Battery cell and its manufacturing method

Abstract

To provide a battery cell capable of uniformly holding an electrode laminate and improving lamination deviation and electrode durability.SOLUTION: A battery cell has an electrode laminate in which a positive electrode and a negative electrode are arranged so as to be alternately laminated via an electrolyte layer. The battery cell has a tubular insulation member that holds the electrode laminate. The insulation member has a thermal contraction property, and its main contraction direction of thermal contraction is in a lamination direction of the electrode laminate. A thermal contraction rate in a current collector tab extension direction of the electrode laminate, of the insulation member is preferably -5% to 5%.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a battery cell and a method for manufacturing the same. [Background technology]

[0002] Conventionally, secondary batteries such as lithium ion secondary batteries have been widely used as secondary batteries with high energy density. Liquid secondary batteries have a cell structure in which a separator is placed between a positive electrode and a negative electrode, and the cell structure is filled with a liquid electrolyte (electrolytic solution). In the case of an all-solid-state battery in which the electrolyte is solid, the cell structure is one in which a solid electrolyte is placed between a positive electrode and a negative electrode. A secondary battery is made up of a stack of multiple such single cells. All of these are sealed and packaged in an exterior body.

[0003] As a cell structure of a secondary battery having the above-mentioned laminate, for example, in a non-aqueous electrolyte secondary battery having a laminated electrode body in which a positive electrode, a separator, and a negative electrode are laminated, a porous sheet that holds a non-aqueous electrolyte is wrapped around the outer periphery of the laminated electrode body, thereby maintaining the laminated structure of the laminated electrode body (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2014-093128 A Summary of the Invention [Problem to be solved by the invention]

[0005] A secondary battery having the above laminate has a problem of lamination slippage occurring between the positive electrode, the negative electrode, and the solid electrolyte. The technology disclosed in Patent Document 1 has a weak force for holding the laminate, so that there is a possibility of lamination slippage occurring when the porous sheet is wound around the laminate, when the laminate is housed in an exterior body, or when an external impact is applied. If the dimensional difference between the positive electrode and the negative electrode is increased to prevent electrodeposition in consideration of the possibility of lamination slippage, the energy density decreases. In addition, when a sheet-like body is wound around the laminate to hold the laminate, a step occurs at the winding end, so that a stress distribution occurs in the laminate, the initial performance and durability decrease, and there is room for improvement in the durability of the electrode itself.

[0006] In order to solve the above problem, it is conceivable to insert the laminate into a heat shrinkable film configured in a tube shape and shrink the heat shrinkable film by heating, thereby holding the laminate and suppressing the laminate misalignment. However, if the heat shrinkable film containing the laminate is simply heated, the stress applied to the laminated surface of the laminate may cause the distance between the electrodes to become uneven or the electrodes to deform. If, for example, only the laminated surface of the heat shrinkable film is heated to shrink it in order to prevent the above situation, the unheated surface of the heat shrinkable film may shrink due to a temperature rise or natural shrinkage during use of the secondary battery, causing the distance between the electrodes to become uneven or the electrodes to deform.

[0007] The present invention has been made in view of the above problems, and has an object to provide a battery cell in which an electrode stack can be held uniformly and in which stacking misalignment and electrode durability can be improved. [Means for solving the problem]

[0008] (1) The present invention relates to a battery cell having an electrode laminate in which positive electrodes and negative electrodes are alternately stacked with an electrolyte layer interposed therebetween, the battery cell having a tubular insulating member that holds the electrode laminate, the insulating member having heat shrinkability, and the main shrinkage direction of the heat shrinkage being the stacking direction of the electrode laminate.

[0009] (2) The battery cell according to (1), wherein the insulating member has a thermal shrinkage rate of −5% to 5% in the direction in which the current collector tab of the electrode laminate extends.

[0010] (3) The battery cell according to (1) or (2), wherein the insulating member has a thermal shrinkage rate in the stacking direction of 5% to 80%.

[0011] (4) The battery cell according to any one of (1) to (3), wherein, when the insulating member is thermally shrunk in the main shrinkage direction, a thickness on the electrode surface side of the electrode laminate is tv and a thickness on the laminate surface side of the electrode laminate is th, the relationship of the following formula (1) is satisfied: 5%<|(tv-th) / tv)|≦150%...Equation (1)

[0012] (5) The battery cell according to any one of (1) to (4), wherein the insulating member has a welding portion on a stacking surface side of the electrode stack, and the extension length of the welding portion is 1.2 to 3 times the thickness of the insulating member.

[0013] (6) The battery cell according to any one of (1) to (5), wherein when the insulating member is thermally shrunk in the main shrinkage direction, a height of an internal space of the insulating member is the same as a stacking height of the electrode stack, and a cross-sectional area of ​​the internal space of the insulating member is 1.0 to 1.2 times the cross-sectional area of ​​the electrode stack.

[0014] (7) The battery cell according to any one of (1) to (6), wherein the electrode stack has a pressure equalizing member between the electrode stack and the insulating member.

[0015] (8) The battery cell according to any one of (1) to (7), wherein the length of the insulating member in the direction in which the current collector tab extends is 0.98 to 1.2 times the length of the electrode laminate in the direction in which the current collector tab extends.

[0016] (9) The battery cell according to any one of (1) to (8), wherein the opening area of ​​the insulating member is smaller than the end face area of ​​the electrode stack.

[0017] (10) The present invention also provides The positive electrode and the negative electrode are connected via an electrolyte layer.The present invention relates to a method for manufacturing a battery cell having electrode laminates arranged in an alternating stack, the method comprising: an arrangement step of arranging the electrode laminate in an internal space of a tubular insulating member having heat shrinkability such that a main shrinkage direction of the insulating member coincides with a stacking direction of the electrode laminate; and a heating step of heating a surface of the insulating member that is to be placed on the stacking surface side of the electrode laminate, thereby causing thermal shrinkage.

[0018] (11) A method for manufacturing a battery cell described in (10), in which the insulating member, whose main direction of thermal shrinkage is the stacking direction of the electrode stack, is formed by pre-heating and thermally shrinking a surface of the insulating member that is to be placed on the electrode surface side of the electrode stack.

[0019] (12) The method for producing a battery cell according to (10) or (11), wherein the heating temperature in the heating step is 60° C. or higher.

[0020] (13) The method for manufacturing a battery cell described in (11), wherein at least one of the heating temperature in the heating step and the temperature at which the surface of the insulating member that is to be placed on the electrode surface side of the electrode laminate is preheated is 60°C or higher.

[0021] (14) The method for producing a battery cell according to any one of (10) to (13), further comprising a drawn portion forming step of heating both end portions of the insulating member in a direction in which the current collector tab of the electrode laminate extends to form drawn portions.

[0022] (15) The method for manufacturing a battery cell described in (14), wherein the narrowed portion forming process includes a first narrowed portion forming process of heating one end of the insulating member in the direction in which the current collector tab of the electrode laminate extends, and a second narrowed portion forming process of heating the other end of the insulating member in the direction in which the current collector tab of the electrode laminate extends, and the arrangement process is performed between the first narrowed portion forming process and the second narrowed portion forming process. Effect of the Invention

[0023] According to the present invention, it is possible to provide a battery cell in which an electrode stack can be held uniformly and stacking misalignment and electrode durability can be improved. [Brief description of the drawings]

[0024] [Figure 1] 1 is a perspective view showing an overview of a battery cell according to an embodiment of the present invention. [Diagram 2] 1 is a cross-sectional view showing an overview of a battery cell according to a first embodiment of the present invention. [Diagram 3] 1 is a perspective view showing an overview of an insulating member according to a first embodiment of the present invention. [Figure 4] 1 is a side view showing a configuration of an insulating member according to a first embodiment of the present invention. [Diagram 5] 1 is a side view showing the configuration of a battery cell according to a first embodiment of the present invention. [Figure 6] 6 is a cross-sectional view showing an overview of a battery cell according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Specific embodiments of the present invention will be described in detail below. However, the present invention is not limited to the following embodiments and can be modified as appropriate within the scope of the object of the present invention.

[0026] First Embodiment <Battery cell> FIG. 1 is a perspective view showing an outline of a battery cell 1 according to the present embodiment. The battery cell 1 according to the present embodiment includes an electrode laminate 3, an insulating member 2 surrounding and holding the electrode laminate 3, and a positive electrode current collector tab 4 and a negative electrode current collector tab 5 extending from both ends of the electrode laminate 3. The battery cell 1 is, for example, a solid battery cell having a solid electrolyte as an electrolyte, but the configuration of the present invention can also be applied to a liquid-based secondary battery having a liquid electrolyte as an electrolyte. The battery cell 1 is housed in an arbitrary exterior body (not shown) formed of a laminate film or the like. In the following description and drawings, the X direction indicates the direction along the electrode surface of the electrode laminate 3 (hereinafter, may be referred to as the "electrode surface direction"), the Y direction indicates the extension direction of the collector tab (hereinafter, may be referred to as the "current collector tab extension direction"), and the Z direction indicates the direction along the stacking surface of the electrode laminate 3 (hereinafter, may be referred to as the "stacking direction").

[0027] (Electrode laminate) Fig. 2 is a cross-sectional view in the Y direction showing an overview of the electrode laminate 3. As shown in Fig. 2, the electrode laminate 3 is a laminate in which negative electrodes 31 and positive electrodes 32 are alternately laminated, and a solid electrolyte layer 33 is laminated between the negative electrodes 31 and the positive electrodes 32. In this embodiment, the electrode laminate 3 has a substantially rectangular parallelepiped shape as a whole, and the height of the cross section in the Y direction is h1 and the cross-sectional area in the Y direction is S1.

[0028] [Negative electrode] There is no particular limitation on the negative electrode 31, and any known negative electrode used as a negative electrode for a solid-state battery can be used. The negative electrode 31 is composed of, for example, a sheet-shaped negative electrode current collector and a sheet-shaped negative electrode active material layer.

[0029] The negative electrode current collector is not particularly limited, and may be, for example, a metal foil such as stainless steel (SUS) foil or copper (Cu) foil. The negative electrode current collectors of the multiple negative electrodes 31 are electrically connected to a negative electrode current collector tab 5. The negative electrode current collector tab 5 may be one integrally formed with the negative electrode current collector, or may be a member different from the negative electrode current collector and electrically connected to the negative electrode current collector by welding, deposition, or the like.

[0030] The material constituting the negative electrode active material layer is not particularly limited, and any material known as a negative electrode active material for solid-state batteries can be used. There is also no particular limitation on the composition, and the layer may contain a solid electrolyte, a conductive assistant, a binder, and the like in addition to the negative electrode active material.

[0031] When the battery cell 1 is, for example, a lithium ion solid-state battery cell, the negative electrode active material is not particularly limited as long as it is capable of absorbing and releasing lithium ions. Examples of the negative electrode active material include metallic lithium, lithium alloys, metal oxides, metal sulfides, metal nitrides, Si, SiO, and carbon materials such as graphite, hard carbon, and soft carbon.

[0032] [Positive electrode] There is no particular limitation on the positive electrode 32, and any known positive electrode used as a positive electrode for a solid-state battery can be used. The positive electrode 32 is composed of, for example, a sheet-shaped positive electrode current collector and a sheet-shaped positive electrode active material layer.

[0033] The positive electrode current collector is not particularly limited, and may be, for example, a metal foil such as stainless steel (SUS) foil or aluminum (Al) foil. The positive electrode current collectors of the multiple positive electrodes 32 are electrically connected to a positive electrode current collector tab 4. The positive electrode current collector tab 4 may be one integrally formed with the positive electrode current collector, or may be a member different from the positive electrode current collector and electrically connected to the positive electrode current collector by welding, deposition, or the like.

[0034] The material constituting the positive electrode active material layer is not particularly limited, and any material known as a positive electrode active material for solid-state batteries can be used. There is also no particular limit to the composition thereof, and the layer may contain a solid electrolyte, a conductive assistant, a binder, and the like in addition to the positive electrode active material.

[0035] The positive electrode active material is not particularly limited, and when the battery cell 1 is, for example, a lithium ion solid-state battery cell, examples of the positive electrode active material include transition metal chalcogenides such as titanium disulfide, molybdenum disulfide, and niobium selenide, and transition metal oxides such as lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMnO2, LiMn2O4), and lithium cobalt oxide (LiCoO2).

[0036] [Solid electrolyte layer] The solid electrolyte layer 33 is laminated between the negative electrode 31 and the positive electrode 32, and is formed, for example, in a layer shape. The solid electrolyte layer 33 is a layer containing at least a solid electrolyte material. Ions can be transferred between the positive electrode active material and the negative electrode active material via the solid electrolyte material.

[0037] The solid electrolyte material is not particularly limited, but examples thereof include sulfide solid electrolyte materials, oxide solid electrolyte materials, nitride solid electrolyte materials, and halide solid electrolyte materials.

[0038] (Insulating material) As shown in Figures 2 to 5, the insulating member 2 is a tubular insulating member having an internal space capable of housing the electrode stack 3. The insulating member 2 is a heat-shrinkable member that shrinks when heated, and is made of, for example, a heat-shrinkable film. By using a tubular insulating member having heat shrinkability as the insulating member 2, the battery cell 1 can be configured so that no steps are generated on the electrode surfaces of the electrode stack 3, as compared to a case in which a sheet-like insulating member is wrapped around the electrode stack 3. This makes it possible to prevent cracks in the electrodes and solid electrolyte.

[0039] Examples of heat shrinkable films that can be used include polyethylene terephthalate shrinkable films, polystyrene shrinkable films, polyolefin shrinkable films, polyvinyl chloride shrinkable films, polycarbonate shrinkable films, polyethylene shrinkable films, polypropylene shrinkable films, etc. The above heat shrinkable films may be used alone or in combination of two or more.

[0040] 3 and 4, the insulating member 2 has a tubular shape having an internal space in which the electrode laminate 3 can be placed. The insulating member 2 has faces A1 and A2 arranged on the electrode surface side of the electrode laminate 3, and faces B1 and B2 arranged on the laminate surface side of the electrode laminate 3, and both ends in the direction in which the current collector tab extends are open. In this embodiment, the insulating member 2 has a seamless shape without any steps, but may be formed by welding the ends of a single heat shrinkable film (this will be described in detail in the second embodiment).

[0041] The insulating member 2 has a main shrinkage direction of thermal shrinkage in the stacking direction of the electrode laminate 3. In this specification, the "main shrinkage direction" refers to a direction in which the thermal shrinkage rate due to thermal shrinkage is higher than other directions when the electrode laminate 3 is placed in the internal space of the insulating member 2 and the insulating member 2 is thermally shrunk by heating to hold the electrode laminate 3. The above configuration of the insulating member 2 is synonymous with the fact that, in this embodiment, the surface B1 and the surface B2 of the insulating member 2 arranged on the stacking surface side of the electrode laminate 3 have a higher thermal shrinkage rate due to thermal shrinkage than the surface A1 and the surface A2 of the insulating member 2 arranged on the electrode surface side of the electrode laminate 3. With the insulating member 2 having the above configuration, after the electrode laminate 3 is placed in the internal space of the insulating member 2, the surface B1 and the surface B2 mainly thermally shrink by heating, so that excessive stress can be suppressed from being applied to the stacking surface of the electrode laminate 3. Therefore, it is possible to prevent the distance between the electrodes from becoming uneven and the electrodes from being deformed. The thermal shrinkage rate is calculated as a ratio (percentage) of the difference between the length before and after shrinkage to the length before shrinkage.

[0042] The above-mentioned configuration in which the main shrinkage direction of the insulating member 2 is the stacking direction of the electrode laminate 3 can be realized, for example, by having the surfaces A1 and A2 of the insulating member 2, which are in the electrode surface direction, thermally shrunk in advance by heating. As a result, even if heat is applied from the outside after the electrode laminate 3 is placed in the internal space of the insulating member 2 and the surfaces B1 and B2 of the insulating member 2 are thermally shrunk by heating to form the battery cell 1, the thermal shrinkage of the insulating member 2 is suppressed. Therefore, it is possible to prevent the inter-electrode distance from becoming non-uniform after the battery cell 1 is formed and to prevent the electrodes from deforming. In addition to the above, the insulating member 2 may be configured such that the surfaces A1 and A2 of the insulating member 2 are made of a material with small thermal shrinkage and the surfaces B1 and B2 are made of a material with large thermal shrinkage, thereby forming the insulating member 2 whose main shrinkage direction is the stacking direction of the electrode laminate 3.

[0043] The heat shrinkage rate of the insulating member 2 in the direction in which the current collector tab extends is preferably -5% to 5%. The heat shrinkable film constituting the insulating member 2 has anisotropy, and generates a holding force for the electrode laminate 3 by shrinking in the TD direction, which is the circumferential direction of the insulating member 2 shown in FIG. 3. On the other hand, when expansion or shrinkage occurs in the MD direction, which is the direction in which the current collector tab extends of the insulating member 2, stress acts in a direction in which the electrodes and electrolyte layers constituting the electrode laminate 3 are displaced. For this reason, the heat shrinkage rate of the insulating member 2 in the MD direction is preferably close to 0%. If the heat shrinkage rate of the insulating member 2 in the MD direction exceeds 5%, the above stress exceeds the static friction force, and there is a risk of lamination displacement. If the heat shrinkage rate of the insulating member 2 in the MD direction is less than -5%, in addition to the occurrence of lamination displacement, the volume of the insulating member 2 increases, and the energy density of the battery cell 1 is likely to decrease.

[0044] The thermal shrinkage rate of the insulating member 2 in the TD direction shown in Fig. 3 is preferably 5% to 80%. If the thermal shrinkage rate of the insulating member 2 in the TD direction is less than 5%, the holding force of the insulating member 2 to the electrode stack 3 due to thermal shrinkage becomes insufficient, and there is a risk of the electrodes shifting in the stacking. If the thermal shrinkage rate of the insulating member 2 in the TD direction exceeds 80%, there is an excessive holding force to the electrode stack 3, and there is a risk of the electrode stack 3 deforming, the electrodes shifting in the stacking, the electrodes deforming, and the like.

[0045] When the thicknesses of surfaces A1 and A2, which are arranged on the electrode surface side of the electrode laminate 3 shown in FIG. 4, are tv, and the thicknesses of surfaces B1 and B1, which are arranged on the laminated surface side of the electrode laminate 3, are th in the state where surfaces B1 and B2 of the insulating member 2 in the main shrinkage direction are heat-shrunk, it is preferable to satisfy the relationship of the following formula (1). 5% < |(tv - th) / tv| ≦ 150% ··· Formula (1)

[0046] When |(tv - th) / tv| in the above formula (1) is less than 5%, there is a risk of deformation of the electrode laminate 3, misalignment of the electrodes, deformation of the electrodes, etc. When |(tv - th) / tv| in the above formula (1) exceeds 150%, the dimensional accuracy decreases because the amount of heat shrinkage is too large, and wrinkles are likely to occur in the insulating member 2.

[0047] When tv > th, the direction in which the insulating member 2 is pre-heat-shrunk is preferably the X direction, and the temperature Tx at which surfaces A1 and A2 are heat-shrunk is higher than the temperature Tz at which surfaces B1 and B2 are heat-shrunk (Tx > Tz), so that a uniform holding force can be applied to the electrode laminate 3. When tv < th, the temperature Tx at which surfaces A1 and A2 are heat-shrunk is lower than the temperature Tz at which surfaces B1 and B2 are heat-shrunk (Tx < Tz), so that a uniform holding force can be applied to the electrode laminate 3. Further, Tx and Tz, which are the heat shrinkage temperatures of the insulating member 2, are preferably 60°C or higher. When the battery cell 1 is a lithium-ion secondary battery, since the upper limit of the operating temperature of the lithium-ion secondary battery is about 60°C, heat shrinkage of the insulating member 2 during operation of the battery cell 1 can be suppressed by heat-shrinking the insulating member 2 at 60°C or higher. That is, deformation of the electrode laminate 3, misalignment of the electrodes, deformation of the electrodes, etc. during operation of the battery cell 1 can be suppressed.

[0048] In a state where the surfaces B1 and B2, which are the main shrinkage directions of the insulating member 2, are thermally shrunk, the height h2 of the internal space of the insulating member 2 is preferably the same as the stack height h1 of the electrode laminate 3. This results in a state where the insulating member 2 exerts a holding force on the electrode laminate 3. In addition, the cross-sectional area S2 of the internal space of the insulating member 2 is preferably 1.0 to 1.2 times the cross-sectional area S1 of the electrode laminate 3. This makes it possible to prevent a decrease in the energy density of the battery cell 1 and deformation of the electrode laminate 3. Note that the cross-sectional area S1 of the electrode laminate 3 means the cross-sectional area of ​​a rectangular region including each electrode when the size of the electrodes constituting the electrode laminate 3 differs depending on the type.

[0049] The compressive stress caused by the thermal contraction of the insulating member 2 is preferably larger than the weakest static friction force between the electrodes and electrolyte layers constituting the electrode stack 3. This allows the insulating member 2 to apply a uniform holding force to the electrode stack 3. If the compressive stress does not satisfy the above, there will be places in the electrode stack 3 where the static friction force is insufficient. Therefore, there is a risk that an external force such as vibration or collision during use of the battery cell 1 will cause the electrodes of the electrode stack 3 to become misaligned, starting from the place where the static friction force is the smallest.

[0050] The length L1 of the insulating member 2 in the extending direction of the current collector tab is preferably 0.98 to 1.2 times the length of the electrode laminate 3 in the extending direction of the current collector tab. If the above is less than 0.98 times, it becomes difficult to ensure sufficient insulation of the electrode laminate 3 and sufficient holding force of the insulating member 2 to hold the electrode laminate 3. If the above exceeds 1.2 times, the volume of the parts that do not contribute to charge and discharge increases, decreasing the energy density of the battery cell 1.

[0051] The opening area of ​​the insulating member 2 is preferably smaller than the end face area of ​​the electrode stack 3. As shown in Fig. 5, narrowed portions 21 are formed at both opening ends of the insulating member 2. This can prevent the electrodes of the electrode stack 3 from shifting in the Y direction.

[0052] The battery cell 1 may have a configuration other than that described above. For example, the electrode stack 3 may have a pressure equalizing member between it and the insulating member 2. This makes it possible to equalize the thickness of the electrode stack 3, and therefore the holding force for the electrode stack 3. Any material that can be deformed by stress can be used as the pressure equalizing member.

[0053] Examples of the pressure equalizing member that can be used include resin materials such as polyimide, polycarbonate, polyacetal, polybutylene terephthalate, polyethylene terephthalate, etc., aluminum with an insulated surface, and surface-insulated metal materials such as SUS, etc. By using a material with high specific rigidity and specific strength, the thickness of the pressure equalizing member can be reduced, so it is more preferable to use a surface-insulated metal material as the pressure equalizing member.

[0054] Second Embodiment A battery cell 1a according to a second embodiment of the present invention will be described below. Descriptions of parts common to the first embodiment may be omitted. The battery cell 1a according to this embodiment has an insulating member 2a having a welded portion 22, as shown in FIG.

[0055] The welded portion 22 is a welded portion formed when the ends of the sheet-like heat-shrinkable film are welded together to obtain the tubular insulating member 2a. The welded portion 22 is formed, for example, by partially overlapping the ends of the sheet-like heat-shrinkable film and heating them to weld and cut them. By configuring the insulating member 2a in this way, a manufacturing method can be applied in which a sheet-like heat-shrinkable film is wrapped around the electrode stack 3 and the ends of the heat-shrinkable film are welded together and cut, simplifying the manufacturing process of the battery cell 1a. The welded portion 22 is disposed on the stacking surface side of the electrode stack 3. Therefore, no step is created on the electrode surface side, which is the installation surface of the battery cell 1a, and the problem of electrode stacking misalignment of the electrode stack 3 does not occur.

[0056] The extension length d of the welded portion 22 is preferably 1.2 to 3 times the thickness of the insulating member 2a. If the above is less than 1.2 times, the heating used to form the welded portion 22 will cause a portion of the insulating member 2a near the welded portion 22 to thermally shrink, resulting in a problem that the holding force in the stacking direction of the electrode stack 3 will not be uniform. If the above is more than 3 times, the volume of the portion that does not contribute to charging and discharging will increase, reducing the energy density of the battery cell 1.

[0057] <Battery cell manufacturing method> The method for manufacturing a battery cell according to the present embodiment includes a step of arranging the electrode laminate in an internal space of a tubular insulating member having heat shrinkability such that the main direction of thermal shrinkage of the insulating member is the stacking direction of the electrode laminate, and a step of heating the surface of the insulating member that is to be placed on the stacking surface side of the electrode laminate to cause thermal shrinkage. The method may also include a step of forming a drawn portion by heating both ends of the insulating member in the direction in which the current collector tab extends of the electrode laminate.

[0058] (Placement process) The disposing step is a step of disposing the electrode laminate in the internal space of a tubular insulating member having heat shrinkability. At this time, the electrode laminate is disposed so that the main shrinkage direction of the insulating member is the stacking direction of the electrode laminate. The tubular insulating member is formed, for example, by welding the ends of a sheet-like heat shrinkable film together. In this case, the disposing step and the formation of the tubular insulating member may be performed simultaneously by wrapping the electrode laminate with a sheet-like heat shrinkable film and welding the ends of the heat shrinkable film together. The insulating member in which the main shrinkage direction of the insulating member is the stacking direction of the electrode laminate is formed, for example, by preheating a part of the heat shrinkable film (a portion to be disposed on the electrode surface side of the electrode laminate) before or after the tubular insulating member is formed by the heat shrinkable film to cause heat shrinkage. At this time, the temperature at which the heat shrinkable film is preheated is preferably 60° C. or higher.

[0059] (Heating process) The heating step is a step of heating the surface of the insulating member disposed on the lamination surface side of the electrode laminate to cause thermal shrinkage. The heating step causes the insulating member to adhere closely to the electrode laminate to exert a holding force. In addition, by heating the surface disposed on the lamination surface side to cause thermal shrinkage, it is possible to suppress the application of excessive stress to the lamination surface of the electrode laminate. Therefore, it is possible to prevent the distance between the electrodes from becoming non-uniform and the electrodes from deforming. The heating temperature in the heating step is preferably 60°C or higher.

[0060] (Drawing section forming process) The drawn portion forming process is a process of forming a drawn portion by pressing a mold formed according to the shape of the end portion against the open end portion of the insulating member after the heating process and heating the molded portion. The formation of the drawn portion can prevent the electrodes of the electrode laminate from shifting in the Y direction. The heating temperature in the drawn portion forming process can be higher than the heating temperature in the heating process.

[0061] The drawn portion forming step includes a first drawn portion forming step of heating one end of the insulating member arranged in the direction in which the current collector tab of the electrode laminate extends, and a second drawn portion forming step of heating the other end of the insulating member arranged in the direction in which the current collector tab of the electrode laminate extends. In addition, it is preferable that an arrangement step is performed between the first drawn portion forming step and the second drawn portion forming step. This makes it possible to easily position the laminate using the drawn portion formed in the first drawn portion forming step.

[0062] Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment and can be modified as appropriate.

[0063] The method for manufacturing a battery cell of the present invention is not limited to the above-described embodiment. For example, an insulating member whose main direction of thermal shrinkage is the stacking direction of the electrode stack may be made of a plurality of materials with different thermal shrinkage rates, and a tubular insulating member may be formed by using a seamless insulating member formed in a tubular shape instead of welding a sheet-shaped heat-shrinkable film. [Explanation of symbols]

[0064] 1, 1a battery cell 2, 2a Insulating material 22 Welded area 3 Electrode laminate 31 Negative electrode 32 Positive electrode 33 Solid electrolyte layer (electrolyte layer)

Claims

1. A method for manufacturing a battery cell having an electrode stack in which positive electrodes and negative electrodes are alternately stacked with an electrolyte layer interposed therebetween, comprising the steps of: a step of preheating a surface of a tubular insulating member having heat shrinkability and disposed on an electrode surface side of the electrode laminate to heat shrink the insulating member; a placement step of placing the electrode stack in the internal space of the insulating member such that the heat-shrunk surface is on the electrode surface side of the electrode stack; and a heating step of heating a surface of the insulating member that is to be disposed on the stacking surface side of the electrode stack to cause thermal shrinkage.

2. The method for manufacturing a battery cell according to claim 1 , wherein the heating step is performed at a heating temperature of 60° C. or higher.

3. The method for manufacturing a battery cell according to claim 1 , wherein at least one of a heating temperature in the heating step and a temperature at which the surface of the insulating member to be disposed on the electrode surface side of the electrode laminate is preheated is 60° C. or higher.

4. 4. The method for manufacturing a battery cell according to claim 1, further comprising a drawn portion forming step of heating both end portions of the insulating member in a direction in which the current collector tabs of the electrode laminate extend to form drawn portions.

5. 5. The method for manufacturing a battery cell according to claim 4, wherein the constricted portion forming step includes a first constricted portion forming step of heating one end of the insulating member in a direction in which the current collector tab of the electrode laminate extends, and a second constricted portion forming step of heating the other end of the insulating member in the direction in which the current collector tab of the electrode laminate extends, and the arrangement step is performed between the first constricted portion forming step and the second constricted portion forming step.

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