Patent Publication Number: US-2021194048-A1

Title: Separator and solid-state battery module

Description:
This application is based on and claims the benefit of priority from Japanese Patent Application No. 2019-228059, filed on 18 Dec. 2019, the content of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a separator and a solid-state battery module. 
     Related Art 
     In recent years, a technology relating to a solid-state battery using a solid electrolyte, which has a high energy density and high safety against heat has been proposed. 
     When a solid-state battery is used for applications requiring a large current and a high voltage, such as for a motor drive of an electric vehicle or a hybrid electric vehicle, a solid-state battery module modularized by combining a plurality of solid-state batteries is used. 
     Patent Document 1: Japanese Unexamined Patent Application, Publication No. 2019-102261 
     Patent Document 1 discloses a configuration in which a laminate constituting a solid-state battery is housed in a laminate film as an exterior packaging body and a plurality of the laminated solid-state  batteries are contained to form a battery module. 
     Solid-state battery modules are required to apply sufficient surface pressure to the batteries to hold the battery cell in a cylindrical, rectangular, laminated, or other type of exterior packaging body, and to avoid degradation of input-output characteristics clue to increased inter facial resistance. 
     The technology disclosed in Patent Document 1 sandwiches together a plurality of solid-state batteries between plates to pressurize and fix the plurality of solid-state batteries.
 
However, in the technology disclosed in Patent Document 1, since the solid-state batteries are fixed in close contact with one another, the influence of the expansion of the solid-state batteries on the constituent member and the influence of vibration, and the like are not sufficiently considered.
 
     SUMMARY OF THE INVENTION 
     The present invention has been made in view of the above, and an object of the present invention is to provide a solid-state battery module and a separator which can apply sufficient surface pressure to a solid-state battery cell and are excellent in durability and vibration resistance. 
     The present invention relates to a separator disposed between adjacent solid-state battery cells in a solid-state battery module including a plurality of solid-state battery cells to electrically insulate the adjacent solid-state battery cells of the plurality of  solid-state battery cells, from each other, and the separator includes an elastically deformable elastic member which applies biasing force in a stacking direction of the plurality of solid-state battery cells. 
     The separator preferably forms a gap between the adjacent solid-state battery cells of the plurality of solid-state battery cells. 
     It is preferable that the separator includes a body including the elastic member and a fixing part, that the fixing part is disposed at least above the body, and that the fixing part regulates movement of the body by a predetermined amount or more. 
     Further, the present invention relates to a solid-state battery module including the separator. The plurality of solid-state battery cells includes a laminate including a positive electrode layer, a negative electrode layer, and a solid electrolyte layer present between the positive electrode layer and the negative electrode layer. A laminating direction of the laminate and the stacking direction of the plurality of solid-state battery cells are the same. 
     In the solid-state battery module, the plurality of solid-state battery cells preferably includes a pressing part that applies surface pressure to a surface substantially perpendicular to the laminating direction of the laminate. 
     In the solid-state battery module, it is preferable that bind bars or end plates are disposed at both ends of the plurality of solid-state battery cells, and that an end separator including an elastically deformable elastic member which applies biasing force in the stacking direction of the plurality of solid-state battery cells is disposed between each end of the plurality of solid-state battery  cells and the bind bar or the end plate. 
     According to the present invention, it is possible to provide the solid-state battery module and the separator which can apply sufficient surface pressure to a solid-state battery cell and are excellent in durability and vibration resistance. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view of a solid-state battery module according to an embodiment of the present invention; 
         FIG. 2  is a cross-sectional view of a solid-state battery cell according to the embodiment of the present invention; 
         FIG. 3  is a cross-sectional view of the solid-state battery module according to the embodiment of the present invention taken along the line A-A′ of  FIG. 1 ; 
         FIG. 4  is an exploded perspective view of a separator according to the embodiment of the present invention; 
         FIG. 5  is a cross-sectional view of the solid-state battery module according to the embodiment of the present invention; and 
         FIG. 6  is a cross-sectional view of a solid-state battery module according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiments of the present invention will be described below with reference to the drawings.  
     Please note that the embodiments shown below illustrate the present invention, and the present invention is not limited to the following. 
     Solid-State Battery Module 
     A solid-state battery module  100  includes a plurality of solid-state battery cells  101 . 
       FIG. 1  is a cross-sectional view showing the configuration of the solid-state battery module  100 .
 
The plurality of solid-state battery cells  101  is disposed in the stacking directions shown by an arrow in  FIG. 1 .
 
Separators  120  are respectively disposed between adjacent solid-state battery cells of the plurality of solid-state battery cells  101 .
 
A gap  111  is formed in the separator  120 .
 
At the top of the plurality of solid-state battery ceils  101 , a module constituent member  110  is disposed.
 
In addition to the above, the solid-state battery module  100  includes a top cover  113 , bind bars  114 , and a lower plate  115 .
 
     Solid-State Battery Cell 
     The solid-state battery cell  101  includes a laminate  102  including a positive electrode layer, a solid electrolyte layer, and a negative electrode layer, and a battery case  103 . 
       FIG. 2  is a cross-sectional view showing the configuration of the solid-state battery cell  101 .
 
The laminate  102  is housed in the battery case  103 .
 
The battery case  103  includes a pressing part  112 .
 
A positive electrode tab  104  and a negative electrode tab  109 , which are connected to the laminate  102 , extend from the upper end of the  laminate  102 .
 
     The laminate  102  includes a positive electrode layer, a negative electrode layer, and a solid electrolyte layer present between the positive electrode layer and the negative electrode layer (not shown). The positive electrode layer and the negative electrode layer are composed of, for example, an electrode material (active material) and a current collector made of a metal foil or the like. 
     The positive electrode layer is electrically connected to the positive electrode tab  104 , and the negative electrode layer is electrically connected to the negative electrode tab  109 .
 
The positive electrode material and the negative electrode material used in the positive electrode layer and the negative electrode layer are not particularly limited, and known materials used in the positive electrodes and the negative electrodes of solid-state batteries are used.
 
The positive electrode material and the negative electrode material contain a solid electrolyte and an active material.
 
In addition to the above, the positive electrode material and the negative electrode material may contain an electroconductive auxiliary agent, a binder, and the like.
 
The solid electrolyte used in the solid electrolyte layer is not particularly limited, and a known solid electrolyte such as an oxide-based solid electrolyte or a sulfide-based solid electrolyte is used, for example.
 
The solid electrolyte may contain a binder or the like, if necessary. The laminating directions of the laminate  102  shown by an arrow in   FIG. 2  and the stacking directions of the solid-state battery cells  101  shown by an arrow in  FIG. 1  are the same.
 
     The battery case  103  is a container that houses the laminate  102 . The battery case  103  includes the pressing part  112 , as shown in  FIG. 2 . 
     The material of the battery case  103  is not particularly limited, but is preferably metal.
 
When the battery case  103  is metal, the heat dissipation property is improved, and the strength of the battery case  103  itself is also improved.
 
Further, the sealing property can be improved because metal welding is possible.
 
The outer shape of the battery case  103  can be made to conform to the outer shape of the laminate  102 .
 
This enables the volume of the solid-state battery to be reduced and the energy density to be improved.
 
 FIG. 3  is a cross-sectional view taken along the line A-A′ of  FIG. 1 . As shown in  FIG. 3 , the battery case  103  is formed along the outer shape of the laminate  102  and includes convex parts for storing the positive electrode tab  104  and the negative electrode tab  109 . Further, a concave part is formed by the convex parts at the top of the battery case  103 .
 
A thermistor  108  or the like as the module constituent member  110  may be disposed in the concave part.
 
     The pressing part  112  is constituted, for example, by an elastic member such as a spring, to apply surface pressure to the laminate  102   by an elastic force. 
     The pressing parts  112  apply surface pressure in the laminating directions of the laminate  102  including the positive electrode layer, the negative electrode layer, and the solid electrolyte layer, which is indicated by an arrow in  FIG. 2 .
 
Thus, it is possible to apply an initial load to the laminate  102 , and to improve the input-output, characteristics and vibration resistance of the solid-state battery.
 
     The pressing part  112  is provided on a surface substantially perpendicular to the laminating directions of the laminate  102 . 
     The pressing part  112  is preferably provided on, for example, a pair of opposed surfaces of the battery case  103 , but may be provided on only one surface of one side of the battery case  103 .
 
The structure of the pressing part  112  is not particularly limited as long as it can apply surface pressure to the laminate  102 , and examples thereof include a stepped shape, a corrugated shape, and a shape composed of a curved surface.
 
     The pressing part  112  may be continuous with the battery case  103 , but is preferably formed as a member discontinuous with the battery case  103 . 
     As shown in  FIG. 2 , the pressing part  112  according to the present embodiment is formed discontinuously from the battery case  103 . Further, the pressing part  112  is configured to be slidable inward of the solid-state battery cell  101 .
 
When biasing force is applied to the solid-state battery cell  101  by an elastic member of the separator  120  described later, the pressing  part  112  can apply surface pressure to the laminate  102  more easily. In addition when the internal pressure of the solid-state battery cell  101  increases, the stress can be released and the safety can be improved.
 
A gap is formed between adjacent solid-state battery cells  101  by the pressing parts  112 .
 
The separator  120  including the gap  111  is disposed in the gap.
 
     The positive electrode tab  104  and the negative electrode tab  109  are electrically connected to a current collecting foil constituting the positive electrode layer and a current collecting foil constituting the negative electrode layer, respectively, and extend outward from an end surface of the laminate  102 . 
     As shown in  FIG. 3 , the positive electrode tab  104  and the negative electrode tab  109  extend from two locations on the same end surface of the laminate  102 , respectively.
 
The positive electrode tab  104  and the negative electrode tab  109  are not particularly limited, and are, for example, metal foils having a thickness of about 5 to 500 μm.
 
The positive electrode tab  104  and the negative electrode tab  109  are stored in the convex parts formed in the battery case  103 .
 
     Separator 
     The separator  120  is disposed between adjacent solid-state battery cells of the plurality of solid-state battery cells  101  to electrically insulate the adjacent solid-state battery cells of the plurality of solid-state battery cells  101 , from each other. The separator  120  electrically insulates the adjacent solid-state  battery cells of the plurality of solid-state battery cells  101 , from each other, by comprising at least partially an insulating material having an insulating property. 
     The separator  120  includes elastic members  123   a  and  123   b , and applies biasing force in the stacking directions of the plurality of solid-state battery cells  101  indicated by the arrow in  FIG. 1 .
 
The separator  120  forms the gap  111  between the solid-state battery cells  101 .
 
 FIG. 4  is an exploded perspective view showing a separator  120  according to the embodiment.
 
As shown in  FIG. 4 , the separator  120  includes a body  123  and fixing parts  121  and  122  disposed above and below the body  123 .
 
     The body  123  includes the elastic members  123   a  and  123   b . The gap  111  is formed between the elastic members  123   a  and  123   b . The configuration of the elastic members  123   a  and  123   b  is not particularly limited, and the elastic members are, for example, a pair of plate spring-like members. 
     The elastic members  123   a  and  123   b  are made of an elastically deformable material.
 
Examples of the material include metal, ceramic, and resin material. The elastic members  123   a  and  123   b  are disposed so as to apply biasing force in the stacking directions of the solid-state battery cells  101  indicated by the arrow in  FIG. 1 .
 
For example, the body  123  is configured such that the direction in which biasing force is applied by the elastic member  123   a  and the direction in which biasing force is applied by the elastic member  123   b   are opposed to each other and the resistance is balanced.
 
This configuration allows biasing force to be applied to both of the solid-state battery cells  101  adjacent to the separator  120 .
 
     The elastic members  123   a  and  123   b  apply surface pressure to the laminates  102  through the pressing parts  112 . 
     The stacking directions of the solid-state battery cells  101  shown by the arrow in  FIG. 1  are the same as the laminating directions of the laminate  102  including the positive electrode layer, the negative electrode layer, and the solid electrolyte layer shown by the arrow in  FIG. 2 .
 
Accordingly, the separator  120  including the elastic members  123   a  and  123   b  applies biasing force between the solid-state battery cells  101 , thereby applying surface pressure in the laminating directions of the laminates  102  through the pressing parts  112 .
 
     The gap  111  is formed between the solid-state battery cells  101  by the separator  120 . 
     As shown in  FIGS. 4 and 5 , the gap  111  is formed between the elastic member  123   a  and the elastic member  123   b , for example.
 
At least any one of a fluid such as air or water, a heat transfer material, a heater, etc., to control the temperature rise of the solid-state battery cell  101 , can be disposed in the gap  111 .
 
As a result, a preferable beat dissipation property of the solid-state battery module  100  can be obtained.
 
In addition to the above, at least any one of an electrical insulating material, an electrical conductive material, a buffer material, a battery case fixing member, etc., to make the solid-state battery  module  100  function, may be disposed in the gap  111 .
 
     On top of the body  123 , an engaging part  124  is provided, which engages with the fixing part  121 . 
       FIG. 5  is a cross-sectional view showing a vicinity of the top of the separator  120  disposed in the solid-state battery module  100 .
 
As shown in  FIG. 5 , the elastic members  123   a  and  123   b  in the body  123  are coupled to the engaging part  124  at the top.
 
A convex part  124   b  is formed at the upper end of the engaging part  124 .
 
The fixing part  121  is disposed on top of the engaging part  124 .
 
     The fixing part  121  is a member engageable with the engaging part  124  provided at the upper end of the body  123 . 
     The fixing part  121  engages with the engaging part  124  to regulate the movement of the body  123  in the horizontal and vertical directions by a predetermined amount or more.
 
As shown in  FIG. 4 , the fixing part  121  is a member having a substantially rectangular parallelepiped shape disposed along the upper end of the body  123 .
 
The fixing part  121  includes an engaging part  121   a  and a concave part  121   b.  
 
The engaging part  121   a  is formed at any location in the longitudinal direction of the fixing part  121 .
 
The engaging part  121   a  engages with a concave part  124   a , which will be described later, and regulates the movement of the body  123 .
 
More specifically, the engaging part  121   a  regulates the movement of the body  123  in the horizontal direction orthogonal to the stacking  directions shown in  FIG. 3  in a state where the separator  120  is disposed between the solid-state battery cells  101 .
 
The concave part  121   b  is formed in a concave shape along the longitudinal direction of the fixing part  121 .
 
The concave part  121   b  is engaged with the convex part  124   b  to be described later, to restrict the movement of the body  123  in the vertical direction.
 
The direction in which the concave part  121   b  opens and the direction in which the engaging part  121   a  is provided are the same.
 
The engaging part  121   a  and the concave part  121   b  are disposed toward the body  123  side so as to be engageable with the concave part  124   a  and the convex part  124   b  to be described later.
 
     A fixing part  122  is a member engageable with an engaging pact  125  provided at the lower end of the body  123 . 
     The fixing part  122  and the engaging part  125  have a vertically symmetrical structure with the fixing part  121  and the engaging part  124  described above.
 
Since the bottom of the separator  120  is in contact with the lower plate  115 , the separator  120  does not protrude downward due to expansion of the solid-state battery cell  101  or other factors. Therefore, the separator  120  may be configured by providing only the fixing part  121  and the engaging part  124  without providing the fixing part  122  and the engaging part  125 .
 
     As shown in  FIG. 5 , the fixing part  121  is disposed above the engaging part  124 . 
     The fixing part  121  is disposed so that the concave part  121   b  is  engageable with the convex part  124   b.  
 
As shown in  FIG. 5 , the fixing part  121  and the body  123  are disposed so that a certain amount of space is formed between the concave part  121   b  and the convex part  124   b.  
 
That is, the fixing part  121  is disposed so as to allow a predetermined amount of upward movement of the body  123 .
 
This allows excessive biasing force to be released upward even if, for example, the solid-state battery cell  101  expands and the gap  111  becomes narrower.
 
In addition to the above, since the upward movement of the body  123  by a predetermined amount or more is regulated, it is possible to prevent the separator  120  from protruding upward with respect to the solid-state battery cell  101  and losing the biasing force applied between the solid-state battery ceils  101 .
 
Further, when vibration is applied to the solid-state battery module  100 , a predetermined amount of upward movement of the body  123  is permitted, and movement of a predetermined amount or more is regulated, so that preferable vibration resistance of the solid-state battery module  100  can be obtained.
 
The space between the concave part  121   b  and the convex part  124   b  is preferably adjusted so that the biasing force by the elastic members  123   a  and  123   b  falls within an appropriate range.
 
     It is preferable that the engaging part  121   a  and the concave part  124   a  are configured such that, similarly to the concave part  121   b  and the convex part  124   b , the movement of the body  123  in the horizontal direction by a predetermined amount is permitted and the movement of  the body  123  by a predetermined amount or more is regulated. 
     For example, the length of the engaging part  121   a  in the longitudinal direction may be configured to be shorter than the length of the concave part  124   a  in the longitudinal direction, 
     Module Constituent Member 
     The module constituent member  110  is a member constituting the solid-state battery module  100 , and is disposed at the top of the plurality of solid-state battery cells  101 . 
     The module constituent member  110  includes, for example, a bus bar  106 , a voltage detection line  107 , and the thermistor  108 .
 
The module constituent member  110  may include a harness, a battery case fixing member, a cell voltage and temperature monitor unit, or the like, in addition to the above.
 
The module constituent member  110  is not particularly limited, and a known constituent member used in common battery modules is used.
 
As shown in  FIG. 3 , the module constituent member  110  may be disposed in concave parts formed in the battery case  103 .
 
This can reduce the volume of the solid-state battery module  100  and increase the energy density.
 
In addition, it is possible to prevent the solid-state battery cell  101  from being displaced or delaminating due to vibration or the like.
 
     Other Constituent Member 
     As shown in  FIG. 1 , the top surface of the solid-state battery module  100  is covered with the top cover  113 . 
     The bind bars  114  are disposed at both ends of the plurality of solid-state battery cells  101 . 
 
The bind bars  114  can enhance the cohesiveness of the plurality of solid-state battery cells  101  and can fix the battery cells to the lower plate  115 .
 
In the solid-state battery module  100  according to the embodiment, since biasing force is applied between adjacent solid-state battery cells of the plurality of solid-state battery cells  101  by the separators  120 , end plates for applying surface pressure to the plurality of solid-state battery cells are not disposed.
 
However, end plates may be disposed to constitute the solid-state battery module.
 
The lower plate  115  constitutes the bottom of the solid-state battery module  100 .
 
Since the solid-state battery module  100  according to the embodiment has a preferable heat dissipation property by the separator  120 , the lower plate  115  does not include a feature for cooling the solid-state battery cell  101 .
 
     However, depending on the application, a heat conductive material such as a silicon compound may be disposed between the lower plate  115  and the solid-state battery cell  101 , or cooling water may be disposed in the lower plate or below the lower plate to constitute the solid-state battery module. 
     Further, a buffer material may be disposed in the lower plate  115  to constitute the solid-state battery module  100 .
 
Thus, the vibration resistance of the solid-state battery module  100  can be improved.
 
     According to the separator  120  and the solid-state battery module   100  of the embodiment, the following effects are achieved. 
     The separator  120  disposed between adjacent solid-state battery cells  101  in the solid-state battery module  100  including the plurality of solid-state battery cells  101  to electrically insulate the adjacent solid-state battery cells of the plurality of the solid-state battery cells  101 , from each other, includes the elastically deformable elastic members  123   a  and  123   b  which apply biasing force in the stacking directions of the plurality of solid-state battery cells  101 . 
     Thus, it is possible to prevent the expansion of the distance between the cells due to the expansion of the solid-state battery cell  101 , and to suppress influence such as stress on the module constituent member such as the bus bar  106 , which leads to excellent durability. Further, since the solid-state battery cells  101  are fixed by the elastic members, the influence of vibration is reduced, and the solid-state battery cells  101  can be adequately fixed. 
     The separator  120  forms the gap  111  between adjacent solid-state battery cells of the plurality of solid-state battery cells  101 . 
     As a result, a member or the like for suppressing the temperature rise of the solid-state battery cell  101  can be disposed in the gap  111 , so that a preferable cooling effect of the solid-state battery cell  101  can be obtained. 
     The separator  120  includes the fixing part  121 , which regulates the movement of the body  123  by a predetermined amount or more, above the body  123  including the elastic members  123   a  and  123   b.    
     This allows for a certain amount of elastic deformation of the  separator  120 , and can prevent the separator  120  from protruding upward.
 
Therefore, the vibration resistance and durability of the solid-state battery module  100  cars be maintained.
 
     In the solid-state battery module  100 , the laminating directions of the laminate  102  of the solid-state battery cell  101  and the stacking directions of the plurality of solid-state battery cells  101  are set to be the same direction. 
     Thus, surface pressure can be applied to the laminate  102  by the separator  120 , and the input-output characteristics and vibration resistance of the solid-state battery can be improved. 
     In the solid-state battery module  100 , the solid-state battery cell  101  includes the pressing part  112  that applies surface pressure to a surface substantially perpendicular to the laminating directions of the laminate  102 . 
     Thus, the biasing force applied by the separator  120  can be applied to the laminate  102  through the pressing part  112 , which can preferably improve the input-output characteristics and vibration resistance of the solid-state battery. 
     Another Embodiment 
       FIG. 6  is a cross-sectional view showing the configuration of a solid-state battery module  100   a  according to another embodiment of the present invention. 
     As shown in  FIG. 6 , in the solid-state battery module  100   a , bind bars  114  are disposed at both ends of a plurality of solid-state battery cells  101 . 
 
An end separator  120   a  is disposed between each end of the plurality of solid-state battery cells  101  and the bind bar  114 .
 
Instead of the bind bars  114 , end plates may be disposed at both ends of the plurality of solid-state battery cells  101 .
 
The features of the solid-state battery module  100   a  other than the above may be the same as those of the solid-state battery module  100 .
 
     The end separator  120   a  includes an elastically deformable elastic member, and applies biasing force in a stacking direction of the plurality of solid-state battery cells  101  illustrated by an arrow in  FIG. 6 . 
     As shown in  FIG. 6 , for example, the end separator  120   a  has a configuration in which the separator  120  according to the above embodiment is divided into two in the vertical direction.
 
The end separator  120   a  includes, for example, one plate spring-like elastic member as the body, and applies biasing force to the adjacent solid-state battery cell  101 .
 
In addition, the end separator  120   a  includes a fixing part at least at the top of the separator, and the movement of the body in at least one of the vertical direction and the horizontal direction is regulated. The features of the end separator  120   a  other than the above may be the same as those of the separator  120 .
 
     According to the solid-state battery module  100   a  of the embodiment, the following effects can be achieved. 
     In the solid-state battery module  100   a , the end separators  120   a  are disposed at both ends of the plurality of solid-state battery cells  101 . 
 
The end separators  120   a  apply biasing force in the stacking directions of the plurality of solid-state battery cells  101 .
 
Therefore, the input-output characteristics and vibration resistance of the solid-state battery can be more preferably improved.
 
     As described above, preferable embodiments of the present invention have been described. 
     However, the present invention is not limited to the above embodiments, and can be modified as appropriate. 
     In the above embodiments, the elastic members included in the separator  120  are described as the elastic members  123   a  and  123   b  which are a pair of plate spring-like members, but the present invention is not limited to the above. 
     The elastic members of the separator  120  may be any member capable of applying biasing force to the adjacent solid-state battery cells  101 . Further, the elastic members are not limited to a pair of elastic members that apply biasing force in both opposing directions of the stacking directions of the adjacent solid-state battery cells  101 . The elastic members may apply biasing force to only one of the stacking directions of the adjacent solid-state battery cells  101 . Alternatively, separators  120  that apply biasing force in one of the stacking directions of the solid-state battery cells  101  and separators  120  that apply biasing force in the opposing stacking direction may be alternately provided. 
     EXPLANATION OF REFERENCE NUMERALS  
       100 ,  100   a  solid-state battery module 
       101  solid-state battery cell 
       102  laminate 
       111  gap 
       112  pressing part 
       120  separator 
       120   a  end separator 
       121  fixing part 
       123  body 
       123   a  elastic member 
       123   b  elastic member