Patent Publication Number: US-2019181392-A1

Title: Battery and battery module

Description:
TECHNICAL FIELD 
     The present invention relates to a battery such as lithium ion secondary battery and a battery module constituted using the battery. 
     BACKGROUND ART 
     Recently, as a solution for environmental problems, clean energy which can be obtained by wind power generation, solar power generation, or the like and is applicable for household uses (for detached houses, etc.) or for industrial uses (for transport equipment, construction equipment, etc.) is attracting attention. However, the clean energy has a disadvantage in that output variation is large depending on the situation. For example, energy by the solar power generation can be obtained in the daytime where the sun is shining, while it cannot be obtained at night where the sun is down. 
     To stabilize the output of the clean energy, a technique that temporarily stores the clean energy in a battery is used. For example, solar energy thus stored in the battery becomes available at night where the sun is down. In general, a zinc battery has been used as a battery for storing the clean energy; however, the zinc battery has a disadvantage in that it is generally large in size and low in energy density. 
     Thus, recently, a lithium ion secondary battery capable of operating at normal temperature and having a high energy density is attracting attention. In addition to the high energy density, the lithium ion secondary battery has a low impedance and is thus excellent in responsiveness. 
     For example, as the lithium ion battery, a laminate battery in which a battery element is encapsulated inside a flexible film is known. The laminate battery generally has a flat plate-like shape and has a configuration in which positive and negative electrodes are drawn outside the flexible film. 
     There is known a technique in which two or more laminate batteries each having the above configuration are modularized by being connected in series and housed in a container (casing) for the purpose of increasing capacity. 
     For example, Patent Document 1 (Japanese Patent No. 3,970,684) discloses a battery module constituted by a battery pack constructed by connecting four sheet-like secondary battery cells in series and a thin rectangular parallelepiped casing that houses the battery pack. 
     Patent Document 1 
     Japanese Patent No. 3,970,684 
     DISCLOSURE OF THE INVENTION 
     Problems to be Solved by the Invention 
     In a battery module as disclosed in Patent Document 1, in which the laminate battery is incorporated in the casing, an electrode laminated body provided in the laminate film is designed to be slightly displaced even though a unit battery is fixed inside the casing by fixing an area around the laminated battery to the casing by bonding or the like, or screw-fixing a lead-out tab of the battery to the casing. Thus, when a long-time vibration or shock is applied to the battery module, the electrode laminated body acts as a pendulum, which may cause breakage of the laminate film and leakage of an electrolyte solution due to the breakage, cause rupture of a member conductively connecting the electrode laminated body and the lead-out tab, or cause rupture of the lead-out tab. 
     Means for Solving the Problems 
     The present invention has been made to solve the above problem, and a battery according to the present invention includes: an electrode laminated body formed by laminating a positive electrode, a negative electrode, and a separator; and a laminate film exterior material that houses the electrode laminated body and an electrolytic solution. The static friction coefficient between the negative electrode and an inner surface of the laminate film exterior material is 0.1 or larger. 
     Further, in the battery according to the present invention, the D90/D10 ratio of an active material for the negative electrode is 1.7 or higher. 
     Further, in the battery according to the present invention, the porosity of the separator is 30% or higher. 
     Further, in the battery according to the present invention, the weight per unit area of the electrode laminated body in the lamination direction is 1 kg/m2 or larger and 40 kg/m2 or smaller. 
     A battery module according to the present invention is a battery module using the above-described battery. The battery module includes an elastic substance that applies a surface pressure of 100 kgf/m2 or higher in the lamination direction of the electrode laminated body. 
     Further, in the battery module according to the present invention, the young&#39;s modulus of the elastic substance in a direction in which the surface pressure is applied is 0.1 MPa or higher and 5 MPa or lower. 
     Further, a battery according to the present invention includes: an electrode laminated body formed by laminating a positive electrode, a negative electrode, and a separator; a laminate film exterior material that houses the electrode laminated body and an electrolytic solution; and an elastic layer that can apply a surface pressure in the lamination direction of the electrode laminated body. The static friction coefficient between the negative electrode and an inner surface of the laminate film exterior material is 0.1 or larger. 
     Further, in the battery according to the present invention, the D90/D10 ratio of an active material for the negative electrode is 1.7 or higher. 
     Further, in the battery according to the present invention, the porosity of the separator is 30% or higher. 
     Further, in the battery according to the present invention, the weight per unit area of the electrode laminated body in the lamination direction is 1 kg/m2 or larger and 40 kg/m2 or smaller. 
     A battery module according to the present invention is a battery module using the above-described battery, wherein the elastic layer applies a surface pressure of 100 kgf/m2 or higher in the lamination direction of the electrode laminated body. 
     Further, in the battery module according to the present invention, the young&#39;s modulus of the elastic layer in a direction in which the surface pressure is applied is 0.1 MPa or higher and 5 MPa or lower. 
     Advantageous Effects of the Invention 
     In the battery according to the present invention, the static friction coefficient between the negative electrode and the inner surface of the laminate film exterior material is 0.1 or larger. Thus, even when a long-time vibration or shock is applied to the battery, the probability of breakage of the laminate film exterior material and leakage of the electrolytic solution associated with the breakage, rapture of a member conductively connecting the electrode laminated body and the lead-out tab, or rapture of the lead-out tab is reduced, whereby the battery having excellent vibration resistance and shock resistance can be provided. 
     Further, even when a long-time vibration or shock is applied to the battery module according to the present invention, the probability of leakage of the electrolytic solution due to breakage of the laminate film exterior material of the battery, rapture of a member conductively connecting the electrode laminated body and the lead-out tab, or rapture of the lead-out tab is reduced, whereby the battery module having excellent vibration resistance and shock resistance can be provided. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a view for explaining the lamination order of components constituting an electrode laminated body  60 ; 
         FIG. 2  is a view illustrating the configuration of the electrode laminated body  60  of a battery  100  according to the embodiment of the present invention; 
         FIG. 3  is a perspective view of the battery  100  according to the embodiment of the present invention; 
         FIG. 4  is a view for explaining the lamination order of the components constituting a battery module  300 ; 
         FIG. 5  is a perspective view illustrating an example of the battery module  300  according to the embodiment of the present invention; 
         FIG. 6  is a schematic cross-sectional view of the battery module  300  according to the embodiment of the present invention; 
         FIG. 7  is a view for explaining the weight per unit area of the electrode laminated body  60  in the lamination direction; and 
         FIG. 8  is a schematic cross-sectional view of the battery module  300  according to another embodiment of the present invention. 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     An embodiment of the present invention will be described below with reference to the accompanying drawings.  FIG. 1  is a view for explaining the lamination order of components constituting an electrode laminated body  60 .  FIG. 2  is a view illustrating the configuration of the electrode laminated body  60  of a battery  100  according to the embodiment of the present invention.  FIG. 3  is a perspective view of the battery  100  according to the embodiment of the present invention. 
     In the present embodiment, a lithium ion secondary battery, which is a kind of an electrochemical element, in which lithium ion is moved between negative and positive electrodes to perform charging and discharging, is taken as an example of the battery  100 ; however, the present invention is also applicable to other kinds of batteries. 
     The battery  100  according to the embodiment of the present invention has a structure in which an electrode laminated body  60  formed by laminating a plurality of positive electrodes  20  and a plurality of negative electrodes  30  through separators  40 , and an electrolytic solution (not illustrated) are housed in a rectangular laminate film exterior material  80 . 
       FIG. 1  is a view for explaining the lamination order of the components constituting the electrode laminated body  60 . As illustrated in  FIG. 1 , the positive electrode  20 , negative electrode  30 , and separator  40  are used to constitute the electrode laminated body  60 . 
     The positive electrode  20  has a rectangular positive electrode body part  22  and a strip-shaped positive electrode terminal part  24  extending from the positive electrode body part  22 . In the positive electrode body part  22 , a positive electrode active material  26  such as lithium-cobalt composite oxide is applied onto a sheet-like aluminum plate. 
     The negative electrode  30  has a rectangular negative electrode body part  32  and a strip-shaped negative electrode terminal part  34  extending from the negative electrode body part  32 . In the negative electrode body part  32 , a negative electrode active material  36  such as graphite is applied onto a sheet-like nickel plate or a sheet-like copper plate. 
     The separator  40  is a rectangular sheet-like member such as a micro-porous film, nonwoven fabric or woven fabric, formed from thermoplastic resin such as polyolefin and capable of being impregnated with an electrolytic solution. 
     When the above-described components are laminated as the electrode laminated body  60 , all the positive electrode terminal parts  24  formed in the respective positive electrodes  20  and all the negative electrode terminal parts  34  formed in the respective negative electrodes  30  are fixed to each other by ultrasonic wave welding. 
     Further, as illustrated in  FIG. 2 , the negative electrode terminal part  34  of each positive electrode  20  is conductively connected to a positive electrode lead-out tab  120 , and the negative electrode terminal part of each negative electrode  30  is conductively connected to a negative electrode lead-out tab  130 . 
     An aluminum plate is used as the positive electrode lead-out tab  120 , and a nickel or copper plate is used as the negative electrode lead-out tab  130 . When a copper plate is used as the negative electrode lead-out tab  130 , nickel plating may be applied onto the surface of the copper plate. 
     Further, when the above-described components are laminated as the electrode laminated body  60 , an adhesive tape  65  is preferably used for fixing at two positions of each of two opposing sides of the electrode laminated body  60  as illustrated in  FIG. 2  so as to surely keep the laminated state. 
     The electrode laminated body  60  formed as illustrated in  FIG. 2  and electrolytic solution (not illustrated) are sealed in the laminate film exterior material  80  in a state where the positive electrode lead-out tab  120  and negative electrode lead-out tab  130  are drawn outside, whereby the battery  100  illustrated in  FIG. 3  is obtained. 
     In the present embodiment, the laminate film exterior material  80  includes two laminate films surrounding the electrode laminated body  60  at positions sandwiching the electrode laminated body  60  from both sides in the lamination direction thereof. First sides  111 , second sides  112 , third sides  113 , and fourth sides  114  of the opposing surfaces of the two respective laminate films overlapped around the periphery of the electrode laminated body  60  are thermally welded to form a thermally-welded part (sealed area)  81 , whereby the electrode laminated body  60  is sealed together with the electrolytic solution (not illustrated). The positive electrode lead-out tab  120  is drawn from the first side  111  of the laminate film exterior material  80 , and the negative electrode lead-out tab  130  is drawn from the second side  112  of the laminate film exterior material  80 . 
     Although two laminate films are used to seal the electrode laminated body  60  and electrolytic solution (not illustrated) in the present embodiment, it is also possible to seal the electrode laminated body  60  and electrolytic solution (not illustrated) by folding one laminate film. 
     As the laminate film constituting the laminate film exterior material  80 , a film commonly used for a film-armored battery of this type can be used as long as it has flexibility and can seal the electrode laminated body  60  and electrolytic solution (not illustrated) so as to prevent leakage of the electrolytic solution. 
     Examples of a typical layer configuration of the laminate film constituting the laminate film exterior material  80  includes a configuration in which a metal thin film layer and a thermally weldable resin layer are laminated, and a protective resin layer composed of a polyester film such as a polyethylene terephthalate film or a nylon film is laminated on the surface of the metal thin film layer opposite to the thermally weldable resin layer. For sealing the electrode laminated body  60  and electrolytic solution, the thermally weldable resin layers are made to face each other to surround the electrode laminated body  60 . 
     As the metal thin film layer, for example, a metal foil of Al, Ti, Ti alloy, Fe, stainless, or Mg alloy having a thickness of 10 μm to 100 μm can be used. 
     The resin used for the thermally weldable resin layer is not particularly limited as long as it is thermally weldable and, for example, polypropylene, polyethylene, acid modification thereof, polyphenylene sulfide, polyester such as polyethylene terephthalate, polyamide, ethylene vinyl acetate copolymer can be used. The thickness of the thermally weldable resin layer is preferably 10 μm to 200 μm and more preferably, 30 μm to 100 μm. 
     The inner surface of the laminate film exterior material  80  is formed as the above-mentioned thermally weldable resin layer of the laminate film exterior material  80 . On the other hand, in the electrode laminated body  60 , the lamination order is prescribed such that the negative electrode  30  is always positioned at the outermost layer. Therefore, in the battery  100 , the negative electrode  30  of the electrode laminated body  60  and the inner surface (thermally weldable resin layer) of the laminate film exterior material  80  are brought into contact with each other. 
     In the battery  100 , in order to prevent the electrode laminated body  60  from being moved inside the laminate film exterior material  80  due to vibration or shock, the static friction coefficient between the negative electrode  30  and the inner surface of the laminate film exterior material  80  needs to be equal to or larger than a predetermined value. The present inventor has experimentally found that the static friction coefficient therebetween is preferably 0.1 or larger. 
     In order to achieve the above static friction coefficient, the ratio between D90 and D10 is preferably 1.7 or higher with respect to the volume particle size distribution (D) of the negative electrode active material  36 . This is because when the D90/D10 ratio is lower than 1.7, the surface of the negative electrode  30  is flat, making it difficult to make the static friction coefficient between the negative electrode  30  and the inner surface of the laminate film exterior material  80  be 0.1 or larger. 
     Further, the porosity of the separator  40  included in the electrode laminated body  60  is preferably 30% or higher. This is because when the porosity thereof is 30% or higher, the flexibility of the separator  40  is improved to allow the young&#39;s modulus to be kept low. 
     In general, the battery  100  as described above is incorporated in a casing and used as a battery module  300 . As such a casing, one constituted by a storage case body  200  and a lid body  210  is taken as an example. Illustration of a configuration related to the electrical connection portion of the positive electrode lead-out tab  120  or negative electrode lead-out tab  130  in the battery module  300  is omitted. 
       FIG. 4  is a view for explaining the lamination order of the components constituting the battery module  300 .  FIG. 5  is a perspective view illustrating an example of the battery module  300  according to the embodiment of the present invention. As illustrated, in the present embodiment, the battery  100  is vertically held by elastic substances  150  between the storage case body  200  and the lid body  210 . 
     The material for use in the elastic substance  150  is not particularly limited as long as required elasticity and durability are satisfied. Examples of the material may include a rubber-like polymer such as isoprene rubber, butadiene rubber, chloroprene rubber, nitrile rubber, acrylic rubber, fluororubber, urethane rubber, or silicone rubber, a sponge-like substance obtained by foaming and making porous the above-mentioned rubber-like polymer, and a sponge-like substance obtained by making porous a polymer such as polyolefin or halogenated polyolefin by phase separation, chemical treatment, particle fusion, or fiberization. 
       FIG. 6  is a schematic cross-sectional view taken along line X-X′ of  FIG. 5 , which illustrates a surface perpendicular to the lamination direction. In  FIG. 6 , the negative electrode  30  of the outermost layer of the electrode laminated body  60  is highlighted. As described above, in the present invention, the static friction coefficient between the negative electrode  30  and the inner surface of the laminate film exterior material  80  is set to 0.1 or larger. 
     Further, in order to apply a sufficient load between the negative electrode  30  of the outermost layer of the electrode laminated body  60  and the laminate film exterior material  80 , the young&#39;s modulus of the elastic substance  150  is set to 0.1 MPa or higher and 5 MPa or lower. As a result, the elastic substance  150  can apply a surface pressure of 100 kgf/m 2  or higher in the lamination direction of the electrode laminated body  60 . 
       FIG. 7  is a view illustrating the electrode laminated body  60  of the battery  100 , which explains the weight per unit area of the electrode laminated body  60  in the lamination direction. In the present invention, the weight per unit area of the electrode laminated body  60  in the lamination direction is set to 1 kg/m 2  or larger and 40 kg/m 2  or smaller. 
     That is, when the weight exceeds 40 kg/m 2 , the entire weight of the electrode laminated body  60  becomes excessively large, failing to prevent the movement of the electrode laminated body  60  by friction force. Conversely, when the weight falls below 1 kg/m 2 , the energy density of the battery  100  is significantly reduced. Therefore, the weight per unit area of the electrode laminated body  60  in the lamination direction is set to 1 kg/m 2  or larger and 40 kg/m 2  or smaller. 
     In the battery  100  according to the present invention, the static friction coefficient between the negative electrode  30  and the inner surface of the laminate film exterior material  80  is set to 0.1 or larger. Thus, even when a long-time vibration or shock is applied to the battery  100  according to the present invention, the probability of breakage of the laminate film exterior material  80  and leakage of the electrolytic solution associated with the breakage, rapture of a member conductively connecting the electrode laminated body  60  and the lead-out tab, or rapture of the lead-out tab is reduced, whereby the battery  100  having excellent vibration resistance and shock resistance can be provided. 
     Further, even when a long-time vibration or shock is applied to the battery module  300  according to the present invention, the probability of leakage of the electrolytic solution due to breakage of the laminate film exterior material  80  of the battery  100 , rapture of a member conductively connecting the electrode laminated body  60  and the lead-out tab, or rapture of the lead-out tab is reduced, whereby the battery module  300  having excellent vibration resistance and shock resistance can be provided. 
     Next, another embodiment of the present invention will be described.  FIG. 8  is a schematic cross-sectional view of the battery module  300  according to another embodiment of the present invention, which corresponds to  FIG. 6  of the previous embodiment. 
     Hereinafter, the difference between the previous and present embodiments will be described. In the previous embodiment, the elastic substance  150  is provided outside the battery  100  so as to apply a sufficient load between the negative electrode  30  of the outermost layer of the electrode laminated body  60  and the inner surface of the laminate film exterior material  80 . 
     On the other hand, in the present embodiment, an elastic layer  250  is provided inside the battery  100  so as to apply a sufficient load between the negative electrode  30  of the outermost layer of the electrode laminated body  60  and the inner surface of the laminate film exterior material  80 . 
     Configurations other than the above difference do not differ between the previous and present embodiments. As illustrated in  FIG. 8 , in the present embodiment, the elastic layer  250  that can apply a surface pressure in the lamination direction of the electrode laminated body  60  is provided in the electrode laminated body  60 . 
     The material for use in the elastic layer  250  is not particularly limited as long as required physical properties and durability are satisfied. Examples of the material may include a rubber-like polymer such as isoprene rubber, butadiene rubber, chloroprene rubber, nitrile rubber, acrylic rubber, fluororubber, urethane rubber, or silicone rubber, a sponge-like substance obtained by foaming and making porous the above-mentioned rubber-like polymer, and a sponge-like substance obtained by making porous a polymer such as polyolefin or halogenated polyolefin by phase separation, chemical treatment, particle fusion, or fiberization. 
     The young&#39;s modulus of the elastic layer  250  is set to 0.1 MPa or higher and 5 MPa or lower. As a result, the elastic layer  250  can apply a surface pressure of 100 kgf/m 2  or higher in the lamination direction of the electrode laminated body  60 . 
     The same effects as those obtained in the previous embodiment can be achieved by the battery  100  according to the present embodiment and battery module  300  using the thus configured battery  100 . 
     INDUSTRIAL APPLICABILITY 
     There is recently available, for example, a laminate battery in which a battery element is encapsulated inside a flexible film as a lithium ion battery having high energy density. In a battery module in which such a laminate battery is incorporated in the casing, an electrode laminated body provided in the laminate film is designed to be slightly displaced even though a unit battery is fixed inside the casing by fixing an area around the laminated battery to the casing by bonding or the like, or screw-fixing a lead-out tab of the battery to the casing. Thus, when a long-time vibration or shock is applied to the battery module, the electrode laminated body acts as a pendulum, which may cause breakage of the laminate film and leakage of an electrolyte solution due to the breakage, cause rupture of a member conductively connecting the electrode laminated body and the lead-out tab, or cause rupture of the lead-out tab. To cope with this problem, in the battery according to the present invention, the static friction coefficient between the negative electrode and the inner surface of the laminate film exterior material is set to 0.1 or larger. According to the thus configured battery of the present invention, even when a long-time vibration or shock is applied to the battery, the probability of breakage of the laminate film exterior material and leakage of the electrolytic solution associated with the breakage, rapture of a member conductively connecting the electrode laminated body and lead-out tab, or rapture of the lead-out tab is reduced, whereby the battery having excellent vibration resistance and shock resistance can be provided. Thus, industrial applicability is very high. 
     REFERENCE SIGNS LIST 
     
         
           20 : Positive electrode 
           22 : Positive electrode body part 
           24 : Positive electrode terminal part 
           26 : Positive electrode active material 
           30 : Negative electrode 
           32 : Negative electrode body part 
           34 : Negative electrode terminal part 
           36 : Negative electrode active material 
           40 : Separator 
           42 : Separator body part 
           44 : Separator extending piece 
           60 : Electrode limited body 
           65 : Adhesive tape 
           80 : Laminate film exterior material 
           81 : Thermally-welded part (sealed area) 
           100 : Battery 
           110 : Battery body part 
           111 : First side 
           112 : Second side 
           113 : Third side 
           114 : Fourth side 
           120 : Positive electrode lead-out tab 
           130 : Negative electrode lead-out tab 
           150 : Elastic substance 
           200 : Storage case body 
           210 : Lid body 
           250 : Elastic layer 
           300 : Battery module