JP2016066541A - Battery module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery module capable of operating a current cutoff device in appropriate timing even when adding a constraint load to an array body in which an elastic body is interposed.SOLUTION: A battery module 1 includes: an array body 2 formed by arraying a plurality of battery cells 11 with which an electrode assembly 13 is accommodated within a case 12; a constraint member 3 which adds the constraint load to the array body 2 in an array direction of the battery cells 11; and an elastic body 4 which is interposed between the array body 2 and the constraint body 3 or between the battery cells 11 and 11. The battery cell 11 includes a current cutoff device 26 which cuts off a charging current in the case where an inner pressure of the case 12 increases as high as or higher than a threshold. A lower limit value of the constraint load from the constraint member 3 to the array body 2 is set equal to or greater than a bottom load amount that does not exceed an expansion allowable value to which an expansion amount of the case 12 is preset in the battery cells 11 when the inner pressure of the case 12 becomes the threshold.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a battery module.

  Conventionally, a battery module in which a plurality of battery cells such as lithium ion secondary batteries are arranged is known. In such a battery module, the battery cell array is sandwiched by a restraining tool such as a metal plate and restrained by a constant load, thereby suppressing fluctuations in characteristics such as internal resistance in the battery cell.

  For example, in the assembled battery described in Patent Document 1, a metal band having bent portions at both ends is fixed to an end plate, and the battery block is constrained in the stacking direction by the end plate. In addition, in the power storage device described in Patent Document 2, in consideration of the fact that the amount of increase in the load when the internal pressure of the battery cell is increased differs depending on the value of the constraint load in the initial state, Load is set.

JP 2013-055069 A JP 2013-200787 A

  The battery cell incorporated in the battery module has a current interrupt device (CID: Current Interrupt Device) that cuts off the current path of the battery cell when gas is generated in the battery cell case due to an abnormality such as overcharge. Built in. The current interrupt device operates to physically interrupt the current path of the battery cell when the internal pressure of the case reaches a preset threshold value due to generation of gas.

  On the other hand, in the battery module, there is a case where an elastic body such as rubber is interposed between the array body and the restraining member or between the battery cells in order to prevent the battery cell from being damaged by the restraining load. In this case, since the elastic body easily deforms, the case of the battery cell easily expands when gas is generated, so the increase in the internal pressure of the case becomes moderate with respect to the set value, and the current interrupting device operates at an appropriate timing. There is a risk that it will not.

  The present invention has been made in order to solve the above-described problems, and is a battery module capable of operating a current interrupting device at an appropriate timing even when a restraining load is applied to an arrayed body interposing elastic bodies. The purpose is to provide.

  In order to solve the above problems, a battery module according to an aspect of the present invention includes an array formed by arranging a plurality of battery cells in which an electrode assembly is housed in a case, and an array direction of the battery cells with respect to the array A restraining member for applying a restraining load to the battery, and an elastic body interposed between the array body and the restraining member or between the battery cells, and the battery cell generates a charging current when the internal pressure of the case rises above a threshold value. The lower limit value of the restraining load applied to the array by the restraining member has a current interrupting device that shuts off, and when the internal pressure of the case becomes a threshold value, the expansion amount of the case in the battery cell exceeds the preset allowable expansion amount There is no minimum load set.

  In this battery module, the lower limit value of the restraining load applied to the array by the restraining member is the minimum load amount at which the expansion amount of the case in the battery cell does not exceed a preset expansion allowance when the internal pressure of the case becomes a threshold value It is set above. Thereby, when gas is generated in the case of the battery cell, the expansion amount of the case is kept below a preset allowable expansion amount until at least the internal pressure of the case reaches the threshold value at which the current interrupting device operates. It is. Therefore, the internal pressure of the case at the time of gas generation can be increased according to the set value, and the current interrupting device can be operated at an appropriate timing.

The minimum load amount is the threshold value of the internal pressure of the case P, the contact area between the battery cell and the adjacent member in the array body is A, and the thickness of the elastic body in the array direction when the load amount P × A is added. B ₀ , where B _{1 is} the allowable expansion amount of the case per battery cell, and N is a positive value equal to or less than the number of battery cells in the array, the thickness B in the array direction of the elastic bodies is B ₀ + ( B ₁ × N) may be applied. By setting such a load amount as the lower limit value of the restraining load applied to the array by the restraining member, the thickness of the elastic body in the array direction decreases when the case expands, and the restraining load on the array The restraint load necessary for the operation of the current interrupting device is maintained until the internal pressure of the case reaches at least the threshold value at which the current interrupting device operates. Therefore, when the case expansion allowance is set, the current interrupt device can be operated at an appropriate timing. Further, the minimum load amount can be reduced as compared with the case where the allowable expansion amount of the battery cell is not taken into consideration. For this reason, the load concerning a restraint member can be set low.

  According to another aspect of the present invention, there is provided a battery module including an array of a plurality of battery cells each having an electrode assembly housed in a case, and a binding load applied to the array in the battery cell array direction. A current interrupting device that interrupts a charging current when the internal pressure of the case rises above a threshold value. The lower limit value of the restraining load applied to the array by the restraining member is set to be equal to or more than the minimum load amount that does not cause the case in the battery cell to expand when the internal pressure of the case reaches the threshold value.

  In this battery module, the lower limit value of the restraining load applied to the array by the restraining member is set to be equal to or more than the minimum load amount that does not cause the case in the battery cell to expand when the internal pressure of the case becomes the threshold value. Therefore, the internal pressure of the case at the time of gas generation can be increased according to the set value, and the current interrupting device can be operated at an appropriate timing.

  Further, the minimum load amount may be a load amount represented by P × A, where P is the threshold value of the internal pressure of the case, and A is the contact area between the battery cell and the adjacent member in the array. By setting such a load amount as the lower limit value of the restraining load on the array by the restraining member, the restraining load necessary for the operation of the current interrupting device until the internal pressure of the case reaches at least the threshold at which the current interrupting device operates. Is maintained. Therefore, the current interrupting device can be operated at an appropriate timing.

  According to the present invention, the current interrupting device can be operated at an appropriate timing even when a restraining load is applied to the array body in which the elastic bodies are interposed.

It is a figure which shows one Embodiment of the battery module which concerns on this invention. It is sectional drawing which shows the internal structure of the battery cell which comprises the battery module shown in FIG. It is the III-III sectional view taken on the line in FIG. It is a figure which shows an example of the compression characteristic of an elastic body.

  Hereinafter, preferred embodiments of a battery module according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram showing an embodiment of a battery module according to the present invention. As shown in the figure, the battery module 1 includes an array 2 in which a plurality of battery cells 11 are arrayed, a restraining member 3 that applies a restraining load to the array 2 in the array direction of the battery cells 11, An elastic body 4 interposed between the array body 2 and the restraining member 3 is provided.

  In the array body 2, for example, a plurality of battery cells 11 are arrayed via a heat transfer plate 5. The battery cell 11 is a nonaqueous electrolyte secondary battery such as a lithium ion secondary battery. As shown in FIG. 1, the elastic body 4 is formed in a rectangular plate shape by, for example, a urethane rubber sponge. The area of the elastic body 4 is smaller than, for example, the area of the side surface 12a in the arrangement direction of the case 12 of the battery cell 11, and is arranged at one end of the arrangement body 2 in the arrangement direction of the battery cell 11.

  Examples of the material for forming the elastic body 4 include ethylene propylene diene rubber (EPDM), chloroprene rubber, and silicon rubber. The elastic body 4 is not limited to rubber and may be a spring material or the like. The elastic body 4 is a member used for the purpose of preventing the battery cell 11 from being damaged by a restraining load, and may be disposed at both ends in the arrangement direction of the battery cell 11 or between the battery cells 11 and 11. May be.

  The restraining member 3 includes, for example, a pair of end plates 31 and a fastening member 32 that fastens the end plates 31 together. The end plate 31 has, for example, a substantially rectangular plate shape having an area larger than the area when the battery cell 11 is viewed from the arrangement direction, and the outer edge portion of the end plate 31 is outside the outer edge portion of the battery cell 11. Are arranged at both ends of the array body 2 and the elastic body 4 in the array direction.

  The fastening member 32 includes, for example, a long bolt 33 and a nut 34 that is screwed into the bolt 33. The bolts 33 are inserted through the end plate 31 at positions corresponding to the four corners of the array 2 at the outer edge portion of the end plate 31, for example. The nut 34 is screwed into both ends of each bolt 33 from the outside of the end plate 31, so that the battery cell 11, the elastic body 4, and the heat transfer plate 5 are sandwiched and unitized and a restraining load is applied. .

  For example, as shown in FIGS. 2 and 3, the battery cell 11 includes a hollow case 12 having a substantially rectangular parallelepiped shape and an electrode assembly 13 accommodated in the case 12. The case 12 is formed of a metal such as aluminum, for example, and an organic solvent-based or non-aqueous electrolyte is injected into the case 12, for example. As shown in FIG. 2, the positive terminal 15 and the negative terminal 16 are disposed on the top surface of the case 12 so as to be separated from each other. The positive electrode terminal 15 is fixed to one side in the width direction on the top surface of the case 12 via the insulating member 17, and the negative electrode terminal 16 is fixed to the other side in the width direction on the top surface of the case 12 via the insulating member 18. Has been.

  As shown in FIG. 3, the electrode assembly 13 includes, for example, a positive electrode 21, a negative electrode 22, and a bag-like separator 23 disposed between the positive electrode 21 and the negative electrode 22. In the electrode assembly 13, the positive electrode 21 is accommodated in the separator 23, and the positive electrode 21 and the negative electrode 22 are alternately stacked via the separator 23 in this state.

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

  On the other hand, 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 surfaces of the metal foil 22a. The negative electrode active material layer 22b is formed including a negative electrode active material and a binder. Examples of the negative electrode active material include carbon such as graphite, highly oriented graphite, mesocarbon microbeads, hard carbon, and soft carbon, alkali metals such as lithium and sodium, metal compounds, SiOx (0.5 ≦ x ≦ 1.5 ) And the like, and boron-added carbon. A tab 22 c is formed at the upper edge of the negative electrode 22 in correspondence with the position of the negative electrode terminal 16. The tab 22 c extends upward from the upper edge portion of the negative electrode 22, and is connected to the negative electrode terminal 16 through the conductive member 25.

  The separator 23 is formed in a bag shape, for example, and accommodates only the positive electrode 21 therein. 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 or a nonwoven fabric made of polypropylene, polyethylene terephthalate (PET), methylcellulose, and the like. The separator 23 is not limited to a bag shape, and a sheet shape may be used.

  Further, as shown in FIG. 2, gas is generated in the case 12 of the battery cell 11 due to an abnormality such as overcharge in the case 12 of the battery cell 11, and the internal pressure of the case 12 rises above a threshold value. In this case, a current interrupt device 26 is provided for interrupting the charging current. The current interrupt device 26 is provided between the negative electrode terminal 16 and the conductive member 25. The current interrupt device 26 has an energization path (not shown), and the negative electrode terminal 16 and the conductive member 25 are connected in series by the energization path.

  When the internal pressure of the case 12 rises above a preset threshold, the current interrupt device 26 interrupts the energization path and interrupts the energization between the electrode assembly 13 and the negative terminal 16. The threshold value of the internal pressure of the case 12 set by the current interrupt device 26 means the internal pressure of the case 12 when the battery cell 11 is overcharged. This threshold value is appropriately set based on conditions such as the capacity of the battery cell 11 and the output voltage.

  Usually, in a battery module, since a restraint load by a restraint member is applied to the array body, expansion of the case can be suppressed even when gas is generated in the battery cell case due to an abnormality such as overcharge. . Accordingly, the internal pressure of the case increases with the generation of gas, and the current interrupt device operates when the internal pressure becomes equal to or higher than the threshold value.

  On the other hand, in the battery module 1, as described above, the elastic body 4 is interposed between the array body 2 and the restraining member 3. For this reason, when gas is generated in the case 12 of the battery cell 11 due to an abnormality such as overcharging, the case 12 may expand in the arrangement direction due to the elastic body 4 being easily deformed. It is done. For this reason, the increase in the internal pressure of the case 12 becomes moderate with respect to the set value, and there is a possibility that the current interrupt device 26 may not operate at an appropriate timing.

  Therefore, in the battery module 1, in consideration of expansion of the case 12 due to deformation of the elastic body 4, an initial restraining load on the array body 2 by the restraining member 3 is set. Hereinafter, the setting of the restraint load will be described in detail.

  In setting an initial restraining load on the array body 2 by the restraining member 3, the relationship (compression characteristics) between the thickness and the restraining load of the elastic bodies 4 arranged in the array body 2 is used. FIG. 4 is a diagram illustrating an example of compression characteristics when the elastic body 4 is a urethane rubber sponge. In the example shown in the figure, the horizontal axis represents the thickness of the elastic body 4, the vertical axis represents the restraining load by the restraining member 3, and the compression characteristic curve of the elastic body 4 is plotted (graph A). In the region where the thickness of the elastic body 4 is large (region where the compression amount is small), the load amount increases as the thickness decreases (A1 portion of the graph A). As the thickness of the elastic body 4 decreases, the load increases with the decrease in thickness (A2 portion of the graph A). When the thickness of the elastic body 4 further decreases, the load increases. On the other hand, the thickness of the elastic body 4 hardly decreases (A3 portion of the graph A).

Here, when the threshold value of the internal pressure of the case 12 is P and the contact area between the battery cell 11 and the adjacent member in the array 2 is A, first, the load amount K ₀ represented by P × A is obtained, and the load amount From the intersection of K ₀ and the compression characteristic curve, the thickness B ₀ in the arrangement direction of the elastic bodies 4 when the load P × A is added is obtained. The threshold value P is preset in the current interrupt device 26. The contact area A is the larger area of the contact areas with adjacent members that are in contact with the side surface 12 a in the arrangement direction of the battery cells 11.

  In the example shown in FIG. 1, the heat transfer plate 5 having the same area as the side surface 12 a is in contact with the side surfaces 12 a and 12 a as adjacent members of the battery cell 11 positioned in the middle of the arrangement direction of the array 2. In addition, in the battery cell 11 located at one end in the arrangement direction of the array body 2, the elastic body 4 having an area smaller than that of the side surface 12a is in contact with one of the side surfaces 12a as an adjacent member, and has the same area as the side surface 12a. The heat plate 5 is in contact with the other side surface 12a as an adjacent member. In the battery cell 11 positioned at the other end in the arrangement direction of the array 2, the heat transfer plate 5 having the same area as the side surface 12 a is in contact with the side surfaces 12 a and 12 a as adjacent members. Therefore, for any battery cell 11, the contact area A coincides with the area of the side surface 12a.

After obtaining the thickness B ₀ of the elastic body 4 in the arrangement direction when the load P × A is added, the expansion allowance of the case 12 per battery cell 11 is B ₁ , and the battery cell 11 in the array 2 is When a positive value equal to or less than the number of arrangements is N, the load K _{1 at} which the thickness B in the arrangement direction of the elastic bodies 4 is B ₀ + (B ₁ × N) is defined as the thickness B ₀ + (B ₁ XN) and the intersection of the compression characteristic curve. The load amount K ₁ is the lowest load amount necessary to ensure that the expansion amount of the case 12 does not exceed the expansion allowance B1 which is set in advance in the battery cell 11 when the internal pressure of the case 12 becomes a threshold value P It is. The lower limit of the initial restraining load on the array 2 by restraining member 3 is set such that the load amount K ₁ or more.

The allowable expansion amount B ₁ is an allowable expansion amount of the case 12 in the arrangement direction of the battery cells 11 and is appropriately set in consideration of the threshold value P of the current interrupt device 26. The positive value N may be equal to the number of battery cells 11 arranged in an ideal model in which each battery cell 11 expands uniformly, but only some of the battery cells 11 included in the array 2 It is also conceivable that the amount of expansion between the battery cells 11 varies due to expansion. When considering such a variation in the expansion amount between the battery cells 11, the battery cell 11 is appropriately set from a range of greater than 0 and less than N. The positive value N is not limited to an integer, and may be a decimal (pure decimal or band decimal).

  As described above, in the battery module 1, when the lower limit value of the restraining load applied to the array 2 by the restraining member 3 is the threshold value of the internal pressure of the case 12, the expansion amount of the case 12 in the battery cell 11 is determined in advance. It is set above the minimum load that does not exceed the set expansion allowance. As a result, when gas is generated in the case 12 of the battery cell 11, the expansion amount of the case 12 is set to a predetermined expansion allowance until the internal pressure of the case 12 reaches at least the threshold value at which the current interrupt device 26 operates. Keep below capacity. Therefore, it becomes possible to raise the internal pressure of the case 12 at the time of gas generation according to the set value, and the current interrupting device 26 can be operated at an appropriate timing.

Moreover, in the battery module 1, the minimum load amount is the elasticity when the threshold value of the internal pressure of the case 12 is P, the contact area between the battery cell 11 and the adjacent member in the array 2 is A, and the load amount P × A is added. When the thickness in the arrangement direction of the body 4 is B ₀ , the allowable expansion amount of the case 12 per battery cell 11 is B ₁ , and the positive value not more than the number of the battery cells 11 in the array 2 is N, the elasticity The thickness B in the arrangement direction of the bodies 4 is a load amount such that B ₀ + (B ₁ × N).

  By setting such a load amount as the lower limit value of the restraining load applied to the array 2 by the restraining member 3, the thickness of the elastic bodies 4 in the array direction decreases when the case 12 expands, and the array The restraint load required for the operation of the current interrupting device 26 is maintained until the internal pressure of the case 12 reaches at least the threshold value at which the current interrupting device 26 operates. Accordingly, when the allowable expansion amount of the case 12 is set, the current interrupt device 26 can be operated at an appropriate timing. In addition, the minimum load amount can be reduced as compared with the case where the allowable expansion amount of the battery cell 11 is not taken into consideration. For this reason, the load applied to the restraining member 3 can be set low.

When the positive value N is set from a range greater than 0 and less than N, it is possible to cope with variations in the expansion amount between the battery cells 11 due to, for example, a difference in deterioration state between the battery cells 11 or a difference in temperature. It becomes possible. When the positive value N is matched with the number of battery cells 11 arranged, the load amount K ₁ corresponding to the thickness B ₀ + (B ₁ × N) of the elastic body 4 is the smallest. On the other hand, by setting the positive value N from a range that is greater than 0 and less than N, the load amount K ₁ (that is, the constraint load) is compared with the ideal model in which each battery cell 11 is uniformly expanded. (Lower limit value) increases. Therefore, even if there is a variation in the amount of expansion between the battery cells 11, the restraining load applied to the array 2 when the thickness of the elastic body 4 decreases due to the expansion of the case 12 causes the current interrupting device 26 to operate. Maintains more than necessary restraint load.

  The present invention is not limited to the above embodiment. For example, in the above-described embodiment, the lower limit value of the restraining load applied to the array 2 by the restraining member 3 is set in consideration of the expansion allowance of the battery cell 11, but the expansion allowance of the battery cell 11 is not considered, The lower limit value of the restraining load applied to the array 2 by the restraining member 3 is not less than the minimum load amount necessary to prevent the case 12 in the battery cell 11 from expanding when the internal pressure of the case 12 becomes a threshold value. You may set so that. In this case, the minimum load amount is a load amount represented by P × A, where P is the threshold value of the internal pressure of the case 12 and A is the contact area between the battery cell 11 and the adjacent member in the array 2.

  Even when such a load amount is set as the lower limit value of the restraining load applied to the array body 2 by the restraining member 3, at least until the internal pressure of the case 12 reaches the threshold value at which the current interrupting device 26 operates, The restraint load necessary for operation is maintained. Therefore, it becomes possible to raise the internal pressure of the case 12 at the time of gas generation according to the set value, and the current interrupting device 26 can be operated at an appropriate timing.

  Moreover, in the said embodiment, although the elastic body 4 of an area smaller than the side surface 12a is contacting one side of the side surface 12a as the adjacent member in the battery cell 11 located in one edge part of the arrangement direction of the array body 2. FIG. The area of the elastic body 4 may be equal to or larger than the area of the side surface 12a. Also in this case, the contact area A of the battery cell 11 is the same as the area of the side surface 12a. In addition, when the area of the heat transfer plate 5 and the elastic body 4 is changed and the contact area A is different between the battery cells 11, the threshold P of the current interrupt device 26 in each battery cell 11 is adjusted, so that P × It is preferable to make the load amount represented by A constant between the battery cells 11.

  In the above embodiment, the current interrupt device 26 is provided between the negative electrode terminal 16 and the conductive member 25. However, the current interrupt device 26 is not limited to this position. The electrode assembly 13 and the negative electrode terminal 16 may be configured to be electrically connected in series. In addition, as above-mentioned, the elastic body 4 may be arrange | positioned at the both ends of the sequence direction of the battery cell 11, and may be arrange | positioned between the battery cells 11 and 11. FIG. When a plurality of elastic bodies 4 are arranged in this way, the total thickness of each elastic body 4 only needs to satisfy the above relational expression.

  DESCRIPTION OF SYMBOLS 1 ... Battery module, 2 ... Array, 3 ... Restraining member, 4 ... Elastic body, 11 ... Battery cell, 12 ... Case, 26 ... Current interruption apparatus.

Claims (4)

An array formed by arranging a plurality of battery cells in which the electrode assembly is housed in a case;
A restraining member for applying a restraining load in the arrangement direction of the battery cells to the array;
An elastic body interposed between the array and the restraining member or between the battery cells,
The battery cell has a current interrupt device that interrupts a charging current when the internal pressure of the case rises above a threshold value,
The lower limit value of the restraining load on the array by the restraining member is:
A battery module in which an expansion amount of the case in the battery cell is set to be equal to or greater than a minimum load amount that does not exceed a preset allowable expansion amount when the internal pressure of the case becomes the threshold value. The minimum load amount is a threshold value of the internal pressure of the case P, a contact area between the battery cell and the adjacent member in the array body, and an array direction of the elastic bodies when a load amount P × A is added. The array of the elastic bodies, where B _{0 is} the thickness of the case, B _{1 is} the allowable expansion amount of the case per battery cell, and N is a positive value less than the number of battery cells in the array. The battery module according to claim 1, wherein the thickness B in the direction is a load amount such that B ₀ + (B ₁ × N). An array formed by arranging a plurality of battery cells in which the electrode assembly is housed in a case;
A restraining member for applying a restraining load in the arrangement direction of the battery cells to the array;
An elastic body interposed between the array and the restraining member or between the battery cells,
The battery cell has a current interrupt device that interrupts a charging current when the internal pressure of the case rises above a threshold value,
The lower limit value of the restraining load on the array by the restraining member is:
The battery module which is set more than the minimum load amount which does not produce expansion | swelling to the said case in the said battery cell when the internal pressure of the said case becomes the said threshold value.   The minimum load amount is a load amount represented by P × A, where P is a threshold value of the internal pressure of the case and A is a contact area between the battery cell and the adjacent member in the array. The battery module as described.

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