Patent Publication Number: US-2023143046-A1

Title: Secondary battery

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2021-183785, filed on Nov. 11, 2021, the entire contents of which are incorporated herein by reference. 
     FIELD 
     The present disclosure relates to a secondary battery. 
     BACKGROUND 
     Patent Literature 1 discloses a secondary battery comprising a rectangular exterior body in a plan view, an electrode body housed in the exterior body, and a cathode terminal and an anode terminal that are at one or respective two sides of the exterior body, wherein the respective two sides are opposite to each other. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: JP 2005-56815 A 
     SUMMARY 
     Technical Problem 
     When plural secondary batteries are stacked and each terminal thereof is connected, the connection is that the terminals protruding from a rectangular exterior body in a plan view are connected to each other as in Patent Literature 1 to form a wasted space. Thus, improvement in structural efficiency (reduction of the space for the secondary batteries) is desired. 
     In view of the above problem, an object of the present disclosure is to provide a secondary battery having a structure that can reduce a space therefor. 
     Solution to Problem 
     As one measure to solve the above problem, the present application discloses a secondary battery comprising: exterior bodies that look a quadrilateral as a whole in a plan view; an electrode body that is housed in the exterior bodies; cutout parts at respective two sides among sides of the quadrilateral, the two sides being opposite to each other; a cathode terminal disposed in one of the cutout parts; and an anode terminal disposed in another one of the cutout parts. 
     The two cutout parts may be provided at respective corners of the quadrilateral, the corners being opposite to each other. 
     The electrode body, which is housed in the exterior bodies, may be also provided with cutout parts, at least part of each of the cutout parts a resin layer being placed. 
     Effects 
     The secondary battery according to the present disclosure can suppress generation of a wasted space due to protrusion of electrode terminals, and can reduce a space for the secondary battery. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is an external perspective view of a secondary battery  10 ; 
         FIG.  2    is a plan view of the secondary battery  10 ; 
         FIG.  3    is an exploded perspective view of the secondary battery  10 ; 
         FIG.  4    is an external perspective view of an electrode body A; 
         FIG.  5    focuses on a portion of a cutout part B′ in  FIG.  4   ; 
         FIG.  6    is an external perspective view of a secondary battery  30 ; 
         FIG.  7    is an external perspective view of a battery stack  100 ; and 
         FIG.  8    illustrates a conventional secondary battery. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     The present disclosure will be hereinafter described using embodiments. Here, the embodiments to be described are examples. The present disclosure is not limited to these embodiments. 
     1. Secondary Battery 
       FIGS.  1  to  5    illustrate a secondary battery  10  according to one embodiment.  FIG.  1    is an external perspective view,  FIG.  2    is a plan view (looking in the direction pointed by the arrow II in  FIG.  1   ),  FIG.  3    is an exploded perspective view,  FIG.  4    is an external perspective view showing an electrode body A that is a layered body to be placed inside exterior bodies of the secondary battery  10 , and  FIG.  5    is an enlarged view focusing on a portion where a cutout part B′ is formed in  FIG.  4   . 
     As seen from  FIGS.  1  to  5   , the secondary battery  10  according to the present embodiment is a quadrilateral as a whole in a plan view (from the viewpoint of  FIG.  2   ) which is provided with cutout parts B at respective two corners that are opposite to each other. Here, “a quadrilateral as a whole” means that: it can be acknowledged that a quadrilateral would be formed if no cutout parts B were cut out; and the quadrilateral is not necessary to be a quadrilateral in a strict sense, but may have roughness with some necessary member and has a form that can be regarded as a quadrilateral as a whole. 
     The secondary battery  10  has a first exterior body  11 , a second exterior body  12 , a cathode current collector layer  13 , a cathode active material layer  14 , a separator layer  15 , an anode active material layer  16 , an anode current collector layer  17 , a cathode terminal  18 , and an anode terminal  19 . The secondary battery  10  is formed by layering these layers. The secondary battery  10  is also provided with resin layers  20  (refer to  FIG.  5   ). The structure of each member and the relationship thereof will be hereinafter described. 
     Here, a layered body portion formed by the cathode current collector layer  13 , the cathode active material layer  14 , the separator layer  15 , the anode active material layer  16 , and the anode current collector layer  17  may be expressed as “electrode body A”. 
     1.1. First Exterior Body and Second Exterior Body 
     The first exterior body  11  and the second exterior body  12  are each a sheet member of an exterior material. The first exterior body  11  and the second exterior body  12  are each formed by joining circumferential end portions thereof as including the electrode body A, a part of the cathode terminal  18 , and a part of the anode terminal  19  therebetween. Therefore, these exterior bodies form a bag. The electrode body A is included and sealed in these exterior bodies. 
     The first exterior body  11  has a depressed part  11   a  including an opening in one face thereof (the opening is invisible in  FIG.  3    because being in the face on the bottom side in the sheet, and thus, entering a blind spot). The electrode body A is housed inside this depressed part  11   a . The circumferential edge of the depressed part  11   a  is provided with a joined part  11   b , so that the joined part  11   b  protrudes from the edge. This joined part  11   b  and a circumferential end portion of a face of the second exterior body  12  are joined to each other. In the present embodiment, the first exterior body  11  is a quadrilateral as a whole in a plan view, and in order to form the cutout parts B, is provided with cutout parts  11   c  at respective two corners that are opposite to each other. 
     The second exterior body  12  is in the form of a sheet, and is a quadrilateral member as a whole in a plan view. In order to form the cutout parts B, the second exterior body  12  is also provided with cutout parts  12   c  at respective two corners that are opposite to each other. 
     As described above, the circumferential end portion of a face among the faces of the second exterior body  12  which faces the first exterior body  11  is superposed on and joined to the joined part  11   b  of the first exterior body  11 . 
     In the present embodiment, the first exterior body  11  and the second exterior body  12  are each formed of a laminate sheet. Here, the laminate sheet is a sheet having a metal layer and a sealant layer. Examples of a metal etc. used for the laminate sheet include aluminum and stainless steel. Examples of the material used for the sealant layer include polypropylene, polyethylene, polystyrene and polyvinyl chloride which are thermoplastic resins. 
     The way of joining the first exterior body  11  and the second exterior body  12  to each other, that is, joining the laminate sheets is not particularly limited, but any known way may be used therefor. Specific examples of the way include: ways of welding (e.g., hot plate welding, ultrasonic welding, vibration welding, and laser welding) the sealant layers of the laminate sheets to each other; and adhering with an adhesive. 
     1.2. Cathode Current Collector Layer 
     The cathode current collector layer  13  is a layer included in the electrode body A, and is layered on the cathode active material layer  14  to collect a current from the cathode active material layer  14 . The cathode current collector layer  13  is in the form of quadrilateral foil as a whole in a plan view, and in order to form the cutout parts B, is provided with cutout parts  13   c  at respective two corners that are opposite to each other. 
     A cathode tab  13   a  to which the cathode terminal  18  is to be connected is arranged inside one of the two cutout parts  13   c  of the cathode current collector layer  13 . The cathode tab  13   a  is a part to electrically connect the cathode current collector layer  13  and the cathode terminal  18 . 
     Examples of the material constituting the cathode current collector layer  13  include stainless steel, aluminum, nickel, iron, titanium, and carbon. 
     1.3. Cathode Active Material Layer 
     The cathode active material layer  14  is a layer included in the electrode body A. The cathode current collector layer  13  is layered on one face of the cathode active material layer  14 ; and the separator layer  15  is layered on the other face of the cathode active material layer  14 . The cathode active material layer  14  is in the form of a quadrilateral sheet as a whole in a plan view, and in order to form the cutout parts B, is provided with cutout parts  14   c  at respective two corners that are opposite to each other. 
     The cathode active material layer  14  is a layer containing a cathode active material, and may further contain at least one of a solid electrolyte material, a conductive material, and a binder, if necessary. 
     Any known active material may be used as the cathode active material. Examples of the cathode active material include cobalt-based (such as LiCoO 2 ), nickel-based (such as LiNiO 2 ), manganese-based (such as LiMn 2 O 4  and Li 2 Mn 2 O 3 ), iron phosphate-based (such as LiFePO 4  and Li 2 FeP 2 O 7 ), NCA-based (such as a compound of nickel, cobalt and aluminum), and NMC-based (such as a compound of nickel, manganese and cobalt) active materials, and a more specific example thereof is LiNi 1/3 Co 1/3 Mn 1/3 O 2 . 
     The surface of the cathode active material may be coated with an oxide layer such as a lithium niobate layer, a lithium titanate layer and a lithium phosphate layer. 
     In some embodiments, the solid electrolyte is an inorganic solid electrolyte because the inorganic solid electrolyte has high ionic conductivity and heat resistance, compared with the organic polymer electrolyte. Examples of the inorganic solid electrolyte include sulfide solid electrolytes and oxide solid electrolytes. 
     Examples of sulfide solid electrolyte materials having Li-ion conductivity include Li 2 S—P 2 S 5 , Li 2 S—P 2 S 5 —LiI, Li 2 S—P 2 S 5 —Li 2 O, Li 2 S—P 2 S 5 —Li 2 O—LiI, Li 2 S—SiS 2 , Li 2 S—SiS 2 —LiI, Li 2 S—SiS 2 —LiBr, Li 2 S—SiS 2 —LiCl, Li 2 S—SiS 2 —B 2 S 3 —LiI, Li 2 S—SiS 2 —P 2 S 5 —LiI, Li 2 S—B 2 S 3 , Li 2 S—P 2 S 5 -ZmSn (m and n are positive numbers, and Z is any of Ge, Zn and Ga), Li 2 S—GeS 2 , Li 2 S—SiS 2 —Li 3 PO 4  and Li 2 S—SiS 2 -Li x MO y  (x and y are positive numbers, and M is any of P, Si, Ge, B, Al, Ga and In). The expression “Li 2 S—P 2 S 5 ” means any sulfide solid electrolyte material made with a raw material composition containing Li 2 S and P 2 S 5 . The same is applied to the other expressions. 
     Examples of oxide solid electrolyte materials having Li-ion conductivity include compounds having a NASICON-type structure. Examples of compounds having a NASICON-type structure include compounds represented by the general formula Li 1+x Al x Ge 2-x (PO 4 ) 3  (0≤x≤2) (LAGP), and compounds represented by the general formula Li 1+x Al x Ti 2-x (PO 4 ) 3  (0≤x≤2) (LATP). Other examples of the oxide solid electrolyte materials include LiLaTiO (such as Li 0.34 La 0.51 TiO 3 ), LiPON (such as Li 2.9 PO 3.3 N 0.46 ) and LiLaZrO (such as Li 7 La 3 Zr 2 O 12 ). 
     The binder is not particularly limited as long as being chemically and electrically stable. Examples of the binder include fluorine-based binders such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE), rubber-based binders such as styrene-butadiene rubber (SBR), olefinic binders such as polypropylene (PP) and polyethylene (PE), and cellulose-based binders such as carboxymethyl cellulose (CMC). 
     As the conductive material, a carbon material such as acetylene black (AB), Ketjen black, or carbon fiber, or a metal material such as nickel, aluminum and stainless steel may be used. 
     The content of each component in the cathode active material layer  14  may be the same as a conventional one. In some embodiments, the cathode active material layer  14  has a thickness of, for example, 0.1 μm to 1 mm, or a thickness of 1 μm to 150 μm. 
     1.4. Separator Layer 
     The separator layer (solid electrolyte layer)  15  is a layer formed by containing a solid electrolyte material as being placed between the cathode active material layer  14  and the anode active material layer  16 . The separator layer  15  contains at least a solid electrolyte material. The solid electrolyte material may be considered in the same manner as that described for the cathode active material layer  14 . 
     The separator layer  15  is a layer included in the electrode body A, is in the form of a quadrilateral sheet as a whole in a plan view, and in order to form the cutout parts B, is provided with cutout parts  15   c  at respective two corners that are opposite to each other. 
     1.5. Anode Active Material Layer 
     The anode active material layer  16  is a layer included in the electrode body A and containing at least an anode active material. The anode active material layer  16  may contain a binder, a conductive material, and a solid electrolyte material, if necessary. The binder, the conductive material, and the solid electrolyte material may be considered in the same manner as those for the cathode active material layer  14 . 
     The anode active material is not particularly limited. When a lithium ion battery is formed, examples of the anode active material include carbon materials such as graphite and hard carbon, various oxides such as lithium titanate, Si and Si alloys, and metallic lithium and lithium alloys. 
     The anode active material layer  16  is in the form of a quadrilateral sheet as a whole in a plan view. The separator layer  15  is layered on one face of the anode active material layer  16 ; and the anode current collector layer  17  is layered on the other face of the anode active material layer  16 . In order to form the cutout parts B, the anode active material layer  16  is provided with cutout parts  16   c  at respective two corners that are opposite to each other. 
     The content of each component in the anode active material layer  16  may be the same as a conventional one. In some embodiments, the anode active material layer  16  has a thickness of, for example, 0.1 μm to 1 mm, or a thickness of 1 μm to 150 μm. 
     1.6. Anode Current Collector Layer 
     The anode current collector layer  17  is a layer included in the electrode body A, and is layered on the anode active material layer  16  to collect a current from the anode active material layer  16 . The anode current collector layer  17  is in the form of quadrilateral foil as a whole in a plan view, and in order to form the cutout parts B, is provided with cutout parts  17   c  at respective two corners that are opposite to each other. 
     An anode tab  17   a  to which the anode terminal  19  is to be connected is arranged inside one of the two cutout parts  17   c  of the anode current collector layer  17 . The anode tab  17   a  is a part to electrically connect the anode current collector layer  17  and the anode terminal  19 . Here, as seen from  FIGS.  1  to  3   , in the electrode body A, the anode tab  17   a  is arranged in the cutout part B on the opposite side of the cutout part B where the cathode tab  13   a  of the cathode current collector layer  13  is arranged, among the two cutout parts  17   c.    
     Examples of the material constituting the anode current collector layer  17  include stainless steel, copper, nickel, and carbon. 
     1.7. Cathode Terminal and Anode Terminal 
     The cathode terminal  18  and the anode terminal  19  are electroconductive members, and are to be terminals for electrically connecting respective electrodes to the outside. Therefore, one end of the cathode terminal  18  is electrically connected to the cathode tab  13   a , and the other end thereof penetrates a joined portion of the first exterior body  11  and the second exterior body  12  to be exposed to the outside. At this time, the cathode terminal  18  is placed in one of the two cutout parts B of the secondary battery  10 . 
     One end of the anode terminal  19  is electrically connected to the anode tab  17   a , and the other end thereof penetrates a joined portion of the first exterior body  11  and the second exterior body  12  to be exposed to the outside. At this time, the anode terminal  19  is placed in the other one of the two cutout parts B of the secondary battery  10 , where the cathode terminal  18  is not placed. 
     1.8. Resin Layers 
     As shown in  FIG.  5   , the resin layer  20  is a resin layer layered on a face that appeared in each of the cutout parts B′ formed by layering the cutout parts ( 13   c ,  14   c ,  15   c ,  16   c ,  17   c ) provided in the respective layers in the electrode body A. This resin layer  20  can prevent short-circuiting. Accordingly, an electrical insulating material may be applied as the material constituting the resin layer  20 , and examples thereof include urethane acrylate resins, epoxy resins, and olefin resins. Any of various curable resins or any of various thermoplastic resins can be used. The curable resin may be a thermosetting resin, a photocurable resin (e.g., UV curable resin) or an electron beam curable resin. The resin layer may be formed from one or plural resin(s). 
     The area the placed resin layer  20  has is not particularly limited. The resin layer  20  may be placed only on part of the face that appeared in the cutout part B′, or may be placed on the entire face, as long as short-circuiting can be prevented. The resin layer  20  like this can be formed by applying, onto the face, a resin before curing, and curing the resin by an appropriate way. 
     1.9. Another Embodiment 
       FIG.  6    is an external perspective view of a secondary battery  30  according to another embodiment. In this embodiment, the secondary battery  30  in the form of a quadrilateral as a whole in a plan view is different from the secondary battery  10  in that the cutout parts B are not provided at corners, but at the respective centers of sides that are opposite to each other. Such a secondary battery also exerts effect as the secondary battery according to the present disclosure. 
     2. Stack of Secondary Batteries 
     As shown in  FIG.  7   , a stack of secondary batteries  100  can be obtained by stacking the plural secondary batteries  10  each as unit cells. At this time, as shown in  FIG.  7   , the secondary batteries can be connected in series by: disposing the secondary batteries  10 , so that the electrodes are different from each other between the facing electrode terminals (cathode and anode terminals) of every two secondary batteries  10  that are adjacent to each other in the stacking direction; and connecting the facing terminals to each other. 
     The secondary batteries can be connected in parallel by: disposing the secondary batteries  10 , so that the electrodes of the facing terminals of every two secondary batteries  10  that are adjacent to each other are the same; and connecting the facing terminals to each other. 
     The secondary battery  30  may be also considered in the same manner. 
     3. Effect etc. 
     The secondary battery according to the present disclosure can suppress generation of a wasted space because, as well understood from, for example,  FIG.  2   , all or most of the cathode terminal  18  and the anode terminal  19  can be housed inside the cutout parts B, and thus, the secondary battery has no protruding portions of the terminals only. For example, as a conventional secondary battery shown in  FIG.  8   , the protruding electrode terminals make it difficult to use the spaces indicated by the dotted lines, and as a result, the spaces adjacent to the electrode terminals are also for the electrode terminals substantially. Accordingly, the shape and size of each of the cutout parts B are not particularly limited, but in some embodiments are made, so that all or most of the cathode terminal and the anode terminal can be housed inside the cutout parts B in a plan view. 
     In this way, the secondary battery according to the present disclosure can suppress generation of a wasted space, can reduce the proportion of the secondary battery in a device, and can realize an efficient arrangement in structure. 
     Arranging the two cutout parts at such positions that these cutout parts are symmetrical in a plan view (point-symmetrical with respect to the center of the quadrilateral in the secondary battery  10 , and line-symmetrical with respect to a center line of the quadrilateral in the secondary battery  30 ) can suppress an unstable reaction (deviation) of the electrodes. 
     In view of the external appearance of a secondary battery, the above effect is exerted even when only exterior bodies are provided with cutout parts corresponding to the cutout parts B but an electrode body is not provided therewith. However, providing the electrode body A to be housed in the exterior bodies with the cutout parts B′ corresponding to the cutout parts B as well makes the shapes inside the exterior bodies and the outer shape of the electrode body similar, which can make the proportion of the electrode body in the space inside the exterior bodies larger, can reduce a wasted space, and can make the space efficiently utilized. Therefore, providing the electrode body with the cutout parts B′ can further suppress generation of a wasted space in the secondary battery, can reduce the proportion of the secondary battery in a device, and can realize an efficient arrangement in structure. 
     REFERENCE SIGNS LIST 
     
         
         
           
               10  secondary battery 
               11  exterior body (first exterior body) 
               12  exterior body (second exterior body) 
               13  cathode current collector layer 
               13   a  cathode tab 
               13   c  cutout part 
               14  cathode active material layer 
               14   c  cutout part 
               15  separator layer (solid electrolyte layer) 
               15   c  cutout part 
               16  anode active material layer 
               16   c  cutout part 
               17  anode current collector layer 
               17   c  cutout part 
               18  cathode terminal 
               19  anode terminal 
               20  resin layer