Patent Publication Number: US-2023147419-A1

Title: All-solid-state battery

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to Japanese Patent Application No. 2021-184117 filed on Nov. 11, 2021, incorporated herein by reference in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to an all-solid-state battery. 
     2. Description of Related Art 
     Japanese Unexamined Patent Application Publication No. 2017-220447 (JP 2017-220447 A) discloses a structure in which a side surface of an electrode laminate is sealed with a cured resin, and Japanese Unexamined Patent Application Publication No. 2021-057321 (JP 2021-057321 A) discloses a technology in which an insulating layer is disposed at an anode end portion. 
     SUMMARY 
     When the cured resin is disposed so as to cover the side surface of the electrode laminate as in JP 2017-220447 A, the electrode laminate can be fixed. However, when such an electrode laminate is sealed with an outer encasement member such as a laminate sheet or the like, the cured resin may damage the outer encasement member by perforating or the like, resulting in reduction of structural reliability (i.e., that a battery has structural stability in order to appropriately exhibit functions of the battery). 
     In view of the above related art, the present disclosure provides an all-solid-state battery of which the structural reliability can be improved. 
     The present application is an all-solid-state battery, including an electrode body that is provided with a laminate including an anode current collector layer, an anode composite material layer, a solid electrolyte layer, a cathode composite material layer, and a cathode current collector layer, an outer encasement member that envelops the electrode body, and a protective member with electrically insulating properties that is disposed on a side surface of the laminate. The protective member has a groove extending along a direction in which a surface of the laminate extends. 
     In the all-solid-state battery, a plurality of the grooves may be arrayed in a laminating direction of the laminate. 
     In the all-solid-state battery, an elastic modulus of the protective member may be 1 MPa or more and 500 MPa or less. 
     In the all-solid-state battery, at least one of the grooves may be located at a position that is located away by a predetermined distance in the laminating direction from one of both end portions of the protective member in the laminating direction. 
     In the all-solid-state battery, an external corner portion at the end portion of the protective member in the laminating direction of the laminate may be provided with an inclined surface or a curved surface. 
     In the all-solid-state battery, the protective member may include a first end portion in a width direction of the protective member and a second end portion in the width direction, the external corner portion is located on the second end portion, the first end portion is disposed on a side of the protective member that is disposed on the side surface of the laminate, and the second end portion is disposed on a side of the protective member that is opposite from the first end portion. 
     In the all-solid-state battery, the external corner portion may be located at a position in contact with the outer encasement member. 
     According to the all-solid-state battery of the present disclosure, the protective member disposed on the side surface of the laminate can suppress trouble from occurring in the outer encasement member, and improve structural reliability. This is because the protective member is configured with high conforming properties, so that the protective member is deformed when an external force is applied to the protective member or when the protective member comes into contact with the outer encasement member, and the force is absorbed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Features, advantages, and technical and industrial significance of exemplary embodiments of the disclosure will be described below with reference to the accompanying drawings, in which like signs denote like elements, and wherein: 
         FIG.  1    is an external perspective view of an all-solid-state battery  10 ; 
         FIG.  2    is a plan view of the all-solid-state battery  10 ; 
         FIG.  3    is a disassembled perspective view of the all-solid-state battery  10 ; 
         FIG.  4    is an external perspective view of an electrode body  12 ; 
         FIG.  5    is a sectional view of the electrode body  12  taken along a line indicated by V-V in  FIG.  4   ; 
         FIG.  6    is a cross-sectional view of the electrode body  12  taken along a line indicated by VI-VI in  FIG.  4   ; 
         FIG.  7    is an enlarged view of part of  FIG.  6   ; 
         FIG.  8    is a diagram illustrating an embodiment in which a laminate A is repeatedly laminated; 
         FIG.  9    is a diagram illustrating a form of a protective member in Comparative Example 1; 
         FIG.  10    is a diagram illustrating a form of a protective member in Example 1; 
         FIG.  11    is a diagram illustrating a form of a protective member in Example 2; and 
         FIG.  12    is a diagram illustrating a tear in an outer encasement member in Comparative Example 1. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     1. All-Solid-State Battery 
       FIGS.  1  to  3    are diagrams illustrating an all-solid-state battery  10  according to an embodiment.  FIG.  1    is an external perspective view,  FIG.  2    is a plan view (as viewed from a direction of arrow II in  FIG.  1   ), and  FIG.  3    is a disassembled perspective view. Further,  FIG.  4    is an external perspective view illustrating an electrode body  12  disposed inside an outer encasement member  11  of the all-solid-state battery  10 ,  FIG.  5    is a sectional view of the electrode body  12  taken along a line indicated by V-V in  FIG.  4   , and  FIG.  6    is a cross-sectional view of the electrode body  12  taken along a line indicated by VI-VI in  FIG.  4   . 
     As can be seen from  FIGS.  1  to  6   , the all-solid-state battery  10  according to the present embodiment has the outer encasement member  11 , the electrode body  12 , an anode terminal  30 , and a cathode terminal  31 . The electrode body  12  is enveloped by the outer encasement member  11 , and each of the anode terminal  30  and the cathode terminal  31  is disposed so that one end thereof is connected to the electrode body  12  and the other end protrudes from the outer encasement member  11 . 
     The electrode body  12  has anode current collector layers  13 , anode composite material layers  14 , separator layers  15 , cathode composite material layers  16 , a cathode current collector layer  17 , insulating members  18 , and protective members  20 . In the present embodiment, the anode current collector layer  13 , the anode composite material layer  14 , the separator layer  15 , the cathode composite material layer  16 , the cathode current collector layer  17 , the cathode composite material layer  16 , the separator layer  15 , the anode composite material layer  14 , and the anode current collector layer  13  are laminated in this order (may be referred to as “laminate A”). The insulating members  18  are disposed on side surfaces of the laminate A, on sides where the anode terminal  30  and the cathode terminal  31  are disposed, and the protective members  20  are disposed on other side surfaces. 
     Each of the configurations, and relations thereof, will be described below. 
     Note that in each layer making up the laminate A, and in the laminate A, the broad surfaces that are layered will be referred to as “surfaces” (hence, each layer and the laminate A have two surfaces (front and back)), and faces that make up a thickness spanning between these two surfaces will be referred to as “side surfaces” (hence, in a case of a shape that is a square in plan view, there will be four side surfaces). 
     1.1. Outer Encasement Member 
     In the present embodiment, the outer encasement member  11  is made up of a sheet-like member, and in the present form, the outer encasement member  11  includes a first outer encasement member  11   a  and a second outer encasement member  11   b . The electrode body  12 , and part of each of the anode terminal  30  and the cathode terminal  31  are enveloped between the first outer encasement member  11   a  and the second outer encasement member  11   b , and the first outer encasement member  11   a  and outer peripheral end portions of the surfaces of the second outer encasement member  11   b  are joined. Accordingly, the outer encasement member  11  has a pouch shape, and the electrode body  12  is enveloped and sealed therein. 
     The first outer encasement member  11   a  has a square shape in plan view, and has a recess  11   aa  (an opening of the recess  11   aa  is on reverse side of the plane of the drawing in the view in  FIG.  3   , and thus is hidden from sight), and the electrode body  12  is accommodated within the recess  11   aa . A joint portion  11   ab  is provided on an outer peripheral edge of the recess  11   aa , projecting from the edge, and the joint portion  11   ab  and the outer peripheral end portions of the surfaces of the second outer encasement member  11   b  are joined. 
     The second outer encasement member  11   b  is a member that is sheet-like, and has a square shape overall in plan view. As described above, the outer peripheral end portion of a face of the second outer encasement member  11   b  facing the first outer encasement member  11   a  is overlapped with and joined to the joint portion  11   ab  of the first outer encasement member  11 . 
     In the present embodiment, the first outer encasement member  11   a  and the second outer encasement member  11   b  are made of laminate sheets. The term “laminate sheet” here refers to a sheet having a metal layer and a sealant material layer. Examples of metal and so forth used for the laminate sheet include aluminum and stainless steel, and examples of material used for the sealant material layer include polypropylene, polyethylene, polystyrene, polyvinyl chloride, and so forth, which are thermoplastic resins. 
     The method of joining the first outer encasement member  11   a  and the second outer encasement member  11   b , i.e., the method of joining the laminate sheets, is not limited in particular, and known methods can be used. Specific examples thereof include a method of welding the sealant material layers of the laminate sheet to each other (e.g., hot plate welding, ultrasound welding, vibration welding, laser welding, and so forth) and adhesion by an adhesive. 
     1.2. Anode Current Collector Layer 
     The anode current collector layer  13  is laminated on the anode composite material layer  14  and collects electricity from the anode composite material layer  14 . The anode current collector layer  13  is film-like and has a square shape overall in plan view, and is, in the present embodiment, made up of an anode current collector foil  13   a  that is a metal foil, and a carbon layer  13   b  laminated on the anode current collector foil  13   a . The carbon layer  13   b  is laminated on the anode composite material layer  14 , whereby the current collector layer  13  is laminated on the composite material layer  14 . 
     Examples of the material making up the anode current collector foil  13   a  include stainless steel, aluminum, nickel, iron, and titanium, and the carbon layer  13   b  is made of a material containing carbon. 
     Now, the anode current collector foil  13   a  of the anode current collector layer  13  has an extending portion  13   c  of which one end side extends far beyond the other layers making up the laminate A. The extending portion  13   c  enables multiple anode current collector layers  13  to be connected, and the anode terminal  30  to be disposed. 
     1.3. Anode Composite Material Layer 
     The anode current collector layer  13  is laminated on one surface of the anode composite material layer  14 , and the separator layer  15  is laminated on the other surface thereof. The anode composite material layer  14  is sheet-like, and has a square shape overall in plan view. 
     The anode composite material layer  14  is a layer containing an anode active material, and may further contain at least one of a solid electrolyte material, a conductive material, and a binder, as necessary. 
     A known active material may be used as the anode active material. Examples include cobalt-based materials (LiCoO 2 , etc.), nickel-based materials (LiNiO 2 , etc.), manganese-based materials (LiMn 2 O 4 , Li 2 Mn 2 O 3 , etc.), iron-phosphate-based materials (LiFePO 4 , Li 2 FeP 2 O 7 , etc.), NCA-based materials (compounds of nickel, cobalt, and aluminum), NMC-based materials (compounds of nickel, manganese, and cobalt), and so forth. More specific examples include LiNi 1/3 Co 1/3 Mn 1/3 O 2  and so forth. 
     The surface of the anode active material may be coated with an oxide layer such as a lithium niobate layer, a lithium titanate layer, a lithium phosphate layer, or the like. 
     The solid electrolyte is preferably an inorganic solid electrolyte. This is because ionic conductivity thereof is high and heat resistance thereof is excellent, as compared with organic polymer electrolytes. Examples of the inorganic solid electrolyte include sulfide solid electrolytes, oxide solid electrolytes, and so forth. 
     Examples of the sulfide solid electrolyte material having Lithium-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 —Z m S n  (in which m and n are positive numerals, and Z is any of Ge, Zn, and Ga), Li 2 S—GeS 2 , Li 2 S—SiS 2 —Li 3 PO 4 , Li 2 S—SiS 2 -Li x MO y  (in which x and y are positive numerals, and M is any of P, Si, Ge, B, Al, Ga, and In), and so forth. Note that the above notation “Li 2 S—P 2 S 5 ” means a sulfide solid electrolyte material using a raw material composition containing Li 2 S and P 2 S 5 , and this holds true regarding other notations as well. 
     On the other hand, examples of the oxide solid electrolyte material having Lithium-ion conductivity include compounds having a NASICON (an acronym for sodium (Na) Super Ionic Conductor) type structure, and so forth. Examples of compounds having a NASICON type structure include a compound (LAGP) represented by the general formula Li 1+x Al x Ge 2-x (PO 4 ) 3  (0≤x≤2), a compound (LATP) represented by a general formula Li 1+x Al x Ti 2-x (PO 4 ) 3  (0≤x≤2), and so forth. Other examples of the oxide solid electrolyte material include LiLaTiO (e.g., Li 0.34 La 0.51 TiO 3 ), UPON (e.g., Li 2.9 PO 3.3 N 0.46 ), LiLaZrO (e.g., Li 7 La 3 Zr 2 O 12 ), and so forth. 
     The binder is not limited in particular as long as it is chemically and electrically stable, and examples thereof include a fluorine-based binder such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), and so forth, rubber-based binders such as styrene-butadiene rubber (SBR) and so forth, olefin-based binders such as polypropylene (PP), polyethylene (PE), and so forth, and cellulose-based binders such as carboxymethyl cellulose (CMC) and so forth. 
     Examples of the conductive material that can be used include carbon materials such as acetylene black (AB), Ketjen black, carbon fiber, and so forth, and metal materials such as nickel, aluminum, stainless steel, and so forth. 
     Also, the thickness of the anode composite material layer  14  preferably is, for example, no less than 0.1 μm and no more than 1 mm or less, and more preferably no less than 1 μm and no more than 150 μm. 
     1.4. Separator Layer 
     The separator layer (solid electrolyte layer)  15  is sheet-like and has a square shape overall in plan view, is disposed between the anode composite material layer  14  and the cathode composite material layer  16 , and is a layer containing the solid electrolyte material. The separator layer  15  contains at least the solid electrolyte material. The solid electrolyte material can be thought of in the same way as the solid electrolyte material described regarding the anode composite material layer  14 . 
     1.5. Cathode Composite Material Layer 
     The cathode composite material layer  16  is a layer containing at least a cathode active material. The cathode composite material layer  16  may contain a binder, a conductive material, and a solid electrolyte material, as necessary. The binder, the conductive material, and the solid electrolyte material can be thought of in the same way as those in the anode composite material layer  14 . 
     When making up a lithium-ion battery, examples of the cathode active material include carbon materials such as graphite, hard carbon, and so forth, various types of oxides such as lithium titanate and so forth, silicon (Si) and Si alloys, or metallic lithium, lithium alloys and so forth, but are not limited in particular thereto. 
     The cathode composite material layer  16  is sheet-like and has a square shape overall in plan view, with the separator layer  15  laminated on one surface and the cathode current collector layer  17  laminated on the other surface. 
     Also, the thickness of the cathode composite material layer  16  preferably is, for example, no less than 0.1 μm and no more than 1 mm or less, and more preferably no less than 1 μm and no more than 150 μm. 
     1.6. Cathode Current Collector Layer 
     The cathode current collector layer  17  is laminated on the cathode composite material layer  16  and collects electricity from the cathode composite material layer  16 . The cathode current collector layer  17  is film-like and has a square shape overall in plan view, and can be made of, for example, stainless steel, copper, nickel, carbon, or the like. 
     Now, the cathode current collector layer  17  has an extending portion  17   c  of which one end side extends far beyond the other layers making up the laminate A. The extending portion  17   c  enables multiple cathode current collector layers  17  to be connected, and the cathode terminal  31  to be disposed. In the present embodiment, the extending portion  17   c  is configured to extend from the side surface opposite to the extending portions  13   c  of the anode current collector layers  13 , but is not limited to this, and may be configured with the extending portion  17   c  extending from the same side surface as the extending portions  13   c.    
     1.7. Insulating Member 
     The insulating members  18  are members having electrically insulating properties, and are disposed covering the side surfaces of the laminate A where the extending portions  13   c  of the anode current collector layers  13  and the extending portion  17   c  of the cathode current collector layer  17  are present. 
     More specifically, as can be clearly seen from  FIGS.  3  and  5   , one of the insulating members  18  is disposed covering the side surfaces of the anode composite material layers  14 , the separator layers  15 , the cathode composite material layers  16 , and the cathode current collector layer  17 , which are the layers other than the anode current collector layers  13 , on the side surface provided with the extending portions  13   c  of the anode current collector layers  13 . On the other hand, the other of the insulating members  18  is disposed so as to cover the side surfaces of the anode composite material layers  14 , the separator layers  15 , the cathode composite material layers  16 , and the anode current collector layers  13 , which are the layers other than the cathode current collector layer  17 , on the side surface provided with the extending portion  17   c  of the cathode current collector layer  17 . 
     Providing the insulating members  18  enables short-circuiting between layers on the side surfaces where the insulating members  18  are disposed to be suppressed. 
     The material making up the insulating members  18  is not limited in particular, as long as it has electrical insulating properties, and various types of resins, such as for example, thermosetting resins, ultraviolet curing resins, thermoplastic resins, and so forth, can be used. Thermosetting resins are particularly preferable. As a specific example, using the same resin as underfill resin in the semiconductor manufacturing field is preferable. That is to say, an epoxy resin or the like can be used. Alternatively, an amine-based resin or the like can also be used. 
     1.8. Protective Member 
     The protective members  20  are members having electrically insulating properties, and are disposed covering the side surfaces of the laminate A where the extending portions  13   c  of the anode current collector layers  13  and the extending portion  17   c  of the cathode current collector layer  17  are not present.  FIG.  7    is an enlarged view focusing on the vicinity of one of the protective members  20  in  FIG.  6   . 
     More specifically, as can be clearly seen from  FIGS.  3 ,  6 , and  7   , the protective members  20  are disposed so as to cover the side surfaces of the anode current collector layers  13 , the anode composite material layers  14 , the separator layers  15 , the cathode composite material layers  16 , and the cathode current collector layer  17 , on the sides of the laminate A on which the protective members  20  are disposed. 
     In the present embodiment, the protective members  20  are disposed on each of two side surfaces. Note that in the present embodiment, the extending portions  13   c  of the anode current collector layers  13  and the extending portion  17   c  of the cathode current collector layer  17  extend in opposite directions, and accordingly the protective members  20  are disposed on two side surfaces where these extending portions are not present. However, when the extending portions  13   c  of the anode current collector layers  13  and the extending portion  17   c  of the cathode current collector layer  17  extend from the same side surface of the laminate A, the protective members  20  can be disposed on three side surfaces of the laminate A where these extending portions are not present. 
     Also, each of the protective members  20  is provided with a groove  20   a  on a face opposite to the face on the side disposed on the side surface of the laminate A. The groove  20   a  is formed extending following the direction of a longitudinal direction in which the surface of each layer making up the laminate A extends, and when a plurality of grooves  20   a  is provided, the grooves  20   a  are arrayed following the direction in which the layers making up the laminate A are laminated. 
     A width w 0  of the protective members  20  (size in a thickness direction in which each of the layers of the laminate A is laminated, w 0  in  FIG.  7   ) is preferably of a size that covers the entire side surfaces of the laminate A (side surfaces of a laminate B in the example described with reference to  FIG.  8   ), or larger. 
     A length L of the protective members  20  (length in a direction in which the groove  20   a  extends, L in  FIG.  4   ) that is also large enough to cover the entire side surfaces of the laminate A (excluding the extending portions  13   c  and the extending portion  17   c ) is sufficient, and depends on the length of the laminate A. 
     A height of the protective members  20  (size in a direction away from the laminate A, h in  FIG.  7   ) that allows for the groove  20   a  to be provided is sufficient, but preferably is around no less than 1 mm and no more than 3 mm. 
     A width w 1  of the groove  20   a  and a width w 2  of portions other than the groove  20   a  (raised portions) are not limited in particular, as long as being capable of absorbing external force by being deformed by pressing force from the external force as described later, but preferably are no more than 0.5 mm. In particular, when w 1  is larger than 0.5 mm, part of the outer encasement member (laminate sheet)  11  may deeply enter into the groove  20   a  when the outer encasement member  11  is drawn to a vacuum to seal the electrode body  12  therein. 
     A depth d of the groove  20   a  denoted by d in  FIG.  7    is not limited in particular, as long as being capable of absorbing external force by being deformed by pressing force from the external force as described later. However, the depth d preferably is no less than 30% and no more than 80% with respect to the height h of the protective member  20  denoted by h in  FIG.  7    (when the height h differs depending on the position, the height of the smallest position other than an external corner portion  20   b ), and even more preferably is no less than 40% and no more than 60%. 
     Note that a bottom shape of the groove  20   a  is flat, as illustrated in the present embodiment, and does not have to have a curved portion (curvature) at an internal corner portion, but may be configured having a curved portion (curvature) at the internal corner portion. Further, the bottom may be a semicircle or an elliptic arc. 
     The layout of the grooves  20   a  is not limited in particular, and at least one groove  20   a  being provided is sufficient, but preferably at least one groove  20   a  is each provided at positions w 3  from one of both end portions in a width direction of the protective member  20 . Here, w 3  is not limited in particular as long as external force can be absorbed by deforming by pressing force from the external force as described later, but preferably is no greater than 0.5 mm, in the same way as with w 2 . 
     Also, the number of grooves  20   a  is not limited to two, and multiple grooves  20   a  may be provided with spacings therebetween. In doing so, the grooves  20   a  preferably are preferentially provided on both end sides of the protective member  20  in the width direction. This is because external force applied to the protective member  20  is often applied to the end portions. Note however, that the grooves  20   a  may be provided evenly over the entire width direction of the protective member  20 . 
     Out of width-direction end portions of the protective member  20 , corner shapes of the external corner portions  20   b  on a side opposite to a side disposed on the side surface of the laminate A preferably are chamfered shapes, i.e., straight chamfers (also known as “C chamfered shape”) or rounded chamfers (also known as “R chamfered shape”). In other words, the external corner portions  20   b  preferably have inclined surfaces or curved surfaces. Thus, the risk of the external corner portions  20   b  perforating the outer encasement member  11  (laminate sheet) can be further reduced. 
     Note that the external corner portions  20   b  may be formed in the protective member  20  so as to connect the side surface direction and the surface direction of the laminate A. 
     The size of the chamfered shape is not limited in particular, but examples include an arc shape having radius of 0.1 mm in a rounded chamfer. 
     The material that the protective member  20  is made of is not limited in particular, as long as it has electrical insulating properties and can be appropriately elastically deformed as described later, and various types of resins, such as for example, thermosetting resins, ultraviolet curing resins, thermoplastic resins, and so forth, can be used. 
     More specifically, the elastic modulus thereof is preferably 1 MPa or more and 500 MPa or less. With an elastic modulus lower than this, the deformation of the protective member  20  tends to be too great, and the role of protecting the laminate A will be reduced. With an elastic modulus higher than this, the protective member  20  becomes hard with respect to the outer encasement member  11 , and the likelihood of the outer encasement member being torn increases. 
     1.9. Anode Terminal, Cathode Terminal 
     The anode terminal  30  and the cathode terminal  31  are members that have conductivity, and each is a terminal for externally electrically connecting a respective pole. One end of the anode terminal  30  is electrically connected to the extending portions  13   c  of the anode current collector layers  13 , and the other end penetrates the joint portion between the first outer encasement member  11   a  and the second outer encasement member  11   b  and is externally exposed. 
     One end of the cathode terminal  31  is electrically connected to the extending portion  17   c  of the cathode current collector layer  17 , and the other end penetrates the joint portion between the first outer encasement member  11   a  and the second outer encasement member  11   b  and is externally exposed. 
     2. Manufacturing 
     The all-solid-state battery  10  can be manufactured by known methods, except for the protective member  20 . Further, the protective member  20  can be manufactured by pouring a molten material into a mold, and curing by an appropriate method, although not limited to this in particular. Curing of thermoplastic resins can be performed by cooling, and curing of ultraviolet curing resins can be performed by irradiation with ultraviolet rays. 
     As described above, the electrode body  12  is housed inside the recess  11   aa  of the first outer encasement member  11   a , and the joint portion  11   ab  provided on the outer peripheral edge of the recess  11   aa  and the outer peripheral end portions of the surfaces of the second outer encasement member  11   b  are joined. At this time, the inside of the recess  11   aa  is drawn to a vacuum, for deaerating thereof. 
     3. Effects, Etc 
     According to the all-solid-state battery  10  of the present disclosure, the side surfaces of the laminate A are protected by the protective members  20  provided thereto. Also, when the electrode body  12  is sealed in the outer encasement member  11 , the protective members  20  are interposed between the corners of the laminate A and the outer encasement member  11  when drawn to a vacuum as described above, and accordingly the corners of the laminate A do not come into contact with the outer encasement member  11 , whereby tearing of the outer encasement member  11  can be suppressed. 
     At this time, the protective member  20  and the outer encasement member  11  come into contact with each other, and the protective member  20  is pressed by the outer encasement member  11 , but the protective member  20  has the grooves  20   a  formed therein, and accordingly the end portions of the protective members  20  can be deformed as indicated by arrows C in  FIG.  7    to absorb the pressing force and reduce the load on the outer encasement member  11 . This enables tearing of the outer encasement member  11  to be suppressed with more sureness. 
     Moreover, providing chamfered shapes to the external corner portions  20   b  of the protective members  20  enables stress concentration due to contact with the outer encasement member  11  at the external corner portions  20   b  to be reduced, and accordingly tearing of the outer encasement member  11  can be further suppressed. 
     Although an arrangement has been described in the above embodiment in which the cathode composite material layers  16 , the separator layers  15 , the anode composite material layers  14 , and the anode current collector layers  13  are laminated on each of the two surfaces of one cathode current collector layer  17 , to make up the laminate A, this is not limiting, and a configuration may be made in which laminating of the layers is further repeated.  FIG.  8    is an explanatory diagram. 
     In the example in  FIG.  8   , a plurality of the laminates A is repeatedly laminated to form the laminate B, with one protective member  20  disposed on each of the two side surfaces of the laminate B. The same effects as described above can be obtained by such an embodiment as well. Accordingly, in this example, one protective member  20  is disposed to each side surface of the laminate B, spanning the side surfaces of the laminates A that are stacked. 
     4. Examples 
     4.1. Form of Laminate 
     In accordance with the example of the laminate B in  FIG.  8 ,  17    laminates A were repeatedly laminated to obtain a laminate B having a thickness of 2.89 mm. 
     4.2. Form of Outer Encasement Member 
     As an outer encasement member, the above-described outer encasement member  11  was formed of a laminate sheet. The recess of the first outer encasement member was formed by embossing. 
     4.3. Form of Protective Member 
     Protective members according to Examples 1 and 2 and Comparative Example 1 were fabricated and disposed on each of the two side surfaces of the laminate B fabricated above. The protective members were formed of an ultraviolet curing resin.  FIG.  9    illustrates the form of the protective member provided to the test piece according to Comparative Example 1,  FIG.  10    illustrates that according to Example 1, and  FIG.  11    illustrates that according to Example 2. Note that the length of each protective member (length indicated by L in  FIG.  4   ) was 225 mm, and the chamfered shape was an arc shape of a rounded chamfer with a radius of 0.1 mm in size. Further, in each Example, the width of the protective member was 3.0 mm, and thus formed slightly larger than that of the laminate. As can be seen from  FIG.  9   , in Comparative Example 1, the protective member has no groove. As can be seen from  FIG.  10   , in Example 1, two grooves in total were provided, one at each end portion of the protective member in the width direction. 
     As can be seen from  FIG.  11   , in Example 2, four grooves in total were provided, two at each end portion of the protective member in the width direction. 
     4.4. Test Method 
     The test performed was a heat cycle test. In this test, each test piece was subjected to one reciprocation in temperature between −15° C. and 95° C. with uniform temperature change over one cycle, with one cycle being one hour, and this was performed a plurality of times (a plurality of cycles). 
     4.5. Results 
     As a result of the tests, the outer encasement member was torn at the contact portion between the external corner portion of the protective member and the outer encasement member in Comparative Example 1, as illustrated in  FIG.  12   , but in Examples 1 and 2, no tearing of the outer encasement member occurred over the same count of cycles as Comparative Example 1.