JP6855770B2 - Battery module - Google Patents

Description

The present invention relates to a battery module.

Conventionally, a battery module including a plurality of battery cells arranged in one direction is known. In such a battery module, an array of battery cells is sandwiched between restraints such as a metal plate and restrained by a constant load, thereby suppressing fluctuations in characteristics such as internal resistance in the battery cells. For example, in Patent Document 1, the minimum load amount applied to the array is calculated based on the relationship between the compression amount of the battery cell and the load amount received by the battery cell, and is included in the electrode assembly in the battery cell. It is described that a constraining load is applied to the array so that there is no clearance between the electrodes and no clearance between the electrode assembly and the inner surface of the case.

Japanese Unexamined Patent Publication No. 2016-39022

However, the components of the battery module may be deformed depending on the usage environment such as the usage environment and the usage time of the battery module. For example, since the coefficient of linear expansion of the battery cell and the coefficient of linear expansion of the restraint member are different, the battery cell and the restraint member can be deformed depending on the temperature of the battery module. Such deformation of the components may reduce the constraining load applied to the array. In the battery module described in Patent Document 1, the amount of decrease in the restraint load due to the usage situation is not taken into consideration. Therefore, when the restraint load is insufficient, the internal resistance of the battery cell increases, and the battery performance may not be sufficiently exhibited.

The present invention provides a battery module capable of satisfactorily exhibiting battery performance regardless of usage conditions.

The battery module according to one aspect of the present invention is a battery module including an array including a plurality of battery cells arranged in a first direction and a constraint member that applies a constraint load to the array in the first direction. Is. Each of the plurality of battery cells includes an electrode assembly having a plurality of electrodes stacked in the first direction, and a case for accommodating the electrode assembly. The minimum load amount, which is the lower limit of the restraint load applied to the array by the restraint member, is the battery cell required load amount calculated based on the relationship between the compression amount of the battery cell and the load amount received by the battery cell. It is set to be equal to or greater than the load amount including the additional load amount calculated based on the decrease amount of the length of the array in one direction. The battery cell required load amount is a load amount required to obtain a compression amount at which there is no clearance between the electrodes of the battery cell and between the electrode assembly and the case when assembling the restraint member to the array. The amount of reduction is the maximum amount of reduction from the length when the restraint member is assembled to the array when the battery module is used under predetermined usage conditions.

In this battery module, the minimum load amount applied to the array by the restraint member is set so as to be equal to or more than the load amount obtained by adding the additional load amount to the required load amount of the battery cell. The battery cell required load amount is a load amount required to obtain a compression amount at which there is no clearance between the electrodes of the battery cell and between the electrode assembly and the case when assembling the restraint member to the array. The additional load is calculated based on the maximum reduction from the length of the array in the first direction when the restraint member is assembled to the array when the battery module is used under predetermined usage conditions. Will be done. That is, if the length of the array in the first direction decreases after the restraint member is assembled to the array, the restraint load decreases, so that the maximum restraint load when the battery module is used under the conditions of use of the battery module. A load amount corresponding to the decrease amount of is added as an additional load amount. Therefore, when the battery module is used under predetermined usage conditions, the plurality of electrodes of the battery cell are in close contact with each other and the electrode assembly and the case are in close contact with each other regardless of the usage status of the battery module. Since the state of the battery is ensured, the battery performance can be satisfactorily exhibited.

The restraint member may include a pair of end plates provided at both ends of the array in the first direction, and a connecting member that connects the pair of end plates. The first linear expansion coefficient, which is the linear expansion coefficient of the array, is larger than the second linear expansion coefficient, which is the linear expansion coefficient of the connecting member, and the amount of decrease is the difference between the first linear expansion coefficient and the second linear expansion coefficient. It may be calculated based on. In this case, since the first linear expansion coefficient of the array is larger than the second linear expansion coefficient of the connecting member, when the temperature of the battery module decreases, the decrease in the distance between the pair of end plates in the first direction Also, the amount of decrease in the length of the array exceeds. As a result, the restraint load applied to the array by the restraint member is reduced. In the above battery module, an additional load amount is calculated based on the amount of decrease in the length of the array calculated based on the difference between the coefficient of linear expansion of the first line and the coefficient of expansion of the second line, and the array is formed by the restraining member. The minimum load amount of is set. As a result, regardless of the temperature of the battery module, the plurality of electrodes of the battery cell are in close contact with each other, and the electrode assembly and the case are in close contact with each other. it can.

The amount of reduction may be calculated based on the charge rate of the battery cell. As the charge rate of the battery cell increases, the battery cell expands, and as the charge rate of the battery cell decreases, the battery cell contracts. Therefore, as the charge rate of the battery cell decreases, the length of the battery cell in the first direction decreases, so that the length of the array in the first direction also decreases. In the battery module, an additional load amount is calculated based on the amount of decrease in the length of the array calculated based on the charge rate of the battery cell, and the minimum load amount on the array by the restraint member is set. As a result, regardless of the charge rate of the battery cell, the plurality of electrodes of the battery cell are in close contact with each other, and the electrode assembly and the case are in close contact with each other, so that the battery performance can be exhibited satisfactorily. Can be done.

The array may further include elastic members arranged in the first direction along with the plurality of battery cells. The amount of reduction may be calculated based on the creep characteristics of the elastic member. In this case, since the restraining load is applied to the elastic member by the restraining member, the elastic member is deformed with the passage of time. That is, with the passage of time, the length of the elastic member in the first direction decreases, so that the length of the array in the first direction also decreases. In the battery module, an additional load amount is calculated based on the amount of decrease in the length of the array calculated based on the creep characteristics of the elastic member, and the minimum load amount on the array by the restraint member is set. As a result, regardless of the usage period of the battery module, the plurality of electrodes of the battery cell are in close contact with each other, and the electrode assembly and the case are in close contact with each other, so that the battery performance can be exhibited satisfactorily. Can be done.

According to the present invention, the battery performance can be satisfactorily exhibited regardless of the usage conditions.

It is a figure which shows the battery module which concerns on one Embodiment. It is a figure which shows the internal structure of the battery cell which comprises the battery module shown in FIG. FIG. 2 is a cross-sectional view taken along the line III-III in FIG. It is a figure which shows the state of applying a load to a battery cell. It is a figure which shows an example of the relationship between the compression amount of a battery cell, and the load amount which a battery cell receives. It is a figure which shows an example of the relationship between the charge rate of a battery cell, and the voltage of a battery cell. It is a figure which shows an example of the relationship between the compression amount of an elastic member, and the load amount which a compression member receives. It is a figure which shows an example of the relationship between the length of an array body and a restraint load after assembling a battery module.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same reference numerals are used for the same or equivalent elements, and duplicate description is omitted.

FIG. 1 is a diagram showing a battery module according to an embodiment. As shown in FIG. 1, the battery module 1 includes an array 2 and a restraint member 3. The battery module 1 is used under predetermined usage conditions. As the usage conditions, the minimum operating temperature, the maximum operating temperature, the guaranteed usage period, the minimum charge rate of the battery cell, the maximum charge rate of the battery cell, and the like are defined. The minimum operating temperature is the minimum temperature of the battery module 1 in which the battery module 1 can normally operate, and the maximum operating temperature is the maximum temperature of the battery module 1 in which the battery module 1 can normally operate. The usage guarantee period is a period during which the battery module 1 can operate normally, and is an elapsed time from the time when the battery module 1 is manufactured. The minimum charge rate is the smallest charge rate (SOC: State Of Charge) that the battery cell can take, and the maximum charge rate is the highest SOC that the battery cell can take.

The array 2 includes a plurality of battery cells 11 and an elastic member 20. The plurality of battery cells 11 are arranged in the arrangement direction D (first direction). The battery cell 11 is a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery. In the present embodiment, the array body 2 is configured by arranging the seven battery cells 11 and the elastic member 20 in the array direction D. Further, in the array body 2, the heat transfer plate may be arranged adjacent to the battery cell 11. The coefficient of linear expansion of the battery cell 11 is, for example, about 1900 ppm / K.

Here, the details of the battery cell 11 will be described with reference to FIGS. 2 and 3. FIG. 2 is a diagram showing an internal structure of a battery cell constituting the battery module shown in FIG. FIG. 3 is a cross-sectional view taken along the line III-III in FIG. As shown in FIGS. 2 and 3, each of the plurality of battery cells 11 includes a case 12 and an electrode assembly 13.

The case 12 houses the electrode assembly 13. The case 12 has, for example, a hollow substantially rectangular parallelepiped shape. The case 12 is made of a metal such as aluminum, and an organic solvent-based or non-aqueous electrolyte solution is injected into the case 12. The positive electrode terminal 15 and the negative electrode terminal 16 are arranged on the top surface of the case 12 so as to be separated from each other. The positive electrode terminal 15 is fixed to the top surface of the case 12 via an insulating ring 17. The negative electrode terminal 16 is fixed to the top surface of the case 12 via an insulating ring 18.

The electrode assembly 13 is housed in the case 12, and is composed of, for example, a positive electrode 21 (electrode), a negative electrode 22 (electrode), and a separator 23 arranged between the positive electrode 21 and the negative electrode 22. In the electrode assembly 13 of the present embodiment, the positive electrode 21 is housed in the bag-shaped separator 23, and in this state, the positive electrode 21 and the negative electrode 22 are alternately laminated via the separator 23. .. The stacking direction of the positive electrode 21 and the negative electrode 22 in the electrode assembly 13 coincides with the arrangement direction D. That is, the electrode assembly 13 has a plurality of electrodes (positive electrode 21 and negative electrode 22) laminated in the arrangement direction D.

The positive electrode 21 has, for example, a metal foil 21a made of aluminum foil and a positive electrode active material layer 21b formed on both sides of the metal foil 21a. The positive electrode active material layer 21b is formed by including the positive electrode active material and the binder. Examples of the positive electrode active material include composite oxides, metallic lithium, sulfur and the like. Composite oxides include, for example, at least one of manganese, nickel, cobalt and aluminum, and lithium. Further, a tab 21c is formed on the upper edge portion of the positive electrode 21 corresponding to the position of the positive electrode terminal 15. The tab 21c extends upward from the upper edge of the positive electrode 21 and is connected to the positive electrode terminal 15 via the conductive member 24.

The negative electrode 22 has, for example, a metal foil 22a made of copper foil and a negative electrode active material layer 22b formed on both sides of the metal foil 22a. The negative electrode active material layer 22b is formed by including the negative electrode active material and the binder. Examples of the negative electrode active material include graphite, highly oriented graphite, mesocarbon microbeads, carbon such as hard carbon and soft carbon, alkali metals such as lithium and sodium, metal compounds, and SiOx (0.5 ≦ x ≦ 1.5). ) And other metal oxides, boron-added carbon and the like. Further, a tab 22c is formed on the upper edge portion of the negative electrode 22 corresponding to the position of the negative electrode terminal 16. The tab 22c extends upward from the upper edge of the negative electrode 22 and is connected to the negative electrode terminal 16 via the conductive member 25.

The separator 23 is formed in a bag shape, for example, and contains only the positive electrode 21 inside. Examples of the material for forming the separator 23 include a porous film made of a polyolefin resin such as polyethylene (PE) and polypropylene (PP), a woven fabric made of polypropylene, polyethylene terephthalate (PET), methyl cellulose and the like, or a non-woven fabric. The separator 23 is not limited to a bag shape, but may be a sheet shape.

Returning to FIG. 1, the description of the battery module 1 will be continued. The elastic member 20 is a member used for the purpose of preventing damage to the battery cell 11 and the like due to a restraining load when the battery cell 11 expands. The elastic member 20 is formed in a rectangular plate shape by, for example, a urethane rubber sponge. The elastic member 20 is arranged in the arrangement direction D together with the plurality of battery cells 11. In the present embodiment, the elastic member 20 is located at one end of the array body 2 in the array direction D. Examples of other forming materials for the elastic member 20 include ethylene propylene diene rubber (EPDM), chloroprene rubber, and silicon rubber. Further, the elastic member 20 is not limited to rubber, and may be a spring material or the like. The coefficient of linear expansion of the elastic member 20 is, for example, about 110 ppm / K.

The restraint member 3 is a member that applies a restraint load to the array body 2 in the arrangement direction D. The restraint member 3 includes a pair of end plates 31 and a connecting member 32. The end plate 31 has a substantially rectangular plate shape having a surface having an area larger than the area when the battery cell 11 is viewed from the arrangement direction D, for example. The end plate 31 is made of a steel material such as SS400. The pair of end plates 31 are provided at both ends of the array 2 in the array direction D. Specifically, the outer edge portions of the pair of end plates 31 are arranged at both ends of the array direction D in the array 2 in a state of projecting outward from the outer edge portions of the battery cell 11. The end plate 31 is provided with a plurality of insertion holes (not shown) for inserting the bolts 33 described later.

The connecting member 32 is a member that connects a pair of end plates 31 to each other. The connecting member 32 includes, for example, a long bolt 33 and a nut 34 screwed into the bolt 33. The bolt 33 and the nut 34 are made of a metal such as iron. The bolts 33 are sequentially inserted into the insertion holes of the pair of end plates 31. The nut 34 is screwed onto the end of the bolt 33 on the outside of the end plate 31 so as to tighten the pair of end plates 31 to each other. As a result, the pair of end plates 31 sandwich the array 2 in the array direction D, and a restraining load is applied to the array 2 (battery cell 11) via the pair of end plates 31. The linear expansion coefficient (second linear expansion coefficient) of the connecting member 32 (bolt 33) is, for example, about 12 ppm / K.

Subsequently, the restraint load on the array 2 by the restraint member 3 will be described in more detail.

In setting the restraint load on the array 2 by the restraint member 3, the relationship between the compression amount of the battery cell 11 and the load received by the battery cell 11 is obtained in advance for the battery cells 11 constituting the array 2. When determining the relationship between the amount of compression of the battery cell 11 and the amount of load received by the battery cell 11, for example, as shown in FIG. 4, the case 12 of the battery cell 11 is sandwiched between a pair of pressure members 41, and the electrode assembly 13 A load is applied to the battery cell 11 from the stacking direction of the above.

FIG. 5 is a diagram showing an example of the relationship (compression characteristic) between the amount of compression of the battery cell and the amount of load received by the battery cell. In the example shown in FIG. 5, the horizontal axis represents the amount of compression of the battery cell 11, and the vertical axis represents the amount of load received by the battery cell 11. In the present embodiment, the compression amount is a case in a direction in which a load is applied by a pair of pressure members 41, with the origin being a state in which no load is applied to the case 12 (a state in which the pressure member 41 is in contact with the case 12). The amount of change in thickness of 12 is shown. Further, in the present embodiment, the load amount is the load amount received by the case 12.

The region shown in FIG. 5 is divided into a low elasticity region R1 and a high elasticity region R2 according to the load amount. Low elasticity region R1, the amount of load is a region from 0 to K _0. In this low elasticity region R1, there is a clearance between the electrodes (positive electrode 21 including the separator 23 and the negative electrode 22) in the electrode assembly 13 and a clearance between the electrode assembly 13 and the inner surface of the case 12 in the battery cell 11. Therefore, the increase in the load amount is gradual with respect to the increase in the compression amount. In the low elasticity region R1, a sufficient load is not applied to the electrodes in the battery cell 11, so that the battery performance of the battery cell 11 is not sufficiently exhibited. The case where the thickness between the positive electrode 21 and the negative electrode 22 is the same as the thickness of the separator 23 means that there is no clearance between the electrodes, and the case where the distance between the positive electrode 21 and the negative electrode 22 is larger than the thickness of the separator 23 is the electrode. It is assumed that there is a clearance between them.

On the other hand, the highly elastic region R2 is a region in which the load amount is larger than _{K 0.} In this highly elastic region R2, due to the progress of compression, the clearance between the electrodes (positive electrode 21 and negative electrode 22 including the separator 23) in the electrode assembly 13 and the inner surface of the electrode assembly 13 and the case 12 in the battery cell 11 There is no clearance between the two, and the increase in the load amount with respect to the increase in the compression amount is large as compared with the low elastic region R1. In the highly elastic region R2, a sufficient load is applied to the electrodes in the battery cell 11, and the battery performance of the battery cell 11 is fully exhibited.

After obtaining the relationship of the load amount with respect to the compression amount of the battery cell 11 in advance, the lower limit value of the restraint load applied to the array 2 by the restraint member 3 (hereinafter, referred to as “minimum load amount”) is determined. The graph shown in FIG. 5 shows the amount of compression of the battery cell 11 and the battery cell 11 at the time of assembling the battery module 1 (that is, the environmental temperature when the restraint member 3 is assembled to the array 2 and the SOC of the battery cell 11). It can be said that it shows the relationship with the amount of load received by.

Here, the length La of the array 2 in the array direction D may change depending on the usage environment such as the usage environment and the usage time of the battery module 1. The length La of the array body 2 is the sum of the length Lb of the plurality of battery cells 11 in the array direction D and the length Le of the elastic member 20 in the array direction D. When the length La changes after the restraint member 3 is assembled to the array body 2, the restraint load changes. When the length La decreases, the amount of load received by the battery cell 11 decreases with respect to the amount of compression of the battery cell 11 when the battery module 1 is assembled. Therefore, the minimum load amount is calculated based on the decrease amount of the length La in the battery cell required load amount calculated based on the relationship between the compression amount of the battery cell 11 and the load amount received by the battery cell 11 described above. It is determined that the load amount is equal to or greater than the added load amount.

The battery cell required load amount obtains a compression amount at which there is no clearance between the electrodes of the battery cell 11 and between the electrode assembly 13 and the case 12 (inner surface) when the restraint member 3 is assembled to the array body 2. It is the amount of load required for this. In the present embodiment, for example, as shown in FIG. 5, the load amount K ₀ that shifts from the low elasticity region R1 to the high elasticity region R2 corresponds to the required load amount of the battery cell.

The additional load amount is added to the required load amount of the battery cell under the usage condition of the battery module 1 in order to set the load amount applied to the battery cell 11 to the highly elastic region R2 regardless of the usage state of the battery module 1. The amount of load. After the restraint member 3 is assembled to the array 2, the amount of load received by the battery cell 11 changes according to the length La. As the reduction amount of the length La, the maximum reduction amount from the length La when the restraint member 3 is assembled to the array 2 when the battery module 1 is used under the usage conditions of the battery module 1 is used. .. The length La can vary depending on, for example, the temperature of the battery module 1, the SOC of the battery cell 11, and the period of use of the battery module 1. Hereinafter, the method of calculating the additional load amount will be described in detail.

First, the amount of decrease ΔLt in the length La due to the temperature of the battery module 1 will be described. The linear expansion coefficient (first linear expansion coefficient) of the array 2 (battery cell 11 and elastic member 20) is larger than the linear expansion coefficient of the connecting member 32. Therefore, when the temperature of the battery module 1 rises, the increase in the length La exceeds the increase in the distance Lend between the pair of end plates 31 in the arrangement direction D. As a result, the restraint load applied to the array 2 by the restraint member 3 increases. On the other hand, when the temperature of the battery module 1 decreases, the decrease amount of the length La exceeds the decrease amount of the distance Lend in the arrangement direction D. As a result, the restraint load applied to the array 2 by the restraint member 3 is reduced.

Regarding the additional load amount, the case where the restraint load decreases is considered. That is, the additional load amount is received by the battery cell 11 even _{when the temperature of the battery module 1 drops from the reference temperature T 0} when the restraint member 3 is assembled to the array 2 to the _{minimum operating temperature TL} of the battery module 1. It is calculated so that the load amount is the high elastic region R2. The amount of decrease ΔLt is calculated based on the difference between the coefficient of linear expansion of the array 2 and the coefficient of linear expansion of the connecting member 32. Specifically, the amount of decrease in length La and the amount of decrease in distance Lend due to the temperature difference ΔT between the reference temperature T ₀ and the minimum operating temperature _{TL are calculated.} By subtracting the distance Lend from the amount of decrease in the length La, the amount of decrease ΔLt in the length La with respect to the distance Lend is calculated.

The reduction amount ΔLsoc of the length La due to the SOC of the battery cell 11 will be described. As shown in FIG. 6, the terminal voltage of the battery cell 11 changes with respect to the SOC of the battery cell 11. The usage range (0% to 100%) of the battery cell 11 is set in the SOC range in which the change in the terminal voltage is small. Thus, the SOC can take a value less than 0% and a value greater than 100%. As the SOC of the battery cell 11 increases, the battery cell 11 expands. Therefore, as the SOC of the battery cell 11 increases, the length La increases. As a result, the restraint load applied to the array 2 by the restraint member 3 increases. On the other hand, as the SOC of the battery cell 11 decreases, the length La decreases. As a result, the restraint load applied to the array 2 by the restraint member 3 is reduced.

Regarding the additional load amount, the case where the SOC of the battery cell 11 decreases is taken into consideration. That is, the additional load amount ranges from the initial charge rate, which is the SOC of the battery cell 11 when the restraint member 3 is assembled to the array 2, to the minimum charge rate, which is the minimum value of the SOC assumed under the usage conditions of the battery module 1. Even if it is lowered, the load amount received by the battery cell 11 is calculated so as to be the high elasticity region R2. The initial charge rate is, for example, 0%. As the minimum charge rate, for example, SOC when the battery cell 11 is over-discharged can be used. That is, the reduction amount ΔLsoc is calculated based on the SOC of the battery cell 11. Specifically, the decrease amount ΔLsoc of the length La with respect to the distance Lend is calculated by subtracting the length La of the array 2 at the minimum charge rate from the length La of the array 2 at the initial charge rate. The length Le and the distance Lend do not change due to the change in the SOC of the battery cell 11. That is, the reduction amount ΔLsoc is the reduction amount of the length Lb.

The decrease amount ΔLc of the length La due to the usage period of the battery module 1 will be described. Since the restraint load is applied to the elastic member 20 by the restraint member 3, the elastic member 20 is deformed with the passage of time. That is, since the length Le decreases with the passage of time, the length La also decreases. In other words, the reduction amount ΔLc is the reduction amount due to creep deformation of the elastic member 20 due to the restraining load. FIG. 7 is a diagram showing an example of the relationship between the amount of compression of the elastic member and the amount of load received by the compression member. In the example shown in FIG. 7, the horizontal axis represents the amount of compression of the elastic member 20, and the vertical axis represents the reaction force of the elastic member 20. Graph G1 shows the characteristics of the elastic member 20 when the restraint member 3 is assembled to the array body 2. Graph G2 shows the characteristics of the elastic member 20 when the warranty period for using the battery module 1 has elapsed. Since the length Le decreases with the passage of time, as shown in FIG. 7, the reaction force of the elastic member 20, that is, the restraint load applied to the array 2 by the restraint member 3 decreases even with the same amount of compression. The relationship shown in FIG. 7 is calculated in advance based on the creep characteristics of the elastic member 20. The creep characteristics of the elastic member 20 are determined by the material of the elastic member 20.

The additional load amount is calculated so that the load amount received by the battery cell 11 is set to the high elasticity region R2 even after the usage guarantee period of the battery module 1 has elapsed. That is, the reduction amount ΔLc is calculated based on the creep characteristics of the elastic member 20. Specifically, by subtracting the length Le of the elastic member 20 when the warranty period has elapsed from the length Le of the elastic member 20 when the restraint member 3 is assembled to the array 2, the length La with respect to the distance Lend is subtracted. The amount of decrease ΔLc of is calculated. The battery cell 11 also deforms slightly with the passage of time. That is, the length Lb decreases with the passage of time. Therefore, by subtracting the length La of the array 2 when the warranty period has elapsed from the length La of the array 2 when the restraint member 3 is assembled to the array 2, the length La with respect to the distance Lend is reduced. The quantity ΔLc may be calculated. The amount of decrease in the length Lb when the guaranteed use period has elapsed is calculated in advance based on the creep characteristics of the battery cell 11. In this case, the reduction amount ΔLc is the reduction amount due to creep deformation of the battery cell 11 and the elastic member 20 due to the restraining load.

Using the reduction amount ΔLt, the reduction amount ΔLsoc, and the reduction amount ΔLc calculated as described above, the length with respect to the distance Lend is calculated by calculating the sum of the reduction amounts as shown in the equation (1). The amount of decrease in La ΔLa is obtained.

Subsequently, a method of determining the additional load amount will be described with reference to FIG. FIG. 8 is a diagram showing an example of the relationship (compression characteristics) between the length of the array and the restraint load after assembling the battery module. In the example shown in FIG. 8, the horizontal axis represents the length La of the array 2, and the vertical axis represents the restraint load. When the amount of load received by the battery cell 11 is included in the highly elastic region R2, as shown in FIG. 8, the length La of the array body 2 and the restraint load after the restraint member 3 is assembled to the array body 2 are abbreviated. It is proportional. Using this relationship, the amount of decrease ΔK of the restraint load with respect to the amount of decrease ΔLa is calculated. The compression characteristic of the battery cell 11 is a characteristic in the highly elastic region R2 shown in FIG. Further, when determining the relationship (compression characteristic) between the amount of compression of the elastic member 20 and the amount of load received by the elastic member 20, the elastic member 20 is sandwiched between a pair of pressure members 41 and the elastic member 20 is sandwiched in the same manner as the battery cell 11. A load is applied to. In this way, the compression characteristics of the battery cell 11 and the compression characteristics of the elastic member 20 are measured in advance. The compression characteristics of the array 2 shown in FIG. 8 are obtained in advance by the sum of the compression characteristics of the battery cell 11 and the elastic member 20.

When the battery module 1 is used under the conditions of use, the length La can be reduced by a maximum reduction amount ΔLa from _{the length La 0 of the array 2 at the time of assembling the battery module 1.} Therefore, the minimum value of the length La of the array 2 can be _{the length La 1} obtained by subtracting the reduction amount ΔLa from _{the length La 0.} When the length La of the array 2 _{is reduced from the length La 0} to the length La ₁ , the load applied to the battery cell 11 (that is, the restraint load) is reduced by the reduction amount ΔK.

In order to keep the load amount applied to the battery cell 11 in the highly elastic region R2 under the usage conditions of the battery module 1, it is necessary to compensate for the decrease amount ΔK of the restraint load. That is, the amount of decrease in the restraint load ΔK corresponds to the amount of additional load. _{Therefore, the load amount K 1} obtained by adding the reduction amount ΔK of the restraint load to the load amount K ₀ is determined as the minimum load amount. The upper limit of the restraint load applied to the array 2 is appropriately determined, for example, as long as the strength of the restraint member 3 or the movement of metal ions between the positive electrode 21 and the negative electrode 22 is not hindered.

As described above, in the battery module 1, the minimum load amount applied to the array 2 by the restraint member 3 is set so as to be equal to or more than the load amount obtained by adding the additional load amount to the battery cell required load amount. .. The required load amount of the battery cell is necessary to obtain a compression amount at which the clearance between the electrodes of the battery cell 11 and between the electrode assembly 13 and the case 12 does not exist when the restraint member 3 is assembled to the array body 2. The amount of load. The additional load amount is the maximum decrease from the length La in the arrangement direction D of the arrangement 2 when the restraint member 3 is assembled to the arrangement 2 when the battery module 1 is used under predetermined usage conditions. Calculated based on the quantity ΔLa. That is, when the length La of the array 2 in the arrangement direction D decreases, the restraint load decreases, which corresponds to the maximum reduction amount ΔK of the restraint load when the battery module 1 is used under the usage conditions of the battery module 1. The amount of load to be applied is added as an additional load amount. Therefore, when the battery module 1 is used under the usage conditions, the plurality of electrodes of the battery cell 11 are in close contact with each other and the electrode assembly 13 and the case 12 are in close contact with each other regardless of the usage status of the battery module 1. Since the state of close contact is ensured, the battery performance can be exhibited satisfactorily.

Specifically, in the battery module 1, the reduction amount ΔLt calculated based on the difference between the linear expansion coefficient of the array 2 and the linear expansion coefficient of the connecting member 32, and the reduction calculated based on the SOC of the battery cell 11. Based on the amount ΔLsoc and the decrease amount ΔLc calculated based on the creep characteristics of the elastic member 20, the decrease amount ΔLa of the length La of the array 2 with respect to the distance Lend between the pair of end plates 31 is calculated. Then, based on the decrease amount ΔLa, an additional load amount for compensating for the decrease amount ΔK of the restraint load due to the decrease amount ΔLa is calculated. The minimum load amount applied to the array 2 by the restraint member 3 is set so as to be equal to or more than the load amount obtained by adding the additional load amount to the required load amount of the battery cell. As a result, regardless of the temperature of the battery module 1, the SOC of the battery cell 11, and the usage period of the battery module 1, the plurality of electrodes of the battery cell 11 are in close contact with each other, and the electrode assembly 13 and the case 12 are brought into close contact with each other. Since the state of close contact is ensured, the battery performance can be exhibited satisfactorily.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. For example, the reduction amount ΔLa of the length La does not have to include all of the reduction amount ΔLt, the reduction amount ΔLsoc, and the reduction amount ΔLc, but at least one of them may be included.

Further, the array body 2 does not have to include the elastic member 20. In this case, since the length La of the array 2 is not reduced by the creep of the elastic member 20, the additional load amount for that amount becomes unnecessary.

Further, in the above embodiment, the load amount obtained by adding the additional load amount to the battery cell required load amount is defined as the minimum load amount, but the load amount is not limited to this. The minimum load amount may be a load amount slightly larger than the load amount obtained by adding the additional load amount to the required load amount of the battery cell. In this case, the amount of load applied to the battery cell 11 can be more reliably set to the highly elastic region R2 regardless of the usage status of the battery module 1.

1 ... Battery module, 2 ... Arrangement, 3 ... Restraint member, 11 ... Battery cell, 12 ... Case, 13 ... Electrode assembly, 20 ... Elastic member, 21 ... Positive electrode (electrode), 22 ... Negative electrode (electrode), 31 ... end plate, 32 ... connecting member, D ... arrangement direction (first direction).

Claims (4)

An array containing a plurality of battery cells arranged in the first direction,
A restraining member that applies a restraining load to the array in the first direction, and
It is a battery module equipped with
Each of the plurality of battery cells includes an electrode assembly having a plurality of electrodes stacked in the first direction, and a case for accommodating the electrode assembly.
The minimum load amount, which is the lower limit of the restraint load applied to the array by the restraint member, is calculated based on the relationship between the compression amount of the battery cell and the load amount received by the battery cell. It is set to be equal to or greater than the load amount obtained by adding the additional load amount calculated based on the decrease in the length of the array in the first direction to the load amount.
The required load amount of the battery cell is necessary to obtain the compression amount at which the clearance between the electrodes of the battery cell and between the electrode assembly and the case does not exist when the restraining member is assembled to the array. The above-mentioned load amount
The amount of reduction in the case where the battery module in a predetermined use conditions are employed, Ri maximum reduction der from the length when assembled said restraining member to said array,
The restraint member includes a pair of end plates provided at both ends of the array in the first direction, and a connecting member for connecting the pair of end plates.
The first linear expansion coefficient, which is the linear expansion coefficient of the array, is larger than the second linear expansion coefficient, which is the linear expansion coefficient of the connecting member.
The reduction amount is calculated based on the difference between the first-line expansion coefficient and the second-line expansion coefficient . An array containing a plurality of battery cells arranged in the first direction,
A restraining member that applies a restraining load to the array in the first direction, and
It is a battery module equipped with
Each of the plurality of battery cells includes an electrode assembly having a plurality of electrodes stacked in the first direction, and a case for accommodating the electrode assembly.
The minimum load amount, which is the lower limit of the restraint load applied to the array by the restraint member, is calculated based on the relationship between the compression amount of the battery cell and the load amount received by the battery cell. It is set to be equal to or greater than the load amount obtained by adding the additional load amount calculated based on the decrease in the length of the array in the first direction to the load amount.
The required load amount of the battery cell is necessary to obtain the compression amount at which the clearance between the electrodes of the battery cell and between the electrode assembly and the case does not exist when the restraining member is assembled to the array. The above-mentioned load amount
The amount of reduction in the case where the battery module in a predetermined use conditions are employed, Ri maximum reduction der from the length when assembled said restraining member to said array,
The array further includes the elastic members arranged in the first direction together with the plurality of battery cells.
The reduction amount is calculated based on the creep characteristics of the elastic member, the battery module. The array further includes the elastic members arranged in the first direction together with the plurality of battery cells.
The battery module according to claim 1 , wherein the reduction amount is calculated based on the creep characteristics of the elastic member. The battery module according to any one of claims 1 to 3, wherein the reduction amount is calculated based on the charge rate of the battery cell.

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