Patent Publication Number: US-2021194063-A1

Title: Lithium battery, lithium battery module, and electronic device

Description:
BACKGROUND 
     1. Technical Field 
     The present invention relates to a lithium battery, a lithium battery module, and an electronic device. 
     2. Related Art 
     With the reduction in size and weight of portable electronic devices, lithium batteries, which are secondary batteries with high energy density, have been used. In such a lithium battery, a wound body formed by winding a laminate of a positive electrode material, a separator, and a negative electrode material is accommodated together with an electrolyte in an exterior body formed of laminate or aluminum. In the lithium battery, the exterior body has a characteristic of expanding due to gas generated by repeated charging/discharging. A technique for coping with the expansion of the exterior body is disclosed in JP 2005-5008 A. 
     The mobile terminal disclosed in JP 2005-5008 A includes a means for bring a case lid into contact with a battery pack or biasing the case lid to the battery pack, and has a space for coping with the deformation of the battery pack due to expansion of the inside of the battery pack in at least one of the case lid or a battery housing portion. 
     In the technique disclosed in JP 2005-5008 A, the exterior body of the battery pack and the case lid or the battery housing portion of the electronic device are not fixed. Thus, when the battery pack expands, the constituent members inside the wound body can slide, which can cause a short circuit between the positive electrode and the negative electrode. 
     SUMMARY 
     In order to solve the above problem, a lithium battery module includes: a wound body formed by winding a positive electrode and a negative electrode with a separator interposed between the positive electrode and the negative electrode; an exterior body enclosing the wound body; a protective case housing the exterior body; and a pressing member provided between the exterior body and the protective case, in which the exterior body includes: a first member serving as a base; and a second member provided in a partial region of the exterior body, the second member has lower stretchability than the first member, and the pressing member transfers pressing force from the protective case to the wound body through the second member to fix the wound body by pressing force from the exterior body. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view of an electronic device according to a first embodiment of the present invention; 
         FIG. 2A  is a perspective view of the back side of the electronic device according to the first embodiment of the present invention; 
         FIG. 2B  is a perspective view of a battery lid of the electronic device according to the first embodiment of the present invention; 
         FIG. 3  is an external view of a lithium battery module housing a lithium battery according to the first embodiment of the present invention; 
         FIG. 4A  is a left side view of the lithium battery module according to the first embodiment of the present invention; 
         FIG. 4B  is a sectional view of the lithium battery module according to the first embodiment of the present invention; 
         FIG. 4C  is a plan view of the lithium battery module according to the first embodiment of the present invention; 
         FIG. 5  is a perspective view of a cell of the lithium battery according to the first embodiment of the present invention; 
         FIG. 6  is a structural diagram of a wound body of the lithium battery according to the first embodiment of the present invention; 
         FIG. 7A  is a left side view of an exterior body of the lithium battery module according to the first embodiment of the present invention in an expanding state; 
         FIG. 7B  is a sectional view of the exterior body of the lithium battery module of the first embodiment of the present invention in an expanding state; 
         FIG. 8A  is a perspective view of the back side of an electronic device according to a second embodiment of the present invention; 
         FIG. 8B  is a perspective view of a battery lid of the electronic device according to the second embodiment of the present invention; 
         FIG. 9A  is a left side view of a lithium battery module according to a third embodiment of the present invention; 
         FIG. 9B  is a sectional view of the lithium battery module according to the third embodiment of the present invention; 
         FIG. 10A  is a left side view of an exterior body of the lithium battery module according to the third embodiment of the present invention in an expanding state; 
         FIG. 10B  is a sectional view of the exterior body of the lithium battery module according to the third embodiment of the present invention in an expanding state; 
         FIG. 11  is a left side view of a lithium battery module according to a first modification of the present invention; 
         FIG. 12  is a plan view of a lithium battery module according to a second modification of the present invention; 
         FIG. 13  is a left side view of a lithium battery module of a third modification of the present invention; 
         FIG. 14A  is a left side view of a lithium battery module of a fourth modification of the present invention; 
         FIG. 14B  is a plan view of a lithium battery module according to a fourth modification of the present invention; and 
         FIG. 15  is a plan view of a lithium battery module according to a fifth modification of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, an embodiment of the present invention (referred to as “the present embodiment” in the following) will be described in detail with reference to the drawings. Note that, the drawings are only schematic diagrams for the present embodiment to be sufficiently understood. In the drawings, common or similar constituent elements are denoted by the same reference signs, and duplicate description thereof is omitted. In addition, a lithium battery module housing a lithium battery is simply referred to as a “lithium battery”. The lithium battery includes a lithium ion battery and a lithium polymer battery. 
     First Embodiment 
     (Electronic Device) 
       FIG. 1  is a plan view of the front side of an electronic device that accommodates a lithium battery according to a first embodiment of the present invention.  FIG. 2A  is a perspective view of the back side of the electronic device, and  FIG. 2B  is a perspective view of a battery lid. 
     An electronic device  300  is a handheld terminal including a casing  200  ( FIG. 2A ) and a battery lid  210  ( FIG. 2B ). The casing  200  is provided with a display unit  202 , a keyboard unit  203 , and the like and formed with a battery housing portion  205 . As shown in  FIG. 2A , the battery housing portion  205  houses a lithium battery  100 . The battery lid  210  ( FIG. 2B ) is attached while the lithium battery  100  is housed. The electronic device is not limited to the handheld terminal and may be a mobile terminal, such as a smartphone or a tablet. 
       FIG. 3  is an external view of the lithium battery according to the first embodiment of the present invention. 
     The lithium battery  100  includes a rectangular parallelepiped protective case  70  and a cell  50  accommodated inside the protective case  70 . The Y-Z plane of the protective case  70  is a large-area face, and the X-Y plane is a side face. The cell  50  is a chargeable/dischargeable secondary battery and has a flat shape. In addition, the cell  50  is provided with a positive electrode  5  and a negative electrode  6 . 
       FIGS. 4A, 4B, and 4C  are structural diagrams of the lithium battery according to the first embodiment of the present invention.  FIG. 4A  is a left side face (X-Z plane),  FIG. 4B  is an IVB cross section thereof, and  FIG. 4C  is a plan view of a Y-Z plane. 
     The lithium battery  100  includes, in addition to the cell  50  and the protective case  70 , two projecting portions  75   a  and  75   b  as fixing means or pressing members. The cell  50  includes an exterior body  20  and a wound body  10  ( FIG. 6 ) accommodated in the exterior body  20 . The exterior body  20  includes a main body portion  21  serving as a base and a non-stretchable member  30  provided in a partial region of the main body portion  21 . Here, in the claims, the main body portion  21  is referred to as a first member, and the non-stretchable member  30  is referred to as a second member. That is, the first member is the base portion of the exterior body  20 , and the second member is provided in a partial region of the exterior body  20 . 
     The non-stretchable member  30  is a circular or rectangular plate material and is, for example, a non-conductive material, such as plastic, glass, ceramic (pottery), or the like. The stretchability of the non-stretchable member  30  is lower than that of the material (for example, laminate or aluminum) of the main body portion  21  of the exterior body  20 . 
     A region that is a flat surface  20   a  or  20   b  and is provided with the non-stretchable member  30  is referred to as a non-stretchable region. The non-stretchable region is on each of a pair of flat surfaces  20   a  and  20   b . The non-stretchable region provided on one flat surface  20   a  (a first non-stretchable region) is provided at a position corresponding to (overlapping) the non-stretchable region provided on the other flat surface  20   b  (a second non-stretchable region). At this time, the projecting portion  75   a  is a first fixing means, and the projecting portion  75   b  is a second fixing means. In other words, the non-stretchable members  30  and  30  provided in partial regions of the exterior body  20  are inserted between the projecting portion  75   a  and the wound body  10 , and between the projecting portion  75   b  and the wound body  10 . In addition, each of the projecting portions  75   a  and  75   b  as the pressing members is sandwiched between the non-stretchable member  30  and the protective case  70 . 
     The protective case  70  is a rectangular parallelepiped case made of resin or metal and accommodates the cell  50  therein. One side (for example, the left side) of the protective case  70  is open, and the cell  50  can be inserted thereinto. Note that, a configuration in which the cell  50  is fitted from the outside of a casing  201  as shown in  FIG. 8A , a projecting portion  211   a  as a pressing member is provided on the inner side of the lid as shown in  FIG. 8B , and a battery lid  211  is used as a part of the protective case  70  to fix the cell  50  may be employed. The two projecting portions  75   a  and  75   b  extend on the protective case  70  in such a manner as to face each other. As shown in  FIG. 4C , the projecting portions  75   a  and  75   b  as the pressing members each have a rectangular parallelepiped shape and a smaller size (area) than that of the non-stretchable member  30 . The two projecting portions each may be a columnar projecting portion  76  as shown in  FIG. 12 . 
     The projecting portions  75   a  and  75   b  each are formed to have a predetermined thickness (height). The thickness is enough for the cell  50  ( FIG. 2 ) having the non-stretchable members  30  and  30  formed on both sides to be inserted. The non-stretchable member  30  has an enough thickness to prevent the projecting portions  75   a  and  75   b  as the pressing members from being in contact with the main body portion  21  of the exterior body  20 . In the protective case  70  in which the cell  50  is inserted, an internal space  80  is formed on both sides of the projecting portions  75   a  and  75   b.    
     Note that, the non-stretchable member may have a smaller area than that of the projecting portions  75   a  and  75   b  as the pressing members, like a non-stretchable member  31  in  FIG. 11 . In that case, the non-stretchable member  31  has an enough thickness to prevent the projecting portions  75   a  and  75   b  as the pressing members from being in contact with the main body portion  21  of the exterior body  20 . 
     Note that, a configuration in which the projecting portions  75   a  and  75   b  are not integrated with the protective case  70 , and the non-stretchable members  30  and  30  and corner portions  75   c ,  75   d ,  75   e , and  75   f  of the projecting portions  75   a  and  75   b  are bonded with, for example, an adhesive may be employed. In that case, the cell  50  and the projecting portions  75   a  and  75   b  are integrated, and the projecting portions  75   a  and  75   b  and the protective case  70  are supplementarily supported when the lithium battery is inserted into the protective case  70 . 
       FIG. 5  is a perspective view of the cell  50 , and  FIG. 6  is a perspective view of the wound body  10 . 
     The cell  50  is formed by enclosing the wound body  10  ( FIG. 6 ) inside the flat-shaped exterior body  20  together with an electrolytic solution, such as an organic solvent, a polymer, or the like. The exterior body  20  is sealed while accommodating the wound body  10 . The exterior body  20  is provided with the non-stretchable members  30  and  30  formed at the center portions of the pair of flat surfaces  20   a  and  20   b . In other words, the non-stretchable members  30  and  30  are formed in the central regions of both surfaces (flat surfaces  20   a  and  20   b ) of the exterior body  20 . The main body portion  21  of the exterior body  20  excluding the non-stretchable members  30  and  30  is formed of laminate or aluminum. Laminate or aluminum has higher stretchability than the plastics, glass, or ceramics that forms the non-stretchable members  30  and  30 . 
     The wound body  10  ( FIG. 6 ) is formed by a laminate of a positive electrode tab  7  coated with a positive electrode material  1 , a separator  2 , and a negative electrode tab  8  coated with a negative electrode material  3 . The wound body  10  is formed by winding the laminate into a flat shape. A plate-shaped positive electrode  5  is welded to the positive electrode tab  7 , and a plate-shaped negative electrode  6  is welded to the negative electrode tab  8 . The positive electrode material  1  is, for example, lithium cobalt oxide, and the negative electrode material  3  is, for example, carbon or polyacetylene. 
       FIGS. 7A and 7B  are structural diagrams of the exterior body  20  of the lithium battery according to the first embodiment of the present invention in an expanding state.  FIG. 7A  shows a left side face, and  FIG. 7B  shows a VIIB cross section. 
     In the lithium battery  100 , gas is generated by repeated charging and discharging, and the exterior body  20  expands. The volume of the internal space  80  ( FIG. 4A ) decreases due to the expansion of the exterior body  20  (main body portion  21 ). The space with a reduced volume is referred to as an internal space  81 . In addition, due to its expansion, the exterior body  20  presses the entire surfaces of the projecting portions  75   a  and  75   b  facing each other through the non-stretchable members  30  and  30 . The pressing force as the reaction of this pressing is transmitted to the wound body  10  through the non-stretchable regions (non-stretchable members  30  and  30 ) of the exterior body  20 , and the pressing force from the exterior body  20  fixes the wound body  10 . Thus, the wound body  10  is fixed with the entire surfaces of the projecting portions  75   a  and  75   b  just by the corner portions  75   c ,  75   d ,  75   e , and  75   f  ( FIGS. 4B and 7B ) supplementarily supporting the non-stretchable members  30  and  30  and the projecting portions  75   a  and  75   b . Furthermore, since the non-stretchable members  30  and  30  have a larger contact area than the projecting portions  75   a  and  75   b  and prevent the exterior body  20  from expanding with a wider region than the projecting portions  75   a  and  75   b . Consequently, sliding of the constituent members of the wound body  10  is reduced, and it is possible to prevent a short circuit between the positive electrode and the negative electrode. 
     Second Embodiment 
       FIG. 8A  is a perspective view of the back side of an electronic device according to a second embodiment of the present invention, and  FIG. 8B  is a perspective view of a battery lid. 
     An electronic device  301  is a handheld terminal including a casing  201  ( FIG. 8A ) and a battery lid  211  ( FIG. 8B ) and houses a cell  50  ( FIG. 5 ) as a lithium battery. The electronic device  301  is not limited to the handheld terminal and may be a mobile terminal, such as a smartphone or a tablet. In addition, as in the first embodiment, non-stretchable members  30  and  30  are formed in the center portions of flat surfaces  20   a  and  20   b  of the cell  50 . 
     A battery housing portion  205  of the casing  201  is provided with a projecting portion  201   a  (pressing member) as a fixing means. The battery lid  211  is provided with a projecting portion  211   a  as a fixing means. That is, in the present embodiment, the battery housing portion  205  and the battery lid  211  serve as the protective case  70 . When the battery housing portion  205  is covered with the battery lid  211 , the projecting portion  201   a  and the projecting portion  211   a  face each other. In addition, when the cell  50  is housed inside the battery housing portion  205  and is covered with the battery lid  211 , the projecting portion  211   a  presses the cell  50 . That is, the projecting portion  201   a  and the projecting portion  211   a  apply pressing force to the wound body  10  through the non-stretchable members  30  and  30  that are a part of the exterior body  20  to fix the wound body  10 . As in the first embodiment, the non-stretchable members  30  and  30  are wider than the projecting portion  201   a  and the projecting portion  211   a.    
     Third Embodiment 
     In the lithium battery  100  and the cell  50  in the first and second embodiments, the non-stretchable members  30  and  30  are fixed in such a manner as to be fitted in a partial region of the exterior body  20 . However, the exterior body  20  and the non-stretchable members can be fixed by bonding the non-stretchable members to a partial region of the exterior body  20  from the outside of the exterior body  20 . 
       FIG. 9A  is a left side view of a lithium battery module according to a third embodiment of the present invention, and  FIG. 9B  is an IXB cross section thereof. 
     A lithium battery  103  includes, similarly to the lithium battery  100  of the first embodiment, a protective case  70  and two projecting portions  75   a  and  75   b , but is different in that a cell  56  is included instead of the cell  50 . 
     The cell  56  includes an exterior body  22 , a wound body  10  ( FIG. 6 ) accommodated in the exterior body  22 , and two non-stretchable members  34  and  34 . The non-stretchable members  34  and  34  are bonded to a partial region of a pair of flat surfaces  22   a  and  22   b  of the exterior body  22 . The exterior body  20  ( FIG. 4A ) in the first embodiment includes the main body portion  21  and the non-stretchable members  30  and  30 , and a combination of them encloses the wound body  10 . However, the exterior body  22  in the present embodiment alone encloses the wound body  10 . In the claims, a combination of the exterior body  22  and the two non-stretchable members  34  and  34  is referred to as an exterior body, the exterior body  22  is referred to as a first member serving as a base, and each of the non-stretchable members  34  and  34  is referred to as a second member. That is, the second member is provided in a partial region of the combined exterior body. The thickness of each of the projecting portions  75   a  and  75   b  is enough for the cell  56  formed by the exterior body  22  and the non-stretchable members  34  and  34  to be inserted. 
       FIGS. 10A and 10B  are structural diagrams of the exterior body  22  of the lithium battery according to the third embodiment of the present invention in an expanding state and correspond to  FIGS. 7A and 7B  in the first embodiment. 
     Due to its expansion, the exterior body  22  presses the entire surfaces of the projecting portions  75   a  and  75   b  facing each other through the non-stretchable members  34  and  34 . The pressing force as the reaction of this pressing is transmitted to the wound body  10  through the non-stretchable members  34  and  34  of the exterior body  22 , and the pressing force from the exterior body  22  fixes the wound body  10 . 
     (Modification) 
     In the lithium battery  100  in the first embodiment, the non-stretchable members  30  and  30  are formed on the flat surfaces  20   a  and  20   b  of the exterior body  20 , and the projecting portions  75   a  and  75   b  as fixing means are provided on the inner face of the protective case  70 . The structure of the lithium battery  100  can be modified as follows, for example. Note that, the following modifications are modifications of the first embodiment, but are also applicable to the third embodiment. 
     (1) A lithium battery  101  (left side view) in  FIG. 11  includes a cell  51 , a protective case  71 , and projecting portions  75   a  and  75   b . The cell  51  includes a wound body  10  and an exterior body  25 . Non-stretchable members  31  and  31  are formed at the center portions of the exterior body  25 . Each of the non-stretchable members  31  and  31  is configured in such a manner that the length L 3  in the Z direction is shorter than the length L 2  of each of the projecting portions  75   a  and  75   b  and that the thickness in the X direction is thick. 
     (2) A lithium battery  102  (plan view) in  FIG. 12  includes a protective case  70  and a cell  52  in which two non-stretchable members  32  and  32  are formed on an exterior body  22 . The protective case  70  is formed in such a manner that cylindrical projecting portions  76  and  76  face each other. The non-stretchable members  32  and  32  are circular plate materials and have a larger area than the projecting portions  76  and  76 . 
     (3) A lithium battery  104  in  FIG. 13  includes a protective case  72  and a cell  53  including a wound body  10  and an exterior body  23 . The protective case  72  has an inner face  72   a  on which a projecting portion  75   g  extends. The exterior body  23  is formed with a non-stretchable member  30  in a partial region thereof. An inner face  72   b  of the protective case  72  and a main body portion  21  of the exterior body  23  are in contact with each other, and the non-stretchable member  30  is not inserted between the inner face  72   b  and the region of the exterior body  23  in contact with the inner face  72   b . The projecting portion  75   g  functions as a fixing means for fixing the wound body  10  by the pressing force from the exterior body  23  (non-stretchable member  30 ). 
     (4) A lithium battery  105  in  FIGS. 14A and 14B  includes a cell  54  and a protective case  73 .  FIG. 14A  is a left side view, and  FIG. 14B  is a plan view. The cell  54  is formed by a wound body  10  and an exterior body  23 . The exterior body  23  includes two non-stretchable members  32  and  32  formed on a main body portion  21 . That is, a large part of each non-stretchable members  32  bites into the inner face of the exterior body  23 . Compared with the protective case  70  ( FIG. 4A ) in the first embodiment, the protective case  73  includes projecting portions  75   k  and  751  that extend in such a manner as to face each other, instead of the projecting portions  75   a  and  75   b . Each of the projecting portions  75   k  and  751  is longer in the Z direction than each of the projecting portions  75   a  and  75   b  ( FIG. 4A ), and the length thereof is close to the width W of the cell  54 . The projecting portions  75   k  and  751  are provided at the center portions of the flat surfaces of the exterior body  23  in such a manner as to face each other. The non-stretchable members  32  and  32  are provided on the exterior body  23  of the cell  54  and have a larger surface area than the projecting portions  75   k  and  75   l . The non-stretchable members  32  and  32  are fixed at the center portions of the flat surfaces of the exterior body  23 . 
     According to the lithium battery  105 , the projecting portions  75   k  and  751  and the non-stretchable members  32  and  32  each are longer in the direction of the width W than the non-stretchable member  30 , which reduces displacement in comparison to the lithium battery  100  in the first embodiment ( FIGS. 4A and 4B ). Consequently, sliding of the members of the wound body  10  is reduced, and it is possible to prevent a short circuit between the positive electrode and the negative electrode. 
     (5)  FIG. 15  is a plan view of a fifth modification of the lithium battery module of the present invention when viewed from above the lithium battery module. The left side view is the same as  FIG. 4A . A lithium battery  106  in  FIG. 15  includes a cell  55  and a protective case  74  formed with projecting portions  75   m  and  75   n . The cell  55  is formed by a wound body  10  and an exterior body  24 . The exterior body  24  is formed by integrally forming two non-stretchable members  33  and  33  with a main body portion  21 . The non-stretchable members  33  and  33  are configured to have a longer length in the y direction than the length L 4  of each of the projecting portions  75   m  and  75   n.    
     In addition, the non-stretchable members  33  and  33  and the projecting portions  75   m  and  75   n  of the lithium battery module in  FIG. 15  each are formed in such a manner that the length in the y direction is longer than the length in the z direction. Consequently, the lithium battery module as a whole is also formed in such a manner that the length in the y direction is longer than the length in the z direction, and it is possible to efficiently transmit the pressing force from the exterior body  24  to the wound body through the non-stretchable members  33  and  33  when the exterior body  24  expands and to more easily prevent the wound body from being displaced. 
     As described above, the lithium battery  100  according to each embodiment includes the cell  50 , the protective case  70  that accommodates the cell  50 , and the projecting portions  75   a  and  75   b . The cell  50  includes the wound body  10  and the exterior body  20  that houses the wound body  10 . The wound body  10  is formed by winding the positive electrode tab  7  and the negative electrode tab  8  with the separator  2  interposed therebetween. The exterior body  20  is provided with the non-stretchable region by being partially formed by the non-stretchable member  30 . Here, the non-stretchable member  30  is formed as a part of the exterior body  20 . The projecting portions  75   a  and  75   b  transmit the pressing force from the protective case  70 , which is the reaction of the pressure generated when the exterior body  20  expands, to the wound body  10  through the non-stretchable region to fix the wound body  10  by the pressing force from the exterior body  20 . 
     Consequently, since the exterior body  20  of the cell  50  is supported by the projecting portions  75   a  and  75   b , it is possible to fix the wound body  10  by the pressing force from the protective case  70  although the exterior body  20  expands due to repeated charging/discharging. 
     In the above embodiments, a “lithium battery module” has been simply referred to as a “lithium battery”, but the “lithium battery” in this specification includes a wound body and an exterior body (a main body portion and a non-stretchable member), and the “lithium battery module” includes a wound body, an exterior body (a main body portion and a non-stretchable member), a protective case, and a pressing member (a projecting portion) a fixing means. 
     The embodiments of the present invention have been described, but the scope of the present invention is not limited to the above described embodiments, and includes the scope described in the claims and equivalents thereof.