Lithium battery cathode material and preparation method thereof

Abstract

The application discloses a lithium battery positive electrode material and a preparation method thereof. 1+x Al x Ti 2‑x (PO4)3、Li 1+x Mo x / 2 Ti 2‑x (PO4)3、LiAlO2 and Li2ZrO3, wherein 0 < x ≤ 0.5. The application remarkably improves the specific capacity, cycle stability and interface safety of the high-nickel ternary material through the synergistic modification of lithium deficiency pre-sintering, double-ion doping and solid-state electrolyte coating.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, specifically to a lithium battery cathode material and its preparation method. Background Technology

[0002] With the rapid development of electric vehicles, portable electronic devices, and other fields, the market has placed higher demands on the energy density of lithium-ion batteries. High-nickel ternary cathode materials (LiNi) are crucial for this development. x Co y Mn 1-x-y O2 (x ≥ 0.8) has become one of the key materials for realizing high energy density batteries due to its high theoretical specific capacity, and has received widespread attention from industry and academia.

[0003] However, traditional polycrystalline high-nickel materials suffer from rapid capacity decay and poor cycle stability during long-term cycling due to the tendency for microcracks to form at grain boundaries and electrolyte side reactions. To overcome this problem, micron-sized single-crystal cathode materials have been proposed, whose dense, grain-bound structure can effectively suppress crack propagation. However, single-crystal materials themselves face new challenges: firstly, the dense structure leads to slow lithium-ion diffusion kinetics and poor rate performance; secondly, their synthesis usually requires higher sintering temperatures, which can easily introduce lattice defects and reduce specific capacity. Although researchers have attempted to modify them through single-phase bulk doping or surface coating, it is often difficult to improve structural stability while simultaneously maintaining ionic conductivity and interfacial compatibility, resulting in complex processes, limited effectiveness, or the introduction of additional impedance.

[0004] Therefore, how to simultaneously address the structural and interfacial stability issues of high-nickel ternary materials (especially single-crystal types) while ensuring high specific capacity, and improve their electrochemical kinetic performance, remains a critical technical challenge in this field. To this end, this invention aims to propose an innovative synergistic modification strategy. This strategy optimizes the bulk structure through lithium-deficient pre-sintering and specific ion doping, combined with a uniform solid electrolyte interfacial coating, to comprehensively enhance the electrochemical performance and long-term cycling stability of the material. Summary of the Invention

[0005] In view of this, the present invention provides a lithium battery cathode material and its preparation method, which significantly improves the specific capacity, cycle stability and interface safety of high-nickel ternary materials through synergistic modification of lithium-deficient pre-sintering, dual-ion doping and solid electrolyte coating.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] In a first aspect, this invention discloses a lithium battery cathode material, which is formed by coating the surface of a lithium nickel cobalt manganese oxide cathode material with an oxide solid electrolyte; the lithium nickel cobalt manganese oxide cathode material incorporates dual-ion co-doping in its crystal lattice; the oxide solid electrolyte is Li 1+x Al x Ti 2-x (PO4)3, Li 1+x Mo x / 2 Ti 2-x At least one of (PO4)3, LiAlO2 and Li2ZrO3, wherein 0 < x ≤ 0.5.

[0008] As a further aspect of the present invention: the doping source for the dual-ion co-doping is any two of aluminum, titanium, zirconium, molybdenum, and phosphorus sources.

[0009] As a further aspect of the present invention: the lithium nickel cobalt manganese oxide cathode material is subjected to a lithium-deficient pre-sintering process before introducing dual-ion co-doping into the lattice.

[0010] Secondly, this invention discloses a method for producing a lithium battery cathode material as described above, comprising the following steps: S1. Lithium-deficient pre-sintering and doping: After mixing nickel-cobalt-manganese precursor, lithium source and doped oxide, the doped modified lithium nickel-cobalt-manganese cathode material is prepared by stepwise high-temperature sintering. S2. Wet coating and heat treatment: The lithium nickel cobalt manganese oxide cathode material is dispersed in a solvent, a coating precursor is added and wet milling is performed. After drying and heat treatment, an oxide solid electrolyte coating is formed on the surface of the material to obtain a high-stability lithium battery cathode material.

[0011] As a further aspect of the present invention: the nickel-cobalt-manganese precursor is Ni 1-x-y-z Co x Mn y (OH)2, where 0.75 < x ≤ 0.95, 0 < y ≤ 0.2, and 0 < z ≤ 0.05.

[0012] As a further aspect of the present invention: in step S1, the molar ratio of the nickel-cobalt-manganese precursor, the lithium source, and the doped oxide is 1:(0.88~1.08):(0.01~0.05).

[0013] As a further aspect of the present invention: step (1) specifically comprises: The nickel-cobalt-manganese precursor, lithium source, and doped oxide are mixed and ground in a molar ratio of 1:(0.88~1.08):(0.01~0.05); firstly, they are pre-sintered at 480~520℃, and then calcined at 930~960℃ to obtain a transition material; the transition material is mixed with a lithium source in a molar ratio of 1:(0.1~0.2) and then calcined again at 830~860℃.

[0014] As a further aspect of the present invention: the doped oxide is at least one of B2O3, Al2O3, MgO, CeO2, WO3, TiO2, ZrO2, Nb2O5, Ta2O5, La2O3, Y2O3, and MoO3.

[0015] As a further aspect of the present invention: in step S2, the coating precursor includes at least one of a lithium source, an aluminum source, a titanium source, a phosphorus source, a zirconium source, and a molybdenum source.

[0016] As a further aspect of the present invention: the heat treatment in step S2 is carried out in an oxygen atmosphere at a temperature of 800-850°C for a holding time of at least 14 hours.

[0017] Thirdly, the present invention discloses a lithium battery comprising the aforementioned lithium battery cathode material.

[0018] Compared with the prior art, the beneficial effects of the present invention are: This invention constructs a homogeneous micron-sized single-crystal structure with a superexchange-permeable network through a synergistic process of low-lithium pre-sintering and secondary annealing for lithium replenishment. This process introduces locally ordered superlattices into the layered structure of the material, acting as rivets to effectively enhance the stability of the bulk structure and suppress lattice collapse during long-term cycling, thereby significantly improving the material's cycle life and high-temperature resistance.

[0019] A uniform and dense fast ion conductor coating (such as Li) was constructed on the material surface using a wet process. 1.3 Mo 0.15 Ti 1.7 (PO4)3). This coating acts as a dual physical and chemical barrier, effectively isolating the active material from direct corrosion by the electrolyte and inhibiting harmful side reactions and microcrack propagation; on the other hand, it reduces Li... + / Ni 2+ The mixing of cations inhibits the formation of rock salt phases and reduces the interfacial charge transfer resistance, thus achieving a simultaneous improvement in interfacial stability and kinetic performance.

[0020] By introducing specific ions such as molybdenum and titanium for co-doping, the metal-oxygen bond energy is enhanced, effectively suppressing oxygen release during cycling and fundamentally improving the structural integrity of the material. Simultaneously, the doped ions regulate lattice strain, further suppressing the initiation and propagation of microcracks caused by volume changes, thus enhancing the material's mechanical stability.

[0021] The aforementioned synergistic modification strategy of surface coating and bulk doping enables the final ternary cathode material to exhibit excellent comprehensive performance in battery applications: it has high discharge specific capacity, excellent rate performance, ultra-high long cycle capacity retention rate, and significantly improved safety performance.

[0022] Although the process route (stepwise sintering and wet coating) adopted in this invention achieves multiple modifications, the steps are clear and highly controllable. It does not use special or expensive equipment. While effectively improving the material properties, it also takes into account the simplicity and scalability of the process, and has good prospects for industrial application. Attached Figure Description

[0023] Figure 1 This is a SEM image of the ternary lithium-ion battery cathode material from Example 2.

[0024] Figure 2 This is a TEM image of the ternary lithium-ion battery cathode material in Example 2.

[0025] Figure 3 The DSC diagrams are for coin cells prepared from the ternary lithium-ion cathode materials of Example 2 and Comparative Example 1. Detailed Implementation

[0026] To facilitate understanding of the present invention, a more comprehensive description will be given below with reference to specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0028] In addition, unless otherwise specified, the preparation processes in the following embodiments are all conventional methods in the prior art, and therefore will not be described in detail; unless otherwise specified, the parts in the following embodiments refer to parts by weight.

[0029] Example 1 (1) Pre-sintering and cation doping: The ternary precursor Ni0.85 Co 0.10 Mn 0.05 (OH)₂, lithium hydroxide, molybdenum oxide, and titanium oxide were mixed in a molar ratio of 1:0.918:0.01:0.01 and mechanically ground until homogeneous. The mixture was then transferred to a tube furnace and calcined in two stages under an oxygen atmosphere: the first stage involved pre-sintering at 500℃ for 5 hours; the second stage involved heating to 940℃ and holding for 11 hours to complete the primary crystallization. After cooling, a transition material was obtained.

[0030] The obtained transition material was mixed and ground again with lithium hydroxide at a molar ratio of 1:0.162, and then placed in a tube furnace for secondary calcination at 845°C under an oxygen atmosphere for 11 hours. After cooling, crushing, and sieving, the calcined product yielded cation-doped modified lithium nickel cobalt manganese oxide cathode material.

[0031] (2) Surface coating and heat treatment: The cathode material obtained in step (1) was dispersed in anhydrous ethanol and subjected to wet mechanical milling. Subsequently, the coating precursor components were added to the milling system in a set ratio. In this embodiment, the molar ratio of lithium nickel cobalt manganese oxide cathode material to lithium nitrate (LiNO3) was set to 1:0.005, and the amounts of lithium nitrate, molybdenum oxide, titanium dioxide, and ammonium dihydrogen phosphate were added to the system as coating precursors in a molar ratio of Li:Mo:Ti:P of 1.3:0.15:1.7:3. Milling was continued to ensure thorough mixing and pre-reaction.

[0032] The above slurry was vacuum dried at 80°C for 13 hours to obtain a dried precursor powder. This powder was then placed in a tube furnace and heat-treated at 820°C for 14 hours in an oxygen atmosphere. After cooling, a Li-coated precursor powder was obtained. 1.3 Mo 0.15 Ti 1.7 A highly stable ternary cathode material with a (PO4)3 solid electrolyte layer.

[0033] (3) Electrode preparation: Using the highly stable ternary material obtained in step (2) as the active material, acetylene black as the conductive agent, polyvinylidene fluoride (PVDF) as the binder, and N-methyl-2-pyrrolidone (NMP) as the dispersant, the materials were mixed in a mass ratio of active material: conductive agent: binder = 90:5:5 to form a slurry. The slurry was uniformly coated onto an aluminum foil current collector, and after drying, rolling, and cutting, a highly stable ternary positive electrode sheet was obtained.

[0034] Example 2 (1) Pre-sintering and cation doping: The ternary precursor Ni 0.85 Co 0.10 Mn 0.05(OH)₂, lithium hydroxide, molybdenum oxide, and titanium oxide were mixed in a molar ratio of 1:0.918:0.01:0.01 and mechanically ground until homogeneous. The mixture was then transferred to a tube furnace and calcined in two stages under an oxygen atmosphere: the first stage involved pre-sintering at 500℃ for 5 hours; the second stage involved heating to 940℃ and holding for 11 hours to complete the primary crystallization. After cooling, a transition material was obtained.

[0035] The obtained transition material was mixed and ground again with lithium hydroxide at a molar ratio of 1:0.162, and then placed in a tube furnace for secondary calcination at 845°C under an oxygen atmosphere for 11 hours. After cooling, crushing, and sieving, the calcined product yielded cation-doped modified lithium nickel cobalt manganese oxide cathode material.

[0036] (2) Surface coating and heat treatment: The cathode material obtained in step (1) was dispersed in anhydrous ethanol and subjected to wet mechanical grinding. Subsequently, the coating precursor components were added to the grinding system in a set ratio. In this embodiment, the molar ratio of lithium nickel cobalt manganese oxide cathode material to lithium nitrate (LiNO3) was set to 1:0.02, and the amounts of lithium nitrate, molybdenum oxide, titanium dioxide, and ammonium dihydrogen phosphate were added to the system as coating precursors in a molar ratio of Li:Mo:Ti:P of 1.3:0.15:1.7:3. Grinding was continued to ensure thorough mixing and pre-reaction.

[0037] The above slurry was vacuum dried at 80°C for 13 hours to obtain a dried precursor powder. This powder was then placed in a tube furnace and heat-treated at 820°C for 14 hours in an oxygen atmosphere. After cooling, a Li-coated precursor powder was obtained. 1.3 Mo 0.15 Ti 1.7 A highly stable ternary cathode material with a (PO4)3 solid electrolyte layer.

[0038] (3) Electrode preparation: Using the highly stable ternary material obtained in step (2) as the active material, acetylene black as the conductive agent, polyvinylidene fluoride (PVDF) as the binder, and N-methyl-2-pyrrolidone (NMP) as the dispersant, the materials were mixed in a mass ratio of active material: conductive agent: binder = 90:5:5 to form a slurry. The slurry was uniformly coated onto an aluminum foil current collector, and after drying, rolling, and cutting, a highly stable ternary positive electrode sheet was obtained.

[0039] Example 3 (1) Pre-sintering and cation doping: The ternary precursor Ni 0.85 Co 0.10 Mn 0.05(OH)₂, lithium hydroxide, molybdenum oxide, and titanium oxide were mixed in a molar ratio of 1:0.918:0.01:0.01 and mechanically ground until homogeneous. The mixture was then transferred to a tube furnace and calcined in two stages under an oxygen atmosphere: the first stage involved pre-sintering at 500℃ for 5 hours; the second stage involved heating to 940℃ and holding for 11 hours to complete the primary crystallization. After cooling, a transition material was obtained.

[0040] The obtained transition material was mixed and ground again with lithium hydroxide at a molar ratio of 1:0.162, and then placed in a tube furnace for secondary calcination at 845°C under an oxygen atmosphere for 11 hours. After cooling, crushing, and sieving, the calcined product yielded cation-doped modified lithium nickel cobalt manganese oxide cathode material.

[0041] (2) Surface coating and heat treatment: The cathode material obtained in step (1) was dispersed in anhydrous ethanol and subjected to wet mechanical grinding. Subsequently, the coating precursor components were added to the grinding system according to a set ratio. In this embodiment, the molar ratio of lithium nickel cobalt manganese oxide cathode material to lithium nitrate (LiNO3) was set to 1:0.04, and the amounts of lithium nitrate, molybdenum oxide, titanium dioxide, and ammonium dihydrogen phosphate were added to the system as coating precursors according to the molar ratio of Li:Mo:Ti:P of 1.3:0.15:1.7:3. Grinding was continued to ensure thorough mixing and pre-reaction.

[0042] The above slurry was vacuum dried at 80°C for 13 hours to obtain a dried precursor powder. This powder was then placed in a tube furnace and heat-treated at 820°C for 14 hours in an oxygen atmosphere. After cooling, a Li-coated precursor powder was obtained. 1.3 Mo 0.15 Ti 1.7 A highly stable ternary cathode material with a (PO4)3 solid electrolyte layer.

[0043] (3) Electrode preparation: Using the highly stable ternary material obtained in step (2) as the active material, acetylene black as the conductive agent, polyvinylidene fluoride (PVDF) as the binder, and N-methyl-2-pyrrolidone (NMP) as the dispersant, the materials were mixed in a mass ratio of active material: conductive agent: binder = 90:5:5 to form a slurry. The slurry was uniformly coated onto an aluminum foil current collector, and after drying, rolling, and cutting, a highly stable ternary positive electrode sheet was obtained.

[0044] Example 4 (1) Pre-sintering and cation doping: The ternary precursor Ni 0.78 Co 0.10 Mn 0.12(OH)₂, lithium hydroxide, molybdenum oxide, and titanium oxide were mixed in a molar ratio of 1:0.918:0.01:0.01 and mechanically ground until homogeneous. The mixture was then transferred to a tube furnace and calcined in two stages under an oxygen atmosphere: the first stage involved pre-sintering at 500℃ for 5 hours; the second stage involved heating to 940℃ and holding for 11 hours to complete the primary crystallization. After cooling, a transition material was obtained.

[0045] The obtained transition material was mixed and ground again with lithium hydroxide at a molar ratio of 1:0.162, and then placed in a tube furnace for secondary calcination at 845°C under an oxygen atmosphere for 11 hours. After cooling, crushing, and sieving, the calcined product yielded cation-doped modified lithium nickel cobalt manganese oxide cathode material.

[0046] (2) Surface coating and heat treatment: The cathode material obtained in step (1) was dispersed in anhydrous ethanol and subjected to wet mechanical milling. Subsequently, the coating precursor components were added to the milling system in a set ratio. In this embodiment, the molar ratio of lithium nickel cobalt manganese oxide cathode material to lithium nitrate (LiNO3) was set to 1:0.005, and the amounts of lithium nitrate, molybdenum oxide, titanium dioxide, and ammonium dihydrogen phosphate were added to the system as coating precursors in a molar ratio of Li:Mo:Ti:P of 1.3:0.15:1.7:3. Milling was continued to ensure thorough mixing and pre-reaction.

[0047] The above slurry was vacuum dried at 80°C for 13 hours to obtain a dried precursor powder. This powder was then placed in a tube furnace and heat-treated at 820°C for 14 hours in an oxygen atmosphere. After cooling, a Li-coated precursor powder was obtained. 1.3 Mo 0.15 Ti 1.7 A highly stable ternary cathode material with a (PO4)3 solid electrolyte layer.

[0048] (3) Electrode preparation: Using the highly stable ternary material obtained in step (2) as the active material, acetylene black as the conductive agent, polyvinylidene fluoride (PVDF) as the binder, and N-methyl-2-pyrrolidone (NMP) as the dispersant, the materials were mixed in a mass ratio of active material: conductive agent: binder = 90:5:5 to form a slurry. The slurry was uniformly coated onto an aluminum foil current collector, and after drying, rolling, and cutting, a highly stable ternary positive electrode sheet was obtained.

[0049] Example 5 (1) Pre-sintering and cation doping: The ternary precursor Ni 0.9 Co 0.05 Mn 0.05(OH)₂, lithium hydroxide, molybdenum oxide, and titanium oxide were mixed in a molar ratio of 1:0.918:0.01:0.01 and mechanically ground until homogeneous. The mixture was then transferred to a tube furnace and calcined in two stages under an oxygen atmosphere: the first stage involved pre-sintering at 500℃ for 5 hours; the second stage involved heating to 940℃ and holding for 11 hours to complete the primary crystallization. After cooling, a transition material was obtained.

[0050] The obtained transition material was mixed and ground again with lithium hydroxide at a molar ratio of 1:0.162, and then placed in a tube furnace for secondary calcination at 845°C under an oxygen atmosphere for 11 hours. After cooling, crushing, and sieving, the calcined product yielded cation-doped modified lithium nickel cobalt manganese oxide cathode material.

[0051] (2) Surface coating and heat treatment: The cathode material obtained in step (1) was dispersed in anhydrous ethanol and subjected to wet mechanical milling. Subsequently, the coating precursor components were added to the milling system in a set ratio. In this embodiment, the molar ratio of lithium nickel cobalt manganese oxide cathode material to lithium nitrate (LiNO3) was set to 1:0.005, and the amounts of lithium nitrate, molybdenum oxide, titanium dioxide, and ammonium dihydrogen phosphate were added to the system as coating precursors in a molar ratio of Li:Mo:Ti:P of 1.3:0.15:1.7:3. Milling was continued to ensure thorough mixing and pre-reaction.

[0052] The above slurry was vacuum dried at 80°C for 13 hours to obtain a dried precursor powder. This powder was then placed in a tube furnace and heat-treated at 820°C for 14 hours in an oxygen atmosphere. After cooling, a Li-coated precursor powder was obtained. 1.3 Mo 0.15 Ti 1.7 A highly stable ternary cathode material with a (PO4)3 solid electrolyte layer.

[0053] (3) Electrode preparation: Using the highly stable ternary material obtained in step (2) as the active material, acetylene black as the conductive agent, polyvinylidene fluoride (PVDF) as the binder, and N-methyl-2-pyrrolidone (NMP) as the dispersant, the materials were mixed in a mass ratio of active material: conductive agent: binder = 90:5:5 to form a slurry. The slurry was uniformly coated onto an aluminum foil current collector, and after drying, rolling, and cutting, a highly stable ternary positive electrode sheet was obtained.

[0054] Comparative Example 1 Weigh out the ternary precursor Ni 0.85 Co 0.10 Mn 0.05(OH)₂ and lithium hydroxide were mixed at a Ni:Li molar ratio of 1:1.08. The mixture was mechanically ground until homogeneous and then placed in a tube furnace for sintering in an oxygen atmosphere: first, it was held at 500℃ for 5 hours, then heated to 940℃ and held for 11 hours, and finally held at 845℃ for 11 hours. The resulting product was cooled, crushed, and sieved to obtain lithium nickel cobalt manganese oxide cathode material. This material was not subjected to any ion doping or surface coating treatment.

[0055] Comparative Example 2 Weigh out the ternary precursor Ni 0.85 Co 0.10 Mn 0.05 (OH)₂, lithium hydroxide, molybdenum oxide, and titanium oxide were mixed in a molar ratio of 1:1.08:0.01:0.01. The mixture was mechanically ground until homogeneous and then placed in a tube furnace for sintering in an oxygen atmosphere: first, it was held at 500℃ for 5 hours, then heated to 940℃ and held for 11 hours, and finally held at 845℃ for 11 hours. The resulting product was cooled, crushed, and sieved to obtain lithium nickel cobalt manganese oxide cathode material. This material was not surface-coated.

[0056] Comparative Example 3 (1) Weigh out the ternary precursor Ni 0.85 Co 0.10 Mn 0.05 (OH)₂ and lithium hydroxide were mixed at a Ni:Li molar ratio of 1:1.08. The mixture was mechanically ground until homogeneous and then placed in a tube furnace for sintering in an oxygen atmosphere: first, it was held at 500℃ for 5 hours, then heated to 940℃ and held for 11 hours, and finally held at 845℃ for 11 hours. The resulting product was cooled, crushed, and sieved to obtain a conventionally prepared, undoped lithium nickel cobalt manganese oxide cathode material matrix.

[0057] (2) The cathode material obtained in step (1) is dispersed in anhydrous ethanol and subjected to wet mechanical grinding. Subsequently, the coating precursor components are added to the grinding system in a set ratio. In this embodiment, the molar ratio of lithium nickel cobalt manganese oxide cathode material to lithium nitrate (LiNO3) is set to 1:0.02, and the amounts of lithium nitrate, molybdenum oxide, titanium dioxide and ammonium dihydrogen phosphate are added to the system in a molar ratio of Li:Mo:Ti:P of 1.3:0.15:1.7:3 as coating precursors. Grinding is continued to ensure thorough mixing and pre-reaction.

[0058] The above slurry was vacuum dried at 80°C for 13 hours to obtain a dried precursor powder. This powder was then placed in a tube furnace and heat-treated at 820°C for 14 hours in an oxygen atmosphere. After cooling, a Li-coated precursor powder was obtained. 1.3 Mo 0.15 Ti 1.7(PO4)3 solid electrolyte layer, but the matrix is ​​not doped or modified into a ternary cathode material.

[0059] (3) Using the material obtained in step (2) as the active material, acetylene black as the conductive agent, polyvinylidene fluoride (PVDF) as the binder, and N-methyl-2-pyrrolidone (NMP) as the dispersant, the materials are mixed in a mass ratio of active material: conductive agent: binder = 90:5:5 to form a slurry. The slurry is uniformly coated onto an aluminum foil current collector, and after drying, rolling, and cutting, a positive electrode sheet is obtained.

[0060] Comparative Example 4 (1) Weigh out the ternary precursor Ni 0.85 Co 0.10 Mn 0.05 (OH)₂, lithium hydroxide, molybdenum oxide, and titanium oxide were mixed in a molar ratio of 1:1.08:0.01:0.01. The mixture was mechanically ground until homogeneous and then placed in a tube furnace for sintering in an oxygen atmosphere: first, it was held at 500℃ for 5 hours, then heated to 940℃ and held for 11 hours, and finally held at 845℃ for 11 hours. The resulting product was cooled, crushed, and sieved to obtain a lithium nickel cobalt manganese oxide cathode material sintered using a conventional stoichiometric lithium source, doped with Mo and Ti elements, but without surface coating.

[0061] (2) Using the material obtained in step (1) as the active material, acetylene black as the conductive agent, polyvinylidene fluoride (PVDF) as the binder, and N-methyl-2-pyrrolidone (NMP) as the dispersant, the materials are mixed in a mass ratio of active material: conductive agent: binder = 90:5:5 to form a slurry. The slurry is uniformly coated onto an aluminum foil current collector, and after drying, rolling, and cutting, a positive electrode sheet is obtained.

[0062] Comparative Example 5 (1) The ternary precursor Ni 0.85 Co 0.10 Mn 0.05 (OH)₂, lithium hydroxide, molybdenum oxide, and titanium oxide were mixed in a molar ratio of 1:0.918:0.01:0.01 and mechanically ground until homogeneous. The mixture was then transferred to a tube furnace and calcined in two stages under an oxygen atmosphere: the first stage involved pre-sintering at 500℃ for 5 hours; the second stage involved heating to 940℃ and holding for 11 hours to complete the primary crystallization. After cooling, a transition material was obtained.

[0063] The obtained transition material was mixed and ground again with lithium hydroxide at a molar ratio of 1:0.162, and then placed in a tube furnace for secondary calcination at 845°C under an oxygen atmosphere for 11 hours. After cooling, crushing, and sieving, the calcined product yielded cation-doped modified lithium nickel cobalt manganese oxide cathode material.

[0064] (2) Using the material obtained in step (1) (uncoated) as the active material, acetylene black as the conductive agent, polyvinylidene fluoride (PVDF) as the binder, and N-methyl-2-pyrrolidone (NMP) as the dispersant, the materials are mixed in a mass ratio of active material: conductive agent: binder = 90:5:5 to form a slurry. The slurry is uniformly coated onto an aluminum foil current collector, and after drying, rolling, and cutting, a positive electrode sheet is obtained.

[0065] Test case The positive electrode material was tested using a CR2032 coin cell: the material was used as the positive electrode active material, lithium metal sheet was used as the negative electrode, and 1.0 mol / L LiPF6 / EC+DMC+EMC (volume ratio 1:1:1) was used as the electrolyte. The battery was assembled in an argon glove box.

[0066] Battery testing was conducted at 25°C, with a voltage range of 2.8V. 4.45 V: First charge-discharge test: The specific capacity and efficiency of the first charge-discharge were determined by constant current charge-discharge at 0.2C (1C=200 mA / g).

[0067] Rate performance test: Charge and discharge at rates of 0.33C and 1C in sequence, and record the corresponding discharge specific capacity.

[0068] Cyclic performance test: Perform continuous charge-discharge cycles at 1C rate and record the capacity retention rate after the 100th cycle.

[0069] The data in Table 1 are the average values ​​of three parallel tests.

[0070] Table 1

[0071] Table 1 shows a comparison of the electrochemical performance of each example and comparative example in a high-nickel ternary coin cell. The data shows that Example 2 exhibits the best overall performance, with an initial discharge specific capacity of 217.9 mAh / g and an initial charge-discharge efficiency of 89.9%. Particularly noteworthy is its ability to maintain a discharge specific capacity of 205.4 mAh / g at 1C rate, and a capacity retention rate of 97.9% after 100 cycles. Comparing the data from Comparative Examples 1-5 reveals that Comparative Example 1 (undoped and uncoated) performs the worst, with a cycle retention rate of only 82.6%. Comparative Examples 3 (coated only) and 4 (conventional doping only) have cycle retention rates of 83.7% and 86.1%, respectively, both significantly lower than Example 2. While Comparative Example 5 (lithium-deficient doping but uncoated) has an initial capacity close to that of Example 2 (216.5 mAh / g), its cycle retention rate (93.1%) is still lower than that of Example 2. This fully demonstrates that there is a significant synergistic effect among lithium-deficient pre-sintering, dual-ion doping, and solid electrolyte coating, and that no single modification method can achieve such excellent comprehensive performance.

[0072] Combination Figure 1-3 Let's take a look. Figure 1 The SEM images show the microstructure of the material in Example 2. It can be seen that the material is distributed with micron-sized single crystal particles. The particles are uniform in size and have smooth surfaces. This dense single crystal structure is beneficial to suppressing the propagation of grain boundary cracks during cycling. Figure 2 TEM further revealed the fine structure of the material, clearly showing a uniform and continuous coating layer on the surface of the lithium nickel cobalt manganese oxide substrate (inferred from the process to be a fast ion conductor coating (Li). 1.3 Mo 0.15 Ti 1.7 (PO4)3), and the coating layer is tightly bonded to the substrate. This structure can effectively isolate electrolyte corrosion and promote lithium-ion transport. Figure 3 The DSC curves were used to compare the thermal stability of Example 2 and Comparative Example 1. The exothermic peak temperature of Example 2 was 238.6℃, which was 14.5℃ higher than that of Comparative Example 1 (224.1℃). This indicates that the thermal stability of the material was significantly improved through the synergistic modification of bulk doping and surface coating, effectively suppressing oxygen release and structural collapse at high temperatures, thereby greatly improving the safety performance of the battery.

[0073] Although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0074] Therefore, the above description is only a preferred embodiment of this application and is not intended to limit the scope of this application; that is, all equivalent modifications made in accordance with the scope of the claims of this application shall be within the protection scope of the claims of this application.

Claims

1. A lithium battery cathode material, characterized in that, The cathode material is formed by coating the surface of a lithium nickel cobalt manganese oxide cathode material with an oxide solid electrolyte; the lithium nickel cobalt manganese oxide cathode material is introduced with dual-ion co-doping in its crystal lattice; the oxide solid electrolyte is Li. 1+x Al x Ti 2-x (PO4)3, Li 1+x Mo x / 2 Ti 2-x At least one of (PO4)3, LiAlO2 and Li2ZrO3, wherein 0 < x ≤ 0.

5.

2. The lithium battery cathode material according to claim 1, characterized in that, The doping source for the dual-ion co-doping is any two of the following: aluminum source, titanium source, zirconium source, molybdenum source, and phosphorus source.

3. The lithium battery cathode material according to claim 1, characterized in that, The lithium nickel cobalt manganese oxide cathode material undergoes a lithium-deficient pre-sintering process before introducing dual-ion co-doping into its crystal lattice.

4. A method for preparing the lithium battery cathode material as described in any one of claims 1-3, characterized in that, Includes the following steps: S1. After mixing nickel-cobalt-manganese precursor, lithium source and doped oxide, the doped modified nickel-cobalt-manganese lithium cathode material is prepared by stepwise high-temperature sintering. S2. The lithium nickel cobalt manganese oxide cathode material is dispersed in a solvent, a coating precursor is added and wet milling is performed. After drying and heat treatment, an oxide solid electrolyte coating is formed on the surface of the material to obtain a highly stable lithium battery cathode material.

5. The preparation method according to claim 4, characterized in that, The nickel-cobalt-manganese precursor is Ni 1-x-y-z Co x Mn y (OH)2, where 0.75 < x ≤ 0.95, 0 < y ≤ 0.2, and 0 < z ≤ 0.

05.

6. The preparation method according to claim 4, characterized in that, In step S1, the molar ratio of the nickel-cobalt-manganese precursor, the lithium source, and the doped oxide is 1:(0.88~1.08):(0.01~0.05).

7. The preparation method according to claim 4, characterized in that, Step S1 is as follows: The nickel-cobalt-manganese precursor, lithium source, and doped oxide are mixed and ground; firstly, they are pre-sintered at 480-520°C, and then calcined at 930-960°C to obtain a transition material; the transition material is mixed with a lithium source at a molar ratio of 1:(0.1-0.2) and then calcined again at 830-860°C.

8. The preparation method according to claim 7, characterized in that, The doped oxide is at least one of B2O3, Al2O3, MgO, CeO2, WO3, TiO2, ZrO2, Nb2O5, Ta2O5, La2O3, Y2O3, and MoO3.

9. The preparation method according to claim 4, characterized in that, In step S2, the coating precursor includes a lithium source and at least one of an aluminum source, a titanium source, a phosphorus source, a zirconium source, and a molybdenum source.

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