Solid-state battery, battery pack, and electric device

Abstract

The solid-state battery of the present disclosure comprises a positive electrode, a first negative electrode and a second negative electrode arranged in a stack, at least one positive electrode is arranged between the first negative electrode and the second negative electrode, and the negative electrode material layers in the first negative electrode and the second negative electrode respectively adopt silicon-carbon composite material and pure silicon material as negative electrode active material, which fully gives play to the combined advantages of silicon-carbon composite material and pure silicon material, can meet the high-rate discharge demand while improving the stability of the negative electrode structure, is beneficial to improve the rate performance of the battery and prolong the cycle life of the battery.

Description

Technical Field

[0001] This disclosure relates to a solid-state battery, a battery pack, and an electrical device. Background Technology

[0002] Solid-state batteries eliminate the safety hazards of flammable and leaking electrolytes by using solid electrolytes instead of liquid electrolytes, and improve cycle life and stability. In solid-state batteries, the choice of anode material is one of the key factors affecting performance. Currently, silicon-based materials are considered the most promising anode materials. However, silicon-based anodes in solid-state battery applications suffer from problems such as easy cracking and even detachment from the current collector surface, leading to poor cycle life and rate performance, thus limiting the application of solid-state batteries. Summary of the Invention

[0003] The purpose of this disclosure is to provide a solid-state battery, battery pack, and electrical device to improve the rate performance and cycle life of the solid-state battery.

[0004] To achieve the above objectives, in a first aspect, this disclosure provides a solid-state battery, the solid-state battery comprising a positive electrode, a first negative electrode, and a second negative electrode stacked together, the first negative electrode comprising a first negative electrode material layer, the second negative electrode comprising a second negative electrode material layer, the first negative electrode material layer comprising a silicon-carbon composite material, a first solid electrolyte, and a first binder, the second negative electrode material layer comprising a pure silicon material and a second binder, and at least one of the positive electrodes being disposed between the first negative electrode and the second negative electrode.

[0005] Optionally, the compression rebound ratio of the first negative electrode material layer is 2.5~5%, and / or the compression rebound ratio of the second negative electrode material layer is 0.5~2%.

[0006] Optionally, based on the total weight of the silicon-carbon composite material, the silicon content of the silicon-carbon composite material is 20-90% by weight, and the carbon content is 10-80% by weight; and / or, The particle size of the pure silicon material is 100 nm to 2 μm; based on the total weight of the pure silicon material, the silicon content of the pure silicon material is 98% by weight or more.

[0007] Optionally, the first negative electrode material layer further includes a first conductive agent, wherein, based on the total weight of the first negative electrode material layer, the content of the silicon-carbon composite material is 48-90% by weight, the content of the first solid electrolyte is 9-50% by weight, the content of the first conductive agent is 0.1-10% by weight, and the content of the first binder is 0.1-10% by weight; and / or, Based on the total weight of the second negative electrode material layer, the content of the pure silicon material is 80-99% by weight, and the content of the second binder is 1-20% by weight.

[0008] Optionally, the first solid electrolyte includes Li3PS4 and Li7P3S. 11 Li 11 GeP2S 12 Li6PS5Cl, Li7P2S8I, Li 10 SnP2S 12 and Li 3.25 Ge 0.25 P 0.75 One or more of S4; The first conductive agent includes one or more of SP conductive agent, CNT conductive agent, VGCF conductive agent and graphene; The first adhesive and the second adhesive each independently comprise one or more of PAA, Li-PAA, PVDF, PVDF-HFP, NBR, HNBR, SBR, SBS, SEBS, PTEF, and PEO.

[0009] Optionally, the thickness of the first negative electrode material layer is 40~60μm, and / or the thickness of the second negative electrode material layer is 15~30μm.

[0010] Optionally, the first negative electrode further includes a first negative electrode current collector, and the first negative electrode material layer is disposed on the surface of the first negative electrode current collector; the second negative electrode further includes a second negative electrode current collector, and the second negative electrode material layer is disposed on the surface of the second negative electrode current collector.

[0011] Optionally, the number of the first negative electrode and the number of the second negative electrode are one or more, and at least one termination layer of the solid-state battery is the second negative electrode; Preferably, the first negative electrode and the second negative electrode are arranged alternately.

[0012] Optionally, the positive electrode is disposed between any two adjacent negative electrodes, and the positive electrode is isolated from the first negative electrode and the second negative electrode through an electrolyte layer.

[0013] Optionally, the positive electrode includes a positive current collector and a composite positive electrode material layer disposed on the surface of the positive current collector, wherein the composite positive electrode material layer includes a positive active material, a second solid electrolyte, a third binder, and an optional second conductive agent; Preferably, based on the total weight of the composite positive electrode material layer, the content of the positive electrode active material is 50-85% by weight, the content of the second solid electrolyte is 5-50% by weight, the content of the third binder is 0.1-10% by weight, and the content of the second conductive agent is 0.1-10% by weight.

[0014] Optionally, the surface of the positive electrode active material has an ion conductor coating layer; Preferably, the material of the ion conductor coating layer includes any one or more of Li2TiO3, LiNbO3, Li3BO3, Li2ZrO3, LiCoO3, LiPO3, Li2MnO4, Al(PO3)3, La(PO3)3 and NaPO3; Preferably, the thickness of the ion conductor coating layer is 1~10 nm.

[0015] Optionally, the positive electrode active material includes LiFePO4, NCM, NCA, LiCoO2, LiMn2O4, and Li4Ti5O. 12 LMO, LiMn y Fe 1-y One or more of PO4 and lithium-rich manganese-based oxides; The second solid electrolyte includes Li3PS4 and Li7P3S. 11 Li 11 GeP2S 12 Li6PS5Cl, Li7P2S8I, Li 10 SnP2S 12 and Li 3.25 Ge 0.25 P 0.75 One or more of S4; The second conductive agent includes one or more of SP conductive agent, CNT conductive agent, VGCF conductive agent and graphene; The third adhesive includes one or more of PAA, Li-PAA, PVDF, PVDF-HFP, NBR, HNBR, SBR, SBS, SEBS, PTEF, and PEO.

[0016] A second aspect of this disclosure provides a battery pack including the solid-state battery described in the first aspect of this disclosure.

[0017] In a third aspect, this disclosure provides an electrical device, including the solid-state battery described in the first aspect of this disclosure or the battery pack described in the second aspect of this disclosure.

[0018] Through the above technical solution, the solid-state battery disclosed herein includes a positive electrode, a first negative electrode, and a second negative electrode stacked together, with at least one positive electrode disposed between the first negative electrode and the second negative electrode. The negative electrode material layers in the first negative electrode and the second negative electrode respectively adopt silicon-carbon composite material and pure silicon material as negative electrode active materials, giving full play to the combined advantages of silicon-carbon composite material and pure silicon material, which can improve the stability of the negative electrode structure while meeting the high-rate discharge requirements, which is conducive to improving the rate performance of the battery and extending the cycle life of the battery.

[0019] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Attached Figure Description

[0020] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of the structure of a solid-state battery according to a specific embodiment of the present disclosure.

[0021] Explanation of reference numerals in the attached figures 1—First negative electrode, 11—First negative electrode material layer, 12—First negative electrode current collector, 2—Second negative electrode, 21—Second negative electrode material layer, 22—Second negative electrode current collector, 3—Positive electrode, 31—Composite positive electrode material layer, 32—Positive electrode current collector, 4—Electrolyte layer. Detailed Implementation

[0022] The specific embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this disclosure.

[0023] In a first aspect, this disclosure provides a solid-state battery, as shown in the reference. Figure 1 The solid-state battery includes a positive electrode 3, a first negative electrode 1, and a second negative electrode 2 stacked together. The first negative electrode 1 includes a first negative electrode material layer 11, and the second negative electrode 2 includes a second negative electrode material layer 21. The first negative electrode material layer 11 includes a silicon-carbon composite material, a first solid electrolyte, and a first binder. The second negative electrode material layer 21 includes a pure silicon material and a second binder. At least one of the positive electrodes 3 is disposed between the first negative electrode 1 and the second negative electrode 2.

[0024] The solid-state battery disclosed herein has a dual negative electrode structure, with at least one positive electrode disposed between the first negative electrode and the second negative electrode. The negative electrode material layers in the first negative electrode and the second negative electrode respectively adopt silicon-carbon composite material and pure silicon material as negative electrode active materials, thereby achieving complementary characteristics of silicon-carbon composite material and pure silicon material and giving full play to the combined advantages of the two, which can improve the stability of the negative electrode structure while meeting the high-rate discharge requirements.

[0025] In this disclosure, the stacking arrangement refers to the arrangement of layers through direct or indirect contact.

[0026] The number of the first negative electrode 1 and the second negative electrode 2 is not limited; there can be one or more of each, which can be adjusted according to the battery capacity and structural stability requirements. In embodiments with multiple negative electrodes, the arrangement order of the multiple first negative electrodes 1 and second negative electrodes 2 is not limited. In a preferred embodiment, the first negative electrodes 1 and second negative electrodes 2 can be arranged alternately to form a stable multilayer negative electrode structure. In other embodiments, the multiple first negative electrodes 1 can be arranged sequentially, followed by the sequential arrangement of the multiple second negative electrodes 2.

[0027] The number of positive electrodes 3 is not limited and can be one or more, specifically adjusted according to the number of negative electrodes. In one specific embodiment, the positive electrode 3 is disposed between any two adjacent negative electrodes, and the positive electrode 3 is isolated from the first negative electrode 1 and the second negative electrode 2 by the electrolyte layer 4. For example, when multiple first negative electrodes 1 are stacked sequentially, a positive electrode 3 is disposed between any two adjacent first negative electrodes 1; when multiple second negative electrodes 2 are stacked sequentially, a positive electrode 3 is disposed between any two adjacent second negative electrodes 2; or, when multiple first negative electrodes 1 and second negative electrodes 2 are stacked alternately, a positive electrode 3 is disposed between any two adjacent first negative electrodes 1 and second negative electrodes 2.

[0028] In one specific embodiment, the compression-rebound ratio of the first negative electrode material layer 11 can be 2.5-5%, and the compression-rebound ratio of the second negative electrode material layer 21 can be 0.5-2%. The compression-rebound ratio characterizes the degree to which the negative electrode material layer recovers to its original thickness after compression. A higher compression-rebound ratio indicates stronger elasticity and deformation recovery capability of the negative electrode material layer. The higher compression-rebound ratio of the first negative electrode material layer 11 helps improve the flexibility and interfacial contact quality of the negative electrode structure, while the lower compression-rebound ratio of the second negative electrode material layer 21 helps reduce volume expansion of the negative electrode material layer, making it less prone to peeling and interfacial failure after high-pressure molding, ensuring the stability of the negative electrode structure and enhancing its mechanical strength. For example, the compression rebound ratio of the first negative electrode material layer 11 can be 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, and 5%, and the compression rebound ratio of the second negative electrode material layer 21 can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, and 2%. Furthermore, the compression-rebound ratio of the first negative electrode material layer 11 is preferably 2.5~3.5%, and the compression-rebound ratio of the second negative electrode material layer 21 is preferably 0.5~1%. This combination design helps to significantly improve the cycle life and overall structural stability of solid-state batteries, and is suitable for practical applications with high energy density and high discharge rate.

[0029] According to this disclosure, the first negative electrode material layer 11 uses silicon-carbon composite material as the negative electrode active material, which has excellent kinetic performance, low interface impedance, and is conducive to lithium ion diffusion, thereby promoting the capacity utilization and rate performance improvement of the electrode sheet. The silicon-carbon composite material is a mixture of silicon and carbon, such as silicon-doped carbon materials (including hard carbon, soft carbon, and graphite). The silicon and carbon content can be adjusted within a certain range. Specifically, based on the total weight of the silicon-carbon composite material, the silicon content can be 20-90% by weight, for example, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, preferably 40-60%, more preferably 50-60% by weight; the carbon content can be 10-80% by weight, for example, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, preferably 40-60%, more preferably 40-50% by weight. Furthermore, the particle size of the silicon-carbon composite material can be 1~10μm, for example 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, preferably 5~8μm; the porosity can be 20~50%, for example 20%, 25%, 30%, 35%, 40%, 45%, 50%, preferably 30~40%.

[0030] In one specific embodiment, the first negative electrode material layer 11 further includes a first conductive agent, wherein the content of each component can be adjusted within a certain range. Specifically, based on the total weight of the first negative electrode material layer 11, the content of the silicon-carbon composite material can be 48-90% by weight, the content of the first solid electrolyte can be 9-40% by weight, the content of the first conductive agent can be 0.1-10% by weight, and the content of the first binder can be 0.1-10% by weight. In a preferred embodiment, based on the total weight of the first negative electrode material layer 11, the content of the silicon-carbon composite material is 60-80% by weight, the content of the first solid electrolyte can be 15-35% by weight, the content of the first conductive agent is 0.5-2% by weight, and the content of the first binder is 1-3% by weight.

[0031] The thickness of the first negative electrode material layer 11 can be adjusted within a certain range as needed, specifically 40~60μm, preferably 25~50μm. When the thickness of the first negative electrode material layer 11 is within the preferred range, it can help to further enhance the ion and electron conduction efficiency and maintain a high capacity output during high-rate discharge.

[0032] According to this disclosure, the second negative electrode material layer 21 uses pure silicon as the negative electrode active material, which helps to fully utilize the material's specific capacity while reducing volume expansion during battery forming and charging / discharging, thus improving the stability of the negative electrode structure. The pure silicon material (high-purity silicon) refers to a material composed of silicon (Si) and essentially free of other impurity elements. Specifically, based on the total weight of the pure silicon material, the silicon content of the pure silicon material can be 98% by weight or more. It should be noted that, given that silicon materials inevitably form a small amount of silicon oxide during contact with the environment, silicon materials with an oxygen content not exceeding 1% by weight can be considered as pure silicon materials as described in this disclosure.

[0033] Furthermore, the particle size of the pure silicon material can be from 100 nm to 2 μm, preferably from 200 to 800 nm. The content of each component in the second negative electrode material layer 21 can be adjusted within a certain range. Specifically, based on the total weight of the second negative electrode material layer 21, the content of pure silicon material can be 80-99% by weight, and the content of the second binder can be 1-20% by weight. In a preferred embodiment, based on the total weight of the second negative electrode material layer 21, the content of pure silicon material is 96-98% by weight, and the content of the second binder is 2-4% by weight.

[0034] The second negative electrode material layer 21 may not contain solid electrolyte and conductive agent, but it can still ensure the specific capacity of the material, while reducing the side reactions that occur during battery forming and charging and discharging.

[0035] The thickness of the second negative electrode material layer 21 can be adjusted within a certain range as needed, specifically 15~30μm, preferably 15~25μm. When the thickness of the second negative electrode material layer 21 is within the preferred range, it can help to further improve the overall stability and mechanical strength of the negative electrode structure.

[0036] According to this disclosure, the first negative electrode 1 may further include a first negative electrode current collector 12, and the second negative electrode 2 may further include a second negative electrode current collector 22. The first negative electrode material layer 11 is disposed on the surface of the first negative electrode current collector 12, and the second negative electrode material layer 21 is disposed on the surface of the second negative electrode current collector 22. Preferably, the first negative electrode material layer 11 is disposed on both opposite surfaces of the first negative electrode current collector 12, and the second negative electrode material layer 21 is disposed on both opposite surfaces of the second negative electrode current collector 22. Figure 1 As shown, it can be understood that the thicknesses of the first negative electrode material layer 11 and the second negative electrode material layer 21 mentioned above refer to the thickness of a single layer, not the sum of the thicknesses of the material layers on the two surfaces of the current collector. The first negative electrode current collector 12 and the second negative electrode current collector 22 can be materials commonly used in the art, such as copper foil.

[0037] In a preferred embodiment, at least one termination layer (i.e., the outermost layer) of the solid-state battery is the second negative electrode 2. The second negative electrode 2 includes a second negative electrode material layer 21. Due to the low compression rebound ratio of the second negative electrode material layer 21, placing it as a termination layer can form a robust outer protective layer during battery molding, preventing detachment, material shedding, etc. Specifically, the solid-state battery has a first termination layer and a second termination layer, which can be the second negative electrode 2 respectively, or the first termination layer can be the second negative electrode 2, and the second termination layer can be the first negative electrode 1. For example, in Figure 1 In the embodiment shown, the solid-state battery includes a second negative electrode 2, a positive electrode 3, a first negative electrode 1, a positive electrode 3, and a second negative electrode 2 stacked in sequence, that is, the first negative electrode 1 is disposed in the inner layer, and the two second negative electrodes 2 are disposed in the termination layer respectively, forming a sandwich structure.

[0038] In one specific embodiment, the positive electrode 3 may include a positive electrode current collector 32 and a composite positive electrode material layer 31 disposed on the surface of the positive electrode current collector 32. Preferably, the composite positive electrode material layer 31 is disposed on both opposite surfaces of the positive electrode current collector 32. Further, the composite positive electrode material layer 31 may include a positive electrode active material, a second solid electrolyte, a third binder, and an optional second conductive agent. The content of each component can be adjusted within a certain range. Specifically, based on the total weight of the composite positive electrode material layer, the content of the positive electrode active material can be 45-85% by weight, the content of the second solid electrolyte can be 5-50% by weight, the content of the third binder can be 0.1-10% by weight, and the content of the second conductive agent can be 0.1-10% by weight. The thickness of the composite positive electrode material layer 31 can be 100-200 μm.

[0039] The positive electrode active material can be olivine-based, layered oxide-based, spinel-based, etc., specifically including LiFePO4, NCM (lithium nickel cobalt manganese oxide), NCA (lithium nickel cobalt aluminum oxide), LiCoO2, LiMn2O4, Li4Ti5O 12 LMO (lithium manganese oxide), LiMn y Fe 1-y The positive electrode active material can be one or more of PO4 (where y can be 0.6 or 0.75) and lithium-rich manganese-based oxide (Li-rch Mn-rch-base, LRMO). Further, the particle size of the positive electrode active material can be 3-8 μm. In a preferred embodiment, the surface of the positive electrode active material has an ion-conducting coating layer. The material of the ion-conducting coating layer can include one or more of Li2TiO3, LiNbO3, Li3BO3, Li2ZrO3, LiCoO3, LiPO3, Li2MnO4, Al(PO3)3, La(PO3)3, and NaPO3. More preferably, the thickness of the ion-conducting coating layer is 1-10 nm. The positive electrode current collector 32 can be a material commonly used in the art, such as aluminum foil.

[0040] In one specific embodiment, the electrolyte layer 4 may include a third solid electrolyte and a fourth binder. The content of each component can be adjusted within a certain range. Specifically, based on the total weight of the electrolyte layer 4, the content of the third solid electrolyte can be 90-99.9% by weight, and the content of the fourth binder can be 0.1-10% by weight. The thickness of the electrolyte layer 4 can be 10-100 μm.

[0041] In the solid-state battery disclosed herein, the specific types of substances used for the solid electrolyte, conductive agent, and binder can be those commonly found in the art.

[0042] In one embodiment, the first solid electrolyte, the second solid electrolyte, and the third solid electrolyte can each be an independent sulfide solid electrolyte with high ionic conductivity and excellent mechanical properties. Specifically, the first solid electrolyte, the second solid electrolyte, and the third solid electrolyte can each independently include Li3PS4 and Li7P3S. 11 Li 11 GeP2S 12 Li6PS5Cl, Li7P2S8I, Li 10 SnP2S 12 and Li 3.25 Ge 0.25 P 0.75 One or more of S4, preferably each independently including one or more of Li6PS5Cl and Li7P2S8I.

[0043] In one embodiment, the first conductive agent and the second conductive agent can each be independently a zero-dimensional conductive agent, a one-dimensional conductive agent, and a two-dimensional conductive agent, etc. Specifically, the first conductive agent and the second conductive agent can each independently include one or more of SP conductive agent (conductive carbon black), CNT conductive agent (carbon nanotube), VGCF conductive agent (conductive carbon fiber) and graphene, preferably each independently includes one or more of SP conductive agent and VGCF conductive agent.

[0044] In one embodiment, the first adhesive, the second adhesive, the third adhesive, and the fourth adhesive may each independently include one or more of PAA (polyacrylic acid), Li-PAA (lithium salt polyacrylic acid), PVDF (polyvinylidene fluoride), PVDF-HFP (polyvinylidene fluoride-hexafluoropropylene copolymer), NBR (nitrile rubber), HNBR (hydrogenated nitrile rubber), SBR (styrene-butadiene rubber), SBS (styrene-butadiene-styrene block copolymer), SEBS (styrene-ethylene-butene-styrene block copolymer), PTEF (polytetrafluoroethylene), and PEO (polyethylene oxide), preferably each independently including one or more of HNBR and PVDF.

[0045] The positive electrode, negative electrode, and electrolyte layer can be prepared using methods commonly found in the art. For example, the positive and negative electrodes can be prepared by wet coating, using solvents such as trimethylbenzene, anisole, and xylene. The electrolyte layer can be prepared by wet coating or dry extrusion. When prepared by wet coating, the solvent used can be the same as that used in preparing the positive or negative electrode by wet coating.

[0046] The solid-state battery can be prepared using methods known in the art, and this disclosure does not impose any special limitations. In one specific embodiment, the preparation method of the solid-state battery may include: isostatically pressing the positive electrode, electrolyte layer, and negative electrode to obtain the solid-state battery. Isostatic pressing can achieve excellent interfacial stability between the electrodes of the solid-state battery, making it suitable for the preparation of solid-state batteries with high energy density and long cycle life. The isostatic pressing conditions may include: a pressure of 200~700 MPa and a time of 0.5~30 min.

[0047] The solid-state battery disclosed herein has significant advantages in high energy density, long lifespan, and high-rate discharge performance, making it an ideal choice for achieving high-safety and high-efficiency energy storage.

[0048] A second aspect of this disclosure provides a battery pack including the solid-state battery described in the first aspect of this disclosure. The battery pack may contain one or more solid-state batteries, which may be connected in series or in parallel.

[0049] A second aspect of this disclosure provides an electrical device, including the solid-state battery described in the first aspect of this disclosure or the battery pack described in the second aspect of this disclosure. The electrical device may be, for example, a power battery module or an energy storage cabinet.

[0050] The present disclosure will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present disclosure and are not intended to limit the present disclosure.

[0051] All raw materials and reagents used in the examples and comparative examples are commercially available products.

[0052] The test method for the compression rebound ratio of the negative electrode material layer is the thickness difference method. Specifically, n layers of different formulation electrode sheets are stacked together and formed under a static press pressure of 400 MPa. The thickness h1 is tested; after standing for 30 minutes, the thickness h2 is tested. The calculation method is: (h2-h1) / n / h1.

[0053] The silicon and carbon content of silicon-carbon composite materials were detected using a carbon-sulfur analyzer; the silicon content of pure silicon materials was detected using an oxygen-nitrogen-hydrogen analyzer; the particle size of silicon-carbon composite materials and pure silicon materials was detected using a laser particle size analyzer; and the porosity of silicon-carbon composite materials was detected using the mercury porosimetry method.

[0054] Example 1 (1) Preparation of the first negative electrode The first negative electrode material layer consists of: silicon-carbon composite material (silicon content 50 wt%, carbon content 50 wt%, particle size 5 μm, porosity 35%), solid electrolyte Li6PS5Cl, conductive agent CNT, and binder HNBR in a weight ratio of 65:32:1:2. HNBR is dissolved in xylene and then mixed with other components to form a slurry (solid content of slurry is 55 wt%). The resulting slurry is coated on both surfaces of a copper foil, then dried and rolled to obtain the first negative electrode sheet. The thickness of the first negative electrode material layer is 50 μm (single-sided), and its compression rebound ratio is tested to be 3.5%.

[0055] (2) Preparation of the second negative electrode The second negative electrode material layer consists of pure silicon material (silicon content 99% by weight, particle size 800nm) and binder HNBR in a weight ratio of 97:3. HNBR is dissolved in xylene and then mixed with pure silicon material to form a slurry (solid content of slurry is 58% by weight). The resulting slurry is spread on both surfaces of a copper foil and dried overnight under vacuum at 80°C to remove the solvent, thus obtaining the second negative electrode sheet. The thickness of the second negative electrode material layer is 25μm (single-sided), and its compression rebound ratio is tested to be 1%.

[0056] (3) Preparation of electrolyte membrane precursor Xylene and binder PVDF-HFP are mixed to form a mixed adhesive solution. The mixed adhesive solution is then ball-milled with solid electrolyte Li6PS5Cl at a weight ratio of 2:3 to form a slurry. The slurry is then coated onto the surface of PET or aluminum foil and dried to obtain an electrolyte membrane precursor with a thickness of 10~50μm, wherein the weight ratio of solid electrolyte to binder is 99:1, for later use.

[0057] (4) Preparation of positive electrode sheet The composite cathode material layer consists of: an active material NCM811 (referred to as NCM811@LiNbO3 with a particle size of 4μm) with an ion-coated LiNbO3 layer (thickness of 1~50nm), a solid electrolyte Li6PS5Cl, a conductive agent SP, and a binder PVDF-HFP, with a weight ratio of 70:25:1:4. PVDF-HFP is dissolved in xylene and then mixed with other components and ball-milled into a slurry (the solid content of the slurry is 60% by weight). The resulting slurry is coated on both surfaces of an aluminum foil, then dried and rolled to obtain a cathode sheet, wherein the thickness of the composite cathode material layer is 150μm (single-sided).

[0058] (5) Preparation of solid-state batteries The first and second negative electrode sheets were cut to 45×58mm size and laminated with the electrolyte membrane precursor, then rolled and laminated. The electrolyte carrier PET / aluminum foil was then removed to obtain the first negative electrode sheet@electrolyte layer (denoted as A) and the second negative electrode sheet@electrolyte layer (denoted as B). The composite positive electrode sheet (denoted as C) was cut to 43×56mm size and laminated with the first and second negative electrode sheets@electrolyte layers. The cell arrangement was BCACACACACB (5 positive electrode layers), with the second negative electrode sheet@electrolyte layer as the termination layer. After lamination, the cells were vacuum-sealed and then subjected to two isostatic pressing processes at 500MPa for 5 minutes to obtain a solid-state battery.

[0059] All of the above preparation processes were completed in a drying room with a dew point below -50°C.

[0060] Example 2 Solid-state batteries were prepared according to the method of Example 1, except that in step (1), the first negative electrode material layer was composed of: silicon-carbon composite material (silicon content of 45 wt%, carbon content of 55 wt%, particle size of 7 μm, porosity of 40%), solid electrolyte Li6PS5Cl, conductive agent CNT, and binder HNBR in a weight ratio of 70:27:1:2, and the first negative electrode sheet was prepared. The thickness of the first negative electrode material layer was 50 μm (single-sided), and its compression rebound ratio was tested to be 5%.

[0061] Example 3 Solid-state batteries were prepared according to the method of Example 1, except that in step (1), the first negative electrode material layer was composed of: silicon-carbon composite material (silicon content of 60 wt%, carbon content of 40 wt%, particle size of 7 μm, porosity of 40%), solid electrolyte Li6PS5Cl, conductive agent CNT, and binder HNBR in a weight ratio of 70:27:1:2, and the first negative electrode sheet was prepared. The thickness of the first negative electrode material layer was 50 μm (single-sided), and its compression rebound ratio was tested to be 2.5%.

[0062] Example 4 Solid-state batteries were prepared according to the method of Example 1, except that in step (1), the first negative electrode material layer was composed of: silicon-carbon composite material (silicon content of 40 wt%, carbon content of 60 wt%, particle size of 7 μm, and porosity of 40%), solid electrolyte Li6PS5Cl, conductive agent CNT, and binder HNBR in a weight ratio of 70:27:1:2, and the first negative electrode sheet was prepared. The thickness of the first negative electrode material layer was 45 μm (single-sided), and its compression rebound ratio was tested to be 6%.

[0063] Example 5 Solid-state batteries were prepared according to the method of Example 1, except that in step (1), the first negative electrode material layer was composed of: silicon-carbon composite material (silicon content of 65 wt%, carbon content of 35 wt%, particle size of 7 μm, and porosity of 40%), solid electrolyte Li6PS5Cl, conductive agent CNT, and binder HNBR in a weight ratio of 70:27:1:2, and the first negative electrode sheet was prepared. The thickness of the first negative electrode material layer was 50 μm (single-sided), and its compression rebound ratio was tested to be 1.5%.

[0064] Example 6 Solid-state batteries were prepared according to the method of Example 1, except that in step (2), the second negative electrode material layer was composed of pure silicon material (silicon content of 99% by weight, particle size of 2μm) and binder HNBR in a weight ratio of 95:5, and the second electrode was prepared. The thickness of the second negative electrode material layer was 25μm, and its compression rebound ratio was tested to be 2%.

[0065] Example 7 Solid-state batteries were prepared according to the method of Example 1, except that in step (2), the second negative electrode material layer was composed of pure silicon material (silicon content of 99% by weight, particle size of 2μm) and binder HNBR in a weight ratio of 98:2, and the second electrode was prepared. The thickness of the second negative electrode material layer was 30μm, and its compression rebound ratio was tested to be 0.5%.

[0066] Example 8 Solid-state batteries were prepared according to the method of Example 1, except that in step (2), the second negative electrode material layer was composed of pure silicon material (silicon content of 99% by weight, particle size of 2μm) and binder HNBR in a weight ratio of 90:10, and the second electrode was prepared. The thickness of the second negative electrode material layer was 30μm, and its compression rebound ratio was tested to be 2.8%.

[0067] Example 9 Solid-state batteries were prepared according to the method of Example 1, except that in step (2), the second negative electrode material layer was composed of pure silicon material (silicon content of 99% by weight, particle size of 2μm) and binder HNBR in a weight ratio of 97:3, and the second electrode was prepared. The thickness of the second negative electrode material layer was 30μm, and its compression rebound ratio was tested to be 0.3%.

[0068] Example 10 Solid-state batteries were prepared according to the method of Example 1, except that in step (5), the cell arrangement was BCACBCACBCB (5 layers of positive electrode) and the termination layer was the second negative electrode sheet @ electrolyte layer.

[0069] Example 11 Solid-state batteries were prepared according to the method of Example 1, except that in step (5), the cell arrangement was ACBCBCBCBCA (5 layers of positive electrode) and the termination layer was the first negative electrode sheet @ electrolyte layer.

[0070] Example 12 Solid-state batteries were prepared according to the method of Example 1, except that in step (5), the cell arrangement was ACACBCACBCB (5 layers of positive electrode), and the termination layers were the second negative electrode @ electrolyte layer and the first negative electrode @ electrolyte layer, respectively.

[0071] Comparative Example 1 Solid-state batteries were prepared according to the method of Example 1, except that in step (5), the cell arrangement was BCBBCBCBCBCB (5 layers of positive electrode), the termination layer was the second negative electrode @ electrolyte layer, and the first negative electrode was not provided.

[0072] Comparative Example 2 Solid-state batteries were prepared according to the method of Example 1, except that in step (5), the cell arrangement was ACACACACACAC (5 layers of positive electrode), the termination layer was the first negative electrode @ electrolyte layer, and no second negative electrode was provided.

[0073] Test case The solid-state batteries of the examples and comparative examples were subjected to rate testing and cycle testing, and the test results are listed in Table 1.

[0074] The rate testing method is as follows: Solid-state batteries prepared in the examples and comparative examples are tested on a battery testing system using a battery fixture at a holding pressure of 10 MPa and 25°C. First, a 0.1C charge-discharge test is performed, and the discharge specific capacity is calculated as D1. Then, a 0.5C charge-discharge test is performed, and the discharge specific capacity is calculated as D2. The capacity retention rate at 0.5C / 0.1C is D2 / D1 × 100%, denoted as the rate performance.

[0075] The cycle test method is as follows: the solid-state batteries prepared in the examples and comparative examples are subjected to charge-discharge cycle tests at a current of 0.5C. During the cycle, when the battery capacity is lower than 80% of the initial discharge capacity, the cycle is terminated. The number of cycles is the cycle life of the battery.

[0076] The test method for the negative electrode material loss ratio is as follows: use a film ruler to measure the length and width of the material loss after isostatic pressing of the electrode sheet, and calculate the following: (length after material loss × width) / (initial length × width) × 100%.

[0077] Table 1

[0078] As can be seen from Table 1, the solid-state battery disclosed herein has both excellent rate and cycle performance and a low negative electrode material loss ratio.

[0079] The preferred embodiments of this disclosure have been described in detail above with reference to the accompanying drawings. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0080] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0081] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A solid-state battery, characterized in that, The solid-state battery includes a positive electrode, a first negative electrode, and a second negative electrode stacked together. The first negative electrode includes a first negative electrode material layer, and the second negative electrode includes a second negative electrode material layer. The first negative electrode material layer includes a silicon-carbon composite material, a first solid electrolyte, and a first binder. The second negative electrode material layer includes a pure silicon material and a second binder. At least one of the positive electrodes is disposed between the first negative electrode and the second negative electrode.

2. The solid-state battery according to claim 1, wherein, The compression rebound ratio of the first negative electrode material layer is 2.5~5%, and / or the compression rebound ratio of the second negative electrode material layer is 0.5~2%.

3. The solid-state battery according to claim 1, wherein, Based on the total weight of the silicon-carbon composite material, the silicon content of the silicon-carbon composite material is 20-90% by weight, and the carbon content is 10-80% by weight; and / or, The particle size of the pure silicon material is 100 nm to 2 μm; based on the total weight of the pure silicon material, the silicon content of the pure silicon material is 98% by weight or more.

4. The solid-state battery according to claim 1, wherein, The first negative electrode material layer further includes a first conductive agent. Based on the total weight of the first negative electrode material layer, the content of the silicon-carbon composite material is 48-90% by weight, the content of the first solid electrolyte is 9-40% by weight, the content of the first conductive agent is 0.1-10% by weight, and the content of the first binder is 0.1-10% by weight; and / or, Based on the total weight of the second negative electrode material layer, the content of the pure silicon material is 80-99% by weight, and the content of the second binder is 1-20% by weight.

5. The solid-state battery according to claim 4, wherein, The first solid electrolyte includes Li3PS4 and Li7P3S. 11 Li 11 GeP2S 12 Li6PS5Cl, Li7P2S8I, Li 10 SnP2S 12 and Li 3.25 Ge 0.25 P 0.75 One or more of S4; The first conductive agent includes one or more of SP conductive agent, CNT conductive agent, VGCF conductive agent and graphene; The first adhesive and the second adhesive each independently comprise one or more of PAA, Li-PAA, PVDF, PVDF-HFP, NBR, HNBR, SBR, SBS, SEBS, PTEF, and PEO.

6. The solid-state battery according to claim 1, wherein, The thickness of the first negative electrode material layer is 40~60μm, and / or the thickness of the second negative electrode material layer is 15~30μm.

7. The solid-state battery according to claim 1, wherein, The first negative electrode further includes a first negative electrode current collector, and the first negative electrode material layer is disposed on the surface of the first negative electrode current collector; the second negative electrode further includes a second negative electrode current collector, and the second negative electrode material layer is disposed on the surface of the second negative electrode current collector.

8. The solid-state battery according to claim 1, wherein, The number of the first negative electrode and the number of the second negative electrode are one or more, and at least one termination layer of the solid-state battery is the second negative electrode; Preferably, the first negative electrode and the second negative electrode are arranged alternately.

9. The solid-state battery according to claim 1, wherein, The positive electrode is disposed between any two adjacent negative electrodes, and the positive electrode is isolated from the first negative electrode and the second negative electrode through an electrolyte layer.

10. The solid-state battery according to claim 1, wherein, The positive electrode includes a positive electrode current collector and a composite positive electrode material layer disposed on the surface of the positive electrode current collector. The composite positive electrode material layer includes a positive electrode active material, a second solid electrolyte, a third binder, and an optional second conductive agent. Preferably, based on the total weight of the composite positive electrode material layer, the content of the positive electrode active material is 45-85% by weight, the content of the second solid electrolyte is 5-50% by weight, the content of the third binder is 0.1-10% by weight, and the content of the second conductive agent is 0.1-10% by weight.

11. The solid-state battery according to claim 10, wherein, The surface of the positive electrode active material has an ion conductor coating layer; Preferably, the material of the ion conductor coating layer includes one or more of Li2TiO3, LiNbO3, Li3BO3, Li2ZrO3, LiCoO3, LiPO3, Li2MnO4, Al(PO3)3, La(PO3)3 and NaPO3; Preferably, the thickness of the ion conductor coating layer is 1~10 nm.

12. The solid-state battery according to claim 10, wherein, The positive electrode active material includes LiFePO4, NCM, NCA, LiCoO2, LiMn2O4, and Li4Ti5O. 12 LMO, LiMn y Fe 1-y One or more of PO4 and lithium-rich manganese-based oxides; The second solid electrolyte includes Li3PS4 and Li7P3S. 11 Li 11 GeP2S 12 Li6PS5Cl, Li7P2S8I, Li 10 SnP2S 12 and Li 3.25 Ge 0.25 P 0.75 One or more of S4; The second conductive agent includes one or more of SP conductive agent, CNT conductive agent, VGCF conductive agent and graphene; The third adhesive includes one or more of PAA, Li-PAA, PVDF, PVDF-HFP, NBR, HNBR, SBR, SBS, SEBS, PTEF, and PEO.

13. A battery pack, characterized in that, Includes the solid-state battery as described in any one of claims 1 to 12.

14. An electrical appliance, characterized in that, Includes the solid-state battery as described in any one of claims 1 to 12 or the battery pack as described in claim 13.

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