An all-solid-state battery

Abstract

This invention relates to the field of battery technology, specifically to an all-solid-state battery; the all-solid-state battery includes a positive electrode, an electrolyte layer, a buffer layer, and a negative electrode arranged sequentially; the buffer layer and the electrolyte layer form a composite layer; the buffer layer includes element A; the sheet resistivity of the buffer layer side of the composite layer is a mΩ·cm. 2 The content of element A in the composite layer is b wt%; the all-solid-state battery satisfies: 9.7 × 10⁻⁶ wt%. ‑6 ≤a×b≤2.815×10 5 Compared with existing technologies, the all-solid-state battery provided by this invention establishes a synergistic relationship by adjusting the surface resistance of the composite layer and the content of specific elements in the buffer layer, thereby improving the safety of the all-solid-state battery while ensuring good cycle performance, rate performance, and fast charging performance.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically, to an all-solid-state battery. Background Technology

[0002] In all-solid-state batteries, the electrochemical window of the solid electrolyte is narrow, especially for sulfide electrolytes, whose stability window is only 1.7~2.3V. Therefore, when the sulfide electrolyte comes into contact with the lithium metal anode, severe side reactions occur at the interface, generating byproducts such as Li₂S and Li₃P, which exacerbate the interfacial charge transport impedance and significantly affect the battery's rate capability and lifespan. More importantly, during the electrochemical process, lithium ions deposit as lithium metal on the anode surface. Uneven interfacial contact (vacancies and other defects) and interfacial byproducts easily lead to uneven lithium nucleation, resulting in the formation of lithium dendrites. On the one hand, fragile dendrites are prone to converting into dead lithium, leading to a decrease in cell capacity. On the other hand, lithium dendrites easily grow along the electrolyte grain boundaries, extending to the cathode and causing short circuits in the all-solid-state battery, greatly shortening its lifespan and triggering a series of safety incidents.

[0003] Therefore, how to improve all-solid-state batteries to achieve uniform lithium-ion deposition and avoid lithium dendrite growth caused by uneven deposition has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0004] In view of this, the present invention aims to at least partially solve one of the technical problems in the related art. To this end, the present invention provides an all-solid-state battery that, by setting a buffer layer between the negative electrode and the electrolyte layer, forming a composite layer together with the electrolyte layer, and regulating the sheet resistance of this composite layer, and establishing a synergistic relationship with the content of specific elements in the buffer layer, can isolate the direct contact between the electrolyte and the lithium metal of the negative electrode, reduce interfacial side reactions, induce uniform lithium-ion deposition, and suppress dendrite growth. This, in turn, improves the safety of the all-solid-state battery while ensuring good cycle performance, rate performance, and fast-charging performance.

[0005] To solve the above-mentioned technical problems, the present invention is implemented as follows: According to one aspect of the present invention, an all-solid-state battery is provided, the all-solid-state battery comprising a positive electrode, an electrolyte layer, a buffer layer and a negative electrode arranged sequentially; the buffer layer and the electrolyte layer constitute a composite layer; the buffer layer includes element A; The sheet resistance of the buffer layer side of the composite layer is a mΩ·cm. 2 The content of element A in the composite layer is bwt% The all-solid-state battery meets the following requirement: 9.7 × 10⁻⁶ -6 ≤a×b≤2.815×10 5 ; The element A includes one or more of Al, Sb, Ga, Sn, Hg, Si, P, Ge, Se, and In.

[0006] In some of these embodiments, the all-solid-state battery satisfies: 0.1 ≤ a × b ≤ 100.

[0007] In some of these implementations, a = 0.5 to 50000.

[0008] In some of these implementations, a = 10 to 100.

[0009] In some of these embodiments, b = 1.94 × 10 -5 ~5.63.

[0010] In some of these implementations, b = 0.01~1.

[0011] In some of these embodiments, the A element includes one or more of Al, Sb, Ga, and Sn.

[0012] In some embodiments, the buffer layer further includes an element B; the element B includes one or more of Cl, Br, and S.

[0013] In some embodiments, the material forming the buffer layer is a compound composed of elements A and B.

[0014] In some embodiments, the material forming the buffer layer includes one or more of AlCl3, SbCl3, GaCl3, SnCl4, HgCl2, SiCl4, PCl3, PCl5, GeCl4, Se2Cl2, InCl3, GaBr3, and Sb2S3.

[0015] In some of these embodiments, the thickness of the buffer layer is 50 nm to 50 μm.

[0016] In some of these embodiments, the electrolyte layer comprises a sulfide electrolyte.

[0017] In some of these embodiments, the sulfide electrolyte includes one or more of lithium phosphorus sulfide chloride, lithium germanium phosphorus sulfide, lithium silicon phosphorus sulfide chloride, and lithium phosphorus sulfide.

[0018] In some embodiments, the average particle size of the sulfide electrolyte is 0.5 μm to 10 μm.

[0019] In some embodiments, the thickness of the electrolyte layer is 10 μm to 200 μm.

[0020] Implementing the technical solution of the present invention has at least the following beneficial effects: This invention, by setting a buffer layer between the negative electrode and the electrolyte layer, can isolate the direct contact between the electrolyte and the lithium metal of the negative electrode, reduce interfacial side reactions, and simultaneously induce uniform lithium-ion deposition, suppress dendrite growth, and improve battery safety. Furthermore, by guiding uniform lithium deposition through the buffer layer, it can further meet the cycle performance requirements of all-solid-state batteries and ensure cycle stability. However, the buffer layer can negatively impact the kinetics of the all-solid-state battery system, affecting the battery's rate performance and fast-charging performance. This invention addresses this by constructing a composite layer together with the electrolyte layer, controlling the sheet resistance of this composite layer, and establishing a synergistic relationship with the content of specific elements in the buffer layer: when the sheet resistance of the composite layer is high... When the battery's rate performance is low, it struggles to meet normal cycle requirements. This can be mitigated by reducing the content of specific elements in the buffer layer. However, if the content of these specific elements is too low, the buffer layer's effect on homogenizing lithium flow is diminished, easily leading to lithium dendrite growth. Therefore, by constructing a synergistic relationship between the composite layer resistance and the content of specific elements in the buffer layer, it is possible to isolate the direct contact between the electrolyte and the negative electrode lithium metal, reduce interfacial side reactions, induce uniform lithium ion deposition, and suppress dendrite growth. This improves the safety of the all-solid-state battery while ensuring good cycle performance, rate performance, and fast-charging performance. Based on this, a comprehensive improvement in the overall electrical performance of the all-solid-state battery can be achieved.

[0021] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0022] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0023] Figure 1 This is a schematic diagram of the structure of the all-solid-state battery provided by the present invention.

[0024] Figure 2 This is a flowchart illustrating the preparation of the buffer layer in the all-solid-state battery provided by the present invention.

[0025] Explanation of reference numerals in the attached figures: 1 is the positive electrode, 2 is the negative electrode, 3 is the electrolyte layer, 4 is the buffer layer, and 5 is the composite layer.

[0026] The accompanying drawings have illustrated specific embodiments of the invention, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the invention in any way, but rather to illustrate the concept of the invention to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0027] The present application will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present application.

[0028] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges or individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0029] In the description of this application, "same chemical composition" should be interpreted broadly, that is, the main components of the two have the same chemical composition, or the two have substantially the same chemical composition, but may have errors or impurities within the acceptable range that can be understood by those skilled in the art.

[0030] In the description of this application, "A and / or B" can include any of the cases of A alone, B alone, or A and B, where A and B are merely examples and can be any technical feature connected by "and / or" in this application.

[0031] Unless otherwise specified, the terms "comprising" and "including" as used in this invention can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0032] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0033] Unless otherwise specified, all technical features and optional technical features of this invention can be combined to form new technical solutions.

[0034] Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order; for example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0035] Currently, the inventors of this invention have discovered during the research and development process that mitigating side reactions between the electrolyte and the negative electrode lithium metal, regulating lithium metal nucleation, and preventing dendrite growth that could cause short circuits are key to obtaining long-cycle, high-performance all-solid-state batteries. This invention, by setting a buffer layer between the negative electrode and the electrolyte layer in the all-solid-state battery, can isolate the direct contact between the electrolyte and the negative electrode lithium metal, reduce interfacial side reactions, and simultaneously induce uniform lithium-ion deposition, inhibit dendrite growth, and improve battery safety. Furthermore, by guiding uniform lithium deposition through the buffer layer, the cycle performance requirements of all-solid-state batteries can be further met, ensuring cycle stability. However, the buffer layer can negatively impact the kinetics of the all-solid-state battery system, affecting the battery's rate performance and fast-charging performance.

[0036] Based on this, the present invention constructs a composite layer by combining a buffer layer and an electrolyte layer, modulates the sheet resistance of this composite layer, and establishes a synergistic relationship with the content of specific elements in the buffer layer. This enables the direct contact between the electrolyte and the negative electrode lithium metal to be isolated, reducing interfacial side reactions, while inducing uniform lithium ion deposition and inhibiting dendrite growth. Therefore, while improving the safety of the all-solid-state battery, it also ensures good cycle performance, rate performance, and fast-charging performance. Specifically, the present invention adopts the following technical solution: According to one aspect of the present invention, an all-solid-state battery is provided, the all-solid-state battery comprising a positive electrode, an electrolyte layer, a buffer layer and a negative electrode arranged sequentially; the buffer layer and the electrolyte layer constitute a composite layer; the buffer layer includes element A; The sheet resistance of the buffer layer side of the composite layer is a mΩ·cm. 2 The content of element A in the composite layer is bwt% The all-solid-state battery meets the following requirement: 9.7 × 10⁻⁶ -6 ≤a×b≤2.815×10 5 ; The element A includes one or more of Al, Sb, Ga, Sn, Hg, Si, P, Ge, Se, and In.

[0037] See Figure 1 As shown, Figure 1 This is a schematic diagram of the structure of the all-solid-state battery provided by the present invention, wherein 1 is the positive electrode, 2 is the negative electrode, 3 is the electrolyte layer, 4 is the buffer layer, and 5 is the composite layer.

[0038] In a specific embodiment of the present invention, the provided all-solid-state battery includes a positive electrode, an electrolyte layer, a buffer layer and a negative electrode arranged sequentially. It can be seen that the buffer layer is disposed between the negative electrode and the electrolyte layer. At the same time, the present invention further defines a composite layer, which is composed of the buffer layer and the electrolyte layer.

[0039] This invention establishes a buffer layer between the negative electrode and the electrolyte layer, forming a composite layer together. The sheet resistance of this composite layer is regulated and synergistically correlated with the content of specific elements within the buffer layer. When the sheet resistance of the composite layer is too high, the battery's rate performance is poor, making it difficult to meet normal battery cycling requirements. Reducing the content of specific elements in the buffer layer can alleviate this issue. However, when the content of specific elements in the buffer layer is too low, the buffer layer's effect on homogenizing lithium flow is weak, easily leading to lithium dendrite growth. Therefore, by establishing a synergistic relationship between the sheet resistance of the composite layer and the content of specific elements in the buffer layer, direct contact between the electrolyte and the negative electrode lithium metal can be isolated, reducing interfacial side reactions while inducing uniform lithium ion deposition and suppressing dendrite growth. This improves the safety of the all-solid-state battery while ensuring good cycle performance, rate performance, and fast-charging performance. Based on this, a comprehensive improvement in the overall electrical performance of the all-solid-state battery is achieved.

[0040] Specifically: the all-solid-state battery meets the following requirement: 9.7 × 10⁻⁶ -6 ≤a×b≤2.815×10 5 Specifically, it could be: 9.7 × 10 -6 10 -4 10 -3 0.01, 0.1, 1, 10, 100, 1000, 10000, 2.815×10 5 Or a value between any two of the above; preferably, the all-solid-state battery satisfies: 0.1 ≤ a × b ≤ 100; wherein, the sheet resistance of the buffer layer side of the composite layer is a mΩ·cm. 2 The content of element A in the composite layer is b wt%. It should be noted that in the calculation of a×b, neither a nor b contains units.

[0041] This invention achieves lithium flow homogenization by limiting the calculated value of a×b to the aforementioned range, further balancing the cycle performance, rate performance, fast charging performance, and safety of all-solid-state batteries. By setting a buffer layer, direct contact between the electrolyte and the negative electrode lithium metal is isolated, reducing interfacial side reactions and simultaneously inducing uniform lithium ion deposition, suppressing dendrite growth, and improving battery safety. Furthermore, guiding uniform lithium deposition through the buffer layer further meets the cycle performance requirements of all-solid-state batteries, ensuring cycle stability. However, the buffer layer can negatively impact the kinetics of the all-solid-state battery system, affecting rate performance and fast charging performance. When a is too large, the battery's rate performance is poor, making it difficult to meet normal cycle performance requirements. When b is too large, the kinetics of the all-solid-state battery system are also poor, resulting in poor rate performance, and the buffer layer consumes active lithium, potentially causing rapid capacity decay. When b is too small, its effect on lithium flow homogenization is minimal, easily leading to lithium dendrite growth, which is also detrimental to battery performance improvement and safety assurance. Therefore, this invention establishes a synergistic relationship between a and b and achieves comprehensive regulation, enabling a comprehensive improvement in the overall electrical performance of all-solid-state batteries.

[0042] In this invention, the sheet resistance test method for the buffer layer side of the composite layer is as follows: The sheet resistance is tested using the four-probe method; the prepared electrolyte membrane is cut into a 5cm × 5cm square and placed on the sample stage of the four-probe tester, ensuring good contact between the tips of the four probes and the membrane; the tester is started, and a current I is applied to the membrane through the outer probes #1 and #4, and the potential difference V between the inner probes #2 and #3 is measured; the sheet resistance Rsq = U / I, in mΩ, is calculated; the thickness of the electrolyte membrane is measured as t (in cm) using a thickness gauge; then the sheet resistance R = Rsq × t. 2 The sheet resistance of the buffer layer side of the composite layer is obtained, in mΩ·cm. 2 The value is a.

[0043] In a specific embodiment of the present invention, a = 0.5~50000 can specifically be: 0.5, 1, 5, 10, 50, 100, 500, 1000, 5000, 10000, 50000, or any value between the above two; preferably, a = 10~100.

[0044] In this invention, the method for testing the content of element A in the composite layer is as follows: the interface of the electrolyte membrane is observed using SEM-EDS, and the content of element A is calculated based on the quantitative feedback results of the energy spectrum; the content of element A in the composite layer is obtained, in wt% and the value is b.

[0045] In a specific embodiment of the present invention, b = 1.94 × 10 -5 ~5.63, specifically: 1.94 × 10 -5 10 -410 -3 The value is 0.01, 0.1, 1, 5.63, or any value between two of the above; preferably, b = 0.01~1.

[0046] In a specific embodiment of the present invention, the buffer layer includes element A; the element A includes one or more of Al, Sb, Ga, Sn, Hg, Si, P, Ge, Se, and In, preferably one or more of Al, Sb, Ga, and Sn, and more preferably Al. It should be noted that the element A in the buffer layer has lithiophilic sites, enabling it to form a Li-A alloy with lithium, which homogenizes the lithium flow and guides uniform lithium ion deposition, thereby avoiding dendrite growth problems caused by uneven deposition.

[0047] In a specific embodiment of the present invention, the buffer layer further includes element B; element B includes one or more of Cl, Br, and S, more preferably Cl; the material forming the buffer layer is a compound composed of elements A and B. It should be noted that the material forming the buffer layer (denoted as AB) can undergo in-situ electrochemical decomposition during the electrochemical process, generating a mixed ion-electron conduction layer, including LiCl and a Li-A alloy. The Li-A alloy has already been described and will not be repeated here; while LiCl is a fast ion conductor and can act as an electronic insulator, promoting rapid lithium-ion conduction while increasing the electronic impedance of the buffer layer, thereby inhibiting dendrite growth to a certain extent.

[0048] In specific embodiments of the present invention, the material forming the buffer layer preferably includes one or more of AlCl3, SbCl3, GaCl3, SnCl4, HgCl2, SiCl4, PCl3, PCl5, GeCl4, Se2Cl2, InCl3, GaBr3, and Sb2S3, and more preferably one or more of AlCl3, SbCl3, GaCl3, and SnCl4. The present invention does not impose any special restrictions on the source of the material forming the buffer layer; commercially available products or homemade materials well known to those skilled in the art can be used.

[0049] In a preferred embodiment of the present invention, the buffer layer is prepared by vapor deposition in a multi-zone tube furnace using the material used to form the buffer layer (hereinafter referred to as the buffer layer material). See [link to relevant documentation]. Figure 2 As shown: like Figure 2As shown in (a), in this invention, the buffer layer material is placed at the carrier gas inlet and the electrolyte layer is placed at the gas outlet. An inert carrier gas (N2, Ar, etc.) is introduced into the tubular furnace. First, the buffer layer material is heated to sublimate / vaporize. Following the airflow direction of the inert carrier gas, the gasified buffer layer material is carried to the electrolyte layer region. Since the temperature of the electrolyte layer region is lower than the sublimation / vaporization point of the buffer layer material, the gasified buffer layer material will change from a gaseous state to a solid state and be deposited into the electrolyte layer. The thickness of the deposited buffer layer can be controlled by adjusting the airflow rate, reaction time, and temperature.

[0050] Similarly, such as Figure 2 As shown in (b), a vacuum pump can be used to extract gas from the outlet on the electrolyte layer side without using a flowing carrier gas. This allows the gaseous buffer layer material to be extracted into the electrolyte layer area and deposited due to the temperature difference.

[0051] Based on this, the buffer layer material specified in this invention has the characteristic of being easily vaporized / sublimated after being heated to 300°C, thereby ensuring that the above preparation method can be realized.

[0052] In a preferred embodiment of the present invention, the deposition time is 0.5h to 50h; and the thickness of the buffer layer is preferably 50nm to 50μm.

[0053] As described above, the buffer layer is disposed on the surface of the electrolyte layer. In this invention, the electrolyte layer preferably comprises a sulfide electrolyte, specifically, the sulfide electrolyte preferably comprises one or more of lithium phosphorus-sulfur-chloride, lithium germanium-phosphorus-sulfide, lithium silicon-phosphorus-sulfur-chloride, and lithium phosphorus-sulfide, more preferably lithium phosphorus-sulfur-chloride. This invention does not impose any special restrictions on the source of the sulfide electrolyte; commercially available products or homemade products well-known to those skilled in the art can be used.

[0054] In a preferred embodiment of the present invention, the average particle size of the sulfide electrolyte is preferably 0.5 μm to 10 μm, specifically 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, or any value between the two mentioned above.

[0055] In a specific embodiment of the present invention, the thickness of the electrolyte layer is preferably 10μm to 200μm, specifically 10μm, 50μm, 100μm, 150μm, 200μm, or any value between the two mentioned above.

[0056] In a specific embodiment of the present invention, the electrolyte layer, in addition to the aforementioned sulfide electrolyte, preferably also includes a binder, the main function of which is to bond the components together to form a uniform integral layer structure. In the present invention, the binder preferably includes one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), and polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), more preferably polytetrafluoroethylene (PTFE); the present invention does not impose any special restrictions on the source of the binder, and commercially available products well known to those skilled in the art can be used.

[0057] In a specific embodiment of the present invention, the mass of the adhesive preferably accounts for 0.1% to 10% of the total mass of the electrolyte layer, specifically it can be: 0.1%, 0.5%, 1%, 1.5%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any value between the above two; more preferably it is 1.5% to 2.5%.

[0058] The present invention does not impose any special restrictions on the preparation method of the electrolyte layer, and dry or wet film-forming techniques well known to those skilled in the art can be used.

[0059] This invention does not impose any particular limitations on the negative electrode. For the lithium metal battery system of this invention, the negative electrode can be either a lithium metal system or a lithium-free negative electrode system. In the lithium metal system, the negative electrode uses lithium metal or a Li-M alloy, where M can be one or more of B, C, Na, Mg, Al, Si, K, Ca, Zn, Ga, Ge, Se, Rb, Sr, Ag, In, Sn, Sb, Te, Cs, Ba, Au, and Bi. It can be used alone as the negative electrode layer or as a coating deposited on the current collector surface, with a thickness ranging from 0 to 500 μm. In the lithium-free negative electrode system, the negative electrode uses a lithium metal guiding layer, whose composition includes a lithiophilic site M (the same as M in the aforementioned Li-M alloy) and an element / compound / mixture containing that lithiophilic site. Its composition can be a single component or a composite of multiple components, with a thickness ranging from 5 nm to 500 μm.

[0060] Meanwhile, this invention does not impose any special restrictions on the source of the negative electrode; commercially available products or self-made products can be used. For example, for lithium metal systems, purchased lithium sheets / Li-M metal / copper foil with M coating can be used directly as the negative electrode. For lithium-free negative electrode systems, the buffer layer is prepared by magnetron sputtering / wet coating. Specifically, 1g of conductive carbon Super P and 1g of 5wt% PVDF adhesive (solvent NMP) are weighed, and the solid content is adjusted to 15% using NMP before being mixed and coated to form a film with a thickness of 30μm.

[0061] In a specific embodiment of the present invention, the positive electrode includes a positive electrode current collector and a positive electrode active material layer disposed on the surface of the positive electrode current collector facing the electrolyte layer, specifically a positive electrode sheet; wherein, the positive electrode current collector can be a metal foil, foamed metal, or a composite current collector. For example, as a metal foil, it can be aluminum or stainless steel with silver or carbon surface treatment, stainless steel, copper, aluminum, nickel, carbon electrode, carbon, or titanium, etc.; the foamed metal can be foamed nickel, foamed copper, foamed aluminum, foamed alloy, etc.; the composite current collector can include a polymer material base layer and a metal layer, and the composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0062] In a specific embodiment of the present invention, the positive electrode active material layer preferably comprises a positive electrode active material and a solid electrolyte; wherein, the positive electrode active material preferably comprises lithium iron phosphate positive electrode material and / or nickel-cobalt-manganese ternary material. In a preferred embodiment of the present invention, the positive electrode active material is a nickel-cobalt-manganese ternary material, specifically high-nickel ternary NCM811, which has advantages such as high specific capacity, high voltage platform, and good cycle stability, and is widely used in the fields of power batteries and consumer electronics batteries. The present invention does not have any special restrictions on the source of the positive electrode active material; commercially available products or self-made products well known to those skilled in the art can be used.

[0063] In a specific embodiment of the present invention, the mass percentage of the positive electrode active material in the positive electrode active material layer is preferably 5% to 95%.

[0064] In a specific embodiment of the present invention, the solid electrolyte preferably includes a sulfide electrolyte (such as Li6PS5Cl and its derivative Li). a M b P c S d Cl e X f (M is a metallic element, X is a halogen or chalcogenide element such as F, Cl, Br, I, O, etc.), Li3PS4 and its derivatives, Li 10 GeP2S5 and its derivatives, Li2S-P2S5-X sulfides and their derivatives) or halide electrolytes (Li a M b Cl c X dM = In, Y, Zr, V, Fe, Al, Ta, Nb, Yb, Fe, Sc, La, Sm, Er, Lu, Hf, X = F, Br, I, O, N, etc. (one or more of these compounds). This invention does not impose any special restrictions on the source of the solid electrolyte; commercially available products or homemade products well-known to those skilled in the art can be used.

[0065] In a specific embodiment of the present invention, the mass percentage of the solid electrolyte in the positive electrode active material layer is preferably 5% to 95%.

[0066] In specific embodiments of the present invention, the positive electrode active material layer may also include a binder, a conductive agent, and other optional additives. For example, the binder may include one or more of polyvinylidene fluoride, polytetrafluoroethylene, NBR (nitrile butadiene rubber) binder, SBR (styrene-butadiene rubber) binder, SEBS (styrene-ethylene-butene-styrene block copolymer) binder, SEEPS (styrene-ethylene-ethylene-propylene-styrene block copolymer) binder, and PIB (polyisobutylene) binder, more preferably polytetrafluoroethylene; the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, Super P (SP), graphene, and carbon fiber; all of these materials are commercially available.

[0067] In a specific embodiment of the present invention, the positive electrode is prepared by a method well known to those skilled in the art, which involves mixing the raw material components in a certain proportion and then pressing the mixture onto a positive electrode current collector to obtain a positive electrode sheet.

[0068] In summary, the present invention can obtain a positive electrode, an electrolyte layer, a buffer layer, and a negative electrode. The present invention does not impose any special restrictions on the preparation method of the all-solid-state battery. The all-solid-state battery can be obtained by stacking the above-mentioned positive electrode, electrolyte layer, buffer layer (the electrolyte layer and the buffer layer constitute a composite layer) and negative electrode in sequence, assembling them, and then pressing them together, as is well known to those skilled in the art.

[0069] In a specific embodiment of the present invention, the outer packaging of the assembly can be a soft package, such as a pouch; the material of the soft package can be plastic, and examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate, which mainly serve a sealing function.

[0070] In a specific embodiment of the present invention, the pressing method is preferably warm isostatic pressing, which is achieved by a warm isostatic press. The temperature of the warm isostatic pressing is preferably 70°C to 90°C, specifically 70°C, 75°C, 80°C, 85°C, 90°C, or any value between the two. The pressure of the warm isostatic pressing is preferably 400MPa to 700MPa, specifically 400MPa, 450MPa, 500MPa, 550MPa, 600MPa, 650MPa, 700MPa, or any value between the two. The time of the warm isostatic pressing is preferably 10min to 20min, specifically 10min, 15min, 20min, or any value between the two. The warm isostatic pressing makes the interface dense, and finally the target product, an all-solid-state battery, is obtained.

[0071] The all-solid-state battery provided by this invention, by setting a buffer layer between the negative electrode and the electrolyte layer, and forming a composite layer together with the electrolyte layer, regulates the sheet resistance of the composite layer and establishes a synergistic relationship with the content of specific elements in the buffer layer. It can isolate the direct contact between the electrolyte and the negative electrode lithium metal, reduce interfacial side reactions, induce uniform lithium ion deposition, and inhibit dendrite growth, thereby improving the safety of the all-solid-state battery while ensuring good cycle performance, rate performance, and fast charging performance.

[0072] The present application will be described in detail below with reference to the accompanying drawings and embodiments. However, the implementation and protection of the present invention are not limited thereto. The following embodiments are only some embodiments of the present application and are not intended to limit the present application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0073] Example 1 (1) Preparation of positive electrode: Weigh 7.5g of NCM811 positive electrode material and 2.2g of sulfide electrolyte Li 5.5 PS 4.5 Cl 1.5 0.2g of VGCF (vapor-grown carbon fiber) was placed in a high-speed mixer and mixed at 4000rpm for 20min at ≤80℃ to achieve uniform dispersion. 0.1g of PTFE binder was added and mixed at 2000rpm for 20min at ≤10℃ to obtain a uniformly mixed powder. The powder was then placed in a dry film forming machine and repeatedly kneaded, shaped and sheared at 80℃ to achieve PTFE fiberization. The PTFE fiber was then composited onto the positive electrode current collector to prepare the positive electrode sheet.

[0074] (2) Preparation of electrolyte layer: Weigh 9.8g of sulfide electrolyte Li 5.5 PS 4.5Cl 1.5 0.2g of PTFE binder was mixed with PTFE in a high-speed mixer at 2000rpm for 20 minutes at ≤10℃ throughout the process to achieve uniform mixing. Subsequently, the mixed powder was repeatedly kneaded, shaped and sheared at 80℃ to achieve PTFE fiberization, and an electrolyte membrane, i.e. electrolyte layer, with a thickness of 80μm was prepared. The average particle size of the sulfide electrolyte in the electrolyte layer was 2μm.

[0075] (3) Preparation of buffer layer: First, weigh 0.1g AlCl3 and place it on side A of the tube furnace temperature zone. Then, lay the 50mm×50mm electrolyte membrane prepared in step (2) on side B of the tube furnace temperature zone. Then, introduce N2 gas from side A to side B and discharge it. The gas flow rate is set to 15mL / min. Set the temperature of temperature zone A to 160℃ and set the temperature of temperature zone B to 70℃. At the same time, increase the temperature at a rate of 5℃ / min. After the temperature of temperature zone A reaches the set value, the deposition is considered to have started. After 1h of vapor deposition, stop the reaction to form a buffer layer with a thickness of 80nm, thus obtaining the electrolyte layer with the buffer layer.

[0076] (4) Negative electrode: Purchased lithium sheets are used as negative electrodes.

[0077] (5) Battery preparation: The positive electrode, electrolyte layer with load buffer layer and negative electrode are stacked in sequence, with the buffer layer facing the negative electrode side; the stacked solid-state cell is encapsulated with aluminum-plastic film for subsequent pressing; the stacked solid-state cell is pressed by a warm isostatic press (warm isostatic pressing conditions are 80℃, 600MPa, isostatic pressing for 10 minutes) to obtain a solid-state battery.

[0078] The parameters of the all-solid-state battery provided in Embodiment 1 of this invention are shown in Table 1 below; wherein, the method for testing the sheet resistance on the buffer layer side of the composite layer is as follows: the sheet resistance is tested using the four-probe method; the prepared electrolyte membrane is cut into a 5cm×5cm square and placed on the sample stage of the four-probe tester, ensuring good contact between the tips of the four probes and the membrane; the tester is started and a current I is applied to the membrane through the outer probes #1 and #4, and the potential difference V between the inner probes #2 and #3 is measured; the sheet resistance Rsq=U / I, in mΩ is calculated; the thickness of the electrolyte membrane is measured as t (in cm) using a thickness gauge; then the sheet resistance R=Rsq×t 2 The method for testing the Al content in the composite layer is as follows: the interface of the electrolyte membrane is observed using SEM-EDS, and the Al content is calculated based on the quantitative feedback results of the energy dispersive spectroscopy.

[0079] Example 2 An all-solid-state battery was obtained using the preparation method provided in Example 1, with the following difference: During the preparation of the electrolyte layer, the thickness of the electrolyte layer was set to 10 μm. Simultaneously, during the preparation of the buffer layer, 0.05 g of AlCl3 was placed on side A of the tubular furnace. No flowing carrier gas was used; instead, a vacuum pump was used to evacuate the gas at the outlet on the electrolyte layer side. The temperature at temperature zone A was set to 150 °C, and the temperature at temperature zone B was set to 80 °C, with a heating rate of 10 °C / min. After 0.8 h of vapor deposition, the reaction was stopped, forming a buffer layer with a thickness of 50 nm. Based on this, the parameters of all-solid-state batteries are different, as shown in Table 1.

[0080] Example 3 An all-solid-state battery was obtained using the preparation method provided in Example 1, with the following difference: During the preparation of the buffer layer, 0.2g of AlCl3 was placed on side A of the tubular furnace; the flow rate of the N2 gas source was set to 10mL / min; the temperature at temperature zone A was set to 165℃, and the temperature at temperature zone B was set to 65℃, with a heating rate of 4℃ / min. Based on this, the parameters of all-solid-state batteries are different, as shown in Table 1.

[0081] Example 4 An all-solid-state battery was obtained using the preparation method provided in Example 1, with the following difference: During the preparation of the buffer layer, 0.1g of AlCl3 was placed on side A of the tubular furnace. No flowing carrier gas was used. A vacuum pump was used to evacuate the gas at the outlet on the electrolyte layer side. The temperature at temperature zone A was set to 155℃, and the temperature at temperature zone B was set to 75℃. The heating rate was 6℃ / min. Based on this, the parameters of all-solid-state batteries are different, as shown in Table 1.

[0082] Example 5 An all-solid-state battery was obtained using the preparation method provided in Example 1, with the following difference: During the preparation of the electrolyte layer, the thickness of the electrolyte layer was set to 200 μm. Simultaneously, during the preparation of the buffer layer, 0.5 g of AlCl3 was placed on side A of the tubular furnace. The flow rate of the N2 gas source was set to 2 mL / min. The temperature at temperature zone A was set to 170℃, and the temperature at temperature zone B was set to 60℃, with a heating rate of 1℃ / min. After 10 h of vapor deposition, the reaction was stopped, forming a buffer layer with a thickness of 1 μm. Based on this, the parameters of all-solid-state batteries are different, as shown in Table 1.

[0083] Example 6 An all-solid-state battery was obtained using the preparation method provided in Example 1, with the following difference: During the preparation of the buffer layer, 0.3g of AlCl3 was placed on side A of the tubular furnace. No flowing carrier gas was used. A vacuum pump was used to evacuate the gas at the outlet on the electrolyte layer side. The temperature at temperature zone A was set to 165℃, and the temperature at temperature zone B was set to 70℃. The heating rate was 5℃ / min. Based on this, the parameters of all-solid-state batteries are different, as shown in Table 1.

[0084] Example 7 An all-solid-state battery was obtained using the preparation method provided in Example 1, with the following difference: During the preparation of the buffer layer, 0.5g of AlCl3 was placed on side A of the tubular furnace; the flow rate of the N2 gas source was set to 8mL / min; the temperature at temperature zone A was set to 160℃, and the temperature at temperature zone B was set to 65℃, with a heating rate of 2℃ / min. Based on this, the parameters of all-solid-state batteries are different, as shown in Table 1.

[0085] Example 8 An all-solid-state battery was obtained using the preparation method provided in Example 1, with the following difference: The buffer layer material was replaced with SbCl3; Based on this, the parameters of all-solid-state batteries are different, as shown in Table 1.

[0086] Example 9 An all-solid-state battery was obtained using the preparation method provided in Example 1, with the following difference: The buffer layer material was replaced with GaCl3; Based on this, the parameters of all-solid-state batteries are different, as shown in Table 1.

[0087] Example 10 An all-solid-state battery was obtained using the preparation method provided in Example 1, with the following difference: The buffer layer material was replaced with SnCl4 instead of AlCl3; Based on this, the parameters of all-solid-state batteries are different, as shown in Table 1.

[0088] Example 11 An all-solid-state battery was obtained using the preparation method provided in Example 1, with the following difference: During the preparation of the electrolyte layer, the sulfide electrolyte of the electrolyte layer is made from Li 5.5 PS 4.5 Cl 1.5 Replace with Li7P3S 11 ; Based on this, the parameters of all-solid-state batteries are different, as shown in Table 1.

[0089] Comparative Example 1 An all-solid-state battery was obtained using the preparation method provided in Example 1, with the following difference: During the preparation of the electrolyte layer, the thickness of the electrolyte layer was set to 200 μm. At the same time, during the preparation of the buffer layer, 1 g of AlCl3 was placed on side A of the tubular furnace. The gas flow rate of the N2 source was set to 1 mL / min. The temperature at temperature zone A was set to 175℃, and the temperature at temperature zone B was set to 60℃, with a heating rate of 1℃ / min. After 10 h of vapor deposition, the reaction was stopped, forming a buffer layer with a thickness of 1 μm. Based on this, the parameters of all-solid-state batteries are different, as shown in Table 1.

[0090] Comparative Example 2 An all-solid-state battery was obtained using the preparation method provided in Example 1, with the following difference: During the preparation of the electrolyte layer, the thickness of the electrolyte layer was set to 10 μm. Simultaneously, during the preparation of the buffer layer, 0.02 g of AlCl3 was placed on side A of the tubular furnace. No flowing carrier gas was used; instead, a vacuum pump was used to evacuate the gas at the outlet on the electrolyte layer side. The temperature at temperature zone A was set to 145 °C, and the temperature at temperature zone B was set to 85 °C, with a heating rate of 12 °C / min. After 1 hour of vapor deposition, the reaction was stopped, forming a buffer layer with a thickness of 50 nm. Based on this, the parameters of all-solid-state batteries are different, as shown in Table 1.

[0091] Table 1 Comparative Example 3 An all-solid-state battery was obtained using the preparation method provided in Example 1, with the following difference: No buffer layer is prepared.

[0092] Comparative Example 4 An all-solid-state battery was obtained using the preparation method provided in Example 1, with the following difference: During battery manufacturing, the buffer layer is oriented towards the positive electrode.

[0093] Performance testing: The following tests were performed on the all-solid-state batteries provided in each embodiment and comparative example: (1) Cyclic performance test: After assembling the battery, place it in a 45℃ environment and let it stand for 2 hours to prepare for testing; charge the battery to 4.25V at 0.1C, then charge it to 0.05C at constant voltage and let it stand for 5 minutes; then discharge the battery to 2.5V at 0.1C to complete the pre-cycle; after standing for 6 hours, charge the battery to 4.25V at 0.33C, then charge it to 0.1C at constant voltage; after standing for 5 minutes, perform a cycle test by discharging the battery to 2.5V at 0.33C. When the capacity is less than 80% of the capacity of the first 0.33C discharge, the cycle is stopped.

[0094] (2) Rate performance test: After assembling the battery, place it in a 45℃ environment and let it stand for 2 hours to prepare for testing; charge the battery to 4.25V at 0.1C, then charge it to 0.05C at constant voltage and let it stand for 5 minutes; then discharge the battery to 2.5V at 0.1C to complete the pre-cycle; after standing for 6 hours, charge the battery to 4.25V at 0.5C, then charge it to 0.1C at constant voltage; after standing for 5 minutes, perform a cycle test by discharging the battery to 2.5V at 0.5C, and record the specific capacity at 0.5C as an indicator for evaluating rate performance.

[0095] (3) Fast charging performance test: The capacity retention rate is determined by cycling 100 times with 1C current: After assembling the battery, place it in a 45℃ environment and let it stand for 2 hours to prepare for testing; charge the battery to 4.25V at 0.1C, then charge it to 0.05C at constant voltage and let it stand for 5 minutes; charge the battery to the upper limit voltage at 0.33C constant current, then charge it to the current less than or equal to 0.1C at constant voltage; then discharge it to the lower limit voltage at 0.33C, repeat the above steps 3 times as activation; charge the cell to 4.25V at 1C, then charge it to 0.1C at constant voltage and let it stand for 10 minutes; then discharge the cell to 2.5V at 1C current, and record the discharge capacity of this cycle as the 1C discharge capacity; the above 1C steps are used as the cycle steps and cycled; after cycling 100 times according to this step, the capacity of the 100th cycle of 1C is compared with the initial 1C discharge capacity, which is the capacity retention rate after 100 cycles of 1C.

[0096] The test results are shown in Table 2.

[0097] Table 2 As shown in Table 2, this invention, by setting a buffer layer between the negative electrode and the electrolyte layer, can isolate the direct contact between the electrolyte and the lithium metal of the negative electrode, reduce interfacial side reactions, and simultaneously induce uniform lithium-ion deposition, suppress dendrite growth, and improve battery safety. Furthermore, by guiding uniform lithium deposition through the buffer layer, it can further meet the cycle performance requirements of all-solid-state batteries and ensure cycle stability. However, the buffer layer can negatively impact the kinetics of the all-solid-state battery system, affecting the battery's rate performance and fast-charging performance. This invention constructs a composite layer by combining the buffer layer and the electrolyte layer, controlling the sheet resistance of this composite layer, and establishing a synergistic relationship with the content of specific elements in the buffer layer: when the composite layer... When the sheet resistance is too high, the battery's rate performance is poor, making it difficult to meet the requirements of normal battery cycling. This can be alleviated by reducing the content of specific elements in the buffer layer. However, when the content of specific elements in the buffer layer is too low, the buffer layer's effect on homogenizing lithium flow is weak, which easily leads to lithium dendrite growth. Therefore, by constructing a synergistic relationship between the sheet resistance and the content of specific elements in the buffer layer, it is possible to isolate the direct contact between the electrolyte and the negative electrode lithium metal, reduce interfacial side reactions, induce uniform lithium ion deposition, and inhibit dendrite growth. This improves the safety of all-solid-state batteries while ensuring good cycle performance, rate performance, and fast charging performance. On this basis, a comprehensive improvement in the overall electrical performance of all-solid-state batteries can be achieved.

[0098] The parts of this invention not described in detail are techniques known to those skilled in the art.

[0099] The basic principles of the present invention have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in the present invention are merely examples and not limitations, and should not be considered as essential features of each embodiment of the present invention. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the present invention to the necessity of employing the aforementioned specific details.

[0100] In the foregoing description of this specification, references to terms such as "one embodiment," "another embodiment," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment is included in at least one embodiment of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples, without contradiction. Additionally, it should be noted that in this specification, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features.

[0101] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An all-solid battery, characterized by, The all-solid-state battery comprises, in sequence, a positive electrode, an electrolyte layer, a buffer layer, and a negative electrode; the buffer layer and the electrolyte layer form a composite layer; the buffer layer comprises an A element; The surface resistance of the side of the buffer layer of the composite layer is a mΩ·cm 2 ; the content of the element A in the composite layer is b wt% The all-solid-state battery satisfies: 9.7 x 10 -6 ≤ a x b ≤ 2.815 x 10 5 ; The A element comprises one or more of Al, Sb, Ga, Sn, Hg, Si, P, Ge, Se, and In.

2. The all-solid battery according to claim 1, characterized by, The all-solid-state battery satisfies 0.1 ≤ a × b ≤ 100.

3. The all-solid battery according to claim 1 or 2, characterized by, The a = 0.5-50000.

4. The all-solid battery according to claim 3, characterized by, The a = 10-100.

5. The all-solid battery according to claim 1 or 2, characterized by, said b = 1.94 x 10 -5 ~5.

63.

6. The all-solid battery according to claim 5, characterized by, The b = 0.01-1.

7. The all-solid battery according to claim 1, characterized by, The A element comprises one or more of Al, Sb, Ga, and Sn.

8. The all-solid battery according to claim 1, 2, or 7, characterized by, The buffer layer further comprises a B element; the B element comprises one or more of Cl, Br, and S.

9. The all-solid battery according to claim 8, characterized by, The material forming the buffer layer is a composition compound of the A element and the B element.

10. The all-solid battery according to claim 9, characterized by, The material forming the buffer layer comprises one or more of AlCl3, SbCl3, GaCl3, SnCl4, HgCl2, SiCl4, PCl3, PCl5, GeCl4, Se2Cl2, InCl3, GaBr3, and Sb2S3.

11. The all-solid battery according to claim 1, 2, or 7, characterized by, The thickness of the buffer layer is 50 nm-50 μm.

12. The all-solid battery according to claim 1, 2, or 7, characterized by, The electrolyte layer comprises a sulfide electrolyte.

13. The all-solid battery according to claim 12, characterized by, The sulfide electrolyte comprises one or more of lithium phosphorus sulfur chloride, lithium germanium phosphorus sulfur, lithium silicon phosphorus sulfur chloride, and lithium phosphorus sulfur.

14. The all-solid battery according to claim 12, characterized by, The average particle size of the sulfide electrolyte is 0.5 μm-10 μm.

15. The all-solid-state battery according to claim 1, 2, or 7, wherein The thickness of the electrolyte layer is 10 μm-200 μm.

Images