Positive electrode material, preparation method and application thereof, and all-solid-state battery

Abstract

The invention relates to the technical field of batteries, in particular to a positive electrode material, a preparation method and application thereof and an all-solid-state battery. The positive electrode material comprises an inner core and an outer core, wherein the inner core contains a nickel-rich ternary material; the interface modification layer is coated on at least part of the surface of the inner core, and the interface modification layer comprises lithium phosphorus oxide and metal sulfide. According to the positive electrode material, the interface impedance of the battery can be better reduced, the critical current density is improved, and the cycle life is prolonged.

Description

Technical Field

[0001] This invention relates to the field of battery technology, specifically to a cathode material, its preparation method and application, and an all-solid-state battery. Background Technology

[0002] All-solid-state batteries use non-flammable solid electrolytes (such as sulfide Li6). P S5Cl has a theoretical energy density >500Wh / kg and is expected to fundamentally eliminate the risk of thermal runaway. However, its actual performance is severely limited by the cathode / electrolyte interface problems: 1. Deterioration of physical contact: Due to the high rigidity of the material, the solid-solid contact area is limited, and the porosity of the contact interface between the cathode and the electrolyte is >30%, resulting in severe degradation of the interface impedance; 2. Difficulty in process mixing: Ideally, the active material (such as NCM) in the cathode electrode sheet is in full contact with the solid electrolyte, and the solid electrolyte can form a continuous ion-conducting channel. However, in actual processes, it is often difficult to avoid various defects, which affect the integrity of the structure and the electrochemical performance.

[0003] Current methods for improving the cathode / electrolyte interface include coating, core-shell structures, composites, and doping. However, current mainstream solutions all have serious drawbacks: 1. Wet LiNbO3 coating technology constructs a 10-20 nm physical isolation layer on the cathode surface, but uneven coating results in a coverage rate of less than 60%, leading to cracking after cycling; 2. The cathode core-shell structure uses a high-nickel core (such as Ni...). 83 The combination design of the core and the outer shell LiAlO2 reduces direct interface contact through structural encapsulation, but the core side reaction caused by shell rupture leads to severe degradation of the cycle volume expansion rate under high active material loading conditions; 3. The composite method using polymers such as PEO and PVDF as buffer layers can improve solid-solid interface contact by means of material flexibility, but its oxidation potential is usually below 4.2V, which is difficult to match with the currently commonly used high-voltage cathode materials (such as ≥4.5V vs. LiAlO2). + / Li), thus its application in high-pressure systems is severely limited.

[0004] In summary, although various technical approaches such as coating, core-shell, and composite have been extensively explored, existing solutions still have significant shortcomings in terms of coverage, structural integrity, and voltage compatibility. Summary of the Invention

[0005] The purpose of this invention is to overcome the aforementioned problems in the prior art and provide a cathode material, its preparation method and application, and an all-solid-state battery. This cathode material can better reduce the interfacial impedance of the battery, increase the critical current density, and extend the cycle life.

[0006] To achieve the above objectives, a first aspect of the present invention provides a cathode material, comprising: The core contains a nickel-rich ternary material; An interface modification layer is provided, which covers at least a portion of the surface of the core, and the interface modification layer comprises lithium phosphorus oxide and metal sulfide.

[0007] A second aspect of the present invention provides a method for preparing a cathode material, the method comprising: S1. Construct oxygen vacancy sites in nickel-rich ternary materials to obtain oxygen vacancy activated materials. S2. The sulfide solid electrolyte and the oxygen vacancy activating material are ball-milled to obtain sulfide composite powder. S3. The sulfide composite powder is subjected to a hot-pressing sulfidation reaction to obtain a cathode material; The sulfide solid electrolyte contains Li, P, and S.

[0008] The third aspect of the present invention provides the application of a cathode material prepared by the method described in the first aspect of the present invention or the method described in the second aspect of the present invention in an all-solid-state battery.

[0009] A fourth aspect of the present invention provides an all-solid-state battery, comprising a positive electrode material prepared by the method described in the first aspect of the invention or the method described in the second aspect of the invention.

[0010] Compared with the prior art, the present invention has at least the following beneficial effects: The cathode material of this invention solves the contact problem at the solid-solid interface between the cathode material and the solid electrolyte in all-solid-state batteries. Furthermore, the cathode material employs a "dual-channel" structure, with lithium phosphorus oxide serving as a continuous ion channel and metal sulfide as a continuous electron pathway, enabling simultaneous and efficient ion and electron transport. This effectively improves the battery's interfacial impedance, cycle life, and critical current density. Attached Figure Description

[0011] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof.

[0012] Figure 1 The diagram shows a flowchart of a method for preparing a cathode material according to an embodiment of the invention. Detailed Implementation

[0013] 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 and 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.

[0014] In this invention, unless otherwise specified, "room temperature" refers to 20℃-30℃.

[0015] Although various technical approaches such as coating, core-shell, and composite have been extensively explored, existing solutions still have significant shortcomings in terms of coverage, structural integrity, and voltage compatibility.

[0016] In view of the above, in a first aspect, embodiments of the present invention provide a cathode material, comprising: The core contains a nickel-rich ternary material; An interface modification layer is provided, which covers at least a portion of the surface of the core, and the interface modification layer comprises lithium phosphorus oxide and metal sulfide.

[0017] In this invention, lithium phosphorus oxide in the interface modification layer can provide continuous phase ion channels, and metal sulfide can provide electronic pathways. Furthermore, the combined effect of lithium phosphorus oxide, metal sulfide and nickel-rich ternary material can effectively improve the interfacial impedance between the cathode material and the solid electrolyte, while improving cycle life and critical current density.

[0018] In some embodiments, the metal sulfide is embedded within the lithium phosphorus oxide in the form of nanoislands. This structure of metal sulfide and lithium phosphorus oxide in the cathode material can better reduce overall impedance and also better achieve synergistic optimization of ion and electron transport, thereby improving charge transfer kinetics and structural stability.

[0019] In some embodiments, the particle size of the nanoislands is no greater than 5 nm, for example, 0.1 nm, 0.5 nm, 1 nm, 1.5 nm, 2 nm, 2.5 nm, 3 nm, 3.5 nm, 4 nm, 4.5 nm, or 5 nm, preferably 1 nm to 4 nm. Controlling the particle size of the metal sulfide nanoislands within the aforementioned suitable range can better achieve the multiplied effect of reducing interfacial impedance, increasing critical current density, and extending cycle life.

[0020] In this invention, the embedding of metal sulfides in the form of nano-islands within lithium phosphorus oxide refers to an interface modification layer formed with lithium phosphorus oxide as the continuous phase and metal sulfides as the dispersed phase. In some embodiments, the mass content of metal sulfides in the lithium phosphorus oxide is 8%-25%. For example, it is 8%, 10%, 11%, 13%, 15%, 18%, 20%, 22%, 25%, or any range of two of the aforementioned values. Controlling the mass content of metal sulfides within the aforementioned range can better reduce interfacial impedance and improve cycle life and critical current density.

[0021] In some embodiments, the core and the interface modification layer are connected via PS-Ni bonds. In this invention, the core and the interface modification layer are connected by PS-Ni covalent bonds (bond energy > 2.5 eV). Compared with the van der Waals force bonding of traditional solutions (< 0.1 eV), the PS-Ni covalent bonds form an irreversible chemical bonding network, which can fundamentally block the interdiffusion pathway of elements, thereby enabling the cathode material to better improve the cycle life and critical current density of all-solid-state batteries.

[0022] In this invention, the presence of PS-Ni bonds can be monitored using Raman spectroscopy (Renishaw in Via), specifically, 810 cm⁻¹ is detected. -1 (PS-Ni) Characteristic peak intensity ≥ 30% of the reference peak (i.e. ≥ 4500 cps).

[0023] In this invention, "at least part" of the interface modification layer covering at least a portion of the surface of the core refers to a portion or all of the surface, preferably all of the surface. The thickness of the interface modification layer can be selected within a wide range as long as the objectives of this invention are achieved. However, considering the need to improve interface stability and charge transport synergy, and to have low negative impact on electrochemical performance, in some embodiments, the thickness of the interface modification layer is 10nm-50nm, for example, 10nm, 15nm, 22nm, 25nm, 30nm, 32nm, 35nm, 38nm, 40nm, 42nm, 45nm, and 50nm.

[0024] In this invention, the particle size of the nanoislands and the thickness of the interface modification layer can be obtained by transmission electron microscopy. Specifically, a curve can be drawn at the outer edge where the core exists, and the distance between this curve and the outer edge of the entire cathode material is the thickness of the interface modification layer. The average value of ten randomly selected locations is recorded as the thickness of the interface modification layer. Specifically, for clearly identifiable and well-defined independent nanoisland particles, their maximum characteristic size can be measured as the particle size.

[0025] In some embodiments, the core is divided into a bulk region and an outer near-surface gradient region. The near-surface gradient region contains oxygen vacancies, and the concentration of these oxygen vacancies gradually decreases from the interface between the interface modification layer and the core towards the bulk region. Furthermore, the thickness of the near-surface gradient region is 2 nm-5 nm, for example, 2 nm, 3 nm, 4 nm, or 5 nm. The presence of an oxygen vacancy gradient in the core optimizes the diffusion and reaction of lithium ions on the outermost layer of the particle. Combined with the efficient transfer of ions and electrons and the protective function of the interface modification layer, this further improves the overall ionic conductivity of the cathode material, thereby effectively reducing interface impedance and enhancing structural tolerance under high-rate charge-discharge conditions, increasing critical current density, and cycle life.

[0026] This invention uses cross-sectional TEM samples to perform nanoscale or even atomic-scale STEM-EELS line scanning, which can directly plot the gradient distribution of the oxidation chemical state in space, thereby accurately determining the thickness of the gradient region. Combined with XPS testing to monitor the O1s spectrum at different sputtering depths, the changes in the intensity of the lattice oxygen binding energy peak can indirectly reflect the changes in oxygen vacancy concentration.

[0027] In this invention, the size of the nickel-rich ternary material is not particularly limited, as long as it achieves the purpose of this invention. In some embodiments, the Dv50 particle size of the nickel-rich ternary material is 3μm-8μm, for example, 3μm, 4μm, 5μm, 6μm, 7μm, or 8μm. Controlling the Dv50 particle size of the nickel-rich ternary material within the aforementioned range allows the cathode material to better balance high volumetric energy density and good reaction kinetics, thereby achieving a comprehensive performance improvement in low impedance, long cycle life, and high critical current density.

[0028] In this invention, Dv50 refers to the particle size corresponding to a cumulative volume distribution percentage of 50%, which is determined by a laser particle size analyzer (e.g., Malvern Mastersizer 3000) according to standard GB / T 19077-2016 / ISO 13320:2009.

[0029] In some embodiments, the general chemical formula of the lithium phosphorus oxide is Li3PO4. In this invention, Li3PO4 possesses a highly stable crystal structure and excellent lithium-ion conductivity. It exhibits better chemical compatibility with solid electrolytes (especially sulfide electrolytes) containing nickel-rich ternary materials, effectively blocking harmful side reactions. Furthermore, with the synergistic effect of ionic / electron dual pathways in the system, it can significantly reduce interfacial charge transfer impedance, thereby improving battery cycle stability while allowing the battery to operate safely and stably at higher critical current densities.

[0030] In some embodiments, the general chemical formula of the metal sulfide is Ni. a S b In this context, elements a and b represent positive integers corresponding to their respective valence states. The general chemical formula for metal sulfides is Ni3S2. Sulfides composed of nickel and sulfur typically exhibit good electronic conductivity. Embedding them as nano-islands within a lithium phosphorus oxide matrix better constitutes an ion-electron dual-pathway interface modification layer. Furthermore, the chemical homology between nickel and the nickel-rich ternary material core helps form a more stable and compatible structure at the interface, reducing lattice mismatch and side reactions caused by heterogeneous interfaces. This synergistically enhances the structural and electrochemical stability of the interface modification layer, further improving the cycle life and rate performance of all-solid-state batteries.

[0031] In this invention, nickel-rich ternary material refers to a ternary lithium-ion battery cathode material composed of three transition metal elements: nickel (Ni), cobalt (Co), and manganese (Mn). The molar fraction of nickel in the nickel-rich ternary material (the proportion of nickel, cobalt, and manganese in the total molar number of the three metals) is not less than 60%, preferably not less than 81%. In some embodiments, the chemical formula of the nickel-rich ternary material is LiNi. x Co y Mn z O2, where x ≥ 0.6, y > 0, z > 0, and x + y + z = 1. There are no special restrictions on the specific selection of nickel-rich ternary materials in this invention; any NCM nickel-rich ternary material well-known to those skilled in the art can be used, including but not limited to NCM622 (chemical formula LiNi). 0.6 Co 0.2 Mn 0.2 O2), NCM811 (chemical formula LiNi) 0.8 Co 0.1 Mn 0.1 O2) and NCM83 (chemical formula LiNi) 0.83 Co 0.12 Mn 0.05 At least one of O2).

[0032] In some embodiments, the nickel-rich ternary material is a single-crystal material. Single-crystal materials possess excellent structural stability, and their combination with the interface modification layer enables the cathode material to exhibit highly efficient ion-electron hybrid conductivity. This achieves high energy density while effectively improving the battery's cycle life and critical current density.

[0033] Based on the same inventive concept, in a second aspect, embodiments of the present invention provide a method for preparing a cathode material, the method comprising: S1. Construct oxygen vacancy sites in nickel-rich ternary materials to obtain oxygen vacancy activated materials. S2. The sulfide solid electrolyte and the oxygen vacancy activating material are ball-milled to obtain sulfide composite powder. S3. The sulfide composite powder is subjected to a hot-pressing sulfidation reaction to obtain a cathode material; The sulfide solid electrolyte contains Li, P, and S.

[0034] It should be understood that all the characteristics and advantages described above regarding "cathode materials" also apply to the "preparation method of cathode materials," and will not be repeated here.

[0035] This invention constructs a Li3PO4 / Ni3S2 nanocomposite interface layer by building oxygen vacancy sites, melting and infiltrating sulfide solid electrolyte, conducting interfacial chemical reactions, and forming a PS-Ni bonding network in the preparation method of cathode materials. This achieves comprehensive improvement in the solid-solid interface between nickel-rich ternary materials and sulfide solid electrolyte, as well as in cycle stability and conductivity.

[0036] In addition, the preparation steps of the cathode material of the present invention are simple, avoiding complex operations such as liquid phase coating and repeated calcination, resulting in high production efficiency and suitability for large-scale production.

[0037] In some embodiments, the oxygen vacancy concentration of the oxygen vacancy activating material is 5%-10%, for example, 5%, 5.1%, 6%, 7%, 7.3%, 7.5%, 7.8%, 8%, 8.2%, 8.5%, 8.8%, 9%, 9.2%, 9.5%, 10%, or any two of the above values, preferably 5%-8%, more preferably 7%-8.5%.

[0038] In this invention, the oxygen vacancy concentration of the oxygen vacancy-activated material can be detected by XPS oxygen vacancy concentration detection (Thermo Scientific K-Alpha). The peak area ratio of the O1s binding energy of 531.5 eV in the XPS oxygen vacancy concentration detection is the oxygen vacancy concentration of the oxygen vacancy-activated material.

[0039] In some embodiments, in step S1, the nickel-rich ternary material is reduced to construct the oxygen vacancy sites.

[0040] The conditions for the reduction treatment described above in this invention are not particularly limited, as long as they can achieve the purpose of this invention or ensure that the oxygen vacancy-activated material has a certain oxygen vacancy concentration. In some embodiments, the conditions for the reduction treatment include: carrying out the treatment in a mixture of hydrogen and an inert gas. Preferably, the volume concentration of hydrogen in the mixture is 3%-8%, for example, 3%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, or any two of the above values, preferably 5%-7%, more preferably 4.5%-5.5%. The inert gas includes nitrogen or at least one of the gases containing Group 0 elements of the periodic table, such as argon; that is, the mixture includes a mixture of argon and hydrogen.

[0041] In some embodiments, the conditions for the reduction treatment include a temperature of 280°C-320°C, such as 280°C, 290°C, 300°C, 310°C, or 320°C. In this invention, the temperature can be increased to 280°C-320°C at a certain rate, for example, at 3°C / min-8°C / min. As an example, the temperature can be increased to 300°C at 5°C / min.

[0042] In this invention, the reduction treatment time can be adjusted according to the corresponding temperature and the oxygen vacancy concentration of the final vacancy-activated material. In some embodiments, the reduction treatment conditions include a time of 60-180 minutes, for example, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, or 180 minutes. That is, holding at 280℃-320℃ for 60-180 minutes.

[0043] In this invention, nickel-rich ternary material refers to a ternary lithium-ion battery cathode material composed of three transition metal elements: nickel (Ni), cobalt (Co), and manganese (Mn). The molar fraction of nickel in the nickel-rich ternary material (the proportion of nickel, cobalt, and manganese in the total molar number of the three metals) is not less than 60%, preferably not less than 81%. In some embodiments, the chemical formula of the nickel-rich ternary material is LiNi. x Co y Mn z O2, where x ≥ 0.6, y > 0, z > 0, and x + y + z = 1. There are no special restrictions on the specific selection of nickel-rich ternary materials in this invention; any NCM nickel-rich ternary material well-known to those skilled in the art can be used, including but not limited to NCM622 (chemical formula LiNi). 0.6 Co 0.2 Mn 0.2 O2), NCM811 (chemical formula LiNi) 0.8 Co0.1 Mn 0.1 O2) and NCM83 (chemical formula LiNi) 0.83 Co 0.12 Mn 0.05 At least one of O2).

[0044] In some embodiments, the nickel-rich ternary material is a single-crystal material. This means that each particle of the nickel-rich ternary material is an independent, complete crystal without grain boundaries. The sulfide solid electrolyte can interact better with the oxygen vacancy-activated material, ultimately resulting in a better-coated interface modification layer.

[0045] In some embodiments, the Dv50 particle size of the nickel-rich ternary material is 3μm-8μm, for example, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm.

[0046] As an example, the specific operation method in step S1 includes: weighing nickel-rich ternary single crystal powder and placing it in an alumina crucible, moving the alumina crucible into a tube furnace, introducing H2 / Ar mixed gas (flow rate 30mL / min-100mL / min), and circulating and replacing it 2-5 times (residual O2 <0.1 ppm); then heating at 3℃ / min-8℃ / min to 280℃-320℃, holding at that temperature for 60min-180min, and then cooling it with the furnace (cooling rate ≤2℃ / min) to obtain the oxygen vacancy activated material end, taking a sample for XPS oxygen vacancy concentration detection (ThermoScientific K-Alpha): the peak area of ​​the O1s binding energy 531.5eV of the oxygen vacancy activated material end is 5%-10%. If it exceeds the range, adjust the H2 concentration ±0.5vol% and reprocess.

[0047] This invention does not impose any particular limitation on the ball milling method in step S2; it can be either wet ball milling or dry ball milling, as long as the objective of this invention is achieved. This invention uses dry ball milling as an example to illustrate its advantages, but this does not imply any limitation on the invention.

[0048] In some embodiments, the conditions for ball milling in step S2 include: a ball milling speed of 100 rpm to 800 rpm, such as 100 rpm, 200 rpm, 300 rpm, 400 rpm, 500 rpm, 600 rpm, 70 rpm, or 800 rpm, preferably 200 rpm to 500 rpm.

[0049] In some embodiments, the ball milling conditions in step S2 include a ball milling time of 10-60 minutes, for example, 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, or 60 minutes, preferably 20-40 minutes. Additionally, to avoid overheating during ball milling affecting the raw materials, the ball milling process can be interrupted by a 1-5 minute pause after 5-15 minutes of milling.

[0050] The ball milling described in step S2 of the present invention can be carried out in a ball milling device, which can be a conventional ball milling device, such as a ball milling jar or a sand mill.

[0051] In some embodiments, in step S2, the conditions for ball milling include: the ball milling media include one or more of zirconia beads, agate beads, and steel beads.

[0052] In some embodiments, the conditions for ball milling in step S2 include: the diameter of the ball milling media is 0.1mm-20mm (e.g., 0.1mm, 0.5mm, 3mm, 1mm, 5mm, 10mm, 15mm, 20mm).

[0053] In some embodiments, the diameter of the milling media includes at least two different specifications. The different specifications refer to different diameters of the milling media. For example, the diameter of the milling media includes two different specifications: 3 mm and 5 mm. Using milling media with at least two different diameter specifications allows for thorough mixing of the raw materials and enables control of the raw material particle size.

[0054] In some embodiments, the ball milling conditions in step S2 include a ball-to-material ratio of (1-100):1, for example, 1:1, 5:1, 10:1, 20:1, 30:1, 40:1, 60:1, 80:1, or 100:1. The aforementioned ball-to-material ratio refers to the mass ratio of the ball milling media to the raw material (sulfide solid electrolyte and the oxygen vacancy activating material).

[0055] In this invention, to avoid the influence of the oxygen-containing atmosphere on the raw materials, in some embodiments, the ball milling conditions in step S2 include: being carried out under an inert atmosphere. This inert atmosphere includes at least one of nitrogen or group 0 element gases from the periodic table, such as argon. That is, the ball milling is carried out under an argon atmosphere.

[0056] In some embodiments, the chemical formula of the sulfide solid electrolyte is Li6PS5X, where X is a halogen (e.g., F, Cl, Br). Li6PS5Cl is used as an example to illustrate the advantages of the present invention, but it does not represent a limitation of the present invention.

[0057] In some embodiments, the mass ratio of the sulfide solid electrolyte to the oxygen vacancy activating material is (5-20):1, for example, 5:1, 6:1, 8:1, 10:1, 12:1, 15:1, 18:1, 20:1.

[0058] As an example, the specific operation method in step S2 includes: weighing the sulfide solid electrolyte and oxygen vacancy activating material according to the amount and loading them into a zirconia ball mill jar for ball milling, purging with inert gas 3-5 times (residual H2O < 0.1 ppm), and the ball milling parameters are: rotation speed 100 rpm-800 rpm, ball-to-material mass ratio (1-10):1 (the grinding material is a mixture of zirconia balls with a mass ratio of 1:1 and a diameter of 3 mm / 5 mm), and effective ball milling time 10 min-60 min (stopping for 1 min-5 min every 5 min-15 min to prevent overheating), and obtaining sulfide composite powder from the ball mill output.

[0059] In some embodiments, the hot-press vulcanization reaction in step S3 is carried out under an inert atmosphere. The inert gas includes nitrogen or at least one of the gases containing Group 0 elements of the periodic table, such as argon.

[0060] The hot-press vulcanization reaction in this invention can be carried out in a hot-press vulcanization reaction device, such as a bidirectional hot press. The material is first loaded into the mold of the bidirectional hot press, and then pre-pressed to eliminate gaps in the powder. Generally, the mechanical pressure used for pre-pressing is 3MPa-10MPa. Specifically, the sulfide composite powder is evenly spread into the mold (generally with a thickness of 0.5mm-2mm), the mold is closed, and the atmosphere control system is connected. A vacuum is drawn until the system pressure is ≤10Pa to fully remove air and adsorbed moisture from the mold cavity. High-purity Ar gas (purity ≥99.999%) is then introduced into the system to 0.8MPa-0.8MPa. This step is repeated at least three times to ensure that the residual O2 concentration in the cavity is <0.1ppm. Then, a pre-pressure of 3MPa-10MPa is applied and maintained for 10 minutes. This stage is generally called loading pre-pressing.

[0061] In some embodiments, the conditions for the hot-press vulcanization reaction in step S3 include a reaction temperature of 330°C-370°C, for example, 330°C, 340°C, 350°C, 360°C, or 370°C.

[0062] In some embodiments, the conditions for the hot-press vulcanization reaction in step S3 include a mechanical pressure of 40 MPa-60 MPa, for example, 40 MPa, 45 MPa, 50 MPa, 55 MPa, or 60 MPa. Here, mechanical pressure refers to the pressure applied to the raw material.

[0063] In some embodiments, the conditions for the hot-press vulcanization reaction in step S3 include a reaction time of 1-3 hours, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours, or 3 hours.

[0064] In some embodiments, in step S3, the reaction temperature in the hot-press vulcanization reaction is denoted as a℃ and the mechanical pressure is denoted as bMPa, where a and b satisfy b≥0.2a-60.

[0065] In this invention, further research revealed that controlling the reaction temperature and mechanical pressure during the hot-pressing sulfidation reaction to meet the above conditions results in a cathode material with superior overall performance. Specifically, the reaction between the sulfide electrolyte (such as Li6PS5Cl) and the oxygen vacancies on the cathode surface requires overcoming a certain activation energy barrier. Temperature (a) provides the thermal energy to break the PS bonds and drive ion diffusion; pressure (b) provides the mechanical energy to promote close contact between reactants and reduce the reaction distance. If the pressure is insufficient, even if the temperature is sufficient, the sulfide melt cannot effectively overcome the surface tension to penetrate the oxygen vacancy nanopores, and the reaction only occurs slightly on the surface, resulting in a porous and discontinuous interfacial layer with high interfacial impedance and poor performance.

[0066] In step S3 of this invention, the temperature can first be rapidly increased to a certain temperature (e.g., from room temperature to 320℃-340℃ within 10-30 minutes) to allow the sulfide solid electrolyte in the sulfide composite powder to melt and penetrate into contact with the oxygen vacancy activation material. During this period, the mechanical pressure is kept constant; this stage can be called the heating and melting penetration stage. Then, the temperature is increased to the reaction temperature (330℃-370℃) at a slower rate (e.g., 1℃ / min-5℃), while the mechanical pressure is linearly increased to 8MPa-15MPa; this stage can be called the pressure increase stage. Afterward, the temperature is kept constant at 330℃-370℃, and the pressure is rapidly increased to the reaction mechanical pressure (e.g., linearly increased to 40MPa-60MPa within 30s-100s). During the reaction, in-situ spectroscopy can be used to monitor the progress of the hot-pressing sulfidation reaction in real time, and the hot-pressing process parameters can be dynamically adjusted based on the monitoring results. The monitored objects include: the 810 cm⁻¹ of the formed PS-Ni bonds. -1 Characteristic peak intensity, dynamically adjustable, may include: when 810 cm⁻¹ -1 When the characteristic peak intensity is below a preset threshold, increase the mechanical pressure. Specifically, in-situ Raman monitoring (Renishaw in Via) can be used during the reaction process at 810 cm⁻¹. -1 (PS-Ni) characteristic peak intensity, typically 810 cm⁻¹ after 30 minutes. -1The (PS-Ni) strength needs to be ≥30% of the reference peak (i.e., ≥4500 cps). If the expected value is not achieved, the system will immediately trigger a pressure control mechanism, instantly increasing the mechanical pressure by 5 MPa and maintaining this pressure for 3-8 minutes before restoring the reaction mechanical pressure (40 MPa-60 MPa) and continuing the reaction for 0.5-1.5 hours. If the expected value is achieved, the reaction continues directly for 0.5-1.5 hours. This stage can be called the isothermal reaction stage. That is, in some embodiments, step S3 includes the following stages of hot-press vulcanization reaction: Heating and melting stage: 10min-30min (e.g., 10min, 12min, 15min, 18min) The temperature is increased from room temperature to 320℃-340℃ (e.g., 320℃, 325℃, 330℃, 335℃, 340℃) within 10min-30min, during which the mechanical pressure is kept constant; Pressurization phase: Subsequently, the temperature is increased to 330℃-370℃ (e.g., 330℃, 335℃, 340℃, 345℃, 350℃, 355℃, 360℃, 365℃, 370℃) at a rate of 1℃ / min-5℃ (e.g., 1℃ / min, 1.5℃ / min, 1.8℃ / min, 2℃ / min, 2.3℃ / min, 2.5℃ / min, 2.8℃ / min, 3℃ / min, 3℃ / min, 3.5℃ / min, 4℃ / min, 4.5℃ / min, 5℃ / min) while the mechanical pressure is linearly increased to 8MPa-15MPa (e.g., 8MPa, 10MPa, 12MPa, 15MPa). Isothermal reaction stage: The temperature is then kept constant at 330℃-370℃, with a linear pressure increase to 40MPa-60MPa within 30-100 seconds (e.g., 30s, 40s, 50s, 60s, 70s, 80s, 90s, 100s). In-situ Raman monitoring (RenishawinVia) is used throughout the reaction at 810cm. -1 (PS-Ni) characteristic peak intensity, 810 cm⁻¹ after 30 min of reaction in this stage. -1 The (PS-Ni) intensity needs to be ≥30% of the reference peak (i.e. ≥4500 cps). If it is insufficient, the pressure is increased instantaneously by 5MPa and maintained at this pressure for 3min-8min (e.g., 3min, 4min, 5min, 6min, 7min, 8min). Then, the mechanical pressure of the reaction is restored to 40MPa-60MPa, and the reaction continues for 0.5h-1.5h (e.g., 0.5h, 0.8h, 1h, 1.2h, 1.5h). If the expected result is achieved, the reaction continues directly for 0.5h-1.5h (e.g., 0.5h, 0.8h, 1h, 1.2h, 1.5h).

[0067] After the hot-pressing sulfidation reaction in step S3 of this invention is completed, the positive electrode material needs to be cooled before the mold is opened and the material is removed. As long as the purpose of this invention can be achieved, the cooling method is not particularly limited. In some embodiments, the cooling method includes: first cooling to 150℃-250℃ (e.g., 150℃, 180℃, 200℃, 230℃, 250℃) at a rate of 0.2℃ / min-0.6℃ / min, then cooling to 60℃-100℃ (e.g., 60℃, 70℃, 80℃, 90℃, 100℃) at a rate of 0.8℃ / min-1.5℃ / min (e.g., 0.8℃ / min, 1℃ / min, 1.2℃ / min, 1.5℃ / min), and finally cooling naturally to room temperature.

[0068] In the preparation method of the present invention, the oxygen vacancy activated material obtained by constructing oxygen vacancy sites in nickel-rich ternary materials has oxygen vacancy V_O·· and lattice oxygen O. 2- To compensate for the charge imbalance caused by oxygen vacancies, nearby transition metal ions may be reduced, such as Ni. 4+ Reduced to Ni 2+ When the sulfide solid electrolyte melts and diffuses onto the surface of the oxygen vacancy activated material, the oxygen vacancies in the activated material can serve as channels for the diffusion of the sulfide solid electrolyte. Upon contact with the oxygen vacancy activated material, the structure of the sulfide solid electrolyte undergoes dissociation, including [PS4]. 3- Tetrahedrons can aggregate to form larger P2S7. 4- Polysulfophosphate ions, and / or direct decomposition to produce P 5+ and S 2- P2S7 4- or S 2- It can be used as a reducing agent to reduce Ni to Ni. 2+ Meanwhile, S 2- Sulfur is oxidized to elemental sulfur or sulfur in higher oxidation states, such as P2S7. 4- The PS bond in the middle is broken, P 5+ With the diffused O 2- And the Li present in the system + The metal ions in the system combine to form stable Li3PO4; some metal ions are also reduced, such as Ni obtained from reduction. 2+ Metal sulfides, which migrate from the lattice of oxygen-vacancy activated materials, react with S in the interface region to form, for example, Ni3S2. This reaction is local and non-uniform, so Ni3S2 will precipitate in the form of "nano islands" and disperse in the Li3PO4 matrix.

[0069] Furthermore, during the interdiffusion and reaction between the oxygen vacancy-activated material and the sulfide solid electrolyte, a mixed or disordered phase of P, S, and Ni chemically bonded exists in the transition region between the nickel-rich ternary material and the Li3PO4 matrix Ni3S2 nano-islands. This means that the nickel-rich ternary material and the Li3PO4 matrix Ni3S2 nano-islands exhibit a complex interdiffusion and reaction. 44 The interface modification layer of the matrix Ni3S2 nanoislands is connected by PS-Ni.

[0070] In addition, in this invention, the oxygen vacancy activating material forms an initial, smooth oxygen vacancy concentration gradient from the surface to the interior. Then, through ball milling and hot-pressing sulfidation, sulfide ions are induced to diffuse inward along the pre-set oxygen vacancy channels to carry out the series of reactions mentioned above, consuming lattice oxygen and generating new oxygen vacancies. After the reaction is completed, a near-surface gradient transition region with a certain thickness and a smooth decrease in oxygen vacancy concentration from the surface to the interior is locked outside the core of the nickel-rich ternary material. Its outer edge is chemically bonded to the composite interface modification layer generated in situ through PS-Ni bonds.

[0071] In some embodiments, the flowchart of the preparation method of the cathode material in this invention is as follows: Figure 1 As shown.

[0072] Thirdly, in some embodiments, the present invention provides an application of the above-mentioned cathode material or cathode material prepared by the above-mentioned cathode material preparation method in an all-solid-state battery.

[0073] In this embodiment, the synergistic effect of the core and the interface modification layer of the cathode material can construct a solid-solid interface with both ultra-high ionic / electronic conductivity and exceptional chemical-mechanical stability. This fundamentally suppresses element interdiffusion, reduces interface impedance, and achieves uniform and rapid charge transfer, thereby better solving the core bottleneck problems that all-solid-state batteries have long faced, such as low critical current density, poor fast-charging performance, and short cycle life.

[0074] Fourthly, in some embodiments, the present invention provides an all-solid-state battery, including the cathode material described above or the cathode material prepared by the cathode material preparation method.

[0075] In some embodiments, the all-solid-state battery further includes a sulfide solid-state electrolyte. The sulfide solid-state electrolyte can be any well-known sulfide solid-state electrolyte in the art, and the present invention does not impose any particular limitation on it, including but not limited to argentite-germanium sulfide solid-state electrolytes.

[0076] In this invention, the positive electrode sheet can be prepared using the positive electrode material described herein in a manner conventional in the art, and a sulfide solid electrolyte layer can be prepared using a conventional solid electrolyte layer in the art. Furthermore, other components in the all-solid-state battery (such as the negative electrode sheet) can be conventionally selected in the art.

[0077] In this invention, the assembly method of the all-solid-state battery can be carried out in accordance with conventional methods in the art.

[0078] The present invention will be described in detail below through embodiments. The embodiments described herein are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0079] The following examples illustrate the preparation method of the cathode material of the present invention and the cathode material obtained therefrom.

[0080] In the following examples and comparative examples: The relevant parameters of the cathode material were obtained by methods such as XPS oxygen vacancy concentration detection, interface detection, Raman monitoring, laser particle size analyzer, and transmission electron microscopy.

[0081] Example 1 Preparation of cathode materials: S1, Oxygen Vacancy Activation Treatment: 100 g of NCM83 single crystal powder (Dv50 = 5.0 ± 0.2 μm, manufactured by Sumitomo Metal Industries, Ni content 83 ± 0.3 mol%) was weighed and placed in an alumina crucible. The alumina crucible was then transferred into a tube furnace, and a H2 / Ar mixed gas with a concentration of 5.0 ± 0.1 vol% (flow rate 50 mL / min) was introduced and circulated three times (residual O2 < 0.1 ppm). The temperature was then increased to 300 °C at 5 °C / min, held for 120 min, and then cooled with the furnace (cooling rate ≤ 2 °C / min) to obtain oxygen vacancy activated NCM83 powder. Samples were taken for XPS oxygen vacancy concentration detection (Thermo Scientific K-Alpha): the peak area of ​​the O1s binding energy of 531.5 eV in the oxygen vacancy activated NCM83 powder accounted for 7.8 ± 0.3%. S2, Pretreatment of sulfide composite powder: Li6PS5Cl powder (15g, Dv50=2.5±0.3μm, produced by Kojundo, Japan, purity>99.9%) and the oxygen vacancy activated NCM83 powder obtained above (85g) were weighed and placed in a 500mL zirconia ball mill jar for ball milling. Argon gas was used for purging three times (residual H2O<0.1ppm). The ball milling parameters were: rotation speed 200rpm, ball-to-powder mass ratio 5:1 (the abrasive was a mixture of zirconia balls with a mass ratio of 1:1 and a diameter of 3mm / 5mm), and effective ball milling time 30min (stopping for 2min every 10min to prevent overheating). The ball milling output yielded sulfide composite powder. The Dv50 of the sulfide composite powder was measured using a laser particle size analyzer (Malvern Mastersizer 3000) and found to be 4.8±0.3μm. S3, Hot-press vulcanization interface reaction: The above-mentioned sulfide composite powder was subjected to hot-press vulcanization interface reaction using a two-way hot press (Kejing YLJ-50 model). The mold material was high-strength graphite (thermal expansion coefficient 3.8×10). -6 / ℃): Pre-compression of the filling material (0-600s): At room temperature, the sulfide composite powder is evenly spread into the mold (1mm thickness), the mold is closed, the atmosphere control system is connected, and the system pressure is evacuated to ≤10Pa to fully remove air and adsorbed moisture from the mold cavity. High-purity Ar gas (purity ≥99.999%) is then introduced into the system to 0.5MPa. This step is repeated three times to ensure that the residual O2 concentration in the cavity is <0.1ppm. Then, a pre-compression of 5MPa is applied (to eliminate gaps between powder particles) and maintained for 10 minutes. Heating and melting (600-1500s): The temperature is raised to 335℃ (reached at t=1500s), during which time the mechanical pressure is kept constant at 5MPa; During the pressurization phase (1500-1800s): the temperature continues to rise from 335℃ to the target temperature of 350℃, while the mechanical pressure is linearly increased from 5MPa to 10MPa (reached at t=1800 s). Isothermal reaction (1800-5400s): Temperature remained constant at 350±2℃, pressure linearly increased from 10MPa to 50MPa within 60s, in-situ Raman monitoring (Renishaw inVia) was initiated: ① At t=1800s, 785cm was detected. -1 (PSP benchmark) Characteristic peak intensity is 14800 cps; ② At t=3600s, 810 cm⁻¹ was detected. -1The characteristic peak intensity of (PS-Ni) is 4100 cps. Calculations show that the PS-Ni peak intensity at this point is only 27.7% (<30%) of the baseline peak intensity, which does not meet expectations. The system then triggers a pressure control mechanism: at t=3600 s, the mechanical pressure is instantaneously increased by 5 MPa (i.e., to 55 MPa) and maintained at this pressure until t=3900 s. At t=3900 s, the pressure returns to 50 MPa and is maintained until the end of this stage (t=5400 s). Gradient cooling (5400-14400s): In the range of 350℃-200℃, the cooling rate is controlled at 0.5℃ / min; in the range of 200℃-80℃, the cooling rate is controlled at 1℃ / min; below 80℃, natural cooling is performed. After cooling, the mold is opened and samples are taken to obtain the positive electrode material.

[0082] The cathode material has an NCM83 single crystal core and an interface modification layer covering the surface of the NCM83 single crystal core. The interface modification layer includes a Li3PO4 matrix and Ni3S2 embedded in the Li3PO4 matrix. The Ni3S2 exists in the form of nano islands. The relevant parameters of the cathode material are shown in Table 1.

[0083] Example 2 The method according to Example 1 differs in that: In the oxygen vacancy activation treatment, an H2 / Ar mixture with an H2 concentration of 5.5 ± 0.1 vol% is introduced; Pressurization phase (1500-1800s): The temperature continues to rise from 335℃ to the target temperature of 355℃, while the mechanical pressure is linearly increased from 5MPa to 10MPa (reached at t=1800 s). Isothermal reaction (1800-5400s): Temperature remained constant at 355±2℃, pressure linearly increased from 10MPa to 52MPa within 60s, in-situ Raman monitoring (Renishaw inVia) was initiated: at t=3600s, 810cm was detected. -1 The intensity of the (PS-Ni) characteristic peak is greater than 4500 cps and remains until the end of this stage (t=5400s). Gradient cooling (5400-14400s): In the range of 355℃-200℃, the cooling rate is controlled at 0.5℃ / min; in the range of 200℃-80℃, the cooling rate is controlled at 1℃ / min; and below 80℃, natural cooling is performed. After cooling, the mold is opened and samples are taken to obtain the positive electrode material.

[0084] The cathode material has an NCM83 single crystal core and an interface modification layer covering the surface of the NCM83 single crystal core. The interface modification layer includes a Li3PO4 matrix and Ni3S2 embedded in the Li3PO4 matrix. The Ni3S2 exists in the form of nano islands. The relevant parameters of the cathode material are shown in Table 1.

[0085] Example 3 The method according to Example 1 differs in that: In the oxygen vacancy activation treatment, an H2 / Ar mixture with an H2 concentration of 4.5 ± 0.1 vol% is introduced; Pressurization phase (1500-1800s): The temperature continues to rise from 335℃ to the target temperature of 345℃, while the mechanical pressure is linearly increased from 5MPa to 10MPa (reached at t=1800 s). Isothermal reaction (1800-5400s): Temperature remained constant at 345±2℃, pressure linearly increased from 10MPa to 48MPa within 60s, in-situ Raman monitoring (Renishaw inVia) was initiated: ① At t=3600s, 810cm was detected. -1 The characteristic peak intensity of (PS-Ni) is 3915 cps. Calculations show that the peak intensity of PS-Ni at this time is only 26.1% (<30%) of the reference peak intensity, which does not meet the expected level. The system then triggers a pressure regulation mechanism: at t=3600s, the mechanical pressure is instantaneously increased by 5 MPa (i.e., to 53 MPa) and maintained at this pressure until t=3900s. At t=3900s, the pressure returns to 53 MPa and is maintained until the end of this stage (t=5400s). Gradient cooling (5400-14400s): The cooling rate is controlled at 0.5℃ / min in the range of 345℃-200℃, and at 1℃ / min in the range of 200℃-80℃. Below 80℃, the material is allowed to cool naturally. After cooling, the mold is opened and samples are taken to obtain the cathode material.

[0086] The cathode material has an NCM83 single crystal core and an interface modification layer covering the surface of the NCM83 single crystal core. The interface modification layer includes a Li3PO4 matrix and Ni3S2 embedded in the Li3PO4 matrix. The Ni3S2 exists in the form of nano islands. The relevant parameters of the cathode material are shown in Table 1.

[0087] Example 4 The method according to Example 1 differs in that: In the oxygen vacancy activation treatment, an H2 / Ar mixed gas with an H2 concentration of 3.0 ± 0.1 vol% is introduced; The rest is the same as in Example 1, and the positive electrode material is finally prepared.

[0088] The cathode material has an NCM83 single crystal core and an interface modification layer covering the surface of the NCM83 single crystal core. The interface modification layer includes a Li3PO4 matrix and Ni3S2 embedded in the Li3PO4 matrix. The Ni3S2 exists in the form of nano islands. The relevant parameters of the cathode material are shown in Table 1.

[0089] Example 5 The method according to Example 1 differs in that: In the oxygen vacancy activation treatment, an H2 / Ar mixed gas with an H2 concentration of 7.0 ± 0.1 vol% is introduced; The rest is the same as in Example 1, and the positive electrode material is finally prepared.

[0090] The cathode material has an NCM83 single crystal core and an interface modification layer covering the surface of the NCM83 single crystal core. The interface modification layer includes a Li3PO4 matrix and Ni3S2 embedded in the Li3PO4 matrix. The Ni3S2 exists in the form of nano islands. The relevant parameters of the cathode material are shown in Table 1.

[0091] Example 6 The method according to Example 1 differs in that: Heating and melting (600-1500 s): The temperature is raised to 315℃ (reached at t=1500s), during which time the mechanical pressure is kept constant at 5MPa; Pressurization phase (1500-1800s): The temperature continues to rise from 315℃ to the target temperature of 330℃, while the mechanical pressure is linearly increased from 5MPa to 10MPa (reached at t=1800 s). Isothermal reaction (1800-5400s): The temperature is kept constant at 330±2℃, and the pressure is linearly increased from 10MPa to 40MPa within 60s and maintained until the end of this stage (t=5400s). Gradient cooling (5400-14400s): In the range of 330℃-200℃, the cooling rate is controlled at 0.5℃ / min; in the range of 200℃-80℃, the cooling rate is controlled at 1℃ / min; and below 80℃, natural cooling is performed. After cooling, the mold is opened and samples are taken to obtain the positive electrode material.

[0092] The cathode material has an NCM83 single crystal core and an interface modification layer covering the surface of the NCM83 single crystal core. The interface modification layer includes a Li3PO4 matrix and Ni3S2 embedded in the Li3PO4 matrix. The Ni3S2 exists in the form of nano islands. The relevant parameters of the cathode material are shown in Table 1.

[0093] Example 7 The method according to Example 1 differs in that: During the pressurization phase (1500-1800s): the temperature continues to rise from 335℃ to the target temperature of 370℃, while the mechanical pressure is linearly increased from 5MPa to 10MPa (reached at t=1800 s). Isothermal reaction (1800-5400s): The temperature is kept constant at 370±2℃, and the pressure is linearly increased from 10MPa to 60MPa within 60s and maintained until the end of this stage (t=5400s). Gradient cooling (5400-14400s): In the range of 370℃-200℃, the cooling rate is controlled at 0.5℃ / min; in the range of 200℃-80℃, the cooling rate is controlled at 1℃ / min; and below 80℃, natural cooling is performed. After cooling, the mold is opened and samples are taken to obtain the positive electrode material.

[0094] The cathode material has an NCM83 single crystal core and an interface modification layer covering the surface of the NCM83 single crystal core. The interface modification layer includes a Li3PO4 matrix and Ni3S2 embedded in the Li3PO4 matrix. The Ni3S2 exists in the form of nano islands. The relevant parameters of the cathode material are shown in Table 1.

[0095] Comparative Example 1 S1. Preparation of slurry: Weigh 100 g of NCM811 single crystal powder (Dv50 = 5.0 ± 0.2 μm, same source as in Example 1) into a 250 mL beaker. Separately weigh 3.43 g of aluminum nitrate nonahydrate and 0.92 g of lithium hydroxide monohydrate into another beaker, add 80 mL of a mixed solvent prepared by deionized water and anhydrous ethanol at a volume ratio of 1:1, and stir at 500 rpm for 30 minutes on a magnetic stirrer until the solid is completely dissolved, obtaining a clear and transparent Li-Al precursor solution (total Li / Al molar ratio of 1.05:1). Under continuous stirring, slowly add this precursor solution dropwise to the NCM811 single crystal powder at a rate of 2 mL / min using a constant flow pump. After the addition is complete, continue stirring for 60 minutes to form a homogeneous slurry. S2. Preparation of precursors: The above slurry was transferred to a vacuum drying oven and dried at 80°C for 12 hours. Afterward, the dried lumpy material was transferred to a corundum crucible, placed in a muffle furnace, and heated to 300°C at a rate of 2°C / min in static air, and held for 120 min to obtain the precursor. S3, Sintering: After the precursor was cooled to room temperature in the furnace, it was removed, lightly ground to disperse soft agglomerates, and then placed back into a new corundum crucible and transferred to a tube furnace. High-purity oxygen (purity ≥99.999%, flow rate 100 mL / min) was introduced into the furnace for 30 minutes to replace the air. Subsequently, under an oxygen atmosphere, the temperature was increased to 700℃ at a rate of 5℃ / min and sintered at this temperature for 5 hours. After the sintering process, the sample was cooled to room temperature in the furnace (cooling rate ≤3℃ / min). After removal, it was placed in a 500 mL zirconia ball mill jar for ball milling, and purged three times with argon gas (residual H2O <0.1 ppm). The ball milling parameters were: rotation speed 200 rpm, ball-to-material mass ratio 5:1 (the abrasive was a mixture of 3 mm / 5 mm diameter zirconia balls with a mass ratio of 1:1), and effective ball milling time 30 min (with a 2 min pause every 10 min to prevent overheating). The ball milling output yielded the cathode material.

[0096] The cathode material has an NCM83 single crystal core and a LiAlO2 coating layer covering the surface of the NCM83 single crystal core.

[0097] Performance testing The following performance tests were conducted using the cathode materials from Examples 1-7 and Comparative Example 1, respectively: 1. Interface impedance test: 1) Take two identical positive electrode materials and use them as the two electrodes of the battery.

[0098] 2) Weigh 80.0 mg of Li6PS5Cl powder, place it in a mold, and cold press it under 100 MPa pressure to form a dense electrolyte isolation layer (thickness approximately ~800 μm).

[0099] 3) Place a positive electrode material on one side of the electrolyte separator and cold press it for 60 seconds under a pressure of 50 MPa to form an "electrode|electrolyte" half cell.

[0100] 4) Press another portion of the positive electrode material onto the other side of the electrolyte separator in the same manner, and finally hold it under a total pressure of 300MPa for 2 minutes to assemble a symmetrical battery with the structure of positive electrode material |Li6PS5Cl|.

[0101] 5) All operations are performed in a glove box filled with high-purity argon (H2O<0.1ppm, O2<0.1ppm).

[0102] 6) Connect the assembled symmetrical cell to the electrochemical workstation.

[0103] 7) At room temperature (25±2℃), apply an AC disturbance amplitude of 10mV, scan the frequency range from 1MHz to 0.1Hz, and record the data.

[0104] 8) Fit the measured impedance spectrum using dedicated equivalent circuit fitting software (such as ZView). The equivalent circuit used is: R e (R i Q i (R) it Q it R e R represents the bulk resistance of the sulfide electrolyte. i Q i : Represents the interfacial impedance between the cathode composite material and the sulfide electrolyte. Where R i Q is the interface resistance. i This is a constant phase angle element used to describe the non-ideal capacitive behavior of an interface. The interface resistance R is directly obtained through software fitting. i The value.

[0105] The formula for calculating interface impedance is: Interface impedance (Ω·cm) 2 )=R i (Ω) × Contact area between positive electrode material and electrolyte separator (cm²) 2 ).

[0106] 2. 4.6V Cycle Retention Rate Test: 1) Assemble an all-solid-state battery using a positive electrode containing the positive electrode material to be tested, a sulfide electrolyte (Li6PS5Cl), and a lithium metal negative electrode.

[0107] 2) Test conditions: at 4.6V (vs. Li + At the charging cutoff voltage of / Li), repeated charge-discharge cycles were performed at 0.5C.

[0108] 3) Record the discharge capacity at the 100th cycle and calculate its percentage relative to the first discharge capacity as the 4.6V cycle retention rate.

[0109] 3. High-load volume expansion rate test: High surface load (35 mg / cm) 2 The electrodes were assembled into a battery and cycled at a rate of 0.5C with a cutoff voltage of 4.3V. After 300 cycles, the battery was disassembled, and the electrode cross-section was observed using a scanning electron microscope (SEM). The thickness change was calculated using image analysis software to determine the volume expansion rate.

[0110] 4. Critical current density test: 1) An all-solid-state battery structure of "positive electrode (containing positive electrode material) | Li6PS5Cl electrolyte | lithium indium alloy negative electrode" was adopted. The test battery was subjected to three complete charge-discharge activation cycles at 0.1C rate at room temperature. The battery was charged to 50% state of charge and left to stand at this potential for 2 hours to allow lithium ions to be evenly distributed at the interface and the system to reach stability.

[0111] 2) Use a battery testing system to conduct tests in a constant temperature environment of 25℃. The test program settings are as follows: at 0.2mA / cm 2 A constant current discharge was applied at the specified current density for 10 minutes. The mixture was then allowed to stand for 5 minutes. The current density was then increased by 0.2 mA / cm². 2 Discharge at a constant current for 10 minutes, then let it stand for 5 minutes. Repeat this "discharge-stand" cycle, gradually increasing the current density.

[0112] 3) Critical Criterion: During the discharge process at any current level, if the battery voltage drops sharply to 0V within 10 minutes, it is determined that the battery has been punctured by lithium dendrites and has experienced an internal short circuit. CCD Value: The value of the current density level preceding the triggering of the short circuit is recorded as the critical current density of the battery.

[0113] 4) For samples from the same batch, at least three parallel cells should be tested. The final reported CCD value is the average of these parallel samples.

[0114] The test results are shown in Table 1.

[0115] Table 1. Relevant parameters and performance test results of the cathode material The test results in Table 1 show that the cathode material of this invention has comprehensive properties such as low interfacial impedance, high cycle retention, low volume expansion rate and high critical current density when used in all-solid-state batteries.

[0116] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A positive electrode material, characterized in that, include: The core contains a nickel-rich ternary material; An interface modification layer is provided, which covers at least a portion of the surface of the core, and the interface modification layer comprises lithium phosphorus oxide and metal sulfide.

2. The cathode material according to claim 1, characterized in that, The metal sulfide is embedded in the lithium phosphorus oxide in the form of nano-islands, the particle size of the nano-islands is no greater than 5 nm, and the mass content of the metal sulfide in the lithium phosphorus oxide is 8%-25%; And / or, the kernel and the interface decoration layer are connected via PS-Ni bonds; And / or, the thickness of the interface modification layer is 10nm-50nm; And / or, the core is divided into a bulk region and a near-surface gradient region located outside it, wherein the near-surface gradient region has oxygen vacancies, the concentration of oxygen vacancies in the near-surface gradient region gradually decreases from the interface between the interface modification layer and the core to the bulk region, and the thickness of the near-surface gradient region is 2nm-5nm. And / or, the Dv50 particle size of the nickel-rich ternary material is 3μm-8μm.

3. The cathode material according to claim 1 or 2, characterized in that, The general chemical formula of the lithium phosphorus oxide is Li3PO4; And / or, the general chemical formula of the metal sulfide is Ni a S b , where a and b are positive integers corresponding to valence states; And / or, the chemical formula of the nickel-rich ternary material is LiNi x Co y Mn z O2, where x≥0.6, y>0, z>0, x+y+z=1; And / or, the nickel-rich ternary material is a single-crystal material.

4. A method for preparing a positive electrode material, characterized in that, The preparation method includes: S1. Construct oxygen vacancy sites in nickel-rich ternary materials to obtain oxygen vacancy activated materials. S2. The sulfide solid electrolyte and the oxygen vacancy activating material are ball-milled to obtain sulfide composite powder. S3. The sulfide composite powder is subjected to a hot-pressing sulfidation reaction to obtain a cathode material; The sulfide solid electrolyte contains Li, P, and S.

5. The method for preparing the cathode material according to claim 4, characterized in that, The oxygen vacancy concentration of the oxygen vacancy activating material is 5%-10%; And / or, in step S1, the nickel-rich ternary material is subjected to reduction treatment to achieve the construction of the oxygen vacancy sites; the conditions of the reduction treatment include: being carried out in a mixed gas containing hydrogen and an inert gas, wherein the volume concentration of hydrogen in the mixed gas is 3%-8%, the temperature is 280℃-320℃, and the time is 60min-180min.

6. The method for preparing the cathode material according to claim 4, characterized in that, In step S2, the conditions for ball milling include: being carried out under an inert atmosphere, a ball milling speed of 100 rpm to 800 rpm, a ball milling time of 10 min to 60 min, and the ball milling media including one or more of zirconia beads, agate beads and steel beads, with a diameter of 0.1 mm to 20 mm and a ball-to-material ratio of (1-100):

1. And / or, in step S3, the conditions for the hot-press vulcanization reaction include: being carried out under an inert atmosphere, with a reaction temperature of 330℃-370℃, a mechanical pressure of 40MPa-60MPa, and a reaction time of 1h-3h. And / or, in step S3, the reaction temperature in the hot-press vulcanization reaction is denoted as a℃ and the mechanical pressure is denoted as bMPa, where a and b satisfy b≥0.2a-60; And / or, the preparation method further includes cooling after hot-press vulcanization reaction, wherein the cooling method includes: first cooling to 150℃-250℃ at 0.2℃ / min-0.6℃ / min, then cooling to 60℃-100℃ at 0.8℃ / min-1.5℃ / min, and finally cooling naturally to room temperature.

7. The method for preparing the cathode material according to any one of claims 4-6, characterized in that, The chemical formula of the nickel-rich ternary material is LiNi. x Co y Mn z O2, where x≥0.6, y>0, z>0, x+y+z=1; And / or, the Dv50 particle size of the nickel-rich ternary material is 3μm-8μm; And / or, the general chemical formula of the sulfide solid electrolyte is Li6PS5X, where X is a halogen; And / or, the mass ratio of the sulfide solid electrolyte to the oxygen vacancy activating material is (5-20):

1.

8. The application of the cathode material according to any one of claims 1-3, or the cathode material prepared by the preparation method according to any one of claims 4-7, in all-solid-state batteries.

9. An all-solid-state battery, characterized in that, The cathode material includes the cathode material according to any one of claims 1-3, or the cathode material prepared by the preparation method according to any one of claims 4-7.

10. The all-solid-state battery according to claim 9, characterized in that, The all-solid-state battery also includes a sulfide solid electrolyte.

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