Patent Description:
The present invention relates to an electrode assembly in which negative electrodes, separators, and positive electrodes are repeatedly stacked, and more particularly, to an electrode assembly in which a heat transfer plate that disperses heat is additionally stacked to reduce a temperature deviation therein.

The demands for high-efficiency secondary batteries are rapidly increasing in the mobile device and electric vehicle fields. Among such the secondary batteries, a lithium secondary battery having high energy density, maintaining a relatively high voltage, and having a low self-discharge rate is commercially widely used, and research and development for improving performance is actively being conducted.

The secondary battery has a structure in which an electrode assembly and an electrolyte are embedded in a case such as a can or a pouch. The electrode assembly has a structure in which positive electrodes, separators, and negative electrodes are repeatedly stacked. In general, the electrode assembly may be classified into a winding type electrode assembly in which the positive electrodes, the separators, and the negative electrodes, which are in the stacked state, are rolled to be embedded in the case and a stack type (stacked) electrode assembly in which the positive electrodes, the separators, and the negative electrodes, each of which is cut to a predetermined size, are stacked.

Since the winding type electrode assembly has a spirally wound structure, the winding type electrode assembly is suitable for being mounted on a cylindrical battery, but is disadvantageous in space utilization for a prismatic or pouch type battery. On the other hand, since the stack type electrode assembly is adjusted in size when the electrode and the separator are cut, the prismatic shape fitted with the case is easily obtained, but a manufacturing process is relatively complicated, and the stack type electrode assembly is relatively vulnerable to an external impact.

As illustrated in <FIG>, which illustrates an internal cross-sectional view of the stack type secondary battery, the number of stacking of negative electrodes <NUM>, separators <NUM>, and positive electrodes <NUM> is adjusted to easily increase in capacity.

Furthermore, as the secondary battery is charged and discharged, heat is generated in the secondary battery. The heat not only adversely affects the lifespan and performance of the secondary battery but also causes flames or explosion. In addition, recently, as a large capacity secondary battery mounted on a vehicle, an ESS (energy storage system), and the like has been developed, a heat generation amount of the secondary battery increases.

As illustrated in <FIG>, which illustrates an exploded view and an assembled state of a secondary battery module, in the secondary battery module, a plurality of secondary batteries <NUM> are stacked and then mounted in a frame <NUM>. Here, both electrode tabs are electrically connected to each other through a busbar <NUM>, and a cooling plate <NUM> for suppressing generation of heat in the mounted secondary batteries <NUM> is attached to one side surface. In the cooling plate <NUM>, a method in which cooling water is introduced and discharged to be heat-exchanged or a method in which a plurality of cooling fins are formed is typically applied.

In the secondary battery module configured as described above, since the cooling plate <NUM> is attached to only one side surface, a thermal deviation inevitably occurs in the electrode assembly within each of the secondary batteries. Since the temperature deviation adversely affects performance and lifespan of each of the secondary batteries within the secondary battery module, it is necessary to solve the temperature deviation. <CIT> and <CIT> disclose electrode assemblies with a separator provided with a heat transfer layer.

Therefore, a main object of the present invention is to provide an electrode assembly for a secondary battery mounted in the secondary battery module, in which a temperature deviation therein is minimized.

According to the present invention for achieving the above object, an electrode assembly is defined in the appended set of claims, the electrode assembly in which positive electrodes, separators, and negative electrodes are repeatedly stacked, and a positive electrode tab, through which the positive electrodes are connected to each other, and a negative electrode tab, through which the negative electrodes are connected to each other, are provided, comprises: a heat transfer layer made of a material having thermal conductivity greater than that of the separator and stacked between the positive electrode and the separator or between the negative electrode and the separator to disperse heat generated at a relatively high temperature point to a relatively low temperature point.

The heat transfer layer may be made of a material containing graphite.

The heat transfer layer has an area less than that of the separator and be stacked so as not to protrude from the separator. Here, the negative electrode may have an area equal to or greater than that of the positive electrode, and the heat transfer layer may have an area equal to or greater than that of the negative electrode.

The heat transfer layer is provided with a plurality of punched holes through which ions passes, and the punched holes may be disposed to be regularly arranged in the heat transfer layer.

In addition, the heat transfer layer may be stacked on each of both sides with the separator therebetween in the one or more separators, and the heat transfer layer may be stacked to contact only one side surface of the separator in the one or more separators.

Furthermore, at least two or more heat transfer layers may be provided, and one heat transfer layer may have a thickness greater than that of the other heat transfer layer.

In addition, the separator may be provided in a state in which a heat transfer material is applied on a surface of the separator so that the heat transfer material forms the heat transfer layer in the electrode assembly. In addition, the heat transfer layer may be provided in the form of a plate having a size capable of being stacked between the positive electrode and the separator or between the negative electrode and the separator and is additionally stacked together when the positive electrode, the separator, and the negative electrode are stacked.

The positive electrode tab and the negative electrode tab may be disposed to protrude in directions opposite to each other.

In addition, the present invention is additionally provided with a secondary battery in which the electrode assembly having the above technical features is embedded in a pouch.

The present invention having the configuration as described above may disperse the heat generated at the relatively high temperature point to the relatively low temperature point to reduce the temperature deviation within the electrode assembly. Therefore, since the factors that adversely affect the charging and discharging performance and the lifespan are removed, the reliability of the product may be improved.

The heat transfer layer is provided with the plurality of punched holes through which the ions pass so as not to interfere with the ion and electron transfer, and the arrangement of the punched holes may vary according to the specifications of the electrode assembly.

Since the heat transfer layer is stacked so that the heat transfer layers are stacked on each of both sides with the separator therebetween or stacked to contact only one side surface in one or more separators, the above-described configurations may be selected in consideration of the heat dispersion effect and the increase in thickness of the electrode assembly.

Furthermore, since any one heat transfer layer has a thickness greater than that of the other heat transfer layer, the heat dispersion effect at the specific location may be more improved.

The present invention relates to an electrode assembly, in which positive electrodes <NUM>, separators <NUM>, and negative electrodes <NUM> are repeatedly stacked, and a positive electrode tab <NUM>, through which the positive electrodes <NUM> are connected to each other, and a negative electrode tab <NUM>, through which the negative electrodes <NUM> are connected to each other, are provided so as to be embedded in a pouch <NUM>.

An object of the present invention is to prevent performance from being deteriorated due to heat. That is, a main point of the present invention is to improve heat dissipation performance and minimize a thermal deviation when cooling is performed by a cooling means at one side in a state in which a plurality of secondary batteries <NUM> are stacked.

Thus, as illustrated in <FIG>, which illustrates an inner configuration of the secondary battery according to the present invention, the electrode assembly according to the present invention comprises a heat transfer layer <NUM> made of a material having thermal conductivity greater than that of the separator <NUM> and stacked between the positive electrode <NUM> and the separator <NUM> or between the negative electrode <NUM> and the separator <NUM> to disperse heat generated at a relatively high temperature point to a relatively low temperature point. In the present invention, the heat transfer layer <NUM> contains a material having high thermal conductivity such as graphite and is provided with a plurality of punched holes <NUM> through which electrons and ions pass.

Here, the heat transfer layer <NUM> has an area less than that of the separator <NUM> so as not to protrude from the electrode assembly. However, the heat transfer layer <NUM> may have an area equal to or greater than that of the negative electrode <NUM> so that an entire heat-exchange area of the negative electrode <NUM> and the positive electrode <NUM> is maximized in consideration of the fact that the negative electrode <NUM> is larger than the positive electrode <NUM> to prevent the lithium from being extracted due to overcharging when lithium gets out of the positive electrode <NUM> to move to the negative electrode <NUM>. The heat transfer layer <NUM> may be stacked on each of both side surfaces with the separator therebetween or stacked to contact only one side surface of the separator <NUM> in one or more separators.

Also, the punched holes <NUM> may be disposed to form a constant arrangement in the heat transfer layer <NUM>, i.e., may be variously arranged according to specifications and characteristics of the secondary battery.

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

Referring to <FIG> which illustrates a state in which a heat transfer layer <NUM> is stacked on one surface of a separator <NUM> according to a first embodiment of the present invention, this embodiment is characterized in that the heat transfer layer <NUM> stacked on the separator <NUM> is provided with punched holes <NUM> having the same size are regularly arranged at a constant interval.

That is, in this embodiment, the punched holes <NUM> are disposed at a constant interval throughout the heat transfer layer <NUM> so that ions and charges moving between a negative electrode <NUM> and a positive electrode <NUM> uniformly passes therethrough. This may be the most basic arrangement structure of the punched holes <NUM> and be applied together with an arrangement structure to be described later. That is, a plurality of heat transfer layers <NUM> are provided in an electrode assembly, but the arrangement structure of the punched holes <NUM> according to the first embodiment may be applied to the most heat transfer layers.

As illustrated in <FIG>, which illustrates a plan view of a heat transfer layer <NUM> according to a second embodiment of the present invention, the heat transfer layer <NUM> according to this embodiment may have punched holes <NUM>, which increase in size at a specific position. For example, when a passing rate of ions and charges at a specific position is more important than heat transfer, the punched hole <NUM> may more increase in size so that the passing rate of the ions and charges more increases.

As illustrated in <FIG> and <FIG>, which illustrate a plan view of a heat transfer layer according to third and fourth embodiments of the present invention, a heat transfer layer <NUM> according to this embodiment is provided with a punched hole <NUM> that extends in a longitudinal direction (a left and right direction in the drawings) and/or a width direction (an upward and downward direction in the drawings). As described above, the structure in which the punched hole <NUM> extends lengthily may further simplify a coating process in a coating method of the heat transfer layer <NUM> to be described later.

As illustrated in <FIG>, which illustrates an inner configuration of a secondary battery in which a heat transfer layer <NUM> is stacked according to a fifth embodiment of the present invention, at least two or more heat transfer layers <NUM> are disposed in an electrode assembly. Here, one heat transfer layer <NUM> has a thickness greater than that of the other heat transfer layer <NUM>.

That is, an intermediate position within the electrode assembly may be relatively difficult to dissipate heat rather than the outer side and thus may increase in temperature. Here, the heat transfer layer <NUM> disposed at the intermediate layer to increase in heat transfer efficiency may have a thickness greater than that of the heat transfer layer <NUM> disposed at the other layer.

The heat transfer layer <NUM> having the above-described configuration may be provided in a state applied on a surface of a separator <NUM> or in the form of a separate plate.

That is, a heat transfer material may be applied on the surface of the separator <NUM>, and after the heat transfer material is cured, the heat transfer material may be stacked together with the separator <NUM> within the electrode assembly to form the heat transfer layer <NUM>.

Alternatively, the heat transfer layer <NUM> may be previously manufactured in the form of a plate having a size capable of being stacked between a positive electrode <NUM> and a separator <NUM> or between a negative electrode <NUM> and the separator <NUM>. The previously manufactured heat transfer layer <NUM> is stacked together when the positive electrode <NUM>, the separator <NUM>, and the negative electrode <NUM> are stacked.

The method for providing the heat transfer layer <NUM> may be selected according to the number of punched holes <NUM> or an arranged state of the punched holes <NUM>. For example, a method, in which the heat transfer layer <NUM> disposed at a specific position is formed in a coating manner, and the heat transfer layer <NUM> disposed at another position is stacked in the form of a plate, may be applied.

The electrode assembly according to the present invention is embedded in a pouch <NUM>, and a positive electrode tab <NUM> and a negative electrode tab <NUM> are disposed in directions opposite to each other, and an end of each of the tabs protrudes from the pouch <NUM>.

<FIG> is a perspective view of a secondary battery in which the heat transfer layer is not provided, i.e., a perspective view illustrating points A to E listed in Table <NUM> and a cross-sectional view taken along line G-G (displayed with a relatively dark color at a low temperature), and <FIG> is a perspective view of a secondary battery in which a heat transfer layer is additionally stacked, i.e., a perspective view illustrating the points A to E listed in Table <NUM> and a cross-sectional view taken along line H-H according to the present invention (in <FIG> and <FIG>, although one secondary battery is illustrated, temperature distribution illustrated in the cross-sectional view is shown when secondary batteries are mounted as a secondary battery module as illustrated in <FIG>). Table <NUM> below shows a temperature difference between when the heat transfer layer is not stacked and when the heat transfer layer is stacked at five points illustrated in <FIG> and <FIG>.

As seen from data in Table <NUM>, when the heat transfer layer <NUM> is provided in an electrode assembly, it may be confirmed that the temperature deviation decreases in an entire region of the secondary battery. That is, when the heat transfer layer <NUM> is not provided, if heat is generated, cooling is easily performed in the vicinity of a cooling plate, but heat dissipation is difficult at a point that is relatively far from the cooling plate, resulting in a relatively high temperature. Also, here, the heat dispersion is not achieved to cause the heat deviation. However, when the heat transfer layer <NUM> is added according to the present invention, it may be confirmed that heat generated at a relatively high temperature point is dispersed to a relatively low temperature point, and thus, a heat exposure area to the outside increases to reduce the overall temperature as well as the temperature deviation.

Therefore, since the structure according to the present invention reduces the temperature deviation and improves the cooling efficiency, the charging/discharging performance and the reliability of the product may be improved.

The heat transfer layer <NUM> may be provided with the plurality of punched holes <NUM> through which the ions pass so as not to interfere with the ion and electron transfer, and the arrangement of the punched holes may vary according to the specifications of the electrode assembly.

Since the heat transfer layer <NUM> is stacked so that the heat transfer layers <NUM> are stacked on each of both sides with the separator <NUM> therebetween or stacked to contact only one side surface in one or more separators <NUM>, the above-described configurations may be selected in consideration of the heat dispersion effect and the increase in thickness of the electrode assembly.

Furthermore, since any one heat transfer layer <NUM> has a thickness greater than that of the other heat transfer layer <NUM>, the heat dispersion effect at the specific location may be more improved.

Claim 1:
An electrode assembly in which positive electrodes (<NUM>), separators (<NUM>), and negative electrodes (<NUM>) are repeatedly stacked, and a positive electrode tab (<NUM>), through which the positive electrodes are connected to each other, and a negative electrode tab (<NUM>), through which the negative electrodes are connected to each other, are provided, the electrode assembly comprising:
a heat transfer layer (<NUM>) made of a material having thermal conductivity greater than that of the separator (<NUM>) and stacked between the positive electrode (<NUM>) and the separator (<NUM>) or between the negative electrode (<NUM>) and the separator (<NUM>) to disperse heat generated at a relatively high temperature point to a relatively low temperature point,
wherein the heat transfer layer (<NUM>) is provided with a plurality of punched holes through which ions pass, and
the heat transfer layer (<NUM>) has an area less than that of the separator (<NUM>) and is stacked so as not to protrude from the separator.