On the other hand, like the structure according to the present invention, the structure in which the stacking unit <NUM> is added to the outer surface (the single-sided electrode is stacked on the outermost layer) of the folding unit <NUM>, which are individually manufactured, may have an advantage of simplifying the manufacturing process. Also, since the stacking unit has s structure in which the plurality of electrodes and the separator are bonded to each other therebetween and has a thickness thicker than that of the single-sided electrode, the stacking unit may be more stably and efficiently stacked compared to the case in which only the single-sided electrode is stacked in the manufacturing process. For example, since the single-sided electrode has a thickness thinner than that of a single positive or negative electrode, a stacking speed may be limited to prevent the electrode from being damaged. However, the stacking unit may have a relatively free advantage in constraint condition.

As described above, when the electrode (the positive electrode or the negative electrode) stacked at the outermost layer is the single-sided electrode rather than the double-sided electrode, degradation of the electrode due to precipitation of the active material may be reduced, and the possibility of occurrence of the short circuit due to the external impact may be reduced.

Thus, in the present invention, the electrode (the positive electrode in <FIG>) disposed at the outermost layer of the stacking unit <NUM> is provided as the single-sided electrode. That is, as illustrated in <FIG>, the positive electrode disposed at the outermost layer of the stacking unit <NUM> is provided as the single-sided electrode in which the positive electrode active material <NUM> is applied on only a surface of the positive electrode collector, which faces the separator <NUM>, and the positive electrode active material <NUM> is not applied to a surface that is exposed to the outside.

As described above, the structure in which the single-sided electrode is disposed at the outermost layer of the stacking unit <NUM> may be applied to the first to third embodiments.

Furthermore, in the present invention, the separator <NUM> stacked between the negative electrode unit and the positive electrode unit in the folding unit has a thickness different from that of the separator <NUM> stacked within the stacking unit <NUM> and that of the separator <NUM> stacked within the bicell when each of the negative electrode unit and the positive electrode unit is provided as the bicell. That is, since the separator <NUM> receives an external force during the folding in the manufacturing process, the separator <NUM> has a thicker thickness or be made of a material having higher durability.

In the present invention, as the electrode assembly having the above technical features is provided, a secondary battery in which the electrode assembly having the above-described structure is embedded in the pouch and a secondary battery module in which a plurality of secondary batteries are mounted to be electrically connected to each other may be additionally provided.

In the present invention having the above structure, since the folding unit <NUM> having the Z-folding structure and the stacking unit <NUM> having the lamination & stacking structure are coupled to each other, the positive electrode may increase in size to increase in capacity compared to the negative electrode in the folding unit <NUM> (that is, as described above, since an allowable tolerance according to the production process, which is a factor that the size of the positive electrode has to be reduced in the state in which the negative electrode has a fixed size, is minimized, the size of the positive electrode is set to a maximum value considering the allowable tolerance), and since the stacking unit <NUM>, in which the electrodes disposed at the outermost layers of the folding unit <NUM> and the separator are bonded to each other, is provided to improve stability (that is, an effect of increasing in size of the positive electrode relative to the negative electrode due to the reduction of the allowable tolerance, which is the advantage of the Z-folding type electrode assembly and an effect of increasing in stability, which is an advantage of the lamination & stacking type electrode assembly, may be realized at the same time.

Furthermore, the positive electrode <NUM> or the negative electrode <NUM>, which is disposed at the outermost layer of the stacking unit <NUM>, may be provided as the single-sided electrode in which the active material is applied to only one surface of the collector to reduce the degradation and also reduce the possibility of occurrence of the short circuit due to the external impact.

The present invention may be easily applied to the electrode assembly having the Z-folding structure according to the related art by only adding the stacking unit <NUM> and provide the structure in which the single-sided electrode is easily disposed at the outermost layer.

Also, the thickness of the separator <NUM> stacked between the negative electrode unit and the positive electrode unit in the folding unit <NUM> and the thickness of the separator <NUM> stacked within the stacking unit may be different from each other to minimize the volume of the electrode assembly.

Furthermore, in the present invention, structures according to fifth to eighth embodiments are additionally provided as structures that are applicable to the electrode assemblies according to the first to third embodiments.

<FIG> is a front view illustrating a process of manufacturing an electrode assembly according to a fifth embodiment of the present invention.

This embodiment is characterized in that a separator is additionally stacked on the outermost layers (the uppermost layer and the lowermost layer) of the electrode assemblies according to the foregoing embodiments.

That is, in the electrode assemblies according to the first to third embodiments, when the electrodes <NUM> and <NUM> are disposed at the outermost layers and then are inserted into the pouch, the electrodes <NUM> and <NUM> may directly contact an inner wall of the pouch.

In general, the pouch is made of a material containing a metal components (aluminum, etc.) although the material is changed according to the types of pouch. Thus, when the electrode assembly is inserted into the pouch, the separator stacked at the outermost layer may protect the electrode assembly against chemical changes or external impacts.

<FIG> is a front view illustrating a process of manufacturing an electrode assembly according to a sixth embodiment of the present invention.

This embodiment has a structure in which an auxiliary cell in which a positive electrode <NUM>, a separator <NUM>, and a negative electrode <NUM>, each of which is cut to a predetermined size, are sequentially stacked, is additionally stacked at the outermost layers (the uppermost layer and the lowermost layer) of each of the electrode assemblies according to the forgoing embodiments.

The auxiliary cell may have a structure in which a separator/a negative electrode/a separator are bonded to each other. Alternatively, as illustrated in <FIG>, the auxiliary cell may have the same structure as the stacking unit <NUM>, i.e., have a structure in which a positive electrode/a separator/a negative electrode/a separator are bonded to each other. Also, in addition, more or fewer electrodes and the structure in which the separator is stacked may be provided according to specification of the electrode assembly.

<FIG> and <FIG> are front views illustrating a process of manufacturing an electrode assembly according to a seventh embodiment of the present invention.

In this embodiment, two or more folding units <NUM> are sequentially stacked between the stacking units <NUM> disposed at the uppermost layer and the lowermost layer of the electrode assembly according to the foregoing embodiments.

In the Z-folding manner, when the number of stacked layers increases, the cumulative tolerance may increase. Thus, even if the folding unit <NUM> has the same stacking number, the cumulative tolerance may be reduced in a structure, in which two folding units, each of which has the same stacking number, are separately manufactured and then be bonded to each other, rather than one folding unit having more stacking number. Thus, in the structure according to this embodiment, two folding units, each of which has less stacking number, may be stacked to reduce the cumulative tolerance, and also, the stacking number may increase to increase in capacity.

Here, one or more stacking units <NUM>, each of which has a structure in which a positive electrode, a separator, and a negative electrode, each of which is cut to a predetermined size, are sequentially stacked, are additionally inserted between the two folding units <NUM> that are continuously stacked (see <FIG>). Each of the stacking units <NUM> may have a bicell in which the uppermost layer and the lowermost layer have the same polarity or a monocell in which the uppermost layer and the lowermost layer have polarities different from each other according to the polarity of the outermost electrode of the folding unit <NUM>. Alternatively, the stacking unit <NUM> may have a structure in which the bicell and the monocell are combined with each other or a structure in which a plurality of specific monocells or bicells are combined and stacked with each other.

In some cases, the structure of the stacking unit <NUM> stacked between the two folding units <NUM> and the structure of the stacking unit <NUM> stacked at the upper and lower layers of the folding units <NUM> may be completely the same.

It is preferable that the negative electrode <NUM> and the positive electrode <NUM> are manufactured so that a gap d between each of the negative electrode <NUM> and the positive electrode <NUM> and a point at which the separator <NUM> is folded becomes zero or be close to zero as possible to reduce the cumulative tolerance and prevent drooping or wrinkles of the separator <NUM> from occurring.

That is, referring to <FIG>, which illustrates a gap d between a point at which the separator <NUM> is folded and the negative electrode, the negative electrode unit stacked in the folding unit <NUM> is one negative electrode <NUM>, and the positive electrode unit stacked in the folding unit <NUM> is one negative electrode <NUM>. In the drawing, the gap d between the point at which the separator <NUM> is folded and the negative electrode is greater than zero due to the thickness of the negative electrode <NUM>. However, since each of the negative electrode <NUM> and the separator <NUM> has an actually sufficient thin thickness, and the separator <NUM> has elasticity, the gap d between the folding point and the negative electrode <NUM> may be zero or close to zero (an end side of the negative electrode <NUM> is disposed to contact the point at which the separator is folded).

Here, since the gap d generated in the negative electrode <NUM> becomes zero, the negative electrode <NUM> may have a maximum area when the electrode assembly has the same volume. As the area of the positive electrode <NUM> increases (which is less than that of the negative electrode and has to be reduced by an allowable tolerance), the positive electrode <NUM> may also increase in area. Thus, as the gap d generated in the negative electrode <NUM> is close to zero, the area of the positive electrode <NUM> increases to increase in capacity. As a result, it is preferable that the folding unit according to the present invention is manufactured so that the gap d between the point at which the separator is folded and the negative electrode <NUM> is zero or close to zero.

<FIG> is a front view illustrating a process of manufacturing an electrode assembly according to an eighth embodiment of the present invention.

This embodiment is characterized in that one end of the separator <NUM> in the folding unit <NUM> has an extension part <NUM> extended by a predetermined length.

As illustrated in the drawing, the extension part <NUM> may surround the folding unit <NUM> and the stacking units <NUM> after stacking units <NUM> are respectively stacked on the upper and lower portions of the folding unit <NUM>, and an end of the extension part <NUM> may be bonded to be fixed to a surface of the folding unit <NUM> or the stacking unit <NUM>.

<FIG> illustrate only the state in which the features according to the sixth to eighth embodiments are applied to the electrode assembly according to the first embodiment. However, the features according to the sixth to eighth embodiments may be applied to the electrode assemblies according to the second to third embodiments in addition to the first embodiment.

The present invention may provide a structure in which the separator <NUM> is stacked at the outermost layer at an opposite side of a direction in which the stacking unit <NUM> faces the folding unit <NUM> and a structure in which the auxiliary cell is additionally stacked on the outer surface of the stacking unit <NUM>. That is, the present invention may provide various structures according to the required specification of the secondary battery.

Two or more folding units <NUM> may be continuously stacked to reduce the cumulative tolerance, and the stacking number may increase to increase in capacity.

Also, in the folding unit <NUM>, one end of the separator <NUM> may have the extension part <NUM> that is extended by the predetermined length. Also, the extension part <NUM> may surround the folding unit <NUM> and the stacking units <NUM>, and an end of the extension part <NUM> may be bonded to be fixed to the surface of the folding unit <NUM> or the stacking unit <NUM> to prevent shaking and improve the durability against the external impact. In addition, when a tape is additionally adheres to fix the electrode assembly, the entire structure may be surrounded by the separator. Thus, a taping operation may be easily performed, and a taping method may be variously performed. For example, according to eighth embodiment, the extension part <NUM> of the separator <NUM> surrounds the entire structure, and then, the tap for enhancing the fixing force may be attached to surround the entire electrode assembly. Here, the tap may be taped to fix the full length direction perpendicular to the width direction rather than the width direction of the electrode assembly surrounded by the extension part <NUM>. Alternatively, the tape may be taped to fix only the upper and lower ends of the electrode assembly or surround the entire electrode assembly to be boned.

Furthermore, according to the present invention, the stacking unit has the structure in which the electrode and the separator are bonded to each other, whereas the folding unit has the structure in which the separator and the electrode are not bonded to each other (are movable in a horizontal direction perpendicular to the stacking direction). Thus, in the state in which the stacking unit <NUM> is stacked on the upper and lower portions of the folding unit <NUM>, an alignment between the folding unit <NUM> and the stacking unit <NUM> may be modified before the taping or the whole thermocompression is performed. That is, since the each electrode and the separator are not bonded to each other in the folding unit <NUM>, some movement between the folding unit <NUM> and the stacking unit <NUM> may be allowed to be uniformly arranged in the vertical direction after the folding unit <NUM> and the stacking unit are stacked. This may be a unique advantage of the present invention having the structure in which the stacking unit <NUM> is stacked in the state in which the folding unit <NUM> is not fixed.

Claim 1:
An electrode assembly in which a positive electrode (<NUM>) and a negative electrode (<NUM>) are alternately stacked, and a separator is disposed between the positive electrode and the negative electrode, the electrode assembly comprising:
a folding unit (<NUM>) in which a negative electrode unit and a positive electrode unit are alternately inserted between layers of the separator (<NUM>) of which one side and the other side are alternately folded in a zigzag shape in a direction perpendicular to a direction in which the positive electrode (<NUM>) and the negative electrode (<NUM>) are stacked; and
a stacking unit (<NUM>) in which the positive electrode (<NUM>), the separator (<NUM>), and the negative electrode (<NUM>), each of which is cut by a predetermined size, are sequentially stacked,
wherein the negative electrode (<NUM>) is disposed at the outermost layer of the negative electrode unit, and the positive electrode (<NUM>) is disposed at the outermost layer of the positive electrode unit,
the stacking unit (<NUM>) is stacked on each of the uppermost layer and the lowermost layer of the folding unit (<NUM>),
the negative electrode unit is one negative electrode, and the positive electrode unit is one positive electrode, and
the separator (<NUM>) stacked between the negative electrode unit and the positive electrode unit in the folding unit (<NUM>) has a thicker thickness than that of the separator (<NUM>) stacked within the stacking unit (<NUM>).