JP2016184470A - Battery pack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery pack having high resistance to vibration.SOLUTION: There is provided a battery pack 10 in which a plurality of battery cells 20 each having a battery case 50, and spacers 40 disposed between the adjacent battery cells 20 are arranged in a predetermined arrangement direction. At least one of the battery case 50 and the spacer 40 is subjected to a surface treatment to increase the frictional force of the contact surface between the battery case 50 and the spacer 40. The battery cell 20 and the spacer 40 are restrained while a predetermined restraining load is applied to them in the arrangement direction. The friction coefficient B of the contact surface between the battery case 50 and the spacer 40 while the restraining load is applied is equal to or larger than 0.7.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a battery pack configured by arranging a plurality of battery cells in a predetermined direction.

  A battery pack (also referred to as an assembled battery) in which a storage element such as a lithium ion battery, nickel metal hydride battery or other secondary battery or capacitor is defined as a battery cell (also referred to as a single battery; hereinafter the same applies). The same shall apply hereinafter) is becoming increasingly important as a power source for mounting on vehicles or as a power source for personal computers and portable terminals. In particular, a battery pack in which a plurality of lithium ion batteries that are lightweight and have a high energy density are connected in series as battery cells is preferably used as a high-output power source for mounting on a vehicle. As a prior art regarding a battery pack, patent document 1, 2 is mentioned, for example.

JP 2014-203746 A JP 2011-228302 A

  In a battery pack, a spacer may be disposed between adjacent battery cells for the purpose of improving heat dissipation. Usually, a plurality of battery cells and spacers constituting this type of battery pack are arranged in a predetermined arrangement direction and restrained with a load applied in the arrangement direction for the purpose of vibration resistance, shock resistance, etc. Yes. However, in the conventional battery pack, a situation in which the battery pack vibrates greatly depending on the usage environment may occur due to such restrictions. In particular, in a battery pack configured by arranging a relatively large number (for example, five or more) of battery cells, when the battery pack is vibrated, the amplitude of the central portion in the arrangement direction of the battery pack tends to increase. was there. When the amplitude of the battery pack increases, local stress is likely to be applied to the battery cells constituting the battery pack, which may be a cause of premature damage to the battery pack.

  The present invention has been created in view of such circumstances, and an object of the present invention is to provide a battery pack having high vibration resistance (that is, performance for suppressing amplitude during vibration).

  According to the present invention, there is provided a battery pack (assembled battery) in which a plurality of battery cells (unit cells) including a battery case and spacers arranged between adjacent battery cells are arranged in a predetermined arrangement direction. . At least one of the battery case and the spacer is subjected to surface processing for increasing the frictional force of the contact surface between the battery case and the spacer. The battery cell and the spacer are restrained in a state where a predetermined load is applied in the arrangement direction. The friction coefficient B of the contact surface between the battery case and the spacer in a state where the restraining load is applied is 0.7 or more. According to the battery pack having such a configuration, it is possible to appropriately suppress the amplitude when the battery pack is vibrated and to obtain a battery pack having improved vibration resistance. Therefore, according to this configuration, the durability of the battery pack against vibration can be improved.

  In addition, the frictional force in this specification refers to a dynamic frictional force. Moreover, the friction coefficient in this specification points out a dynamic friction coefficient.

It is a perspective view which shows the structure of the battery pack which concerns on one Embodiment. It is a side view which shows the structure of the battery pack which concerns on one Embodiment. It is a figure which illustrates the measuring method of a friction coefficient typically. It is a figure which illustrates typically the behavior at the time of vibrating the battery pack concerning one embodiment on predetermined conditions. It is a figure which illustrates typically the behavior at the time of vibrating the conventional battery pack on predetermined conditions. It is a side view which shows the structure of the battery pack which concerns on one Embodiment. It is a side view which shows the structure of the battery pack which concerns on other one Embodiment. It is a side view which shows the structure of the battery pack which concerns on other one Embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the dimensional relationship (length, width, thickness, etc.) in each figure does not reflect the actual dimensional relationship. Further, matters other than matters specifically mentioned in the present specification and necessary for the implementation of the present invention (for example, battery structures that do not characterize the present invention) are known to those skilled in the art based on the prior art in this field. It can be grasped as a design item. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field. Further, in the following drawings, members / parts having the same action may be described with the same reference numerals, and overlapping descriptions may be omitted or simplified.

  A typical configuration of the battery pack disclosed herein will be described with reference to FIGS. FIG. 1 is a perspective view schematically showing the configuration of the battery pack 10 of the present embodiment.

  The battery pack 10 of this embodiment is a battery pack 10 mounted on a vehicle. The battery pack 10 includes a plurality of chargeable / dischargeable battery cells (for example, lithium ion secondary batteries) 20 connected in series. In the illustrated example, the battery cells 20 having the same shape are arranged in series at regular intervals. The number of battery cells constituting the battery pack disclosed herein is not particularly limited. When the battery pack disclosed here is used as a vehicle-mounted power source, the number of battery cells constituting the battery pack is preferably 3 to 35 (for example, 10 to 25).

  The battery cell 20 includes an electrode body that includes a positive electrode and a negative electrode, and a battery case 50 that houses the electrode body and an electrolyte. The electrode body of the present embodiment is composed of predetermined battery constituent materials (active material for each positive and negative electrode, current collector for each positive and negative electrode, separator, etc.) in the same manner as the battery cell 20 equipped in a typical battery pack 10. Has been. Here, a flat wound electrode body is used as the electrode body.

  The battery case 50 of the present embodiment has a shape (box shape in the illustrated example) that can accommodate a flat wound electrode body. The material of the battery case 50 is not particularly limited as long as it is the same as that used in a typical battery cell (for example, a lithium ion secondary battery) 20, but from the viewpoint of reducing the weight of the battery pack 10 itself, for example, A battery case 50 made of thin metal (such as aluminum) or synthetic resin can be used.

  On the upper surface of the battery case 50, a positive electrode terminal 60 and a negative electrode terminal 62 that are electrically connected to the positive electrode and the negative electrode of the wound electrode body, respectively, are provided. The plurality of battery cells 20 of the present embodiment are arranged so as to be inverted one by one so that the positive terminals 60 and the negative terminals 62 are alternately arranged, and the side walls 52 of the battery case 50 (of the battery case 50). Wide surfaces 52) are arranged in opposite directions. Then, between the adjacent battery cells 20, one positive terminal 60 and the other negative terminal 62 are electrically connected by a connector 64. Thus, the battery pack 10 which has a desired voltage can be constructed | assembled by connecting each battery cell 20 in series.

  Next, the spacer 40 which comprises the battery pack 10 of this embodiment is demonstrated. As shown in FIGS. 1 and 2, spacers 40 are arranged between adjacent battery cells 20 and both outsides in the battery cell arrangement direction. The spacer 40 is a plate-like member and is preferably made of a resin material such as polypropylene (PP) or polyphenylene sulfide (PPS). The spacer 40 is disposed in close contact with the battery case side wall 52 of the adjacent battery cell 20, and serves as a heat radiating plate for efficiently radiating the heat generated in the battery cell 20 due to charge / discharge or the like to the outside. Have.

  In the spacer 40 of the present embodiment, a plurality of grooves that can be used as a passage for a refrigerant (typically, a fluid such as water or air) are formed substantially parallel (in a comb shape) on at least one surface. Has been. As shown in FIG. 2, the spacer 40 is typically disposed such that the surface on which the groove as the refrigerant passage is formed is in contact with the adjacent battery cell side wall 52.

  A restraining member that restrains the plurality of battery cells 20 and the spacers 40 together is disposed around the battery cells 20 and the spacers 40 arranged in this manner. That is, a pair of restraining plates 70A and 70B are arranged on the outer side of the battery cell 20 located on the outermost side in the battery cell arrangement direction. Further, a fastening beam member 72 is attached so as to bridge the pair of restraining plates 70A and 70B. Then, by tightening and fixing the end portion of the beam material 72 to the restraining plates 70A and 70B with screws 74, the battery cell 20 can be restrained so that a predetermined load (constraint load) is applied in the arrangement direction. Thus, the battery cell 10 of this embodiment is comprised.

What is necessary is just to select the magnitude | size of the said restraint load suitably according to the number of battery cells 20 which comprise the battery pack 10, a size, etc. FIG. For example, it is preferable to restrain by applying a load such that the surface pressure applied to the side wall 52 of the battery cell 20 is 10 ⁴ Pa to 10 ⁶ Pa.

<Friction coefficient>
Next, friction of the contact surface between the battery case 50 and the spacer 40 in the battery pack 10 disclosed herein will be described. Here, the friction on the contact surface between the battery case 50 and the spacer 40 refers to the friction between the side wall 52 of the battery case and the surface of the spacer 40 in contact with the side wall 52.
In the battery pack 10 disclosed herein, when the friction coefficient of the contact surface between the battery case 50 and the spacer 40 in a state where a stress corresponding to a predetermined restraining load is applied is B, B is 0.7 or more. . Such a battery pack 10 exhibits good vibration resistance and can be excellent in durability against vibration. The friction coefficient B is more preferably 0.75 or more, and further preferably 0.8 or more. As the friction coefficient B increases, the vibration resistance tends to improve. The upper limit of the friction coefficient B is not particularly limited. In order to disperse the stress applied to the battery case 50 in order to suppress vibration, it is usually appropriate to set the friction coefficient B to 1.5 or less, for example.

  The frictional force and the friction coefficient in this specification can be measured according to JIS K7125. For example, the frictional force can be measured using a precision universal testing machine (manufactured by Shimadzu Corporation, model: Autograph AG-IS). Specifically, as shown in FIG. 3, the battery case 50 to be measured and the spacer 40 are brought into contact with each other so that the contact surfaces thereof are horizontal, and a vertical load F is applied by a weight 30 from above both. Pull the spacer 40 horizontally, and measure the force (ie, frictional force) F ′ necessary to continue moving the spacer 40 with the scale 32. Further, the friction coefficient μ can be obtained by substituting the vertical load F and the measured value F ′ of the friction force into the general formula: F ′ = μF;

  In the battery pack 10 disclosed herein, surface processing (hereinafter also referred to as friction increasing processing) is performed on at least one of the battery case 50 and the spacer 40 to increase the frictional force of the contact surface between the battery case 50 and the spacer 40. Is given. Here, the friction increasing process refers to a process that contributes to an increase in the frictional force between the contact surfaces. The battery pack 10 is configured to satisfy the relationship of B> A, where A is the friction coefficient of the contact surface of the battery case 50 and the spacer 40 when the friction increasing process is not performed. Here, the friction coefficient A is obtained by measuring a state in which a load corresponding to the restraint load of the battery pack is applied to the battery case 50 that has not been subjected to the friction increasing process and the spacer 40 in contact with each other. It is a thing.

  Examples of the surface processing for increasing the frictional force include processing for applying, sticking, and spraying a material that prevents slipping to the surface; processing for roughening the surface; projections or grooves for preventing slipping on the surface The process which forms is mentioned. These processes can be used singly or in combination of two or more.

  The value of the friction coefficient A can depend on the material and surface shape (surface state) of the contact surface of the battery case and the spacer. Although it does not specifically limit, the technique disclosed here is a battery pack provided with the battery case and spacer whose friction coefficient A is 0.1-0.7 (for example, 0.2-0.5). It can be preferably applied to. In the battery pack in which the friction coefficient A is in the above range, it is particularly significant that the friction coefficient B is set to 0.7 or more by performing friction increasing processing on at least one of the battery case and the spacer.

  The battery pack disclosed herein may include a plurality of types of contact surfaces with different frictional forces depending on the combination of the facing surfaces of each battery case and the spacer adjacent thereto. For example, in the example shown in FIGS. 1 and 2, the frictional force of the contact surface between the comb tooth surface of the spacer 40 (the surface on which the comb teeth are formed) and the side wall 52 of the battery case 50 is the flat surface (comb tooth of the spacer 40. The frictional force of the contact surface between the battery case 50 and the side wall 52 of the battery case 50 may be different. In such a case, at least one of the battery case 50 and the spacer 40 is subjected to a surface treatment for increasing the frictional force of at least one contact surface, and is the same as the contact surface subjected to the surface treatment. Alternatively, if the friction coefficient B of at least one different contact surface is 0.7 or more, the application effect of the technique disclosed herein can be exhibited. It is preferable that the friction coefficient B of at least the contact surface subjected to the surface processing is 0.7 or more. It is particularly preferable that the friction coefficient B of all types of contact surfaces is 0.7 or more.

Hereinafter, the vibration resistance of the battery pack will be described. FIG. 4 shows one embodiment of the battery pack 10 disclosed herein. FIG. 5 shows a conventional battery pack 12.
In the conventional battery pack 12, when external vibration is applied, the battery cells 22 and the spacers 42 located in the center of the battery pack 12 in the arrangement direction tend to exhibit a large amplitude as schematically shown in FIG. is there. If the amplitude of the battery pack 12 is large, a large stress is locally applied to the battery case 52 of the battery cell 22 (particularly, the battery cell 22 located at the center of the battery pack 12). (As a result, the battery cell 22) is likely to be damaged such as deformation.

  Since the battery pack 10 disclosed herein is subjected to a process for increasing the frictional force on the contact surface between the battery case 50 and the spacer 40, the friction increasing process is performed even when external vibration is applied. The amplitude of the battery pack 10 can be suppressed as compared with the case where it is not. Thereby, durability (for example, durability time and the number of times of durability) with respect to vibration of the battery pack 10 is improved. Further, since the battery pack 10 is configured so that the frictional force is 0.7 or more, the battery pack 10 is excellent in vibration resistance, and thus can exhibit high durability against use under conditions where vibration can be applied. it can.

  Several specific embodiments will be described below. In the following description of each embodiment, a surface of the side wall 52 of the battery case 50 that is in contact with the spacer is referred to as a contact surface of the battery case 50. The surface of the spacer 40 that is in contact with the battery case 50 is referred to as the contact surface of the spacer 40.

FIG. 6 shows a preferred embodiment of the battery pack disclosed herein. In the battery pack 10 </ b> A shown in FIG. 6, a coating layer 80 is formed on the contact surface of the battery case 50. The coating layer 80 is coated with a material that acts as an anti-slip material (for example, an anti-slip agent, an adhesive, an adhesive, etc.) The contact surface of the battery case 50 is in contact with the contact surface of the spacer 40 through the coating layer 80.
According to the battery pack 10 </ b> A having such a configuration, the presence of the coating layer 80 can improve the frictional force of the contact surface between the battery case 50 and the spacer 40. The region where the coating layer 80 is formed may be on the contact surface of the battery case 50 as in the example shown in FIG. 6 or on the contact surface of the spacer 40. Furthermore, it may be on the contact surfaces of both the battery case 50 and the spacer 40.

  For the formation of the coating layer 80, a known material capable of imparting an anti-slip effect to the metal surface or the synthetic resin surface can be appropriately used. The coating layer 80 is formed by, for example, coating the contact surface of the battery case 50 with a paint such as urethane resin, acrylic resin, acrylic urethane resin, acrylic silicone resin, ethylene-vinyl acetate resin, or rubber. A non-slip coating. Other materials that can be used as the coating layer 80 include pressure-sensitive adhesives and adhesives such as acrylic pressure-sensitive adhesives, rubber-based pressure-sensitive adhesives, vinyl acetate-based adhesives, silicone rubber-based adhesives, and rubber-based adhesives. In general, by forming the coating layer 80 with a material that is more flexible than the material of the contact surface of the battery case 50 (for example, aluminum), a good anti-slip effect tends to be exhibited. The coating layer 80 made of a material more flexible than both the battery case 50 and the spacer 40 (for example, made of synthetic resin such as PP or PPS) is preferable. Instead of or in addition to the coating layer 80, a flexible resin sheet (rubber sheet, urethane resin sheet, etc.) or a porous sheet (for example, a foamed resin sheet such as a foamed rubber sheet or a urethane foam sheet; paper or Or the like may be sandwiched between the battery case 50 and the spacer 40, or may be fixed to any contact surface of the battery case 50 and the spacer 40 with an adhesive or the like.

  FIG. 7 shows another preferred embodiment of the battery pack disclosed herein. In the battery pack 10 </ b> B illustrated in FIG. 7, the contact surface of the battery case 50 is subjected to a roughening process (roughening process). As a result, the contact surface of the battery case 50 is a rough surface 81. In the battery pack 10 </ b> B, by making the contact surface of the battery case 50 a rough surface 81, the frictional force of the contact surface between the battery case 50 and the spacer 40 can be improved.

  As a method of forming the rough surface 81 (that is, a method of roughening the surface of the battery case), a method conventionally used for increasing the surface roughness of the surface of the metal or the synthetic resin is adopted. Can do. For example, roughening processing such as sanding, sanding, cloth blasting, shot blasting, etching, shot peening, press working (for example, imparting uneven shapes such as embossing and embossing) can be employed. The surface of the battery case 50 can also be roughened by forming a film (typically a resin film) in which hard particles are dispersed. As the hard particles, appropriate inorganic particles, metal particles, resin particles and the like can be appropriately employed.

  The area to be roughened may be the contact surface of the battery case 50 as shown in FIG. 7 or the contact surface of the spacer 40. Moreover, the contact surface of both the battery case 50 and the spacer 40 may be sufficient. Different friction increasing processes may be applied to the contact surfaces of both the battery case 50 and the spacer 40. For example, the anti-slip coating layer may be formed on the contact surface of the battery case 50 while the contact surface of the spacer 40 may be roughened.

  FIG. 8 shows another preferred embodiment of the battery pack disclosed herein. In the battery pack 10 </ b> C shown in FIG. 8, a protrusion 82 as a friction generating part for preventing slipping is formed on the contact surface of the battery case 50. The protrusion 82 formed on the contact surface of the battery case 50 is in contact with the contact surface of the adjacent spacer 40, and thereby the frictional force of the contact surface between the battery case 50 and the spacer 40 can be improved. The method for forming the protrusions 82 is not particularly limited, and for example, a method such as pressing, bending, bonding of the members for protrusions can be employed.

  Next, examples relating to the present invention will be described, but the present invention is not intended to be limited to those shown in the examples.

<Production of battery pack>
(Example)
A lithium ion secondary battery was prepared as a battery cell (single battery). A lithium ion secondary battery has a flat wound electrode body comprising a sheet-like electrode in which an active material for each positive and negative electrode is held on a current collector for each positive and negative electrode, and a separator interposed between the electrodes. In addition to the non-aqueous electrolyte, the battery case is housed in a flat, rectangular parallelepiped battery case made of aluminum. In addition, the battery cell is configured to have positive and negative terminals protruding upward. The size of the flat surface of the battery cell (that is, the wide surface facing the battery cell arrangement direction) was 50 mm long × 150 mm wide. Appropriate amount of adhesive (product name: Cemedine, manufactured by Cemedine Co., Ltd.) is applied to the entire area of the flat surface of each battery cell that faces the comb teeth surface of the spacer when the battery pack described later is constructed. Thus, a coating layer was formed.

  In addition, a plate-like spacer made of polypropylene (PP) was prepared. The size of the flat surface of the spacer (that is, the wide surface facing the arrangement direction) was 50 mm long × 150 mm wide. As the spacer, a spacer in which a plurality of comb-shaped grooves as a refrigerant passage was formed on one surface of the flat surface was used.

  A battery cell was constructed using the battery cell on which the coating layer was formed and the spacer. As shown in FIG. 4, 19 battery cells were arranged so that the protruding directions of the respective terminals were the same direction. Then, a total of 20 spacers were disposed between the battery cells and on both outsides in the battery cell arrangement direction, with the comb tooth surfaces of the spacers in contact with the coating layers of the battery cells. And the restraint member was arrange | positioned around the arranged cell and spacer, and restrained so that the load (restraint load) of 138 kgf might be added to the sequence direction of a battery cell. Between adjacent battery cells, one positive electrode terminal and the other negative electrode terminal were electrically connected by a connector. Thus, the battery pack according to Example 1 was produced.

(Comparative example)
A battery pack was produced in the same manner as in the example except that the anti-slip agent was not applied to the flat surface of the battery cell.

<Measurement of friction coefficient>
(Friction coefficient A)
About the battery pack which concerns on the said Example, the friction coefficient A of the side surface of the battery case which comprises a battery cell, and the comb-tooth surface of a spacer was measured. Specifically, the comb teeth surface of the spacer is placed on the side surface of the battery case that has not been subjected to the friction increasing process (in the above embodiment, the process of forming the coating layer by applying the anti-slip agent). And a 138 kg weight was placed thereon, and this was set on a precision universal testing machine (Shimadzu Corporation model: Autograph AG-IS). Next, the spacer was pulled in the horizontal direction at a pulling speed of 10 mm / second, and the friction coefficient A (dynamic friction coefficient) was determined from the friction force (dynamic friction force) measured at that time.

(Friction coefficient B)
For the battery pack according to the above example, except that the measurement target was the battery case used for the construction of the battery pack (that is, the coating layer forming surface of the battery case after forming the coating layer) and the spacer, The friction coefficient B was determined in the same manner as the measurement of the friction coefficient A. The friction coefficient B of the battery pack according to the comparative example corresponds to the friction coefficient A of the battery pack according to the example.

<Vibration experiment>
The battery pack according to each example was vibrated under a resonance frequency of 36 Hz, and the number of vibrations until a part of the battery pack was damaged was examined. Moreover, the behavior of the battery cell in the center part of the battery pack when it was vibrated under the above conditions was observed. Specifically, the displacement amount and the maximum angle of the position of the center portion of the battery pack showing the maximum amplitude were measured. The results are shown in Table 1. Table 1 also shows the results of the coefficient of friction according to each example.

  As is apparent from the results shown in Table 1, in the vibration experiment under the above-described conditions, it was confirmed that the displacement amount of the battery pack according to the example was reduced to about 1/10 compared with the comparative example. Similarly, it was found that the maximum angle of the battery pack according to the example by the vibration experiment is significantly reduced as compared with the comparative example. From this, according to the battery pack according to the example, it was confirmed that the amplitude at the time of vibration was greatly reduced (vibration resistance was improved) and durability against vibration was improved.

The battery pack according to an embodiment, after vibrated ¹⁰⁷ times under the conditions of the vibration test to above also, any of the battery cells or the spacer was confirmed that not corrupted. On the other hand, when the battery pack according to the comparative example was vibrated 1000 times under the above-described vibration experiment conditions, it was visually confirmed that a part of the battery case made of aluminum was damaged. From the above results, according to the battery pack according to the example, it was confirmed that the durability of the battery case due to the vibration was significantly improved.

  From the above results, the contact surface (flat surface) of the battery case is subjected to surface treatment for increasing the frictional force so that the friction coefficient of the contact surface between the battery case and the spacer is 0.7 or more (0.8 in the embodiment). According to the battery pack according to the example, it was confirmed that the vibration resistance of the battery pack was improved, thereby suppressing the damage of the battery pack and improving the durability of the battery pack.

  As mentioned above, although the specific example of this invention was demonstrated in detail, these are only illustrations and do not limit a claim. The invention disclosed herein can include various modifications and alterations of the specific examples described above. The invention disclosed herein can include a mode in which two or more of the above specific examples are appropriately combined.

10, 10A, 10B, 10C Battery pack 20 Battery cell 40 Spacer 50 Battery case 60 Positive electrode terminal 62 Negative electrode terminal 80 Coating layer 81 Rough surface 82 Projection

Claims (1)

A battery pack in which a plurality of battery cells including a battery case and spacers arranged between adjacent battery cells are arranged in a predetermined arrangement direction,
At least one of the battery case and the spacer is subjected to surface treatment for increasing the frictional force of the contact surface between the battery case and the spacer,
The battery cell and the spacer are restrained in a state where a predetermined restraining load is applied in the arrangement direction,
A battery pack, wherein a friction coefficient B of a contact surface between the battery case and the spacer in a state where the predetermined restraining load is applied is 0.7 or more.

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