High-nickel positive electrode material, preparation method thereof and solid-state battery

Abstract

The invention relates to a high-nickel positive electrode material, a preparation method thereof and a solid-state battery. The high-nickel positive electrode material comprises a high-nickel core, and a LiAlO2 coating layer and a Li3PO4 coating layer which are sequentially formed on the surface of the high-nickel core in situ, and the median particle diameter D50 of the high-nickel core is 5 [mu] m-12 [mu] m. According to the invention, the LiAlO2 / Li3PO4 composite coating layer in gradient distribution is constructed in situ on the surface of the high-nickel core, and when the composite coating layer is applied to the sulfide solid electrolyte, the transmission of lithium ions is effectively optimized, and meanwhile, the side reaction of the high-nickel core and the sulfide solid electrolyte can be thoroughly inhibited, so that the first effect, the rate capability and the cycle performance of a solid-state battery are improved.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, specifically to solid-state batteries, and more particularly to a high-nickel cathode material, its preparation method, and a solid-state battery. Background Technology

[0002] High-nickel layered oxide cathode materials, such as lithium nickel cobalt manganese oxide (NCM) and lithium nickel cobalt aluminum oxide (NCA), with a nickel molar ratio of nickel exceeding 80% in the transition elements, are key to realizing next-generation high-energy-density lithium-ion batteries. However, when combined with sulfide solid electrolytes (SSEs), such as Li6PS5Cl and Li... 10 GeP2S 12 When applied to all-solid-state batteries (ASSB), there are two major challenges: First, severe interfacial side reactions. The strong oxidizing properties of the high-nickel cathode in the charging state will oxidize the sulfide electrolyte, generating electron / ion insulating layers such as Li2S, Li3P, and elemental sulfur, leading to a surge in interfacial impedance and rapid capacity decay. Second, poor solid-solid interface contact. The point contact between the high-nickel cathode and the solid electrolyte results in poor ion transport channels.

[0003] CN119786581A discloses a coating method for a high-nickel layered oxide cathode material. The coating is achieved by using an acid-base neutralization reaction. The coating components include three elements: a high-valence metal, a halogen element with high electronegativity (F or Cl), and a Li element. The purpose of coating the first two is to improve the structural stability of the high-nickel layered oxide, while the latter provides a lithium source for the cathode material. At the same time, it avoids contact between the high-nickel layered oxide and the sulfide electrolyte, suppresses the occurrence of side reactions, and is beneficial to the long-cycle stability of the sulfide all-solid-state lithium battery.

[0004] CN118315557A discloses a modified high-nickel cathode material and its preparation method, as well as a sulfide all-solid-state battery. The method involves coating a fast-ion conductor silicate onto the surface of the cathode matrix material using a solution and heat treatment. The resulting modified high-nickel cathode material avoids direct contact between the cathode and the sulfide electrolyte, preventing the accumulation of byproducts at the interface. It also accelerates lithium-ion transport at the interface, reduces interface impedance, and improves lithium-ion diffusion kinetics at the interface, which is beneficial for constructing high-energy-density sulfide all-solid-state batteries.

[0005] CN115050930A discloses a composite high-nickel layered cathode material, a cathode sheet, and an all-solid-state lithium battery. The method involves preparing an Al-doped high-nickel layered cathode material using a co-precipitation method, followed by spray drying to obtain a high-nickel layered cathode material co-coated with fluorophenylboronic acid and thiophosphate, i.e., the composite high-nickel layered cathode material. The cathode sheet and all-solid-state lithium battery are then prepared by mixing and compressing the composite high-nickel layered cathode material, a sulfide solid electrolyte, a conductive agent, and all-trans βPVDF. The composite high-nickel layered cathode material in this invention, through elemental doping and the construction of an optimized CEI film, effectively suppresses the continuous degradation of the high-nickel layered cathode material, reduces impedance, promotes internal lithium-ion transport, and avoids direct contact between high-nickel particles and the solid electrolyte, thus improving the cycle life and electrochemical stability of the cathode sheet.

[0006] Existing technologies often employ a single coating strategy to alleviate the aforementioned problems, which frequently fails to balance high voltage stability and good compatibility with sulfides. Furthermore, the uniform coating process is complex and expensive. More importantly, existing technologies only address the material preparation stage and fail to actively optimize the secondary interface between the coating layer and the SSE after battery molding. This interface remains a performance bottleneck and a source of failure.

[0007] Therefore, it is of great significance to provide a strategy for synergistically optimizing the interface throughout the entire process from the material bulk to the solid-state battery fabrication. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a high-nickel cathode material, its preparation method, and a solid-state battery. This invention uses a high-nickel substrate as its core and constructs a LiAlO2 / Li3PO4 composite coating layer in situ on the surface of the high-nickel core. This helps maintain the high voltage stability of the high-nickel core itself, effectively isolates the high-nickel cathode from corrosion of the sulfide electrolyte, and when applied to a sulfide solid electrolyte, the LiAlO2 / Li3PO4 composite coating layer can also form a lithium-ion conductor gradient interface layer with a chemical gradient distribution between it and the sulfide electrolyte. This optimizes lithium-ion transport while completely suppressing side reactions between the high-nickel core and the sulfide solid electrolyte, thereby improving the first-pass efficiency, rate performance, and cycle performance of the solid-state battery.

[0009] To achieve this objective, the present invention employs the following technical solution: In a first aspect, the present invention provides a high-nickel cathode material, the high-nickel cathode material comprising a high-nickel core, and a LiAlO2 coating layer and a Li3PO4 coating layer sequentially formed in situ on the surface of the high-nickel core; the median particle size D50 of the high-nickel core is 5μm~12μm.

[0010] In this invention, the high-nickel core is composed of Ni. x Co y Mnz O2, where 0.8≤x<1, y≥0, z≥0, x+y+z=1.

[0011] The high-nickel cathode material provided by this invention comprises a LiAlO2 coating layer and a Li3PO4 coating layer sequentially formed in situ on the surface of a high-nickel core. By constructing a gradient-distributed LiAlO2 / Li3PO4 composite coating layer in situ on the surface of the high-nickel core, LiAlO2 helps maintain the high voltage stability of the high-nickel core itself and effectively protects the sulfide solid electrolyte from oxidation and corrosion of the high-nickel core. Li3PO4 provides the basis for efficient lithium-ion conduction and effectively optimizes ion transport between the high-nickel cathode and the sulfide electrolyte. Furthermore, when the high-nickel cathode material is present in the sulfide solid electrolyte, controllable interdiffusion and in-situ reactions can occur between the LiAlO2 / Li3PO4 composite coating layer and the sulfide electrolyte, forming a chemically gradient-distributed lithium-ion conductor gradient interface layer. This perfectly bridges the LiAlO2 / Li3PO4 composite coating layer and the sulfide electrolyte, achieving low-impedance "seamless" ion transport, further optimizing ion transport and completely suppressing side reactions between the high-nickel core and the sulfide solid electrolyte.

[0012] Preferably, the LiAlO2 comprises γ-phase LiAlO2.

[0013] Preferably, in the high-nickel cathode material, the total mass percentage of the LiAlO2 coating layer and the Li3PO4 coating layer is 0.5wt.%~2.5wt.%.

[0014] In a second aspect, the present invention provides a method for preparing a high-nickel cathode material as described in the first aspect, the method comprising: The high-nickel cathode material is prepared by mixing a high-nickel precursor, a lithium source, and AlPO4 powder, and then sequentially performing a first-stage sintering and a second-stage sintering. The molar ratio of Li in the lithium source to the transition metal element TM in the high-nickel precursor is 1.03~1.10.

[0015] This invention introduces AlPO4 powder into the high-nickel precursor and lithium source during the preparation of high-nickel cathode materials. Through a first-stage sintering low-temperature pretreatment followed by a second-stage sintering high-temperature crystallization and in-situ coating, a high-nickel core with a well-structured lattice is formed. Simultaneously, AlPO4 powder uniformly coats the surface of the high-nickel core and reacts in-situ with excess lithium source to form Li2O, creating a LiAlO2 / Li3PO4 composite coating layer. The reaction is as follows: .

[0016] LiAlO2 tends to be distributed closer to the high-nickel core, while Li3PO4 tends to be distributed further away from the high-nickel core. This is attributed to the fact that in a high-lithium environment (Li / TM>1), Li2O is in excess, and the reaction between AlPO4 and Li2O is not a one-step process. Because Al... 3+ For O 2- The affinity of γ-LiAlO2 and its low free energy at high temperatures make it highly active Li + It will preferentially interact with Al in AlPO4. 3+ Bonding occurs, making it easier to first form a Li-Al-O structure (i.e., LiAlO2), and this structure has a better lattice match with the high-nickel oxide core (both are layered or distorted layered / spinel structures), thus AlPO4... 3+ It preferentially reacts with Li₂O, heterogeneously nucleating on the surface of the high-nickel core to form a thermodynamically more stable and more tightly bound initial LiAlO₂ layer, which lowers the overall system energy. As the reaction proceeds, PO₄ is "stripped" of its AlPO₄ framework. 3- With the subsequent spread of Li + They combine at a more outer position to form Li3PO4.

[0017] Preferably, the average particle size of the AlPO4 powder is 20 nm to 200 nm.

[0018] Preferably, the mass of the AlPO4 powder is 0.5 wt.% to 2.5 wt.% of the mass of the high-nickel precursor.

[0019] Preferably, the heating rates of the first sintering stage and the second sintering stage are each independently 2℃ / min to 5℃ / min.

[0020] Preferably, the first sintering stage and the second sintering stage are each carried out independently in an oxygen-containing atmosphere.

[0021] Preferably, the sintering temperature of the first stage is 450℃~550℃.

[0022] Preferably, the sintering time of the first stage is 2h to 6h.

[0023] Preferably, the sintering temperature of the second stage is 700℃~850℃.

[0024] Preferably, the sintering time of the second stage is 10h to 20h.

[0025] Preferably, the mixing method includes ball milling.

[0026] Preferably, the rotational speed of the ball mill is 300 rpm to 500 rpm.

[0027] Preferably, the ball milling mixing time is 30 min to 90 min.

[0028] Preferably, the preparation method further includes grinding and sieving the high-nickel cathode material.

[0029] Preferably, the mesh size of the sieve used for sieving is 200 to 400 mesh.

[0030] Thirdly, the present invention provides a solid-state battery, the solid-state battery comprising the high-nickel cathode material as described in the first aspect; The solid-state battery also includes a lithium-ion conductor gradient interface layer that has been activated and formed in situ between the surface of the high-nickel cathode material and the sulfide solid electrolyte. The material of the lithium-ion conductor gradient interface layer includes Li-Al-POS lithium-ion conductor phase or Li-Al-SO lithium-ion conductor phase.

[0031] When the high-nickel cathode material provided by this invention is applied in a sulfide solid electrolyte, the LiAlO2 / Li3PO4 composite coating layer and the sulfide electrolyte can undergo controllable interdiffusion and in-situ reaction through the regulation of the activation process, forming a lithium-ion conductor gradient interface layer with a chemical gradient distribution. This perfectly bridges the LiAlO2 / Li3PO4 composite coating layer and the sulfide electrolyte, achieving low-impedance "seamless" ion transport. The material of the lithium-ion conductor gradient interface layer includes a Li-Al-POS lithium-ion conductor phase (such as a phase with a LISICON-type structure) or a Li-Al-SO lithium-ion conductor phase, which has a better ionic conductivity than Li3PO4 and good compatibility with the sulfide electrolyte. This further optimizes ion transport and reduces interface impedance, and completely suppresses the side reactions between the high-nickel core and the sulfide solid electrolyte.

[0032] Preferably, the thickness of the lithium-ion conductor gradient interface layer is 5 nm to 50 nm.

[0033] Preferably, the activation process includes charging the solid-state battery at a constant current to the activation voltage, then charging it at a constant voltage to the cutoff current, and continuing to maintain it at the activation voltage until activation is complete.

[0034] Preferably, the constant current charging rate is 0.02C~0.1C.

[0035] Preferably, the activation voltage is 4.4V~4.8V.

[0036] Preferably, the cutoff current is 0.002C~0.01C.

[0037] Preferably, the holding time is 1 hour to 24 hours.

[0038] Compared with the prior art, the present invention has the following beneficial effects: This invention uses a high-nickel substrate as the core and constructs a LiAlO2 / Li3PO4 composite coating layer in situ on the surface of the high-nickel core. This helps maintain the high voltage stability of the high-nickel core itself and effectively isolates the high-nickel cathode from the corrosion of the sulfide electrolyte. When applied to sulfide solid electrolytes, the LiAlO2 / Li3PO4 composite coating layer can also form a lithium-ion conductor gradient interface layer with a chemical gradient distribution between the LiAlO2 / Li3PO4 composite coating layer and the sulfide electrolyte. This optimizes lithium-ion transport while completely suppressing the side reactions between the high-nickel core and the sulfide solid electrolyte, thereby improving the first-efficiency, rate performance and cycle performance of solid-state batteries. Detailed Implementation

[0039] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0040] The "range" disclosed in this invention can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific range. This type of range definition can include or exclude endpoints; any endpoint can be independently included or excluded, and they can be arbitrarily combined, meaning any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for specific parameters, it is understood that ranges of 60~110 and 80~120 are also expected. Furthermore, if minimum range values ​​1 and 2 are listed, and maximum range values ​​3, 4, and 5 are also listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this invention, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0" and "5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For instance, when a parameter is described as an integer selected from "2~10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0041] In this invention, "a combination of at least two" refers to a quantity greater than or equal to two, unless otherwise specified. For example, "any combination of one or at least two" means one or more or more items. It can be understood that when referring to "a combination of at least two," it refers to any suitable combination of multiple items, that is, a combination of "at least two" items carried out in a manner that does not conflict with and enables the implementation of this invention.

[0042] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0043] The term "embodiment" as used in this invention means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this invention can be combined with other embodiments.

[0044] Those skilled in the art will understand that the order in which the steps are written in the methods of the various embodiments does not imply a strict execution order. The detailed execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, but are preferably performed sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), meaning that step (c) can 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.

[0045] In this invention, open-ended technical features or solutions described using terms such as "comprising" do not exclude additional members beyond those listed unless otherwise specified. They can be considered as providing both closed-ended features or solutions comprised of the listed members and open-ended features or solutions that include additional members beyond the listed members. For example, A includes a1, a2, and a3. Unless otherwise specified, it may also include other members or exclude additional members. This can be considered as providing both technical features or solutions where "A is composed of a1, a2, and a3" or "A is selected from a1, a2, and a3," and technical features or solutions where "A includes not only a1, a2, and a3, but also other members."

[0046] In this invention, unless otherwise specified, the features or solutions corresponding to "and / or" include any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" represents a group consisting of A, B, and "a combination of A and B". "Containing A and / or B" can mean "containing A, containing B, and containing A and B", or "containing A, containing B, or containing A and B", and can be appropriately understood according to the context.

[0047] In this invention, the terms "first aspect," "second aspect," "third aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on the quantity.

[0048] In this invention, "room temperature" generally refers to 4℃~35℃, and can refer to 20℃±5℃. In some embodiments of this invention, room temperature refers to 20℃~30℃.

[0049] In one specific embodiment, the present invention provides a high-nickel cathode material, the high-nickel cathode material comprising a high-nickel core, and a LiAlO2 coating layer and a Li3PO4 coating layer sequentially formed in situ on the surface of the high-nickel core; the median particle size D50 of the high-nickel core is 5μm~12μm, for example, it can be 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm or 12μm.

[0050] In this invention, the high-nickel core is composed of Ni. x Co y Mn z Al w O2, where 0.8 ≤ x < 1, for example, can be 0.8, 0.82, 0.84, 0.86, 0.88, 0.9, 0.92, 0.94 or 0.96, y ≥ 0, z ≥ 0, w ≥ 0, y, z and w are each independent, for example can be 0, 0.02, 0.04, 0.06, 0.08, 0.1, 0.12, 0.14, 0.16, 0.18 or 0.2, x + y + z + w = ​​1.

[0051] The high-nickel cathode material provided by this invention comprises a LiAlO2 coating layer and a Li3PO4 coating layer sequentially formed in situ on the surface of a high-nickel core. By constructing the LiAlO2 / Li3PO4 composite coating layer in situ on the surface of the high-nickel core, LiAlO2 helps maintain the high voltage stability of the high-nickel core itself and effectively protects the sulfide solid electrolyte from oxidation and corrosion of the high-nickel core. Li3PO4 provides the basis for efficient lithium-ion conduction and effectively optimizes ion transport between the high-nickel cathode and the sulfide electrolyte. In addition, when the high-nickel cathode material is present in the sulfide solid electrolyte, the LiAlO2 / Li3PO4 composite coating layer and the sulfide electrolyte can undergo controllable interdiffusion and in-situ reaction, forming a lithium-ion conductor gradient interface layer with a chemical gradient distribution. This perfectly bridges the LiAlO2 / Li3PO4 composite coating layer and the sulfide electrolyte, achieving low-impedance "seamless" ion transport, further optimizing ion transport and completely suppressing side reactions between the high-nickel core and the sulfide solid electrolyte.

[0052] In some embodiments, the LiAlO2 comprises γ-phase LiAlO2.

[0053] In some embodiments, the total mass percentage of the LiAlO2 coating layer and the Li3PO4 coating layer in the high-nickel cathode material is 0.5 wt.% to 2.5 wt.%, for example, it can be 0.5 wt.%, 0.75 wt.%, 1 wt.%, 1.25 wt.%, 1.5 wt.%, 1.75 wt.%, 2 wt.%, 2.25 wt.%, or 2.5 wt.%.

[0054] In some embodiments, the average particle size of the high-nickel cathode material is 35μm to 75μm, for example, it can be 35μm, 40μm, 45μm, 50μm, 55μm, 60μm, 65μm, 70μm or 75μm.

[0055] In another specific embodiment, the present invention provides a method for preparing a high-nickel cathode material as described in one of the foregoing specific embodiments, the preparation method comprising: The high-nickel cathode material is prepared by mixing a high-nickel precursor, a lithium source, and AlPO4 powder, and then sequentially performing a first-stage sintering and a second-stage sintering. The molar ratio of Li in the lithium source to the transition metal element TM in the high-nickel precursor is 1.03 to 1.10, for example, it can be 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09 or 1.10.

[0056] In this invention, the high-nickel precursor includes Ni x Co y Mn z (OH)2 and / or Nix Co y Mn z CO3 where 0.8 ≤ x < 1, y ≥ 0, z ≥ 0, x + y + z = 1; the lithium source includes any one or a combination of at least two of lithium hydroxide, lithium oxide, lithium carbonate, or lithium nitrate.

[0057] This invention introduces AlPO4 powder into the high-nickel precursor and lithium source during the preparation of high-nickel cathode materials. Through a first-stage sintering low-temperature pretreatment followed by a second-stage sintering high-temperature crystallization and in-situ coating, a high-nickel core with a well-structured lattice is formed. Simultaneously, AlPO4 powder uniformly coats the surface of the high-nickel core. Under lithium-rich and high-temperature conditions, it reacts in-situ with excess lithium source-formed Li2O to form a LiAlO2 / Li3PO4 composite coating layer. The presence of excess Li2O promotes the formation of a composite lithium aluminum oxide, LiAlO2, rather than Al2O3. The reaction is as follows: .

[0058] LiAlO2 tends to be distributed closer to the high-nickel core, while Li3PO4 tends to be distributed further away from the high-nickel core. This is attributed to the fact that in a high-lithium environment (Li / TM>1), Li2O is in excess, and the reaction between AlPO4 and Li2O is not a one-step process. Because Al... 3+ For O 2- The affinity of γ-LiAlO2 and its low free energy at high temperatures make it highly active Li + It will preferentially interact with Al in AlPO4. 3+ Bonding occurs, making it easier to first form a Li-Al-O structure (i.e., LiAlO2), and this structure has a better lattice match with the high-nickel oxide core (both are layered or distorted layered / spinel structures), thus AlPO4... 3+ It preferentially reacts with Li₂O, heterogeneously nucleating on the surface of the high-nickel core to form a thermodynamically more stable and more tightly bound initial LiAlO₂ layer, which lowers the overall system energy. As the reaction proceeds, PO₄ is "stripped" of its AlPO₄ framework. 3- With the subsequent spread of Li + They combine at a more outer position to form Li3PO4.

[0059] To promote the full reaction of AlPO4 powder with Li2O formed by excess lithium source, this invention selects AlPO4 powder with extremely high specific surface area and reactivity to mix and react with high nickel precursor and lithium source.

[0060] In some embodiments, the average particle size of the AlPO4 powder is 20nm to 200nm, for example, it can be 20nm, 40nm, 60nm, 80nm, 100nm, 120nm, 140nm, 160nm, 180nm or 200nm.

[0061] In some embodiments, the mass of the AlPO4 powder is 0.5 wt.% to 2.5 wt.% of the mass of the high-nickel precursor, for example, it can be 0.5 wt.%, 0.75 wt.%, 1 wt.%, 1.25 wt.%, 1.5 wt.%, 1.75 wt.%, 2 wt.% or 2.5 wt.%.

[0062] In some embodiments, the heating rates of the first sintering stage and the second sintering stage are each independently 2°C / min to 5°C / min, for example, 2°C / min, 2.5°C / min, 3°C / min, 3.5°C / min, 4°C / min, 4.5°C / min or 5°C / min.

[0063] In some embodiments, the first sintering stage and the second sintering stage are each carried out independently in an oxygen-containing atmosphere, which includes an oxygen atmosphere or an air atmosphere.

[0064] In some embodiments, the sintering temperature of the first stage is 450°C to 550°C, for example, it can be 450°C, 470°C, 490°C, 500°C, 510°C, 530°C or 550°C.

[0065] In some embodiments, the sintering time of the first stage is 2h to 6h, for example, it can be 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h or 6h.

[0066] This invention achieves simultaneous crystallization of high-nickel materials and reactions of AlPO4 and Li2O by precisely controlling the temperature of the second sintering stage. At the same time, it drives the reaction of AlPO4 and Li2O to form a thermodynamically more stable γ-phase LiAlO2, resulting in a LiAlO2 / Li3PO4 composite coating layer.

[0067] In some embodiments, the sintering temperature of the second stage is 700°C to 850°C, for example, it can be 700°C, 725°C, 750°C, 775°C, 800°C, 825°C or 850°C.

[0068] In some embodiments, the sintering time of the second stage is 10h to 20h, for example, it can be 10h, 12h, 14h, 16h, 18h or 20h.

[0069] In some implementations, the mixing method includes ball milling.

[0070] In some embodiments, the ball mill rotates at a speed of 300 rpm to 500 rpm, for example, 300 rpm, 350 rpm, 400 rpm, 450 rpm or 500 rpm.

[0071] In some embodiments, the ball milling mixing time is 30 min to 90 min, for example, it can be 30 min, 40 min, 50 min, 60 min, 70 min, 80 min or 90 min.

[0072] In some embodiments, the preparation method further includes grinding and sieving the high-nickel cathode material.

[0073] In some embodiments, the mesh size of the sieve used for sieving is 200 to 400 mesh, for example, 200 mesh, 250 mesh, 300 mesh, 350 mesh or 400 mesh.

[0074] In yet another embodiment, the present invention provides a solid-state battery comprising a high-nickel cathode material as described in the preceding embodiment; The solid-state battery also includes a lithium-ion conductor gradient interface layer that has been activated and formed in situ between the surface of the high-nickel cathode material and the sulfide solid electrolyte. The material of the lithium-ion conductor gradient interface layer includes Li-Al-POS lithium-ion conductor phase or Li-Al-SO lithium-ion conductor phase.

[0075] When the high-nickel cathode material provided by this invention is applied in a sulfide solid electrolyte, the LiAlO2 / Li3PO4 composite coating layer and the sulfide electrolyte can undergo controllable interdiffusion and in-situ reaction through the regulation of the activation process, forming a lithium-ion conductor gradient interface layer with a chemical gradient distribution. This perfectly bridges the LiAlO2 / Li3PO4 composite coating layer and the sulfide electrolyte, achieving low-impedance "seamless" ion transport. The material of the lithium-ion conductor gradient interface layer includes a Li-Al-POS lithium-ion conductor phase (such as a phase with a LISICON-type structure) or a Li-Al-SO lithium-ion conductor phase, which has a better ionic conductivity than Li3PO4 and good compatibility with the sulfide electrolyte. This further optimizes ion transport and reduces interface impedance, and completely suppresses the side reactions between the high-nickel core and the sulfide solid electrolyte.

[0076] In some embodiments, the thickness of the lithium-ion conductor gradient interface layer is 5nm to 50nm, for example, it can be 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm or 50nm.

[0077] In some embodiments, the activation process includes charging the solid-state battery at a constant current to the activation voltage, then charging it at a constant voltage to the cutoff current, and continuing to maintain it at the activation voltage until activation is complete.

[0078] In some embodiments, the constant current charging rate is 0.02C to 0.1C, for example, it can be 0.02C, 0.04C, 0.06C, 0.08C or 0.1C.

[0079] In some embodiments, the activation voltage is 4.4V to 4.8V, for example, it can be 4.4V, 4.5V, 4.6V, 4.7V or 4.8V.

[0080] In some embodiments, the cutoff current is 0.002C to 0.01C, for example, it can be 0.002C, 0.004C, 0.006C, 0.008C or 0.01C.

[0081] In some implementations, the retention time is 1 hour to 24 hours, for example, it can be 1 hour, 3 hours, 5 hours, 7 hours, 9 hours, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours or 24 hours.

[0082] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0083] To further clarify the technical solution provided by this invention, the method for preparing a solid-state battery in the application examples of this invention includes: High-nickel cathode material was thoroughly mixed with Li6PS5Cl electrolyte and SuperP in a mortar at a mass ratio of 90:8:2 to obtain a cathode composite material. Then, 80 mg of the cathode composite material was pressed into a cathode sheet (10 mm in diameter) in a mold under a pressure of 60 MPa. A sulfide electrolyte layer (100 mg, pressed at 300 MPa) and a lithium metal anode (200 μm thick, pressed at 50 MPa) were then stacked sequentially to assemble a CR2032 type coin cell all-solid-state battery.

[0084] Example 1 This embodiment provides a high-nickel cathode material, the high-nickel cathode material comprising Ni 0.8 Co 0.1 Mn 0.1 O2 core, and in-situ formed in Ni 0.8 Co 0.1 Mn 0.1The surface of the O2 core has a γ-phase LiAlO2 / Li3PO4 composite coating layer, the mass percentage of which is 1.5 wt.%, and the average particle size of the high-nickel cathode material is 8 μm.

[0085] The preparation method of the high-nickel cathode material includes: According to Li and Ni in lithium hydroxide 0.8 Co 0.1 Mn 0.1 The molar ratio of the transition metal element TM in (OH)₂ is 1.06, and Ni is added. 0.8 Co 0.1 Mn 0.1 (OH)₂, lithium hydroxide, and Ni (by mass) 0.8 Co 0.1 Mn 0.1 1.5 wt.% (OH)2 was ball-milled with AlPO4 powder of average particle size 50 nm at a speed of 400 rpm for 60 min. The mixture was then sintered under an oxygen atmosphere. First, the temperature was increased to 500 °C at a rate of 3 °C / min for 4 h, followed by a second sintering at 780 °C at a rate of 3.5 °C / min for 15 h. The sintered product was then ground and sieved through a 325-mesh sieve to obtain the high-nickel cathode material.

[0086] Example 2 This embodiment provides a high-nickel cathode material, the high-nickel cathode material comprising Ni 0.8 Co 0.1 Mn 0.1 O2 core, and in-situ formed in Ni 0.8 Co 0.1 Mn 0.1 The surface of the O2 core has a γ-phase LiAlO2 / Li3PO4 composite coating layer, the mass percentage of which is 0.5 wt.%, and the average particle size of the high-nickel cathode material is 5 μm.

[0087] The preparation method of the high-nickel cathode material includes: Li and Ni in lithium hydroxide 0.8 Co 0.1 Mn 0.1 The molar ratio of the transition metal element TM in (OH)₂ is 1.03, and Ni is added. 0.8 Co 0.1 Mn 0.1 (OH)₂, lithium hydroxide, and Ni (by mass) 0.8 Co 0.1Mn 0.1 0.5 wt.% (OH)2 was ball-milled with AlPO4 powder of average particle size 20 nm at a rotation speed of 300 rpm for 30 min. The mixture was then sintered under an oxygen atmosphere. First, the temperature was increased to 450°C at a rate of 2.5°C / min for 2 h, followed by a second sintering at 700°C at a rate of 2°C / min for 10 h. The sintered product was then ground and sieved through a 400-mesh sieve to obtain the high-nickel cathode material.

[0088] Example 3 This embodiment provides a high-nickel cathode material, the high-nickel cathode material comprising Ni 0.85 Co 0.05 Mn 0.1 O2 core, and in-situ formed in Ni 0.85 Co 0.05 Mn 0.1 The surface of the O2 core has a γ-phase LiAlO2 / Li3PO4 composite coating layer, the mass percentage of which is 2.5 wt.%, and the average particle size of the high-nickel cathode material is 12 μm.

[0089] The preparation method of the high-nickel cathode material includes: Li and Ni in lithium hydroxide 0.85 Co 0.05 Mn 0.1 The molar ratio of transition metal element TM in CO3 is 1.10, and Ni is added. 0.85 Co 0.05 Mn 0.1 CO3, lithium hydroxide, and Ni 0.85 Co 0.05 Mn 0.1 2.5 wt.% of AlPO4 powder (based on CO3 mass) was ball-milled to obtain the high-nickel cathode material. The average particle size of the AlPO4 powder was 200 nm. The ball milling speed was 500 rpm, and the milling time was 90 min. The mixture obtained by ball milling was sintered under an oxygen atmosphere. First, the temperature was increased to 550°C at a rate of 5°C / min for 6 h, followed by a second sintering at 850°C at a rate of 5°C / min for 20 h. The sintered product was ground and passed through a 200-mesh sieve.

[0090] Example 4 This embodiment provides a high-nickel cathode material, which is the same as in Example 1 except that the mass percentage of the γ-phase LiAlO2 / Li3PO4 composite coating layer is 0.3 wt.%.

[0091] Example 5 This embodiment provides a high-nickel cathode material, which is the same as in Example 1 except that the mass percentage of the γ-phase LiAlO2 / Li3PO4 composite coating layer is 2.7 wt.%.

[0092] Example 6 This embodiment provides a high-nickel cathode material, which is the same as in Example 1 except that the average particle size of the AlPO4 powder used to prepare the high-nickel cathode material is 15 nm.

[0093] Example 7 This embodiment provides a high-nickel cathode material, which is the same as in Example 1 except that the average particle size of the AlPO4 powder used to prepare the high-nickel cathode material is 210 nm.

[0094] Example 8 This embodiment provides a high-nickel cathode material, which is the same as that in Example 1 except that the sintering temperature of the second stage of the preparation of the high-nickel cathode material is 680°C.

[0095] Example 9 This embodiment provides a high-nickel cathode material, which is the same as that in Example 1, except that the sintering temperature of the second stage of the preparation of the high-nickel cathode material is 870°C.

[0096] Comparative Example 1 This comparative example provides a high-nickel cathode material, which is the same as that in Example 1 except that it does not include the LiAlO2 / Li3PO4 composite coating.

[0097] The preparation method of the high-nickel cathode material is the same as that in Example 1, except that AlPO4 powder is not added during the ball milling process.

[0098] Comparative Example 2 This comparative example provides a high-nickel cathode material, except that the high-nickel cathode material only includes Ni. 0.8 Co 0.1 Mn 0.1 O2 core, and in-situ formed in Ni 0.8 Co 0.1 Mn 0.1 Except for the γ-phase LiAlO2 on the surface of the O2 core, everything else is the same as in Example 1.

[0099] The preparation method of the high-nickel cathode material is the same as in Example 1, except that AlPO4 powder is replaced with Al2O3 of the same particle size.

[0100] Comparative Example 3 This comparative example provides a high-nickel cathode material, except that the high-nickel cathode material only includes Ni. 0.8 Co 0.1 Mn 0.1 O2 core, and in-situ formed in Ni 0.8 Co 0.1 Mn 0.1 Except for the Li3PO4 on the surface of the O2 core, everything else is the same as in Example 1.

[0101] The preparation method of the high-nickel cathode material is the same as in Example 1, except that AlPO4 powder is replaced with NH4H2PO4 of the same particle size.

[0102] Application Example 1 This application example provides a solid-state battery, which includes the high-nickel cathode material described in Example 1; the solid-state battery also includes an activation treatment and an in-situ formed lithium-ion conductor gradient interface layer between the high-nickel core and the LiAlO2 / Li3PO4 composite coating; the lithium-ion conductor gradient interface layer is made of Li-Al-POS lithium-ion conductor phase or Li-Al-SO lithium-ion conductor phase, and the thickness of the lithium-ion conductor gradient interface layer is 20 nm. The activation treatment methods include: The solid-state battery was charged at a constant current rate of 0.05C to 4.6V, then charged at a constant voltage rate to 0.01C, and then maintained at 4.6V for 10 hours to complete the activation.

[0103] Application Example 2 This application example provides a solid-state battery, which includes the high-nickel cathode material described in Example 2; the solid-state battery also includes an activation treatment to form an in-situ lithium-ion conductor gradient interface layer between the high-nickel core and the LiAlO2 / Li3PO4 composite coating; the lithium-ion conductor gradient interface layer is made of Li-Al-POS lithium-ion conductor phase or Li-Al-SO lithium-ion conductor phase, and the thickness of the lithium-ion conductor gradient interface layer is 10 nm. The activation process includes: The solid-state battery was charged at a constant current rate of 0.02C to 4.4V, then charged at a constant voltage rate to 0.01C, and then kept at 4.4V for 24 hours to complete the activation.

[0104] Application Example 3 This application example provides a solid-state battery, which includes the high-nickel cathode material described in Example 3; the solid-state battery also includes an activation treatment to form an in-situ lithium-ion conductor gradient interface layer between the high-nickel core and the LiAlO2 / Li3PO4 composite coating; the lithium-ion conductor gradient interface layer is made of Li-Al-POS lithium-ion conductor phase or Li-Al-SO lithium-ion conductor phase, and the thickness of the lithium-ion conductor gradient interface layer is 40 nm. The activation process includes: The solid-state battery was charged at a constant current rate of 0.1C to 4.8V, then charged at a constant voltage rate to 0.002C, and then maintained at 4.8V for 1 hour to complete the activation.

[0105] Application Examples 4 to 10 This application example provides a solid-state battery, which is the same as application example 1 except that the high-nickel cathode material described in example 1 is replaced with the high-nickel cathode material in examples 4 to 10 respectively.

[0106] Compare application examples 1 to 3 This application example provides a solid-state battery, which is the same as application example 1 except that the high-nickel cathode material described in Example 1 is replaced with the high-nickel cathode material in Comparative Examples 1 to 3 respectively.

[0107] Comparative Application Example 4 This application example provides a solid-state battery that is identical to Application Example 1, except that the activation voltage is 4.3V.

[0108] Comparative Application Example 5 This application example provides a solid-state battery that is identical to Application Example 1 except that it does not undergo activation treatment.

[0109] Performance testing: At 25℃, 2.5V~4.3V (vs. Li + Within the / Li) voltage range, the first-efficiency, discharge specific capacity, cycle performance, and rate performance of the solid-state batteries provided in all the above application examples and comparative application examples were tested. The specific test regime is as follows: (1) First-efficiency & first-discharge specific capacity test regime Charge to 4.3V with a constant current of 0.1C, then charge with a constant voltage until the current decays to 0.05C; let stand for 5 minutes; then discharge to 2.5V with a constant current of 0.1C. Calculate its initial efficiency and initial discharge specific capacity.

[0110] (2) Capacity retention test regime at 1C rate after 100 cycles Pre-activation was performed using three cycles of 0.1C charge-discharge, with the discharge capacity of the third cycle recorded as the initial capacity (C0). The vehicle was then charged at a constant current of 1C to 4.3V, followed by constant voltage charging until the current decayed to 0.05C. After resting for 5 minutes, it was discharged at a constant current of 1C to 2.5V. This charge-discharge cycle was repeated 100 times at a 1C rate. The cycle capacity retention rate (%) was calculated using the formula: (Discharge capacity C0 of the 100th cycle) = (Discharge capacity C0 of the 100th cycle) / (C ... 100 Calculate the capacity retention rate by multiplying the initial capacity (C0) by 100%.

[0111] (3) 1C / 0.1C discharge capacity ratio test regime First, charge and discharge were performed at a rate of 0.1C (constant current and constant voltage), and the discharge capacity (C) was recorded. 0.1C Then, after fully charging the battery, discharge it directly at a constant current of 1C to 2.5V (constant current discharge only, no constant voltage charging), and record the discharge capacity (C). 1C According to the formula: 1C / 0.1C discharge capacity ratio (%) = (C 1C / C 0.1C )×100% to calculate the scaling performance.

[0112] The test results are shown in Table 1.

[0113] Table 1 Based on the test results in Table 1, the following conclusions can be drawn: In Application Examples 1 to 3, the solid-state batteries prepared using the high-nickel cathode materials provided in Examples 1 to 3 exhibited the highest initial efficiency (>88.5%), excellent cycle performance (capacity retention rate >93% after 100 cycles), and outstanding rate performance (capacity retention rate >92% at 1C / 0.1C), demonstrating the best overall performance. This proves the synergistic effect of the combination of materials and processes provided by the present invention.

[0114] Based on the test results of Application Examples 1 and 4 through 9, an insufficient coating content (Application Example 4) leads to inadequate interface protection, increased side reactions, and decreased first-efficiency and cycle performance; an excessively high content (Application Example 5) hinders lithium-ion transport, resulting in reduced capacity and rate performance. AlPO4 particle size that is too large or too small (Application Examples 6 and 7) and improper sintering temperature (Application Examples 8 and 9) both affect the uniformity, crystallinity, and gradient structure formation of the coating, thereby impacting overall performance.

[0115] Based on the test results of Application Example 1 and Comparative Application Examples 1 to 5, Comparative Application Example 1, without any coating, exhibited the worst performance, with severe interfacial side reactions, extremely low first-efficiency, and rapid capacity decay, demonstrating the necessity of coating. Comparative Application Examples 2 and 3 both use a single coating layer, failing to simultaneously address interface protection (LiAlO2) and ion conduction (Li3PO4), resulting in performance far inferior to the composite gradient coating structure of this invention. In particular, Comparative Application Example 2, which only coating LiAlO2, suffered from the worst rate performance due to its poor ion conduction. Insufficient activation voltage (Comparative Application Example 4) or complete lack of activation (Comparative Application Example 5) both failed to form an effective lithium-ion conductor gradient interface layer, resulting in high interfacial impedance and significantly deteriorated first-efficiency and cycle performance, demonstrating the crucial role of the activation process in this invention.

[0116] In summary, this invention uses a high-nickel substrate as its core, and sequentially forms a LiAlO2 coating layer and a Li3PO4 coating layer in situ on the surface of the high-nickel core. This in-situ construction of a gradient-distributed LiAlO2 / Li3PO4 composite coating layer is beneficial for maintaining the high voltage stability of the high-nickel core itself, effectively isolating the high-nickel cathode from corrosion of the sulfide electrolyte, and when applied to sulfide solid electrolytes, the LiAlO2 / Li3PO4 composite coating layer can also form a chemically gradient-distributed lithium-ion conductor gradient interface layer with the sulfide electrolyte. This optimizes lithium-ion transport while completely suppressing side reactions between the high-nickel core and the sulfide solid electrolyte, thereby improving the first-efficiency, rate performance, and cycle performance of the solid-state battery.

[0117] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A high-nickel cathode material, characterized in that, The high-nickel cathode material includes a high-nickel core, and a LiAlO2 coating layer and a Li3PO4 coating layer formed in situ on the surface of the high-nickel core in sequence. The median particle size D50 of the high-nickel core is 5μm~12μm.

2. The high-nickel cathode material as described in claim 1, characterized in that, The LiAlO2 includes γ-phase LiAlO2; And / or, in the high-nickel cathode material, the total mass percentage of the LiAlO2 coating layer and the Li3PO4 coating layer is 0.5wt.%~2.5wt.%.

3. A method for preparing the high-nickel cathode material as described in claim 1 or 2, characterized in that, The preparation method includes: The high-nickel cathode material is prepared by mixing a high-nickel precursor, a lithium source, and AlPO4 powder, and then sequentially performing a first-stage sintering and a second-stage sintering. The molar ratio of Li in the lithium source to the transition metal element TM in the high-nickel precursor is 1.03~1.

10.

4. The preparation method according to claim 3, characterized in that, The average particle size of the AlPO4 powder is 20 nm to 200 nm. And / or, the mass of the AlPO4 powder is 0.5 wt.% to 2.5 wt.% of the mass of the high-nickel precursor.

5. The preparation method according to claim 3 or 4, characterized in that, The heating rates of the first sintering stage and the second sintering stage are each 2℃ / min to 5℃ / min independently; And / or, the first sintering and the second sintering are each carried out independently in an oxygen-containing atmosphere; And / or, the sintering temperature of the first stage is 450℃~550℃; And / or, the sintering time of the first stage is 2h~6h; And / or, the sintering temperature of the second stage is 700℃~850℃; And / or, the sintering time for the second stage is 10h~20h.

6. The preparation method according to any one of claims 3 to 5, characterized in that, The mixing method includes ball milling, wherein the ball milling speed is 300 rpm to 500 rpm; And / or, the preparation method further includes grinding and sieving the high-nickel cathode material, wherein the sieve used for sieving has a mesh size of 200 to 400 mesh.

7. A solid-state battery, characterized in that, The solid-state battery includes the high-nickel cathode material as described in claim 1 or 2; The solid-state battery also includes a lithium-ion conductor gradient interface layer that has been activated and formed in situ between the surface of the high-nickel cathode material and the sulfide solid electrolyte. The material of the lithium-ion conductor gradient interface layer includes Li-Al-POS lithium-ion conductor phase or Li-Al-SO lithium-ion conductor phase.

8. The solid-state battery as described in claim 7, characterized in that, The thickness of the lithium-ion conductor gradient interface layer is 5nm~50nm.

9. The solid-state battery as described in claim 7, characterized in that, The activation process includes charging the solid-state battery at a constant current to the activation voltage, then charging it at a constant voltage to the cutoff current, and continuing to maintain the activation voltage until activation is complete.

10. The solid-state battery as described in claim 9, characterized in that, The constant current charging rate is 0.02C~0.1C; And / or, the activation voltage is 4.4V~4.8V; And / or, the cutoff current is 0.002C~0.01C; And / or, the retention time is 1h to 24h.

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