Cylindrical solid-state battery and its manufacturing method

Abstract

The problem this invention aims to solve is to improve the adhesion between the solid electrolyte layer and the electrodes, and prevent a decrease in ion conductivity, even in a cylindrical solid-state battery with a winding assembly. To address this problem, a cylindrical solid-state battery is provided, comprising a winding assembly with sheet-like electrode stacks wound around it. The sheet-like electrode stacks have a positive electrode and a negative electrode stacked between them and a solid electrolyte layer. A sheet-like outer packaging material is joined to or extends to the outer periphery of the electrode stacks, and the outer packaging material is continuously wound from the electrode stacks and fixed at its ends, thereby forming the outermost periphery of the cylindrical solid-state battery.

Description

Technical Field

[0001] This invention relates to a wound cylindrical solid-state battery and its manufacturing method. Background Technology

[0002] A wound cylindrical solid-state battery has a winding assembly formed by winding sheet-like electrode stacks, wherein positive and negative electrodes are stacked in the sheet-like electrode stacks with a solid electrolyte layer in between. The wound cylindrical solid-state battery has a structure in which current collectors extending from the positive and negative electrodes are collected by cover materials on the top and bottom of the cylindrical winding assembly.

[0003] In all-solid-state batteries such as lithium-ion batteries, positive and negative electrodes are stacked in layers separated by a solid electrolyte layer, allowing for the conduction of lithium ions. Therefore, if the seal between the solid electrolyte layer and the two electrodes decreases, the ion conductivity will decrease. Consequently, when a module is constructed from single cells, it is necessary to constrain and apply pressure to maintain the seal.

[0004] However, existing wound cylindrical solid-state batteries, due to their structure of inserting the winding assembly into an outer packaging container such as a can, create a gap between the winding assembly and the outer packaging container. Therefore, it is difficult to apply pressure to maintain this gap. To address this, a technique for sealing the winding assembly to the outer packaging container has been disclosed (see Patent Document 1), but it still uses an outer packaging container, and there is a need for a simpler method to maintain pressure through this constraint.

[0005] [Preliminary Technology Documents]

[0006] (Patent Documents)

[0007] Patent Document 1: Japanese Patent Application Publication No. 2014-082105 Summary of the Invention

[0008] [The problem the invention aims to solve]

[0009] The present invention was made in view of the above-mentioned problems, and its object is to provide a means, with a simple structure, to improve the adhesion between the solid electrolyte layer and the electrode and prevent the reduction of ion conductivity, even in a cylindrical solid battery with a winding assembly.

[0010] [Technical means to solve the problem]

[0011] The inventors discovered that by pre-integrating a sheet-like outer packaging material by joining or extending it to the outer peripheral end of the electrode stack of the winding assembly, and then winding the outer packaging material while applying tension, the aforementioned problems can be solved, thus completing the present invention. Specifically, the present invention provides the following:

[0012] (1) A cylindrical solid-state battery comprising a winding assembly, wherein a sheet-like electrode stack is wound around the winding assembly, and a positive electrode and a negative electrode are stacked on the sheet-like electrode stack with a solid electrolyte layer in between, wherein,

[0013] The sheet-like outer packaging material is joined to or extends to the outer peripheral end of the aforementioned electrode laminate.

[0014] The aforementioned outer packaging material is continuously wound around the aforementioned electrode stack and fixed at the ends, thereby forming the outermost periphery of the aforementioned cylindrical solid battery.

[0015] According to the invention of (1), the outer peripheral end of the electrode stack is pre-integrated with the sheet-like outer packaging material by joining or extending, and the outer packaging material is wound while being stressed, thereby maintaining the constraint state between the solid electrolyte layer and the two electrodes. Moreover, since the outer packaging material directly becomes the outer packaging container, there is no need for an outer packaging container and no need to insert the winding assembly into the container, thus resulting in a simple structure.

[0016] (2) According to the cylindrical solid battery of (1), the aforementioned negative electrode is composed of an electrode current collector and an electrode composite material, the electrode current collector is composed of a metal porous body, and the electrode composite material is filled in the pores of the aforementioned metal porous body.

[0017] According to the invention of (2), even when the negative electrode uses an active material that is easily expanded, such as graphite, the expansion can still be effectively absorbed by utilizing the three-dimensional network structure of the metal porous body.

[0018] (3) The cylindrical solid battery according to (2), wherein the electrode composite material of the aforementioned negative electrode contains an expanding agent.

[0019] According to the invention of (3), by utilizing the expansion of the negative electrode, not only can a pushing effect from the outside of the winding be obtained, but also a pushing effect from the inside of the winding be obtained.

[0020] (4) The cylindrical solid battery according to any one of (1) to (3), wherein the aforementioned outer packaging material is a current collector extending from the aforementioned electrode stack.

[0021] According to the invention of (4), for example, by making the current collector of the negative electrode stainless steel and extending it directly in a manner that does not form an electrode composite material, it can be used as an outer packaging material of stainless steel.

[0022] (5) The cylindrical solid battery according to any one of (1) to (4), wherein the width of the outer packaging material in the cylindrical height direction is narrower than the width of the electrode stack and wider than the width of the electrode composite material layer of the electrode stack, and at least a portion of the electrode current collector extends from the width end of the outer packaging material.

[0023] According to the invention of (5), the engagement with the cover component connected to the external terminal is improved, and the manufacturing steps can be further shortened.

[0024] (6) A method for manufacturing a cylindrical solid-state battery, the cylindrical solid-state battery comprising a winding assembly, the winding assembly having a sheet-like electrode stack wound around it, the sheet-like electrode stack having a positive electrode and a negative electrode stacked therebetween, separated by a solid electrolyte layer, and the manufacturing method comprising:

[0025] The first step involves joining or extending the sheet-like outer packaging material to the outer peripheral end of the aforementioned electrode laminate; and...

[0026] The second step involves fixing the ends by winding the aforementioned electrode stack and outer packaging material with a specified tension, thereby forming the outermost periphery of the aforementioned cylindrical solid-state battery.

[0027] According to the invention of (6), the same effect as that of (1) can be obtained. In addition, by winding and fixing with a specified tension, a so-called tightly wound state is achieved, thus maintaining sufficient pressure between the layers of the electrode stack.

[0028] (7) The method for manufacturing a cylindrical solid-state battery according to (6), wherein, in the aforementioned second step, the winding is performed while being squeezed from the outside of the aforementioned winding assembly.

[0029] According to the invention of (7), the material is also pressed from the outside using a roller press or the like, thereby further maintaining sufficient pressure between the layers of the electrode laminate.

[0030] (8) The method for manufacturing a cylindrical solid-state battery according to (6) or (7), wherein, in the aforementioned second step, the outer diameter of the cylindrical solid-state battery is kept approximately constant by adjusting the winding length of the aforementioned outer packaging material.

[0031] According to the invention of (8), even if the layer structure, layer thickness, etc. of the electrode stack change, the outer diameter of the cylindrical solid battery can be made to be approximately the same. Attached Figure Description

[0032] Figure 1 This is a schematic perspective view illustrating one embodiment of the cylindrical solid-state battery of the present invention.

[0033] Figure 2This is a cross-sectional view illustrating one embodiment of the layered structure of the electrode current collector.

[0034] Figure 3 It is illustrated in the first step, formed by a roller press. Figure 2 A schematic perspective view of the state of the electrode current collector.

[0035] Figure 4 This is a side view illustrating an example of joining the winding assembly and outer packaging material in the second step.

[0036] Figure 5 This is a side view illustrating another example of joining the winding assembly and outer packaging material in the second step.

[0037] Figure 6 This is a side view illustrating the state of the winding being squeezed from the outside by a roller press in the second step.

[0038] Figure 7 This is a schematic perspective view illustrating a variation of the winding assembly. Detailed Implementation

[0039] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. The content of the present invention is not limited to the embodiments described below. It should be noted that in the following embodiments, a lithium-ion battery as a solid-state battery is used as an example, but the invention can also be applied to solid-state batteries other than lithium-ion batteries.

[0040] <Overall Structure of Cylindrical Solid-State Battery>

[0041] like Figure 1 As shown, this embodiment of the method Figure 1 The cylindrical solid-state battery 100 is a wound lithium-ion secondary battery, comprising a cylindrical winding assembly 110, a negative electrode cap component 140 electrically bonded to the upper and bottom surfaces of the winding assembly 110, and a positive electrode cap component 150. The winding assembly 110 comprises a sheet-like electrode laminate 120 wound around a core material (not shown) and an outer packaging material 130 continuously wound around the outer periphery of the electrode laminate 120.

[0042] <Structure of Electrode Laminate>

[0043] like Figure 2As shown, the electrode stack 120 in this embodiment is the counter electrode constituting the basic structure of positive electrode / solid electrolyte layer / negative electrode / solid electrolyte layer / positive electrode. Current collectors are formed on each electrode; in this embodiment, it is a layer structure of positive electrode current collector 122 / positive electrode composite material 122a / solid electrolyte layer 160 / negative electrode composite material 121a / negative electrode current collector 121 / negative electrode composite material 121a / solid electrolyte layer 160 / positive electrode composite material 122a / positive electrode current collector 122. On the extension surface of each current collector ( Figure 2 An insulating layer 170 is formed on both sides of the cross-section.

[0044] The structure of the electrode stack in this invention can be any stack of positive and negative electrodes separated by a solid electrolyte layer. For example, it can be a structure of negative electrode / solid electrolyte layer / positive electrode / solid electrolyte layer / negative electrode.

[0045] like Figure 3 As shown, the electrode stack 120 can be obtained by extruding and stacking the first stack 120A, the second stack 120B, and the third stack 120C using a roller press P, etc. (first step). The first stack 120A is a positive electrode current collector 122 / positive electrode composite material 122a / solid electrolyte layer 160, the second stack 120B is a negative electrode composite material 121a / negative electrode current collector 121 / negative electrode composite material 121a, and the third stack 120C is a solid electrolyte layer 160 / positive electrode composite material 122a / positive electrode current collector 122.

[0046] The result, such as Figure 2 , Figure 3 As shown, a negative current collector 121 and a positive current collector 122 extend from the respective end edges of the electrode stack 120 in the width direction of the winding assembly 110. Furthermore, in the state of the winding assembly 110, the negative current collector 121 is electrically bonded to the negative electrode cap member 140 to form a negative electrode, and the positive current collector 122 is electrically bonded to the positive electrode cap member 150 to form a positive electrode (see reference). Figure 1 ).

[0047] <Structure of the current collector>

[0048] In this invention, the current collector can be a conventionally known current collector foil made of metal foils such as nickel, aluminum, stainless steel, titanium, copper, and silver, but it is preferred to have it at least disposed on... Figure 2 The central electrode current collector ( Figure 2 The negative electrode current collector 121 is a current collector composed of a porous metal body with interconnected holes (connecting holes) and is filled with an electrode composite material inside.

[0049] In this case, in the hole of the current collector, the composite material filling region filled with electrode composite material containing electrode active material constitutes the electrode layer, and the unfilled region of composite material not filled with electrode composite material constitutes the current collector.

[0050] The current collector is composed of a porous metal body with continuously connected pores. By having continuously connected pores, positive electrode composite materials or negative electrode composite materials containing electrode active materials can be filled inside the pores, increasing the mass of electrode active material per unit area of ​​the electrode layer. As for the aforementioned porous metal body, there are no particular limitations as long as it has continuously connected pores; examples include foamed metal, metal mesh, expanded metal, perforated metal, and metal nonwoven fabric with foamed pores.

[0051] The metal used in a porous metal body is not particularly limited as long as it is conductive; examples include nickel, aluminum, stainless steel, titanium, copper, and silver. Among these, foamed aluminum, foamed nickel, and foamed stainless steel are preferred as current collectors constituting the positive electrode, while foamed copper and foamed stainless steel are preferred as current collectors constituting the negative electrode.

[0052] By using porous metal current collectors, the mass of active material per unit area of ​​the electrode can be increased, resulting in improved volumetric energy density of lithium-ion secondary batteries. Furthermore, since the immobilization of the positive and negative electrode composite materials becomes easier, unlike existing electrodes using metal foil as current collectors, thickening the coating slurry used to form the electrode composite layer is unnecessary when creating a thick film. This reduces the need for binders such as organic polymers required for thickening. Consequently, the capacity per unit area of ​​the electrode can be increased, enabling high-capacity lithium-ion secondary batteries.

[0053] In particular, in this invention, even when the negative electrode uses an easily expandable active material such as graphite, the expansion can be effectively absorbed by utilizing the three-dimensional network structure of the metal porous body.

[0054] <Structure of Electrode Composite Materials>

[0055] The positive electrode composite material and the negative electrode composite material are respectively coated on the current collector foil, or filled into the pores when the current collector is a porous metal body. The positive electrode composite material and the negative electrode composite material respectively contain positive electrode active material and negative electrode active material as essential components.

[0056] (Electrode active material)

[0057] As a positive electrode active material, there are no particular limitations as long as it can absorb and release lithium ions. Examples include LiCoO2 and Li(Ni)2. 5 / 10 Co2 / 10 Mn 3 / 10 O2, Li(Ni) 6 / 10 Co 2 / 10 Mn 2 / 10 O2, Li(Ni) 8 / 10 Co 1 / 10 Mn 1 / 10 O2, Li(Ni) 0.8 Co 0.15 Al 0.05 O2, Li(Ni) 1 / 6 Co 4 / 6 Mn 1 / 6 O2, Li(Ni) 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiCoO4, LiMn2O4, LiNiO2, LiFePO4, lithium sulfide, sulfur, etc.

[0058] As a negative electrode active material, there are no particular limitations as long as it can absorb and release lithium ions. Examples include metallic lithium, lithium alloys, metal oxides, metal sulfides, metal nitrides, Si, SiO, as well as carbon materials such as artificial graphite, natural graphite, hard carbon, and soft carbon.

[0059] (Other ingredients)

[0060] Electrode composite materials can contain any components other than electrode active materials and ion-conducting particles. There are no particular limitations on these other components, as long as they can be used in the manufacture of lithium-ion secondary batteries. Examples include conductive additives and binders. Examples of conductive additives for the positive electrode include acetylene black, and examples of binders for the positive electrode include polyvinylidene fluoride. Examples of binders for the negative electrode include sodium carboxymethyl cellulose, styrene-butadiene rubber, and sodium polyacrylate.

[0061] In this invention, the negative electrode composite material may be intentionally made to contain SiO or Si as an expanding agent. In this case, the positive electrode composite material may contain Li-aluminum alloy or olivine iron Li, which releases Li at a lower potential than active materials such as NCM. This structure can also be made to operate outside the battery's State of Charge (SOC) range, using the expanding agent in the negative electrode to generate internal pressure from the winding assembly, thereby maintaining contact between the solid electrolyte layer and the electrode composite material layer.

[0062] <Solid Electrolyte Layer>

[0063] The solid electrolyte constituting the solid electrolyte layer is not particularly limited, and examples include sulfide-based solid electrolyte materials, oxide-based solid electrolyte materials, nitride-based solid electrolyte materials, and halide-based solid electrolyte materials. For example, in lithium-ion batteries, examples of sulfide-based solid electrolyte materials include LPS-based halogens (Cl, Br, I), Li₂S-P₂S₅, and Li₂S-P₂S₅-LiI. It should be noted that the description of "Li₂S-P₂S₅" refers to a sulfide-based solid electrolyte material made using a combination of raw materials containing Li₂S and P₂S₅, and the same applies to other descriptions. For example, in lithium-ion batteries, examples of oxide-based solid electrolyte materials include NASICON-type oxides, garnet-type oxides, and perovskite-type oxides. As for NASICON (Na superionic conductor) type oxides, examples include oxides containing Li, Al, Ti, P, and O (e.g., Li₂S₅). 1.5 Al 0.5 Ti 1.5 (PO4)3). As garnet-type oxides, examples include oxides containing Li, La, Zr, and O (e.g., Li7La3Zr2O). 12 Examples of perovskite oxides include oxides containing Li, La, Ti, and O (e.g., LiLaTiO3).

[0064] <Winding assembly and outer packaging materials>

[0065] Next, we will refer to Figures 4 to 6 The outer packaging material 130, which is a feature of this invention, is described in detail. It should be noted that, for... Figures 1 to 3 For identical structures, use the same reference numerals and omit their descriptions.

[0066] like Figure 4 As shown, the winding assembly 110 forms a joint portion 180 with the outer packaging material 130 in the region including the end edge 120e of the wound electrode stack 120 via a joining member 190. The end edge of the outer packaging material 130 in the longitudinal direction (MD direction) is fixed by welding or the like. The width of the outer packaging material 130 is approximately the same as the width of the electrode stack 120 (excluding the extension portion of the current collector). The length of the outer packaging material 130 in the longitudinal direction (MD direction) can be formed as long as it covers at least the entire circumference of the winding assembly 110, or it can be wound multiple times. The diameter of the cylindrical solid-state battery can be adjusted by adjusting the number of turns (winding length) of the outer packaging material.

[0067] The outer packaging material 130 is a sheet-like component, and is preferably made of a thin sheet of metal or the like. The joining component 190 is an insulating component such as double-sided tape.

[0068] like Figure 5 As shown, the outer packaging material 130 can be formed to be rolled into the electrode stack 120 without the use of bonding members. In this invention, "bonding" also includes the stacked state resulting from such rolling.

[0069] The outer packaging material in this invention does not necessarily have to be a different component from the electrode laminate. For example, a current collector extending from the electrode laminate can also constitute the outer packaging material. For example, it is also possible to... Figure 2 The negative electrode current collector 121 of the electrode laminate 120 is made of stainless steel. The coating of the negative electrode composite material 121a formed on both sides of the negative electrode composite material 121a ends in the length direction (MD direction) to form the end edge of the negative electrode composite material 121a. From this end edge, only the negative electrode current collector 121 extends outward, which serves as the outer packaging material. That is, the outer packaging material in this invention includes not only the "joint" with the electrode laminate, but also the outer packaging material "extending" from the electrode laminate.

[0070] like Figure 6 As shown, the electrode laminate 120 and the outer packaging material 130 continuous therewith are wound at a specified tension to form a winding shape, resulting in a winding assembly 110 (second step). At this time, in addition to tension adjustment, adjustments can also be made from the outside of the winding assembly 110 (in... Figure 6 The winding process is carried out simultaneously with extrusion by rollers such as P from point 3.

[0071] According to the present invention, the outer peripheral end of the electrode laminate and the sheet-like outer packaging material are pre-integrated by joining or extending, and the end is fixed by winding while applying tension to the outer packaging material. Thus, since the constraint state between the solid electrolyte layer and the two electrodes can be maintained without forming a gap with the outer packaging container, the adhesion between the solid electrolyte layer and the electrodes can be improved, preventing a decrease in ion conductivity. Furthermore, since the outer packaging material directly becomes the outer packaging container, an outer packaging container is not required, and there is no need to insert a winding assembly inside the container, resulting in a simple structure and shortening the manufacturing steps.

[0072] <Example of a modified winding>

[0073] like Figure 7 As shown, the width of the outer packaging material 130a in the height direction of the cylinder in the winding assembly 110a is narrower than the width of the electrode laminate 120, but wider than the width of the electrode composite materials (121a, 122a). As a result, a portion of the electrode current collectors 121, 122 protrudes from both ends in the width direction of the outer packaging material 130a, which is consistent with... Figure 1 The winding group 110 is different, but the structure is the same as the above embodiment.

[0074] According to this embodiment, within the range of expansion and contraction of the electrode composite material, the constraint generated by the outer packaging material can be maintained. The electrode current collector extends from the outer packaging material, thereby improving the fit with the cover parts 140 and 150 connected to the external terminals (e.g., ensuring the joint of ultrasonic bonding, resistance welding, laser welding, etc.), and further shortening of the manufacturing steps can also be achieved.

[0075] Alternatively, a portion of either electrode current collector 121 or 122 may extend from the end of the outer packaging material 130a. Alternatively, either electrode may be connected to the outer packaging material at the same potential. However, since the potential of the positive electrode is higher, the negative electrode side is preferred while maintaining the electrode potential in the outer packaging material.

[0076] The preferred embodiments of the present invention have been described above, but the content of the present invention is not limited to the above embodiments and can be appropriately modified.

[0077] Figure Labels

[0078] 100: Cylindrical solid-state battery

[0079] 110: Winding assembly

[0080] 120: Electrode laminate

[0081] 130: Outer packaging materials

[0082] 140: Negative electrode cover component

[0083] 150: Positive electrode cap component

[0084] 160: Solid electrolyte layer

[0085] 170: Insulation layer

[0086] 180: Joint

[0087] 190: Connecting components

Claims

1. A cylindrical solid-state battery comprising a jelly-roll, the jelly-roll being wound with a sheet-like electrode laminate, the sheet-like electrode laminate being laminated with a positive electrode and a negative electrode with a solid electrolyte layer interposed therebetween, wherein a current collector extending from the electrode laminate constitutes an outer packaging material, the outer packaging material is continuously wound from the electrode laminate with the end portion being fixed, thereby constituting an outermost periphery of the cylindrical solid-state battery, and the outer packaging material directly constitutes an outer packaging container.

2. The cylindrical solid-state battery according to claim 1, wherein the negative electrode is constituted by an electrode current collector composed of a metal porous body and an electrode composite material filled in the pores of the metal porous body.

3. The cylindrical solid-state battery according to claim 2, wherein the electrode composite material of the negative electrode contains an expander.

4. The cylindrical solid-state battery according to claim 1, wherein the width of the outer packaging material in the direction of the height of the cylinder is narrower than the width of the electrode laminate and wider than the width of the electrode composite layer of the electrode laminate, and a portion of at least one electrode current collector extends from the end portion of the outer packaging material in the width direction.

5. A manufacturing method of a cylindrical solid-state battery, the cylindrical solid-state battery comprising a jelly-roll, the jelly-roll being wound with a sheet-like electrode laminate, the sheet-like electrode laminate being laminated with a positive electrode and a negative electrode with a solid electrolyte layer interposed therebetween, and the manufacturing method comprising: a first step of taking a current collector extending from the electrode laminate as an outer peripheral end of the electrode laminate; and a second step of winding the electrode laminate and an outer packaging material with a prescribed tension to fix the end portion, thereby forming an outermost periphery of the cylindrical solid-state battery, wherein the current collector extending from the electrode laminate constitutes the outer packaging material, and the outer packaging material directly constitutes an outer packaging container.

6. The manufacturing method of a cylindrical solid-state battery according to claim 5, wherein in the second step, winding is performed while being pressed from the outside of the jelly-roll.

7. The manufacturing method of a cylindrical solid-state battery according to claim 5 or 6, wherein in the second step, the outer diameter of the cylindrical solid-state battery is made constant by adjusting the winding length of the outer packaging material. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

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