SOLID-STATE Li-ION BATTERY

Abstract

To provide a solid-state Li-ion battery capable of suppressing the decrease in discharge capacity.SOLUTION: A solid-state Li-ion battery includes a positive electrode current collector, a positive electrode layer, a solid electrolyte layer, a negative electrode layer, a resin layer, and a negative electrode current collector containing aluminum in this order. In the solid-state Li-ion battery, at least one end of the negative electrode current collector is located at the back when viewed from the side in the stacking direction with respect to each end face of the positive electrode current collector, the positive electrode layer, the solid electrolyte layer, the negative electrode layer, and the resin layer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to solid-state Li-ion batteries. [Background technology]

[0002] Various techniques have been proposed for solid-state Li-ion batteries such as those disclosed in Patent Document 1. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-091997 Summary of the Invention [Problem to be solved by the invention]

[0004] At parts of the current collector where no coating layer is formed, such as the ends (end faces and sides), where the current collector is easily exposed, the aluminum (Al) and lithium (Li) of the current collector may alloy when the battery is charged, which may reduce the battery's discharge capacity.

[0005] The present disclosure has been made in view of the above circumstances, and has as its main object to provide a solid-state Li-ion battery that can suppress a decrease in discharge capacity. [Means for solving the problem]

[0006] <1> A solid-state Li-ion battery, the solid-state Li-ion battery includes, in this order, a positive electrode current collector, a positive electrode layer, a solid electrolyte layer, a negative electrode layer, a resin layer, and a negative electrode current collector containing aluminum; a solid-state lithium-ion battery in which at least one end face of the negative electrode current collector is disposed on the farther side of any end face of the positive electrode current collector, the positive electrode layer, the solid electrolyte layer, the negative electrode layer, and the resin layer, as viewed from the side surface in the stacking direction. [Effects of the Invention]

[0007] The solid-state Li-ion battery of the present disclosure can suppress a decrease in discharge capacity. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional schematic diagram showing an example of a solid-state Li-ion battery according to the present disclosure. [Figure 2] FIG. 2 is a cross-sectional schematic view showing another example of the solid-state Li-ion battery of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present disclosure will be described. Note that matters other than those specifically mentioned in this specification that are necessary for implementing the present disclosure (for example, the general configuration and manufacturing process of a solid-state Li-ion battery that does not characterize the present disclosure) can be understood as design matters for those skilled in the art based on conventional technology in the relevant field. The present disclosure can be implemented based on the contents disclosed in this specification and common general technical knowledge in the relevant field. The diagram also shows the orientation of a three-dimensional Cartesian coordinate system. Here, the xy plane is the horizontal plane, the z axis is the vertical direction, and the larger dimension along the z axis is the top. In the present disclosure, unless otherwise specified, the average particle size of particles is the median diameter (D50) value, which is the particle size at 50% of the cumulative value in the volume-based particle size distribution measured by laser diffraction / scattering particle size distribution measurement.

[0010] In the present disclosure, there is provided a solid-state Li-ion battery, the solid-state Li-ion battery includes, in this order, a positive electrode current collector, a positive electrode layer, a solid electrolyte layer, a negative electrode layer, a resin layer, and a negative electrode current collector containing aluminum; Provided is a solid-state Li-ion battery in which at least one end face of a negative electrode current collector is disposed on the farther side, as viewed from the side in the stacking direction, with respect to any end face of the positive electrode current collector, the positive electrode layer, the solid electrolyte layer, the negative electrode layer, and the resin layer.

[0011] In the present disclosure, a resin layer is provided between the negative electrode layer and the negative electrode current collector containing aluminum, and the negative electrode current collector is arranged such that at least one end (end face, side face) of the negative electrode current collector is located inside the end of the resin layer when viewed from the stacking direction, making it difficult for lithium to reach the end of the negative electrode current collector, thereby suppressing the direct reaction between aluminum and Li and suppressing a decrease in the discharge capacity of the solid-state Li-ion battery.

[0012] FIG. 1 is a cross-sectional schematic diagram showing an example of a solid-state Li-ion battery according to the present disclosure. The solid state Li-ion battery 100 shown in FIG. 1 includes, in this order, a positive electrode current collector 10, a positive electrode layer 11, a solid electrolyte layer 12, a negative electrode layer 13, a resin layer 14, and a negative electrode current collector 15 containing aluminum. FIG. 2 is a cross-sectional schematic view showing another example of the solid-state Li-ion battery of the present disclosure. The solid-state Li-ion battery 200 shown in FIG. 2 includes, in this order, a positive electrode current collector 10, a positive electrode layer 11, a solid electrolyte layer 12, a negative electrode layer 13, a resin layer 14, a negative electrode current collector 15 containing aluminum, the resin layer 14, the negative electrode layer 13, the solid electrolyte layer 12, the positive electrode layer 11, and the positive electrode current collector 10. 1 and 2, at least one of the multiple end faces (side faces) of the negative electrode current collector 15 is disposed on the far side, as viewed from the side in the stacking direction, with respect to any of the end faces of the positive electrode current collector 10, the positive electrode layer 11, the solid electrolyte layer 12, the negative electrode layer 13, and the resin layer 14. One of the multiple end faces of the negative electrode current collector 15 is provided with a connection part 16 that extends to an external terminal (not shown). Yet another example of the solid state Li-ion battery of the present disclosure may include, in this order, an anode current collector containing aluminum, a resin layer, an anode layer, a solid electrolyte layer, a cathode layer, a cathode current collector, a cathode layer, a solid electrolyte layer, an anode layer, a resin layer, and an anode current collector containing aluminum.

[0013] The positive electrode includes a positive electrode layer and a positive electrode current collector.

[0014] The positive electrode layer contains a positive electrode active material, and optionally contains a conductive material, a solid electrolyte, a binder, and the like. The positive electrode active material is lithium nickel cobalt aluminum oxide (NCA), LiCoO2, LiNi x Co 1-x O2(0 <x<1)、Li 1.15 Ni 1 / 3 Co 1 / 3 Mn 1 / 3 Examples of the Li-Mn spinel substituted with different elements include O2, LiMnO2, LiMn2O4, LiNiO2, LiVO2, Li-Mn spinel substituted with different elements, lithium titanate, lithium metal phosphate, LiCoN, Li2SiO3, and Li4SiO4. The Li-Mn spinel substituted with different elements is, for example, LiMn 1.5 Ni 0.5 O4, LiMn 1.5 Al 0.5 O4, LiMn 1.5 Mg 0.5 O4, LiMn 1.5 Co 0.5 O4, LiMn 1.5 Fe 0.5 O4 and LiMn 1.5 Zn 0.5 O4, etc. Lithium titanate is, for example, Li4Ti5O 12 Lithium metal phosphates include, for example, LiFePO4, LiMnPO4, LiCoPO4, and LiNiPO4. The shape of the positive electrode active material is not particularly limited, but may be in the form of particles (positive electrode active material particles).The average particle size of the positive electrode active material particles is not particularly limited, and may be 1 nm to 100 μm. A coating layer containing a Li-ion conductive compound may be formed on the surface of the positive electrode active material, because this can suppress the reaction between the positive electrode active material and the solid electrolyte. Examples of Li-ion conductive compounds include LiNbO3 and Li4Ti5O 12 , and Li3PO4. The thickness of the coating layer is, for example, 0.1 nm or more, and may be 1 nm or more. On the other hand, the thickness of the coating layer is, for example, 100 nm or less, and may be 20 nm or less. The coverage of the coating layer on the surface of the positive electrode active material is, for example, 70% or more, and may be 90% or more. Known conductive materials can be used, including, for example, carbon materials and metal particles. Examples of carbon materials include acetylene black (AB), furnace black, vapor grown carbon fiber (VGCF), carbon nanotubes, and carbon nanofibers. Among these, from the viewpoint of electron conductivity, at least one selected from the group consisting of VGCF, carbon nanotubes, and carbon nanofibers may be used. Examples of metal particles include particles of Ni, Cu, Fe, and SUS. The solid electrolyte may be a sulfide solid electrolyte, etc. The sulfide solid electrolyte may be a Li2S-P2S5-based glass ceramic, etc. Examples of binders include rubber-based binders and fluoride-based binders. Examples of rubber-based binders include BR (butadiene rubber), hydrogenated butadiene rubber, styrene butadiene rubber (SBR), hydrogenated styrene butadiene rubber, nitrile butadiene rubber, hydrogenated nitrile butadiene rubber, acrylonitrile butadiene rubber (ABR), and ethylene propylene rubber. Examples of fluoride-based binders include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-polyhexafluoropropylene copolymer (PVDF-HFP), polytetrafluoroethylene, and fluororubber.

[0015] The positive electrode current collector may be a known metal that can be used as a current collector for solid-state batteries. Examples of such metals include metal materials containing one or more elements selected from the group consisting of Cu, Ni, Al, V, Au, Pt, Mg, Fe, Ti, Co, Cr, Zn, Ge, and In. Examples of the positive electrode current collector include SUS, aluminum, nickel, iron, titanium, and carbon. The form of the positive electrode current collector is not particularly limited, and it can be in various forms such as a foil form, a mesh form, or the like.

[0016] The solid electrolyte layer contains a solid electrolyte and, if necessary, a binder and the like. Examples of the solid electrolyte include the solid electrolytes that can be contained in the positive electrode layer described above. The proportion of the solid electrolyte in the solid electrolyte layer is not particularly limited, but may be, for example, 50 mass % or more and 99 mass % or less. Examples of the binder include the binders that can be contained in the positive electrode layer described above. The thickness of the solid electrolyte layer may be 10 μm or more from the viewpoint of suppressing short circuits in the solid battery, and may be 100 μm or less from the viewpoint of reducing the resistance of the solid battery.

[0017] The negative electrode includes a negative electrode layer and a negative electrode current collector. The negative electrode layer contains a negative electrode active material, and may contain at least one of a solid electrolyte, a conductive material, and a binder, as necessary. The negative electrode active material may be a material having a reaction potential with Li of 0.3 V or less relative to Li. The negative electrode active material may be a Si-based active material. Examples of the Si-based active material include simple Si, Si oxide, Si-C composite, and Si alloy. The negative electrode active material may be negative electrode active material particles. The average particle size of the negative electrode active material particles is not particularly limited, and may be 1 nm to 100 μm. Examples of the conductive material, solid electrolyte, and binder used in the negative electrode layer include the same conductive materials, solid electrolytes, and binders as those exemplified as the conductive material, solid electrolyte, and binder that can be contained in the positive electrode layer.

[0018] The negative electrode current collector may be an aluminum (Al) foil, a copper foil, or the like. The thickness of the negative electrode current collector may be 7 to 50 μm, or may be 15 μm. At least one end face of the negative electrode current collector may be located 10 μm or more further back than any of the end faces of the positive electrode current collector, the positive electrode layer, the solid electrolyte layer, the negative electrode layer, and the resin layer when viewed from the side in the stacking direction. One of the end faces of the negative electrode current collector may be provided with a connection part for connecting to an external terminal, and the connection part may extend to the external terminal. The surface of the negative electrode current collector may be chemically treated or coated with a resin layer, or may be coated with a resin layer and chemically treated in combination.

[0019] The resin layer contains a resin and, if necessary, carbon. The resin may be a vinyl resin or the like. The resin layer may be formed on a film such as PEF (polyethylene furanoate) or PET (polyethylene terephthalate). The resin layer may have a thickness of 10 μm or less.

[0020] The chemical treatment may be, for example, Fe plating treatment, Ni plating treatment, silane coupling treatment, etc. The film thickness of the chemical treatment may be 5 μm or less.

[0021] Instead of the resin layer, a vapor deposition film of Ni, Fe, or the like may be coated on the laminate including the positive electrode current collector, the positive electrode layer, the solid electrolyte layer, and the negative electrode layer by performing a vapor deposition process. The deposited film thickness may be, for example, 1 μm or less.

[0022] In the present disclosure, a solid-state battery refers to a battery containing a solid electrolyte. The solid-state battery may be a semi-solid-state battery that contains a solid electrolyte and a liquid-based material, or an all-solid-state battery that does not contain a liquid-based material. When a set of a positive electrode, a solid electrolyte layer, and a negative electrode is considered as a power generation unit, the solid-state Li-ion battery may have only one power generation unit or may have two or more power generation units. When the solid-state Li-ion battery has two or more power generation units, the power generation units may be connected in series or in parallel. The solid-state Li-ion battery may be a primary battery or a secondary battery. Examples of applications of solid-state Li-ion batteries include power sources for vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), electric vehicles (BEVs), gasoline-powered vehicles, and diesel-powered vehicles. In particular, the solid-state Li-ion battery may be used as a driving power source for hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), or electric vehicles (BEVs). The solid-state Li-ion battery may also be used as a power source for mobile objects other than vehicles (for example, trains, ships, and aircraft), and may also be used as a power source for electrical appliances such as information processing devices. [Example]

[0023] Example 1 [Preparation of positive electrode layer] Using a rolling fluidized coating device, positive electrode active material particles (Li 1.15 Ni 1 / 3 Co 1 / 3 Mn 1 / 3 The positive electrode active material particles with a lithium niobate coating layer were obtained by coating the particles with lithium niobate (particles with O2 as the main phase) with lithium niobate and firing them in an air atmosphere. PVdF (polyvinylidene fluoride), the above-mentioned positive electrode active material particles, a sulfide solid electrolyte (LiS-P2S5-based glass ceramic), and vapor-grown carbon fiber (VGCF) (manufactured by Showa Denko K.K.) were added to a polypropylene container, and the resulting slurry for the positive electrode layer was stirred for 30 seconds using an ultrasonic disperser. Next, the container was shaken for 3 minutes using a shaker, and the positive electrode layer slurry was further stirred for 30 seconds using an ultrasonic disperser. After shaking the container for 3 minutes using a shaker, the positive electrode layer slurry was applied to an aluminum foil using a blade method with an applicator. The positive electrode layer slurry was then air-dried and then dried on a hot plate at 100 °C for 30 minutes to obtain a positive electrode layer on the aluminum foil ((positive electrode current collector)). The positive electrode slurry was then similarly applied to the back side of the positive electrode current collector and dried, obtaining a positive electrode layer on the back side as well. [Creating the negative electrode layer] PVdF, negative electrode active material particles (silicon particles), and the same sulfide solid electrolyte (Li2S-P2S5-based glass ceramic) as above were added to a polypropylene container, and the resulting negative electrode layer slurry was stirred for 30 minutes using an ultrasonic disperser. The negative electrode layer slurry was then applied to an aluminum foil using a blade method with an applicator. The negative electrode layer slurry was then air-dried and then dried on a hot plate at 100 °C for 30 minutes to obtain a negative electrode layer on the aluminum foil (substrate). [Creating the resin layer] Vinyl resin and carbon were weighed and mixed in a weight ratio of 4:1, and then a solvent was added to form a resin slurry, which was then coated onto the substrate PET film using the blade method. The resin was then dried on a hot plate at 50°C for 20 minutes, and then further dried on a hot plate at 150°C for 30 minutes, yielding a resin layer on the substrate PET film. [Preparation of solid electrolyte layer] Heptane, BR, and a sulfide solid electrolyte (Li2S-P2S5-based glass ceramic) were added to a polypropylene container, and the resulting solid electrolyte layer slurry was stirred for 30 seconds using an ultrasonic disperser. Next, the container was shaken for 30 minutes using a shaker, and the solid electrolyte layer slurry was further stirred for 30 seconds using an ultrasonic disperser. After shaking the container for 3 minutes using a shaker, the solid electrolyte layer slurry was applied to an aluminum foil using a blade method with an applicator. The solid electrolyte layer slurry was then air-dried and then dried on a hot plate at 100°C for 30 minutes to form a solid electrolyte layer on the aluminum foil substrate. [Laminate fabrication] (1) Laminated body obtaining process Solid electrolyte layers were attached to both sides of the positive electrode so that each positive electrode layer and each solid electrolyte layer were in direct contact, and pressed at 1.6 t / cm. The aluminum foil substrate was then peeled off from each solid electrolyte layer. Next, a negative electrode layer was attached to each solid electrolyte layer so that each negative electrode layer and each solid electrolyte layer were in direct contact, and pressed at 1.6 t / cm. The aluminum foil substrate was then peeled off from each negative electrode layer. Furthermore, a resin layer was attached to each negative electrode layer so that each negative electrode layer and each resin layer were in direct contact, and pressed at 1.6 t / cm. The PET film substrate was then peeled off from each resin layer. (2) Cutting process The obtained laminate was pressed at 5 t / cm and 170° C. Thereafter, the laminate was cut to a size of 70.0 mm × 70.0 mm, and a negative electrode terminal was welded to one side of the laminate. (3) Adhesion process The aluminum foil used as the negative electrode current collector was cut to a size of 69.5 x 69.5 mm and coated with a hot melt adhesive. It was then placed on the laminate so that all four sides of the resin layer were visible. These were heated to 140°C, and the negative electrode current collector and laminate were bonded and fixed with the hot melt adhesive. Thereafter, a positive electrode terminal was welded, and the assembly was vacuum sealed to obtain an all-solid-state battery.

[0024] When the all-solid-state battery of Example 1 was charged and discharged multiple times, it was confirmed that the discharge capacity after multiple charge and discharge was maintained at the same level as the initial discharge capacity. [Explanation of symbols]

[0025] 10 Positive electrode current collector 11 Positive electrode layer 12 Solid electrolyte layer 13 Negative electrode layer 14 Resin layer 15 Negative electrode current collector 16 Connection 100 Solid-state Li-ion battery 200 Solid-state Li-ion battery

Claims

[Claim 1] A solid-state Li-ion battery, the solid-state Li-ion battery includes, in this order, a positive electrode current collector, a positive electrode layer, a solid electrolyte layer, a negative electrode layer, a resin layer, and a negative electrode current collector containing aluminum; a solid-state Li-ion battery, wherein at least one end face of the negative electrode current collector is disposed on a rear side of any end face of the positive electrode current collector, the positive electrode layer, the solid electrolyte layer, the negative electrode layer, or the resin layer, as viewed from a side surface in the stacking direction.

Images