Battery Cell

Abstract

The present invention provides a battery cell that can evenly maintain an electrode stack and can make the manufacturing process faster. The battery cell of the present invention has an electrode stack, which is formed by alternating positive and negative electrode dielectric layers, and a tubular insulating component that has heat shrinkage and maintains the electrode stack, and the insulating component has at least two bending portions for positioning components arranged in the internal space. The lengths between the two bending portions in the circumferential direction of the insulating component are preferably equal.

Description

Technical Field

[0001] The invention relates to a battery unit. Background Art

[0002] In the past, as secondary batteries with high energy density, lithium-ion secondary batteries and other secondary batteries have been widely used. Liquid-based secondary batteries have a unit structure in which a separator is present between the positive electrode and the negative electrode and a liquid electrolyte (electrolyte) is filled. In addition, in the case of an all-solid-state battery in which the electrolyte is solid, there is a unit structure in which a solid electrolyte is present between the positive electrode and the negative electrode. A stacked body formed by stacking a plurality of single units constitutes a secondary battery. They are all sealed and packaged by an exterior body.

[0003] As a unit structure of a secondary battery having the above-mentioned stacked body, for example, the following unit structure is known: in a non-aqueous electrolyte secondary battery having a stacked electrode body formed by stacking a positive electrode, a separator and a negative electrode, a porous thin sheet retaining the non-aqueous electrolyte is wound around the outer periphery of the stacked electrode body so as to maintain the stacked structure of the stacked electrode body (for example, refer to patent document 1).

[0004] [Prior art literature]

[0005] [Patent Document]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2014-093128 Summary of the invention

[0007] [Problems to be solved by the invention]

[0008] The secondary battery having the above-mentioned stack has the following problem: stacking deviation may occur between the positive electrode, the negative electrode, and the solid electrolyte. In the technology disclosed in Patent Document 1, since the force holding the stack is weak, stacking deviation may occur when the porous sheet is wound on the stack, when the stack is housed in an exterior body, when an impact is applied from the outside, etc. In the case where the size difference between the positive electrode and the negative electrode is increased to prevent electrodeposition in consideration of the possibility of stacking deviation, the energy density is reduced. In addition, when it is desired to wind a thin sheet body on the stack and hold the stack, a height difference will occur at the winding end, so there is a concern that the electrode will be deformed.

[0009] In order to solve the above-mentioned problem, it is also considered to insert the laminate into the heat shrink film formed into a tubular shape, shrink the heat shrink film by heating, thereby holding the laminate and suppressing the stacking deviation. However, if the heat shrink film containing the laminate is simply heated, the shrinkage length may sometimes be different depending on the surface, and there is a concern that wrinkles will be generated on the outer surface of the heat shrink film. Because of the generation of such wrinkles, the holding force applied by the heat shrink film will not be constant depending on the surface, and there is a concern that the distance between the electrodes will become uneven or the electrodes will be deformed. In order to prevent the above situation, the heat shrink film is positioned and arranged in a manner so that it shrinks uniformly, which takes time and there is a problem that the manufacturing process cannot be made fast.

[0010] The present invention has been made in view of the above-mentioned problems to be solved, and an object of the present invention is to provide a battery cell capable of uniformly holding an electrode stack and speeding up the manufacturing process.

[0011] [Technical means to solve the problem]

[0012] (1) The present invention relates to a battery cell having an electrode stack in which positive electrodes and negative electrodes are alternately stacked with electrolyte layers, the battery cell having a tubular insulating member, the tubular insulating member having heat shrinkability and holding the electrode stack, the insulating member having at least two bent portions for positioning components arranged in an internal space.

[0013] (2) The battery cell according to (1), wherein the lengths between the two bent portions of the insulating member in the circumferential direction are equal.

[0014] (3) The battery cell according to (1) or (2), wherein at least two of the bent portions are provided on a diagonal line of a cross section of the member disposed in the internal space.

[0015] (4) The battery cell according to any one of (1) to (3), wherein an inner angle of the bent portion is greater than 0 degrees and less than or equal to 90 degrees.

[0016] [Effects of the Invention]

[0017] According to the present invention, it is possible to provide a battery cell capable of uniformly holding an electrode stack and speeding up the manufacturing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a perspective view schematically showing a battery unit according to an embodiment of the present invention.

[0019] Figure 2 It is a cross-sectional view schematically showing a battery cell according to the first embodiment of the present invention.

[0020] Figure 3 It is a perspective view schematically showing an insulating member according to a first embodiment of the present invention.

[0021] Figure 4 It is a side view showing the structure of the insulating member according to the first embodiment of the present invention.

[0022] Figure 5 It is a cross-sectional view during the manufacturing process of the battery cell according to the first embodiment of the present invention.

[0023] Figure 6 It is a side view showing the structure of the battery unit according to the first embodiment of the present invention.

[0024] Figure 7 It is a cross-sectional view schematically showing a battery cell according to a second embodiment of the present invention. DETAILED DESCRIPTION

[0025] Hereinafter, specific embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments at all and can be implemented with appropriate modifications within the scope of the purpose of the present invention.

[0026] 《First Implementation Method》

[0027] <Battery unit>

[0028] Figure 1 : is a perspective view showing the outline of the battery cell 1 of the present embodiment. The battery cell 1 of the present embodiment has an electrode stack 3, an insulating member 2 that surrounds and holds the electrode stack 3, and a positive electrode collector tab 4 and a negative electrode collector tab 5 extending from both ends of the electrode stack 3. The battery cell 1 is, for example, a solid-state battery cell having a solid electrolyte as an electrolyte. The battery cell 1 is accommodated in an arbitrary outer body (not shown) formed by a laminate film or the like. In the following description and drawings, the so-called X direction indicates the direction along the electrode surface of the electrode stack 3 (hereinafter, sometimes described as "electrode surface direction"), the so-called Y direction indicates the extension direction of the collector tab (hereinafter, sometimes described as "collector tab extension direction"), and the so-called Z direction indicates the direction along the stacking surface of the electrode stack 3 (hereinafter, sometimes described as "stacking direction").

[0029] (Electrode stack)

[0030] Figure 2 2 is a cross-sectional view in the Y direction showing the outline of the electrode stack 3. The electrode stack 3 is a stack as follows: Figure 2As shown, a plurality of negative electrodes 31 and positive electrodes 32 are alternately stacked, and a solid electrolyte layer 33 is stacked between the negative electrodes 31 and the positive electrodes 32. In this embodiment, the electrode stack 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 section area in the Y direction is S1.

[0031] [negative electrode]

[0032] The negative electrode 31 is not particularly limited, and a known negative electrode that can be used as a negative electrode of a solid-state battery can be applied. The negative electrode 31 is composed of, for example, a thin sheet-like negative electrode current collector and a thin sheet-like negative electrode active material layer.

[0033] The negative electrode current collector is not particularly limited, and for example, metal foil such as stainless steel (SUS) foil and copper (Cu) foil can be used. The negative electrode current collectors of the plurality of negative electrodes 31 are electrically connected to the negative electrode current collector tab 5. The negative electrode current collector tab 5 may be formed integrally with the negative electrode current collector, or may be a component different from the negative electrode current collector and electrically connected to the negative electrode current collector by welding, fusion, etc.

[0034] 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. The composition of the material is also not particularly limited, and in addition to the negative electrode active material, it may also include a solid electrolyte, a conductive additive, or a binder.

[0035] When the battery cell 1 is a lithium ion solid-state battery cell, for example, the negative electrode active material is not particularly limited as long as it can absorb and release lithium ions. For example, 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.

[0036] [positive electrode]

[0037] The positive electrode 32 is not particularly limited, and a known positive electrode that can be used as a positive electrode of a solid-state battery can be applied. The positive electrode 32 is composed of, for example, a thin sheet-shaped positive electrode current collector and a thin sheet-shaped positive electrode active material layer.

[0038] The positive electrode current collector is not particularly limited, and for example, metal foil such as stainless steel (SUS) foil and aluminum (Al) foil can be used. The positive electrode current collectors of the plurality of positive electrodes 32 are electrically connected to the positive electrode current collector tab 4. The positive electrode current collector tab 4 may be formed integrally with the positive electrode current collector, or may be a component different from the positive electrode current collector and electrically connected to the positive electrode current collector by welding, fusion, etc.

[0039] The material constituting the positive electrode active material layer is not particularly limited, and a material known as a positive electrode active material for a solid-state battery can be applied. There is no particular limitation on the composition of the material, and in addition to the positive electrode active material, it may also include a solid electrolyte, a conductive additive or a binder.

[0040] The positive electrode active material is not particularly limited. When the battery cell 1 is, for example, a lithium-ion solid-state battery cell, examples thereof include: transition metal sulfides such as titanium disulfide, molybdenum disulfide, niobium selenide, transition metal oxides such as lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMnO2, LiMn2O4), lithium cobalt oxide (LiCoO2), etc.

[0041] [Solid electrolyte layer]

[0042] The solid electrolyte layer 33 is stacked between the negative electrode 31 and the positive electrode 32, and is formed in a layered form, for example. 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 through the solid electrolyte material.

[0043] The solid electrolyte material is not particularly limited, and examples thereof include sulfide solid electrolyte materials, oxide solid electrolyte materials, nitride solid electrolyte materials, and halide solid electrolyte materials.

[0044] (Insulation parts)

[0045] The insulating member 2 is as follows Figures 2 to 6 As shown, a tubular insulating member having an internal space capable of accommodating the electrode stack 3. The insulating member 2 is a member having heat shrinkability that shrinks by heating, and is composed of, for example, a heat shrink film. By using a tubular insulating member having heat shrinkability as the insulating member 2, the battery cell 1 can be constructed in a manner that does not generate a height difference on the electrode surface of the electrode stack 3, compared with the case where a thin sheet-like insulating member is wound around the electrode stack 3. Therefore, it is possible to prevent the electrode or the solid electrolyte from being broken.

[0046] As the heat shrink film, for example, polyethylene terephthalate shrink film, polystyrene shrink film, polyolefin shrink film, polyvinyl chloride shrink film, polycarbonate shrink film, polyethylene shrink film, polypropylene shrink film, etc. can be used. The heat shrink film can be used alone or in combination of two or more.

[0047] Insulation component 2 such as Figure 3 and Figure 4As shown, it has a tubular shape having an internal space in which the electrode stack 3 can be arranged. The insulating member 2 has a surface A1 and a surface A2 arranged on the electrode surface side of the electrode stack 3, and a surface B1 and a surface B2 arranged on the stacking surface side of the electrode stack 3, and both ends of the collector tab extension direction are open. In this embodiment, the insulating member 2 is a seamless shape without a height difference, but it can also be formed by fusing the ends of a heat shrink film to each other (described in detail in the second embodiment).

[0048] The main shrinkage direction of the insulating component 2 is preferably the stacking direction of the electrode stack 3. In this specification, the so-called "main shrinkage direction" means: when the electrode stack 3 is arranged in the internal space of the insulating component 2 and the insulating component 2 is heat-shrunk by heating to maintain the electrode stack 3, the heat shrinkage rate based on heat shrinkage is higher than that in other directions. The above-mentioned structure of the insulating component 2 has the same meaning as the following situation in this embodiment: the heat shrinkage rate based on heat shrinkage of the surface B1 and surface B2 of the insulating component 2 arranged on the stacking surface side of the electrode stack 3 is higher than that of the surface A1 and surface A2 of the insulating component 2 arranged on the electrode surface side of the electrode stack 3. By having the insulating component 2 with the above-mentioned structure, after the electrode stack 3 is arranged in the internal space of the insulating component 2, the surface B1 and surface B2 are mainly heat-shrunk by heating, so that excessive stress can be suppressed from being applied to the stacking surface of the electrode stack 3. Therefore, it is possible to prevent the distance between the electrodes from becoming uneven or the electrodes from being deformed. In addition, the heat shrinkage rate is the ratio (percentage) of the difference between the length before shrinkage and the length after shrinkage relative to the length before shrinkage.

[0049] The configuration in which the main shrinkage direction of the insulating component 2 is the stacking direction of the electrode stack 3 can be achieved, for example, in the following manner: the electrode surface direction of the insulating component 2, namely, surface A1 and surface A2, is a surface that is pre-heated and shrunk by heating. Thus, after the electrode stack 3 is arranged in the internal space of the insulating component 2, and the surfaces B1 and surface B2 of the insulating component 2 are heat-shrunk by heating to form the battery cell 1, the heat shrinkage of the insulating component 2 is suppressed even when heat is applied from the outside. Therefore, it is possible to prevent the distance between the electrodes from becoming uneven or the electrodes from being deformed after the battery cell 1 is formed. In addition to the above, the surfaces A1 and A2 of the insulating component 2 can be formed of a material with a small heat shrinkage, and the surfaces B1 and surface B2 can be formed of a material with a large heat shrinkage, thereby forming an insulating component 2 in which the main shrinkage direction is the stacking direction of the electrode stack 3.

[0050] The insulating member 2 is as follows Figure 2 and Figure 5 The member disposed in the inner space of the insulating member 2 has a bent portion a and a bent portion b for positioning the electrode stack 3 . Figure 2This is a diagram showing a state where the electrode stack 3 is arranged inside the insulating member 2 and the insulating member 2 is thermally shrunk. Figure 5 This is a diagram showing a state where the electrode stack 3 is arranged and positioned in the internal space of the insulating member 2, and the insulating member 2 is subjected to the heat shrinkage. When the corners of the electrode stack 3 are arranged at the positions of the bends a and b, the bends a and b are elastically deformed and biasing forces act in the direction of clamping the corners of the electrode stack 3. By utilizing this state, the electrode stack 3 can be easily positioned and arranged by arranging the corners of the electrode stack 3 at the bends a and b in the internal space of the insulating member 2, so that the manufacturing process of the battery cell 1 can be accelerated.

[0051] In this embodiment, the bends of the insulating member 2 are two bends a and b provided on diagonal lines of the cross section in the Y direction of the electrode stack 3. The bends are preferably four bends provided at the four corners of the electrode stack.

[0052] The circumferential direction of the insulating component 2 is Figure 3 The lengths of the bends a and b in the TD direction shown are preferably equal. Thus, when the electrode stack 3 having a substantially rectangular parallelepiped shape is positioned in the internal space of the insulating component 2, the lengths of the surface B1 and the surface B2 in the TD direction can be made equal, so that the lengths of the surface B1 and the surface B2 in the TD direction that are heat-shrunk by heating are also equal, thereby preventing wrinkles from being generated on the outer surface of the heat-shrinkable film. In addition, the holding force of the insulating component 2 on the electrode stack 3 can be made uniform. Therefore, deformation of the electrode stack 3, stacking deviation of the electrode, deformation of the electrode, etc. can be prevented.

[0053] The folding method for forming the bent portion in the insulating member 2 is not particularly limited as long as it is a method that can give plastic deformation to the material to form the fold. A simple method is, for example, a method in which a force is applied to the tubular insulating member 2 from the circumferential direction to bend it, thereby applying pressure to the folded portion. In addition, even after the insulating member 2 is folded to form the battery cell 1, by disassembling the insulating member 2 and cutting it, the bent portion can remain as a fold and can be detected.

[0054] The inner angle θ2 of the bends a and b before the insulating member 2 is thermally shrunk and brought into close contact with the electrode stack 3 is preferably as follows: Figure 5 The angle is shown to be greater than 0 degrees and less than 90 degrees. As a result, a clear bending ridge line can be formed on the insulating member 2, so that the manufacturing process of the battery cell 1 can be more preferably accelerated. In addition, when the insulating member 2 is heat-shrunk and closely attached to the electrode stack 3, Figure 2The inner angle θ1 of the bend a and the bend b shown is larger than the inner angle θ2, and becomes an angle corresponding to the shape of the corner of the electrode stack 3 (approximately 90 degrees in this embodiment). However, the inner angle θ1 is less than 90 degrees. In contrast, when the insulating member without a bend is heat-shrunk and closely attached to the electrode stack, the inner angle of the fold formed along the corner of the electrode stack is sometimes larger than 90 degrees. In addition, a clear bend ridge line is not formed.

[0055] In a state where the insulating member 2 is thermally shrunk and closely adhered to the electrode stack 3, when the thickness of the insulating member 2 is t, Figure 2 The length of the bend R formed by the bend a and the bend b shown is preferably 0.2t≦R<2t. When the length of R is less than 0.2t, there is a concern that the electrode stack 3 may be deformed due to the stress applied to the corners of the electrode stack 3. When the length of R exceeds 2t, the volume of the insulating component 2 that does not contribute to charging and discharging increases, thereby reducing the energy density of the battery cell 1.

[0056] The heat shrinkage rate of the collector tab extension direction of the insulating component 2 is preferably -5% to 5%. The heat shrinkable film constituting the insulating component 2 has anisotropy. Figure 3 The insulating component 2 shown shrinks in the circumferential direction, i.e., the TD direction, and generates a holding force on the electrode stack 3. On the other hand, if the insulating component 2 expands or shrinks in the MD direction, i.e., the direction in which the collector tab extends, stress acts in the direction in which the electrodes and electrolyte layers constituting the electrode stack 3 deviate. Therefore, the thermal shrinkage rate of the insulating component 2 in the MD direction is preferably close to 0%. In the case where the thermal shrinkage rate of the insulating component 2 in the MD direction exceeds 5%, the stress exceeds the static friction force, and there is a concern that stacking offset will occur. In the case where the thermal shrinkage rate of the insulating component 2 in the MD direction is less than -5%, in addition to stacking offset, the volume of the insulating component 2 will also increase, and there is a concern that the energy density of the battery cell 1 will be reduced.

[0057] Insulation part 2 Figure 3 The heat shrinkage rate in the TD direction shown is preferably 5% to 80%. When the heat shrinkage rate in the TD direction of the insulating member 2 is less than 5%, the holding force of the electrode stack 3 obtained by the heat shrinkage of the insulating member 2 becomes insufficient, and there is a concern that the stacking of the electrodes may shift. When the heat shrinkage rate in the TD direction of the insulating member 2 exceeds 80%, there is an excessive holding force on the electrode stack 3, and there is a concern that the electrode stack 3 may be deformed, the stacking of the electrodes may shift, the electrodes may be deformed, and the like may occur.

[0058] While the insulating member 2 is being thermally shrunk in the main shrinking directions of the surface B1 and the surface B2, Figure 4When the thickness of the surface A1 and the surface A2 arranged on the electrode surface side of the electrode stack 3 is tv and the thickness of the surface B1 and the surface B1 arranged on the stacking surface side of the electrode stack 3 is th, the relationship of the following formula (1) is preferably satisfied.

[0059] 5%<|(tv-th) / tv)|≦150%···Formula (1)

[0060] When |(tv-th) / tv)| in the above formula (1) is less than 5%, there is a concern that deformation of the electrode stack 3, stacking deviation of the electrodes, deformation of the electrodes, etc. may occur. When |(tv-th) / tv)| in the above formula (1) exceeds 150%, the amount of thermal shrinkage is too large, resulting in reduced dimensional accuracy and easy wrinkling of the insulating member 2.

[0061] In addition, when tv>th, the direction in which the insulating member 2 is preliminarily thermally shrunk is preferably the X direction, and the temperature Tx at which the surfaces A1 and A2 are thermally shrunk is greater than the temperature Tz at which the surfaces B1 and B2 are thermally shrunk (Tx>Tz), thereby enabling a uniform holding force to be applied to the electrode stack 3. In the case of tv<th, the temperature Tx at which the surfaces A1 and A2 are thermally shrunk is less than the temperature Tz at which the surfaces B1 and B2 are thermally shrunk (Tx<Tz), thereby enabling a uniform holding force to be applied to the electrode stack 3. In addition, the thermal shrinkage temperatures Tx and Tz of the insulating member 2 are preferably 60°C or higher. In the case where the battery cell 1 is a lithium ion secondary battery, the upper limit of the operating temperature of the lithium ion secondary battery is about 60°C, so by thermally shrinking the insulating member 2 at 60°C or higher, thermal shrinkage of the insulating member 2 during use of the battery cell 1 can be suppressed. That is, deformation of the electrode stack 3, stacking deviation of the electrode, deformation of the electrode, etc. during use of the battery cell 1 can be suppressed.

[0062] When the main contraction directions of the insulating component 2, namely, the surface B1 and the surface B2 are thermally contracted, the height h2 of the internal space of the insulating component 2 is preferably the same as the stacking height h1 of the electrode stack 3. Thus, the insulating component 2 exerts a holding force on the electrode stack 3. In addition, the cross-sectional area S2 of the internal space of the insulating component 2 is preferably 1.0 to 1.2 times the cross-sectional area S1 of the electrode stack 3. Thus, it is possible to prevent the energy density of the battery cell 1 from being reduced and the electrode stack 3 from being deformed. In addition, when the sizes of the electrodes constituting the electrode stack 3 differ depending on the type, the cross-sectional area S1 of the electrode stack 3 refers to the cross-sectional area of ​​the rectangular region containing each electrode.

[0063] The compressive stress generated by the thermal contraction of the insulating component 2 is preferably greater than the weakest static friction between the electrodes and the electrolyte layer constituting the electrode stack 3. Thus, a uniform holding force can be applied to the electrode stack 3 by the insulating component 2. Assuming that the compressive stress does not satisfy the above conditions, a portion with insufficient static friction will be generated in the electrode stack 3. Therefore, there is a concern that the stacking deviation of the electrodes of the electrode stack 3 will occur starting from the portion with the smallest static friction due to external forces such as vibration or collision during use of the battery cell 1.

[0064] The length L1 of the insulating member 2 in the direction in which the collector tab extends is preferably 0.98 to 1.2 times the length of the collector tab of the electrode stack 3. When the length L1 is less than 0.98 times, it is difficult to fully ensure the insulation of the electrode stack 3 and the holding force of the insulating member 2 on the electrode stack 3. When the length L1 exceeds 1.2 times, the volume of the portion that does not contribute to charging and discharging increases, so the energy density of the battery cell 1 decreases.

[0065] The opening area of ​​the insulating member 2 is preferably smaller than the end surface area of ​​the electrode stack 3. Figure 6 As shown in FIG. 1 , constricted portions 21 are formed at both ends of the opening of the insulating member 2 . This can prevent the electrode stack 3 from shifting in the Y direction.

[0066] The battery cell 1 may have a configuration other than the above. For example, the electrode stack 3 may have a voltage equalization member between the electrode stack 3 and the insulating member 2. This makes it possible to make the thickness of the electrode stack 3 uniform, and thus make the holding force on the electrode stack 3 uniform. As the voltage equalization member, any material that can be deformed by stress can be used.

[0067] Examples of the voltage equalizing member include resin materials such as polyimide, polycarbonate, polyacetal, polybutylene terephthalate, and polyethylene terephthalate, and surface-insulated metal materials such as aluminum and SUS with surface insulation treatment. By using a material with high relative rigidity and relative strength, the thickness of the voltage equalizing member can be reduced. In this regard, it is more preferable to use a surface-insulated metal material as the voltage equalizing member.

[0068] <<Second Implementation Method>>

[0069] Hereinafter, a battery cell 1a according to a second embodiment of the present invention will be described. The description of the parts common to the first embodiment may be omitted. Figure 7 As shown, the battery cell 1 a of the present embodiment includes an insulating member 2 a including a fusion bond 22 .

[0070] The fusion portion 22 is a fusion portion formed when the ends of the thin sheet-like heat shrink film are fused to each other to obtain the tubular insulating component 2a. The fusion portion 22 is formed, for example, by partially overlapping the ends of the thin sheet-like heat shrink film with each other and heating them, thereby fusing and melting. By constructing the insulating component 2a in this way, a manufacturing method in which a thin sheet-like heat shrink film is wound on the electrode stack 3 to fuse and melt the ends of the heat shrink film can be applied, thereby simplifying the manufacturing process of the battery cell 1a. In addition, the fusion portion 22 is arranged on the stacking surface side of the electrode stack 3. Therefore, there is no height difference on the installation surface of the battery cell 1a, that is, the electrode surface side, so there is no problem of stacking deviation of the electrodes of the electrode stack 3.

[0071] The extension length d of the fusion bond 22 is preferably 1.2 to 3 times the thickness of the insulating member 2a. When the extension length d is less than 1.2 times, the heating during the formation of the fusion bond 22 causes the heat shrinkage of the vicinity of the fusion bond 22 of the insulating member 2a, thereby causing a problem that the holding force in the stacking direction of the electrode stack 3 becomes uneven. When the extension length d exceeds 3 times, the volume of the portion that does not contribute to charging and discharging increases, so the energy density of the battery cell 1 decreases.

[0072] <Battery cell manufacturing method>

[0073] The manufacturing method of the battery cell of the present embodiment comprises: a placement step of placing the electrode stack in the internal space of the heat-shrinkable tubular insulating member in such a manner that the main shrinkage direction of the heat shrinkage of the insulating member becomes the stacking direction of the electrode stack; and a heating step of heating the surface of the insulating member disposed on the stacking surface side of the electrode stack to heat shrink it. In addition, after the heating step, there may be a shrinkage portion forming step of heating both ends of the electrode stack of the insulating member in the extension direction of the current collector tab to form the shrinkage portion.

[0074] (Configuration process)

[0075] The configuration step is a step of configuring the electrode stack in the internal space of a tubular insulating component that has heat shrinkability. At this time, the electrode stack is configured in such a way that the main shrinkage direction of the heat shrinkage of the insulating component becomes the stacking direction of the electrode stack, and the corner of the electrode stack is configured at the bending portion of the insulating component. In addition, the tubular insulating component is formed, for example, by fusing the ends of a thin sheet of heat shrinkable film to each other. In this case, the configuration step and the formation of the tubular insulating component can be performed simultaneously in the following manner: the electrode stack is wrapped with a thin sheet of heat shrinkable film, and the ends of the heat shrinkable film are fused to each other. In addition to the above steps, a crease processing step can also be provided, which is to pre-form the insulating component, bend it by applying force in the circumferential direction of the tubular insulating component, and apply pressure to the folded portion, thereby forming a bent portion in the insulating component.

[0076] An insulating component in which the main shrinkage direction of heat shrinkage becomes the stacking direction of the electrode stack is formed, for example, by preheating a part of the heat shrinkable film (the part arranged on the electrode surface side of the electrode stack) to heat shrink it before or after the tubular insulating component is formed from the heat shrinkable film.

[0077] (Heating process)

[0078] The heating process is a process of heating the surface of the insulating component disposed on the stacking surface side of the electrode stack to heat shrink it. Through the heating process, the insulating component is closely attached to the electrode stack to exert a holding force. In addition, by heating the surface disposed on the stacking surface side to heat shrink it, it is possible to suppress excessive stress on the stacking surface of the electrode stack. Therefore, it is possible to prevent the distance between the electrodes from becoming uneven or the electrodes from deforming. The heating temperature in the heating process is preferably above 60°C.

[0079] (Constriction Forming Step)

[0080] The shrinkage forming step is a step of forming the shrinkage by pressing a mold formed according to the end shape against the open end of the insulating component after the heating step. By forming the shrinkage, the electrode deviation in the Y direction of the electrode stack can be prevented. The heating temperature in the shrinkage forming step can be set to a temperature higher than the heating temperature in the heating step.

[0081] The shrinkage forming step includes: a first shrinkage forming step of heating one end of the insulating component arranged in the direction in which the collector tab of the electrode stack extends; and a second shrinkage forming step of heating the other end of the insulating component arranged in the direction in which the collector tab of the electrode stack extends. In addition, it is preferred that the arrangement step is performed between the first shrinkage forming step and the second shrinkage forming step. Thus, the shrinkage formed by the first shrinkage forming step can be used to easily position the stack.

[0082] As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, It can change suitably.

[0083] The manufacturing method of the battery cell of the present invention is not limited to the description of the above-mentioned embodiment. For example, the insulating component whose main shrinkage direction of heat shrinkage is the stacking direction of the electrode stack can be composed of multiple materials with different heat shrinkage rates, and the formation of the tubular insulating component can use a seamless insulating component formed into a tubular shape instead of fusing a thin sheet of heat shrinkable film.

[0084] Reference numerals

[0085] 1,1a:Battery unit

[0086] 2,2a: Insulation parts

[0087] 3: Electrode stack

[0088] 31: Negative electrode

[0089] 32: Positive electrode

[0090] 33: Solid electrolyte layer (electrolyte layer)

[0091] a,b: bending part

[0092] θ2: interior angle

Claims

1. A battery cell comprising an electrode stack, wherein the electrode stack is formed by alternately stacking positive electrodes and negative electrodes with electrolyte layers interposed therebetween. The battery cell includes a tubular insulating member having heat shrinkability and holding the electrode stack. The insulating member has at least two bent portions for positioning the members arranged in the internal space. The corner of the electrode stack is arranged at the position of the bent portion, Wherein, either an internal angle θ2 of the bending portion before the insulating component is thermally shrunk and closely attached to the electrode stack or an internal angle θ1 of the bending portion when the insulating component is thermally shrunk and closely attached to the electrode stack is greater than 0 degrees and less than 90 degrees, and the internal angle θ1 is greater than the internal angle θ2. 2 . The battery cell according to claim 1 , wherein the lengths between the two bent portions of the insulating member in the circumferential direction are equal. 3 . The battery cell according to claim 1 , wherein at least two of the bent portions are provided on a diagonal line of a cross section of the member disposed in the internal space.

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