Patent Publication Number: US-2023155232-A1

Title: Battery pack

Description:
This nonprovisional application is based on Japanese Patent Application No. 2021-185645 filed on Nov. 15, 2021 with the Japan Patent Office, the entire contents of which are hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present technology relates to a battery pack. 
     Description of the Background Art 
     Attempts have been conventionally made to improve waterproofness of a battery pack. For example, Japanese Patent Laying-Open No. 2011-100619 discloses a battery pack including a sealing member provided at a joining surface between a case body and a cover plate to seal the joining interface in a waterproof state. 
     SUMMARY OF THE INVENTION 
     The conventional structure is based on such a premise that the pack case is dissembled afterward. On the other hand, there is room for further improvement in strength against an expansion pressure of the case. It is an object of the present technology to provide a battery pack having a large strength against an expansion pressure of a case. 
     A battery pack according to the present technology includes: a plurality of battery cells arranged side by side along a first direction; and a case having an inner space for accommodating the plurality of battery cells. The case includes a first member, a second member that forms the inner space together with the first member, and a sealing portion that seals a joining portion between the first member and the second member. The first member has a first portion in abutment with the sealing portion. The second member has a second portion facing the first portion with the sealing portion being interposed between the second portion and the first portion. When an expansion pressure of the inner space acts on the case, a force in a shearing direction acts on the sealing portion sandwiched between the first portion and the second portion. 
     The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is an exploded perspective view showing a configuration of a battery pack. 
         FIG.  2    is a diagram showing a battery cell included in the battery module. 
         FIG.  3    is a diagram showing a schematic shape of a case of a battery pack according to a comparative example 1. 
         FIG.  4    is a cross sectional view showing a shape of a portion IV in  FIG.  3   . 
         FIG.  5    is a diagram showing a schematic shape of a case of a battery pack according to a comparative example 2. 
         FIG.  6    is a cross sectional view showing a shape of a portion VI in  FIG.  5   . 
         FIG.  7    is a diagram showing a schematic shape of a case of a battery pack according to one embodiment. 
         FIG.  8    is a cross sectional view showing a shape of a portion VIII in  FIG.  7   . 
         FIG.  9    is a diagram showing a state before a case of a battery pack according to an example 1 is assembled. 
         FIG.  10    is a diagram showing a state in which the case of the battery pack according to example 1 is assembled. 
         FIG.  11    is a diagram showing a state before a case of a battery pack according to an example 2 is assembled. 
         FIG.  12    is a diagram showing a state in which the case of the battery pack according to example 2 is assembled. 
         FIG.  13    is a diagram showing a state before a case of a battery pack according to an example 3 is assembled. 
         FIG.  14    is a diagram showing a state in which the case of the battery pack according to example 3 is assembled. 
         FIG.  15    is a diagram showing a state before a case of a battery pack according to an example 4 is assembled. 
         FIG.  16    is a diagram showing a state in which the case of the battery pack according to example 4 is assembled. 
         FIG.  17    is a diagram showing a state before a case of a battery pack according to an example 5 is assembled. 
         FIG.  18    is a diagram showing a state in which the case of the battery pack according to example 5 is assembled. 
         FIG.  19    is a diagram showing a state before a case of a battery pack according to an example 6 is assembled. 
         FIG.  20    is a diagram showing a state in which the case of the battery pack according to example 6 is assembled. 
         FIG.  21    is a diagram showing a state before a case of a battery pack according to an example 7 is assembled. 
         FIG.  22    is a diagram showing a state in which the case of the battery pack according to example 7 is assembled. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, embodiments of the present technology will be described. It should be noted that the same or corresponding portions are denoted by the same reference characters, and may not be described repeatedly. 
     It should be noted that in the embodiments described below, when reference is made to number, amount, and the like, the scope of the present technology is not necessarily limited to the number, amount, and the like unless otherwise stated particularly. Further, in the embodiments described below, each component is not necessarily essential to the present technology unless otherwise stated particularly. Further, the present technology is not limited to one that necessarily exhibits all the functions and effects stated in the present embodiment. 
     It should be noted that in the present specification, the terms “comprise”, “include”, and “have” are open-end terms. That is, when a certain configuration is included, a configuration other than the foregoing configuration may or may not be included. 
     Also, in the present specification, when geometric terms and terms representing positional/directional relations are used, for example, when terms such as “parallel”, “orthogonal”, “obliquely at 45°”, “coaxial”, and “along” are used, these terms permit manufacturing errors or slight fluctuations. In the present specification, when terms representing relative positional relations such as “upper side” and “lower side” are used, each of these terms is used to indicate a relative positional relation in one state, and the relative positional relation may be reversed or turned at any angle in accordance with an installation direction of each mechanism (for example, the entire mechanism is reversed upside down). 
     In the present specification, the term “battery” is not limited to a lithium ion battery, and may include another battery such as a nickel-metal hydride battery. In the present specification, the term “electrode” may collectively represent a positive electrode and a negative electrode. Further, the term “electrode plate” may collectively represent a positive electrode plate and a negative electrode plate. 
       FIG.  1    is an exploded perspective view showing a configuration of a battery pack  1 . Battery pack  1  includes a plurality of battery cells  100 , a case  200 , heat conducting members  300 , and a cooling plate  400 . 
     The plurality of battery cells  100  are stacked along a Y axis direction (first direction). Case  200  accommodates the plurality of battery cells  100 . Case  200  may be a casted part (die cast material) composed of a metal material such as aluminum or magnesium, or may be a press-molded part composed of a carbon-containing material. Case  200  is not limited to the above configuration, and may be any case as long as predetermined characteristics such as strength, heat radiation, and thermal conductivity are satisfied. For example, in some cases, case  200  may be composed of a resin. 
     Each of heat conducting members  300  is provided between battery cell  100  and case  200 , and promotes transfer of heat generated in battery cell  100  to case  200 . 
     Cooling plate  400  (heat radiation promoting mechanism) promotes radiation of heat from case  200 . As an example, cooling plate  400  is a water-cooling type cooling unit including a flow path through which coolant is to flow; however, the heat radiation promoting mechanism is not limited to such a water-cooling type cooling device, and a forced air cooling type heat radiation promoting mechanism or a natural heat radiation type heat radiation promoting mechanism (such as a heat radiation fin) may be used, for example. Moreover, case  200  and cooling plate  400  may be integrated with each other, or cooling plate  400  may be provided inside case  200 . The radiation of heat from battery cell  100  is not limited to indirect radiation of heat via case  200 , and may be direct radiation of heat from battery cell  100 . 
       FIG.  2    is a diagram showing battery cell  100 . As shown in  FIG.  2   , battery cell  100  includes electrode terminals  110  and a housing  120 . Electrode terminals  110  include a positive electrode terminal  111  and a negative electrode terminal  112 . Electrode terminals  110  are formed on housing  120 . An electrode assembly (not shown) and an electrolyte solution (not shown) are accommodated in housing  120 . 
     Housing  120  is formed to have a flat rectangular parallelepiped shape. Housing  120  has an upper surface  121  and a bottom surface  122  each extending along an X-Y plane. Upper surface  121  and bottom surface  122  face each other along a Z axis direction (second direction). 
     As an example, battery cell  100  is a lithium ion battery. Battery cell  100  may be another battery such as a nickel-metal hydride battery. Moreover, the battery cell according to the present technology is not limited to the prismatic battery cell, and may be, for example, a cylindrical battery cell. 
       FIG.  3    is a diagram showing a schematic shape of a case  200 A according to a comparative example  1 , and  FIG.  4    is a cross sectional view showing a shape of a portion IV in  FIG.  3   . 
     As shown in  FIG.  3   , case  200 A includes a first member  210 A and a second member  220 A that forms an inner space  230 A together with first member  210 A. 
     As shown in  FIG.  4   , a sealing portion  240 A is provided to seal a joining portion between first member  210 A and second member  220 A. First member  210 A has a first portion  211 A in abutment with sealing portion  240 A, and second member  220 A has a second portion  221 A facing first portion  211 A with sealing portion  240 A being interposed therebetween. 
     Sealing portion  240 A is provided along the X-Y plane orthogonal to the Z axis direction. When a pressure of an inner space  230 A of case  200 A is increased, forces in detachment directions (directions of arrows A in  FIG.  4   ) act on sealing portion  240 A sandwiched between first portion  211 A of first member  210 A and second portion  221 A of second member  220 A. 
       FIG.  5    is a diagram showing a schematic shape of a case of a battery pack according to a comparative example  2 , and  FIG.  6    is a cross sectional view showing a shape of a portion VI in  FIG.  5   . 
     Also in comparative example 2 shown in  FIGS.  5  and  6   , a sealing portion  240 A is provided along the X-Y plane orthogonal to the Z axis direction. When a pressure of an inner space  230 A is increased, forces in the detachment directions (directions of arrows A in  FIG.  6   ) act on sealing portion  240 A sandwiched between first portion  211 A of first member  210 A and second portion  221 A of second member  220 A. 
       FIG.  7    is a diagram showing a schematic shape of case  200  of the battery pack according to the present embodiment, and  FIG.  8    is a cross sectional view showing a shape of a portion VIII in  FIG.  5   . 
     As shown in  FIG.  7   , case  200  has an inner space  230  for accommodating the plurality of battery cells  100 . Case  200  includes a first member  210  and a second member  220  that forms inner space  230  together with first member  210 . First member  210  constitutes a cover portion of case  200 , and second member  220  constitutes a bottom portion of case  200 . 
     As shown in  FIG.  8   , a sealing portion  240  is provided to seal a joining portion between first member  210  and second member  220 . First member  210  has a first portion  211  in abutment with sealing portion  240 , and second member  220  has a second portion  221  facing first portion  211  with sealing portion  240  being interposed therebetween. 
     Sealing portion  240  is provided along a side wall portion of case  200 . The side wall portion of case  200  extends in the Z axis direction substantially in parallel with a side surface of battery cell  100 . Sealing portion  240  is provided along the Z axis direction. Sealing portion  240  is provided along the entire periphery of case  200  on the X-Y plane. In this way, inner space  230  of case  200  is sealed. 
     For example, when one of the plurality of battery cells  100  exhibits thermal runaway to emit gas from housing  120 , the pressure of inner space  230  of case  200  is increased. The increased pressure of inner space  230  acts on case  200  as an expansion pressure. On this occasion, forces in shearing directions (directions of arrows A in  FIG.  8   ) act on sealing portion  240  sandwiched between first portion  211  of first member  210  and second portion  221  of second member  220 . 
     In the battery pack according to the present embodiment, when the expansion pressure acts on case  200 , the forces in the shearing directions, rather than the detachment directions, act on sealing portion  240 , with the result that a large strength can be obtained as compared with a case where forces in the detachment directions act on sealing portion  240 . In each of the battery packs according to comparative examples 1 and 2, it is expected to disassemble case  200 A (remove first member  210 A from second member  220 A) after assembling case  200 A, whereas case  200  according to the present embodiment is obtained based on such a change in thinking that it is not necessarily premised that case  200  is disassembled. 
     Each of  FIGS.  9  and  10    is a diagram showing a case  200  according to an example 1.  FIG.  9    shows a state before case  200  is assembled, and  FIG.  10    shows a state in which case  200  is assembled. 
     In example 1 shown in  FIGS.  9  and  10   , first portion  211  of first member  210  is located on the outer side of case  200  with respect to second portion  221  of second member  220 . First portion  211  and second portion  221  extend in parallel with each other. Each of first portion  211  and second portion  221  is formed to extend in the Z axis direction. 
     Each of  FIGS.  11  and  12    is a diagram showing a case  200  according to an example  2 .  FIG.  11    shows a state before case  200  is assembled, and  FIG.  12    shows a state in which case  200  is assembled. 
     Also in example 2 shown in  FIGS.  11  and  12   , as with example  1 , first portion  211  of first member  210  is located on the outer side of case  200  with respect to second portion  221  of second member  220 . First portion  211  is formed to extend in the Z axis direction. Second portion  221  is inclined with respect to the Z axis direction in the direction toward its tip side so as to orient toward the inner side of case  200 . Accordingly, first portion  211  and second portion  221  are separated further away from each other (an interval therebetween is increased) in a direction from the root side of second portion  221  (the bottom portion side of case  200 ) toward the tip side of second portion  221  (the cover portion side of case  200 ). Since second portion  221  is inclined as described above, first member  210  and second member  220  are readily combined with each other. Further, since sealing portion  240  can be received by second portion  221  from the bottom portion side of case  200 , a sealing material can be suppressed from flowing down when combining first member  210  and second member  220  with each other. 
     Each of  FIGS.  13  and  14    is a diagram showing a case  200  according to an example 3.  FIG.  13    shows a state before case  200  is assembled, and  FIG.  14    shows a state in which case  200  is assembled. 
     Also in example 3 shown in  FIGS.  13  and  14   , as with each of examples 1 and 2, first portion  211  of first member  210  is located on the outer side of case  200  with respect to second portion  221  of second member  220 . First portion  211  is inclined with respect to the Z axis direction in the direction toward its tip side so as to orient toward the outer side of case  200 . Second portion  221  is formed to extend in the Z axis direction. Accordingly, first portion  211  and second portion  221  are separated further away from each other (an interval therebetween is increased) in a direction from the root side of first portion  211  (the cover portion side of case  200 ) toward the tip side of first portion  211  (the bottom portion side of case  200 ). Since first portion  211  is inclined as described above, first member  210  and second member  220  are readily combined with each other. Further, in the structure of example 3, the members can be processed more readily than those in the structure of example 2. 
     Each of  FIGS.  15  and  16    is a diagram showing a case  200  according to an example 4.  FIG.  15    shows a state before case  200  is assembled, and  FIG.  16    shows a state in which case  200  is assembled. 
     In example 4 shown in  FIGS.  15  and  16   , first portion  211  of first member  210  is located on the inner side of case  200  with respect to second portion  221  of second member  220 . First portion  211  is formed to extend in the Z axis direction. Second portion  221  is inclined with respect to the Z axis direction in a direction toward its tip side so as to orient toward the outer side of case  200 . Accordingly, first portion  211  and second portion  221  are separated further away from each other (an interval therebetween is increased) in a direction from the root side of second portion  221  (the bottom portion side of case  200 ) toward the tip side of second portion  221  (the cover portion side of case  200 ). Since second portion  221  is inclined as described above, first member  210  and second member  220  are readily combined. Further, since sealing portion  240  can be received by second portion  221  from the bottom portion side of case  200 , the sealing material can be suppressed from flowing down when combining first member  210  and second member  220  with each other. Further, in the structure of example 4, as with the structure of example 3, the members can be processed more readily than those in the structure of example 2. Further, since first portion  211  and second portion  221  are formed to expose the end portion of sealing portion  240  on the cover portion side of case  200 , sealing portion  240  can be recognized from the upper side (cover portion side) of case  200  when combining first member  210  and second member  220  with each other, thereby facilitating positioning. 
     Each of  FIGS.  17  and  18    is a diagram showing a case  200  according to an example  5 .  FIG.  17    shows a state before case  200  is assembled, and  FIG.  18    shows a state in which case  200  is assembled. 
     Also in example 5 shown in  FIGS.  17  and  18   , as with example  4 , first portion  211  of first member  210  is located on the inner side of case  200  with respect to second portion  221  of second member  220 . Second portion  221  of second member  220  is formed to have its tip located in a direction away from the bottom portion of case  200 . Second portion  221  is inclined with respect to the Z axis direction in a direction toward its tip side so as to orient toward the outer side of case  200 . First portion  211  is formed to extend in the Z axis direction. Accordingly, first portion  211  and second portion  221  are separated further away from each other (an interval therebetween is increased) in a direction from the root side of first portion  211  (the cover portion side of case  200 ) toward the tip side of first portion  211  (the bottom portion side of case  200 ). Since second portion  221  is inclined as described above, first member  210  and second member  220  are readily combined with each other. Further, since first portion  211  and second portion  221  are formed to expose the end portion of sealing portion  240  on the cover portion side of case  200 , sealing portion  240  can be recognized from the upper side (the cover portion side) of case  200  when combining first member  210  and second member  220  with each other, thereby facilitating positioning. 
     Each of  FIGS.  19  and  20    is a diagram showing a case  200  according to an example  6 .  FIG.  19    shows a state before case  200  is assembled, and  FIG.  20    shows a state in which case  200  is assembled. 
     Also in example 6 shown in  FIGS.  19  and  20   , as with example 5, second portion  221  of second member  220  is formed to have its tip located in a direction away from the bottom portion of case  200 . Each of first portion  211  and second portion  221  is inclined with respect to the Z axis direction in a direction toward its tip side so as to orient toward the outer side of case  200 . First portion  211  and second portion  221  are closer to each other (an interval therebetween is decreased) in a direction from the root side of each of first portion  211  and second portion  221  (the cover portion side of case  200 ) toward its tip side (the bottom portion side of case  200 ). Since second portion  221  is inclined as described above, sealing portion  240  can be received by second portion  221  from the bottom portion side of case  200 , with the result that a sealing material can be suppressed from flowing down when combining first member  210  and second member  220  with each other. 
     Each of  FIGS.  21  and  22    is a diagram showing a case  200  according to an example 7.  FIG.  21    shows a state before case  200  is assembled, and  FIG.  22    shows a state in which case  200  is assembled. 
     In example 7 shown in  FIGS.  21  and  22   , first portion  211  of first member  210  is located on the inner side of case  200  with respect to second portion  221  of second member  220 . A protrusion  222  is formed on a side wall of second member  220  so as to protrude toward inner space  230 . When first member  210  and second member  220  are combined with each other, the tip of first portion  211  is in abutment with protrusion  222 . 
     As long as sealing characteristics are ensured, the thickness of sealing portion  240  when first member  210  and second member  220  are combined with each other is preferably as small as possible, such as about 10 mm or less. 
     The length of sealing portion  240  in the Z axis direction when first member  210  and second member  220  are combined with each other is appropriately determined in accordance with the characteristics of the sealing material, the size of case  200 , and the like, and is preferably, for example, about 100 mm or less. 
     Sealing portion  240  can be formed using, for example, the following materials. 
     (1) Materials in gel form 
     (a) Sikaflex221 (polyurethane-based) of moisture-curable type [manufactured by sika]
         Chemical resistance: resistant to fresh water, seawater, lime water, drained/waste water, dilute acid, and dilute alkaline solution.   Hardness (CQP023-1/ISO868): ShoreA40   Tensile strength (CQP036-1/ISO37): 1.8 MPa   Elongation at break (CQP036-1/ISO37): 500%   Tear strength (CQP045-1/ISO34): 7 N/mm   Long-term heat resistance temperature (CQP513-1): +90° C.   Short-term heat resistance temperature: about +120° C. for 1 day at maximum; about +140° C. for 1 hour at maximum   Applied temperature range: −40° C. to +90° C.       

     (b) BESIL9339 (silicone-based) of room-temperature-curable type [manufactured by BEGINOR]
         Hardness (GB/T531-2008): ShoreA40   Tensile strength (CQP036-1/ISO37): 2.8 MPa   Elongation at break (GB/T528-2009): 500%   Shear strength (GB/T7124-2008): 2.3 MPa   Applied temperature range: −60° C. to +250° C.       

     (c) DOWSILEA-4700 (silicone-based) of room-temperature-curable type [manufactured by Toray]
         Hardness: JIS Type A19   Tensile strength (CQP036-1/ISO37): 3.7 MPa   Elongation at break (GB/T528-2009): 630%   Applied temperature range: −45 to 150° C.       

     (d) SU-3802 (urethane-based) of room-temperature-curable type [manufactured by SANYU REC].
         Chemical resistance: LLC, engine oil   Hardness: ASTMD2240, TypeA43   Elastic modulus (DMS method): 2.4 MPa   Tensile strength (JISK6301): 1.5 MPa   Elongation at break (JISK6301): 100%       

     (e) MS650 (modified-silane-based) of moisture-curable type [manufactured by Henkel]
         Hardness (ISO868, Durometer A): ShoreA 60     Tensile strength (ISO37): 3.0 MPa   Elongation at break (ISO37): 180%   Shear strength (DINEN1465): 2.0 MPa   Applied temperature range: −40° C. to +90° C.       

     (f) EAE-60HP (epoxy-based) of room-temperature-curable type [manufactured by Henkel]
         Chemical resistance: organic solvent   Hardness (ISO868, Durometer D): 80   Tensile strength (ISO527-2): 35 MPa   Elongation at break (ISO527-3): 9%       

     (2) Reworkable Materials 
     (a) TB3081J (acrylic-based) of UV-curable type [manufactured by ThreeBond]
         Heat resistance and cold resistance   Hardness (3TS-215-01, Durometer A): A27   Elastic modulus (3TS-501-04): 2.1 MPa   Tensile strength (3TS-320-01): 1.8 MPa   Elongation at break (3TS-320-01): 180%   Applied temperature range: −40° C. to +120° C.       

     (b) LoctiteAA5884 (acrylic-based) of UV-curable type [manufactured by Henkel]
         Chemical resistance: oil resistance   Hardness (ISO868, Durometer A): A55-65   Tensile strength (ISO37): 4.0 MPa   Elongation at break (ISO37): 200%   Applied temperature range: −40° C. to +150° C.       

     (c) ACG-576 (acrylic-based) of UV-curable type [manufactured by Sekisui Chemical]
         Chemical resistance: oil resistance   Hardness (Durometer A): 30   Tensile strength (ISO37): 2.1 MPa   Elongation at break (ISO37): 285%       

     According to battery pack  1  of the present embodiment, the size of sealing portion  240  can be reduced to reduce the cost of the material for forming sealing portion  240 , and a fastening member for first member  210  and second member  220  to obtain strength of case  200  can be omitted, with the result that the manufacturing cost of battery pack  1  can be reduced without compromising the sealing characteristics of case  200 . 
     Although the embodiments of the present invention have been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the scope of the present invention being interpreted by the terms of the appended claims. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.