A ternary single-crystal lithium-ion battery positive electrode material suitable for high voltage and a preparation method thereof

Abstract

This application discloses a ternary single-crystal lithium-ion battery cathode material suitable for high voltage and its preparation method. The lithium-ion battery cathode material comprises the following components in parts by weight: modified LiNi 0.6 Mn 0.2 Co 0.2 O2 90-95 parts, conductive agent 1-3 parts, binder 3-5 parts, heat stabilizer 2-4 parts; modified LiNi 0.6 Mn 0.2 Co 0.2 The O2 surface is coated with gallium-doped lithium lanthanum zirconium oxide; the preparation method includes modifying LiNi 0.6 Mn 0.2 Co 0.2 O2, conductive agent and binder are mixed; N-methylpyrrolidone solvent is added and stirred to form a slurry; the slurry is coated on aluminum foil current collector, dried and rolled into a sheet; the resulting lithium-ion battery cathode material has excellent cycle stability under high voltage and slow capacity decay.

Description

Technical Field

[0001] This application relates to the field of lithium-ion battery cathode material technology, and in particular to a ternary single-crystal lithium-ion battery cathode material suitable for high voltage and its preparation method. Background Technology

[0002] Lithium-ion batteries, as a core component in the current energy storage field, rely heavily on the structure and chemical properties of their cathode materials for performance. Currently, mainstream cathode materials mainly include three systems: layered oxides, spinel-type, and olivine-type phosphates. Layered oxide materials achieve high energy density by adjusting the proportions of transition metals such as nickel, cobalt, and manganese. High-nickel ternary materials, in particular, improve electron transport efficiency and cycle stability through doping and surface coating strategies. Spinel-type lithium manganese oxide is used in small-scale power applications due to its low cost and good safety, while olivine-type lithium iron phosphate dominates the energy storage and low-to-mid-range electric vehicle markets due to its high safety and long cycle life. Furthermore, lithium-rich manganese-based materials, as a next-generation technology, theoretically surpass existing systems in specific capacity by activating the oxygen anion redox reaction; cobalt-free technology reduces costs by replacing scarce elements.

[0003] Although existing cathode materials have made some progress in energy density, their cycle stability and capacity retention under high voltage conditions still have shortcomings. Ternary materials are prone to structural degradation under high voltage, transforming from a layered structure to a spinel or rock salt phase, which leads to blockage of lithium-ion migration channels and dissolution of transition metal ions, accelerating capacity decay. Summary of the Invention

[0004] To improve the problems of poor cycle stability and rapid capacity decay under high voltage, a ternary single-crystal lithium-ion battery cathode material and its preparation method suitable for high voltage are provided.

[0005] The first inventive objective of this invention is achieved through the following technical solution: A ternary single-crystal lithium-ion battery cathode material suitable for high voltage, comprising the following components in parts by weight: Modified LiNi 0.6 Mn 0.2 Co 0.2 O2 90-95 servings, 1-3 parts conductive agent 3-5 parts adhesive 2-4 parts heat stabilizer; Modified LiNi 0.6 Mn 0.2 Co 0.2 The O2 surface is coated with gallium-doped lithium lanthanum zirconium oxide.

[0006] By adopting the above technical solution, single-crystal LiNi0.6 Mn 0.2 Co 0.2 O2 is the core active material. This material has a layered structure, in which nickel contributes high reversible capacity, manganese provides structural framework stability, and cobalt enhances electronic conductivity and inhibits cation mixing. Under high voltage conditions, LiNi 0.6 Mn 0.2 Co 0.2 O2 readily causes lattice oxygen precipitation, transition metal ion dissolution, and harmful phase transitions, leading to decreased cycle stability. Gallium-doped lithium-lanthanum-zirconium-oxygen (LCA) coating is employed. LCA possesses an inherent garnet crystal structure, exhibiting excellent thermodynamic stability over a wide voltage window and withstanding strong oxidizing environments under high voltage conditions. Gallium doping, by substituting zirconium sites in the LCA lattice and introducing cation vacancies or lattice distortion, effectively stabilizes the cubic garnet structure, reducing its transition to the tetragonal phase with lower ionic conductivity during cycling. This maintains and enhances lithium-ion mobility within the coating layer. Gallium doping optimizes the size and continuity of lithium-ion transport channels, lowering the lithium-ion diffusion activation energy. The coating layer physically isolates the active material from direct contact with the electrolyte. This coating structure helps to suppress the catalytic oxidation reaction pathway between the electrolyte and the surface of the positive electrode material under high voltage, inhibit the formation of electrolyte decomposition products, such as polymer films or gases formed by the oxidation of carbonate solvents, and reduce the dissolution of transition metal ions in the positive electrode material. This helps to reduce the migration of these ions to the negative electrode and their damage to the solid electrolyte interface film. The rapid transport of lithium ions through the gallium-doped lithium lanthanum zirconium oxide layer ensures that the charge transfer impedance at the interface is at a low level, which helps to avoid the increase in polarization caused by the accumulation of lithium ions at the interface. This coating structure reduces the side reaction rate at the interface between the positive electrode and the electrolyte under high voltage, slows down the growth of electrode impedance, maintains the structural integrity of the active material, improves the cycle stability of the battery under high voltage, and reduces the capacity decay problem. The addition of conductive agents constructs an electronic conduction network inside the electrode, enabling electrical contact between active particles and reducing polarization; binders provide mechanical integrity, fix the active material and conductive agents, and buffer volume changes; thermal stabilizers absorb and disperse local heat through their high thermal stability, thus delaying thermal runaway. Overall, the system improves cycling stability and capacity retention at high voltage through a combination of a coating layer protecting the interface, a single crystal core maintaining structural stability, a conductive network ensuring electron transport, a binder maintaining mechanical integrity, and a thermal stabilizer enhancing thermal safety.

[0007] Preferably, the conductive agent includes conductive carbon black and carbon nanotubes.

[0008] By adopting the above technical solution, conductive carbon black, being nanoscale spherical particles with a high specific surface area, can form a dense electron tunnel network between active particles through point contact, providing short-range electron conduction. Carbon nanotubes, being one-dimensional nanomaterials with a high aspect ratio, can construct long-range conductive pathways within the electrode, enabling electron transport over long distances. When the two are used in combination, conductive carbon black fills the gaps between active particles and between carbon nanotubes, forming a multi-dimensional conductive network, reducing the overall resistance of the electrode and improving the uniformity of electron conduction. Under high voltage, the uniform electron distribution helps reduce side reactions caused by excessively high local current density, such as electrolyte oxidation or overcharging of active materials, thereby slowing down capacity decay and improving cycle stability.

[0009] Preferably, the carbon nanotubes are nickel-coated multi-walled carbon nanotubes.

[0010] By adopting the above technical solution, nickel-coated multi-walled carbon nanotubes are loaded with nickel nanoparticles on the surface or inside the cavity of carbon nanotubes. Nickel is an excellent conductor, which can reduce the contact resistance of the carbon nanotubes themselves and enhance their overall electronic conductivity. Nickel catalyzes the interfacial bonding between carbon nanotubes and the surface of active materials, forming a tighter electrical contact. Under high voltage conditions, a passivation layer is formed on the nickel surface, reducing its further oxidation, thereby maintaining the long-term stability of the conductive network. The introduction of nickel-coated multi-walled carbon nanotubes further optimizes the conductive network of the electrode, promotes rapid electron transport, reduces polarization under high rate or high voltage, and helps maintain capacity stability during cycling.

[0011] Preferably, the mass ratio of the conductive carbon black to carbon nanotubes is (3:2)-(4:1).

[0012] By adopting the above technical solution, at this ratio, conductive carbon black effectively fills the gaps between active particles and carbon nanotubes, forming dense short-range contacts, while carbon nanotubes connect each conductive cluster, constructing a conductive framework that runs through the electrode. Under the synergistic effect, the pore structure of the electrode is also optimized, which is conducive to electrolyte wetting and uniform lithium ion transport. During high-voltage cycling, this conductive network reduces the risk of uneven current distribution, suppresses local overheating and side reactions, thereby improving cycle stability.

[0013] Preferably, the adhesive is polyvinylidene fluoride.

[0014] By adopting the above technical solution, polyvinylidene fluoride (PVDF) exhibits excellent chemical stability and electrochemical inertness, and is not easily swollen or decomposed in high-voltage electrolyte systems. The fluorine atoms in its molecular chain endow it with strong polarity, enabling it to form strong adhesion to the surfaces of active materials and conductive agents, thereby effectively fixing the various components of the electrode. During high-voltage cycling, the active material undergoes repeated volume changes, and PVDF, through its elasticity, buffers mechanical stress, which helps reduce the cracking of the electrode coating or its peeling off from the current collector. This helps maintain the structural integrity of the electrode and reduces capacity decay caused by the loss of electrical contact of the active material.

[0015] Preferably, the average molecular weight of the polyvinylidene fluoride is 500,000 to 700,000.

[0016] By adopting the above technical solution, at this average molecular weight, polyvinylidene fluoride can form a continuous and tough bonding network in the electrode, effectively buffering the volume change of the active material under high voltage, inhibiting the generation and propagation of microcracks, and further consolidating the mechanical stability of the electrode.

[0017] Preferably, the heat stabilizer is yttrium-stabilized zirconium oxide.

[0018] By adopting the above technical solution, yttrium oxide doping can stabilize the cubic phase structure of zirconium oxide, endowing it with high thermal stability, low coefficient of thermal expansion and high thermal conductivity. In the electrode, yttrium-stabilized zirconium oxide particles are dispersed between the active materials, which can absorb and disperse the local heat generated during cycling, delay thermal diffusion, and reduce the intensification of interfacial side reactions and heat generation under high voltage. Yttrium-stabilized zirconium oxide suppresses the local temperature rise of the electrode through its high heat capacity and thermal stability, reducing the risk of thermal runaway. Moreover, its chemical inertness can reduce side reactions with the electrolyte and indirectly stabilize the interface, thereby helping to improve the cycling stability under high voltage.

[0019] Preferred, modified LiNi 0.6 Mn 0.2 Co 0.2 The method for preparing O2 includes the following steps: preparing single-crystal LiNi 0.6 Mn 0.2 Co 0.2 O2 powder, lithium nitrate, lanthanum nitrate, zirconium oxychloride, and gallium nitrate are mixed in a solvent, and the pH is adjusted to deposit a precursor hydroxide layer. This layer is then sintered at high temperature in LiNi. 0.6 Mn 0.2 Co 0.2 Modified LiNi was obtained by forming a gallium-doped lithium lanthanum zirconium oxide coating on the O2 surface. 0.6 Mn 0.2 Co 0.2 O2.

[0020] By adopting the above technical solution, uniform coating of gallium-doped lithium lanthanum zirconium oxide is achieved through deposition and sintering. During the deposition process, gallium, lanthanum, and zirconium precursors are deposited on LiNi... 0.6 Mn 0.2 Co 0.2 A hydroxide deposition layer forms on the O2 surface, which transforms into a crystalline lithium lanthanum zirconium oxide coating layer during high-temperature sintering. Simultaneously, gallium ions partially substitute zirconium sites, enhancing the lithium-ion conductivity of the lithium lanthanum zirconium oxide coating and reducing lattice distortion. This method fosters strong chemical bonding between the coating layer and the substrate, helping to prevent coating peeling during cycling. Furthermore, gallium doping helps suppress LiNi... 0.6 Mn 0.2 Co 0.2 The lithium-nickel mixture on the O2 surface stabilizes the layered structure, and the resulting coating layer has both high ionic conductivity and interface protection functions, improving the capacity retention rate under high voltage.

[0021] The second objective of this invention is achieved through the following technical solution: The above-mentioned method for preparing ternary single-crystal lithium-ion battery cathode materials suitable for high voltage includes the following steps: modifying LiNi 0.6 Mn 0.2 Co 0.2 O2, conductive agent and binder are mixed; N-methylpyrrolidone solvent is added and stirred to form a slurry; the slurry is coated on aluminum foil current collector, dried and rolled into a sheet.

[0022] By adopting the above technical solution, the electrode microstructure is optimized through slurry mixing, coating, and rolling. The N-methylpyrrolidone solvent fully dissolves the binder and conductive agent and disperses the components evenly, which helps to avoid the aggregation of conductive agent. After drying, rolling increases the electrode density and the contact strength between components, allowing the conductive network to be in close contact with the active material, reducing interfacial impedance. The dense electrode structure also reduces the tortuosity of the lithium ion diffusion path and promotes rapid ion migration under high voltage. The electrode prepared by this method has low polarization, high bonding strength, and good structural stability, which is beneficial to improving high-voltage cycling performance.

[0023] In summary, this application has at least the following beneficial effects: (1) Using single-crystal LiNi 0.6 Mn 0.2 Co 0.2 O2, as the positive electrode active material, is prone to lattice oxygen precipitation and phase transition under high voltage due to its layered structure. Gallium-doped lithium lanthanum zirconium oxide is used to treat LiNi. 0.6 Mn 0.2 Co 0.2 The O2 coating stabilizes the cubic garnet structure, optimizes lithium-ion transport channels, and physically isolates electrolyte contact, thereby suppressing interfacial side reactions and transition metal dissolution, which helps to improve cycle stability. (2) Through the synergistic effect of multiple components, such as the coating layer protecting the electrochemical interface, the single crystal core maintaining structural stability, the conductive network ensuring electron transmission, the binder maintaining mechanical integrity, and the thermal stabilizer improving thermal safety, the side reaction rate and impedance growth under high voltage are reduced, and the capacity retention rate is improved. Detailed Implementation

[0024] raw material LiNi 0.6 Mn 0.2 Co 0.2 O2, 99.9 wt% purity, purchased from Shanghai Xianding Biotechnology Co., Ltd. Polyvinylidene fluoride, powder, with average molecular weights of 500,000, 600,000, and 700,000, was purchased from Zhejiang Juhua Co., Ltd. Polytetrafluoroethylene, with an average particle size of 3µm, was purchased from Shanghai Maclean Biochemical Technology Co., Ltd. Conductive carbon black with an average particle size of 30 nm and a specific surface area of ​​125 m². 2 / g, purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd.; Nickel-coated multi-walled carbon nanotubes, with a diameter of 8 nm, an inner diameter of 3 nm, a length of 50 µm, and a nickel content of 65 wt%, were purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd. The carbon nanotubes, specifically multi-walled carbon nanotubes, are 8 nm in diameter, 3 nm in inner diameter, 30 µm in length, and 95 wt% pure. They were purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd. Yttrium-stabilized zirconium oxide, model JA-TAP-3mol, zirconium oxide content 94.7wt%, 5.3wt% yttrium stabilized, primary particle size 30nm, secondary particle size 1µm, purchased from Shandong Shengtai Zirconium Resources Co., Ltd. N-methylpyrrolidone, lithium nitrate, lanthanum nitrate, zirconium oxychloride, gallium nitrate, lithium phosphate, and zirconium oxide are all commercially available.

[0025] Preparation Example 1 A modified LiNi 0.6 Mn 0.2 Co 0.2 O2 is prepared as follows: Add 280 mL of deionized water and 120 mL of anhydrous ethanol to the reaction vessel, then add 1.076 g of lithium nitrate, 2.604 g of lanthanum nitrate, 1.22 g of zirconium oxychloride, and 0.11 g of gallium nitrate. Stir and mix at 100 rpm for 15 min to obtain the precursor solution. 200g of single-crystal LiNi 0.6 Mn 0.2 Co 0.2O2 powder was added to a reaction vessel and kept in a constant temperature water bath at 55°C. 300 mL of deionized water was added and the mixture was stirred at 500 rpm for 30 min. The precursor solution was then added dropwise to the reaction vessel at a rate of 2 mL / min while stirring at 800 rpm. After the addition was complete, 0.5 mol / L ammonia was added dropwise to adjust the pH to 10.5. The mixture was kept at 55°C for 6 h to allow for deposition. The mixture was filtered to obtain a filter cake, which was washed three times with deionized water and dried at 80°C and -0.095 MPa vacuum for 15 h. The powder was then passed through a 200-mesh sieve to obtain the precursor-coated powder. The precursor-coated powder was placed in a tube furnace and heated to 500°C at a rate of 5°C / min under an oxygen atmosphere, held for 2 hours, then heated to 850°C at a rate of 3°C / min, held for 10 hours, and cooled to 200°C in the furnace before being removed and ground through a 325-mesh sieve to obtain modified LiNi. 0.6 Mn 0.2 Co 0.2 O2.

[0026] Preparation Example 2 A modified LiNi 0.6 Mn 0.2 Co 0.2 O2 is prepared as follows: Weigh out 200.0g of single-crystal LiNi 0.6 Mn 0.2 Co 0.2 O2 powder was used as the matrix material, and 2.0 g of lithium phosphate (Li3PO4) powder was weighed as the coating precursor. LiNi 0.6 Mn 0.2 Co 0.2 O2 powder and Li3PO4 powder were placed in a mixer and mixed at 1200 rpm for 60 min to obtain a mixed powder. The mixed powder was placed in a tube furnace and heated to 450°C at a heating rate of 3°C / min under an oxygen atmosphere, and held at this temperature for 5 hours. The Li3PO4 coating layer and LiNi 0.6 Mn 0.2 Co 0.2 The O2 surface reacts and densifies. After the heat treatment is completed, the furnace is cooled to room temperature (25°C), then removed and ground. The mixture is then passed through a 325-mesh sieve to obtain modified LiNi. 0.6 Mn 0.2 Co 0.2 O2.

[0027] Example 1 A ternary single-crystal lithium-ion battery cathode material suitable for high voltage is prepared by the following method: 8g of polyvinylidene fluoride (average molecular weight 600,000) was added to 92g of N-methylpyrrolidone solvent and stirred at 1000rpm for 4h to obtain a gel solution. 2.8g of conductive carbon black and 1.2g of nickel-coated multi-walled carbon nanotubes were added to the gel solution and dispersed at 2000rpm for 60min. 184g of modified LiNi was then added. 0.6 Mn 0.2 Co 0.2 O2 and 6g of yttrium-stabilized zirconium oxide were mixed and stirred at 500rpm for 120min to form a slurry. The slurry was coated onto an aluminum foil current collector (15μm thick, surface roughness 0.3μm) at a coating speed of 2m / min. After drying at 120℃ and -0.095MPa for 12h, it was rolled into a sheet at a rolling speed of 2m / min, a linear pressure of 2tonf / cm, and a compaction density of 3.5g / cm³. 3 The electrode thickness is 75µm (including aluminum foil), thus obtaining the positive electrode material for lithium-ion batteries.

[0028] Comparative Example 1 A ternary single-crystal lithium-ion battery cathode material suitable for high voltage differs from Example 1 in that it uses LiNi. 0.6 Mn 0.2 Co 0.2 O2 and other mass substitutes for modified LiNi 0.6 Mn 0.2 Co 0.2 O2.

[0029] Comparative Example 2 A ternary single-crystal lithium-ion battery cathode material suitable for high voltage differs from Example 1 in that it uses modified LiNi. 0.6 Mn 0.2 Co 0.2 O2 was derived from Preparation Example 2; the rest was the same as in Example 1.

[0030] Example 2 A ternary single-crystal lithium-ion battery cathode material suitable for high voltage differs from Example 1 in that: conductive carbon black is not added, and 4.0g of nickel-coated multi-walled carbon nanotubes are used; the rest is the same as in Example 1.

[0031] Example 3 A ternary single-crystal lithium-ion battery cathode material suitable for high voltage differs from Example 1 in that: nickel-coated multi-walled carbon nanotubes are not added, and the conductive carbon black content is 4.0 g; the rest of the components are the same as in Example 1.

[0032] Example 4 A ternary single-crystal lithium-ion battery cathode material suitable for high voltage differs from Example 1 in that: carbon nanotubes of equal mass are used instead of nickel-coated multi-walled carbon nanotubes; the rest is the same as in Example 1.

[0033] Example 5 A ternary single-crystal lithium-ion battery cathode material suitable for high voltage differs from Example 1 in that: the conductive carbon black is 2.0g and the nickel-coated multi-walled carbon nanotubes are 2.0g; the rest is the same as in Example 1.

[0034] Example 6 A ternary single-crystal lithium-ion battery cathode material suitable for high voltage differs from Example 1 in that: the conductive carbon black is 2.4g and the nickel-coated multi-walled carbon nanotubes are 1.6g; the rest is the same as in Example 1.

[0035] Example 7 A ternary single-crystal lithium-ion battery cathode material suitable for high voltage differs from Example 1 in that: the conductive carbon black content is 3.2 g, and the nickel-coated multi-walled carbon nanotube content is 0.8 g; the rest is the same as in Example 1.

[0036] Example 8 A ternary single-crystal lithium-ion battery cathode material suitable for high voltage differs from Example 1 in that: the conductive carbon black is 3.4g and the nickel-coated multi-walled carbon nanotubes are 0.6g; the rest is the same as in Example 1.

[0037] Example 9 A ternary single-crystal lithium-ion battery cathode material suitable for high voltage differs from Example 1 in that: polytetrafluoroethylene is used in place of polyvinylidene fluoride by an equal mass; the rest is the same as in Example 1.

[0038] Example 10 A ternary single-crystal lithium-ion battery cathode material suitable for high voltage differs from Example 1 in that the average molecular weight of polyvinylidene fluoride is 500,000; the rest is the same as in Example 1.

[0039] Example 11 A ternary single-crystal lithium-ion battery cathode material suitable for high voltage differs from Example 1 in that the average molecular weight of polyvinylidene fluoride is 700,000; the rest is the same as in Example 1.

[0040] Example 12 A ternary single-crystal lithium-ion battery cathode material suitable for high voltage differs from Example 1 in that zirconium oxide is used in place of yttrium-stabilized zirconium oxide; the rest is the same as in Example 1.

[0041] Example 13 A ternary single-crystal lithium-ion battery cathode material suitable for high voltage differs from Example 1 in that it uses modified LiNi. 0.6 Mn 0.2 Co 0.2 180g of O2, 6g of polyvinylidene fluoride, 1.4g of conductive carbon black, 0.6g of nickel-coated multi-walled carbon nanotubes, and 4g of yttrium-stabilized zirconium oxide; the rest of the ingredients are the same as in Example 1.

[0042] Example 14 A ternary single-crystal lithium-ion battery cathode material suitable for high voltage differs from Example 1 in that it uses modified LiNi. 0.6 Mn 0.2 Co 0.2 O2 190g, polyvinylidene fluoride 10g, conductive carbon black 4.2g, nickel-coated multi-walled carbon nanotubes 1.8g, yttrium-stabilized zirconium oxide 8g; the rest of the ingredients are the same as in Example 1.

[0043] The following tests were conducted on Examples 1-14 and Comparative Examples 1-2: The positive electrode sheets prepared in Examples 1-14 and Comparative Examples 1-2 were stamped into discs with a diameter of 12 mm as positive electrode sheets, and lithium metal sheets with a diameter of 15 mm and a thickness of 0.5 mm were used as negative electrodes. Celgard 2400 was used as a separator, and 1.2 M LiPF6 dissolved in EC / EMC (volume ratio 3:7, containing 2 wt% vinylene carbonate and 1 wt% 1,3-propanesulfonate lactone) was used as electrolyte. The cells were assembled into coin cells in an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm).

[0044] First, the battery was charged to 4.5V using a constant current and constant voltage (DC) rate at 0.1C. Then, it was charged at a constant voltage until the current dropped to 0.05C. Next, it was discharged at a constant current rate at 0.1C to 3.0V, repeated twice. This was followed by cycles at 0.2C, 0.5C, and 1C, with the discharge specific capacity recorded at each rate. Starting from the 6th cycle, constant current and constant voltage charge / discharge cycles were performed at a 1C rate for 500 cycles. The discharge specific capacity of the 6th cycle (i.e., the first 1C cycle) was recorded as the initial capacity (C1), and the discharge specific capacity after the 500th cycle (C...) was recorded. 500 The capacity retention rate is calculated as follows: Capacity retention rate = (C 500 / C1) × 100%, the test results are shown in Table 1.

[0045] Table 1. Detection results of Examples 1-14 and Comparative Examples 1-2

[0046] Based on Table 1, the analyses of Examples 1-14 and Comparative Examples 1-2 are as follows: Comparing Example 1 and Comparative Examples 1-2, the capacity retention rate of Example 1 after 500 cycles is greater than that of Comparative Examples 1-2 after 500 cycles. The difference between Example 1 and Comparative Examples 1-2 is that the LiNi in Example 1... 0.6 Mn 0.2 Co 0.2 The O2 surface is modified by gallium-doped lithium lanthanum zirconium oxide coating. The inherent garnet structure of gallium-doped lithium lanthanum zirconium oxide coating provides thermodynamic stability over a wide voltage window. Gallium doping helps stabilize the cubic phase structure, optimizes lithium-ion transport channels, and thus improves ionic conductivity. This coating layer physically isolates the positive electrode active material from the electrolyte, helping to suppress interfacial side reactions, reduce transition metal dissolution, and alleviate capacity decay, thereby improving the battery's cycle stability at high voltages. Therefore, LiNi 0.6 Mn 0.2 Co 0.2 Gallium-doped lithium lanthanum zirconium oxide coating modification of O2 surface helps improve the cycle stability of battery under high voltage and reduce capacity decay problem.

[0047] Comparing Examples 1 and 2-3, Example 1 exhibits a higher capacity retention rate after 500 cycles than Examples 2-3. The difference between Examples 1 and 2-3 lies in the following: Example 1's conductive agent comprises conductive carbon black and carbon nanotubes. Conductive carbon black, as nanoscale spherical particles, forms a short-range electron conduction network through point contact due to its high specific surface area. Carbon nanotubes, as a one-dimensional material, construct long-range conductive pathways with their high aspect ratio. When used in combination, the carbon black fills the gaps, synergistically forming a multi-dimensional conductive network with the carbon nanotubes. This helps reduce electrode resistance and improve electron distribution uniformity. Under high voltage conditions, this uniform electron distribution can suppress side reactions caused by excessive local current, thereby mitigating capacity decay and improving cycle stability. Therefore, the inclusion of conductive carbon black and carbon nanotubes in the conductive agent helps improve the battery's cycle stability under high voltage and alleviate capacity decay issues.

[0048] Comparing Examples 1 and 4, Example 1 showed a higher capacity retention rate after 500 cycles than Example 4. The difference between Examples 1 and 4 is that Example 1 used nickel-coated multi-walled carbon nanotubes. By loading nickel nanoparticles onto the surface or inside multi-walled carbon nanotubes to construct nickel-coated multi-walled carbon nanotubes, the good conductivity of nickel can be used to reduce contact resistance and enhance electronic conduction. Nickel can also catalyze the formation of tighter electrode interface contacts and form a passivation layer at high voltage to maintain the stability of the conductive network, which helps to mitigate polarization and is beneficial to the capacity retention of the electrode during cycling. Therefore, using nickel-coated multi-walled carbon nanotubes helps to improve the cycling stability of the battery at high voltage and reduce capacity decay.

[0049] Comparing Examples 1 and 5-8, Examples 1 and 6-7 showed greater capacity retention after 500 cycles than Examples 5 and 8. The difference between Examples 1 and 5-8 lies in the mass ratio of conductive carbon black to carbon nanotubes: Examples 1 and 6-7 had a mass ratio of (3:2) to (4:1). At this ratio, the conductive carbon black effectively filled the gaps between the active particles and the carbon nanotubes, forming dense short-range contacts, while the carbon nanotubes connected the conductive clusters, constructing a conductive framework that runs through the electrode. Under this synergistic effect, the pore structure of the electrode was also optimized, which is beneficial for electrolyte wetting and uniform lithium-ion transport. During high-voltage cycling, this conductive network reduces the risk of uneven current distribution, suppresses local overheating and side reactions, thereby improving cycle stability. Therefore, a mass ratio of conductive carbon black to carbon nanotubes of (3:2) to (4:1) helps improve the cycle stability of the battery under high voltage and alleviate capacity decay.

[0050] Comparing Examples 1 and 9, Example 1 showed a higher capacity retention rate after 500 cycles than Example 9. The difference between Examples 1 and 9 lies in the binder used in Example 1: Polyvinylidene fluoride (PVDF). PVDF possesses excellent chemical stability and electrochemical inertness, and is not prone to swelling or decomposition in high-voltage electrolyte systems. The fluorine atoms in its molecular chain provide strong polarity, which helps to form a strong adhesion with the active material and conductive agent surface, effectively fixing the electrode components. During cycling, PVDF can elastically buffer the mechanical stress caused by volume changes, helping to reduce coating cracking or peeling, thereby supporting the integrity of the electrode structure and mitigating capacity decay caused by active material failure. Therefore, using PVDF as a binder helps improve the cycle stability of the battery under high voltage and reduce capacity decay.

[0051] Comparing Examples 1 and 12, Example 1 showed a higher capacity retention rate after 500 cycles than Example 12. The difference between Examples 1 and 12 is that Example 1 uses yttrium-stabilized zirconium oxide as the heat stabilizer. Zirconium oxide has a stable cubic phase structure and excellent thermal stability and chemical inertness, which helps absorb and disperse local heat generated by interfacial side reactions under high voltage, suppresses local temperature rise of the electrode, mitigates the risk of thermal runaway, and reduces side reactions with the electrolyte, thus improving the cycle stability of the battery under high voltage conditions. Therefore, using yttrium-stabilized zirconium oxide as the heat stabilizer helps improve the cycle stability of the battery under high voltage and reduce capacity decay.

[0052] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of protection claimed in this application.

Claims

1. A ternary single-crystal lithium-ion battery cathode material suitable for high voltage, characterized in that, The components include the following parts by weight: Modified LiNi 0.6 Mn 0.2 Co 0.2 O2 90-95 servings, 1-3 parts conductive agent 3-5 parts adhesive 2-4 parts heat stabilizer; The modified LiNi 0.6 Mn 0.2 Co 0.2 The O2 surface is coated with gallium-doped lithium lanthanum zirconium oxide.

2. The ternary single-crystal lithium-ion battery cathode material suitable for high voltage according to claim 1, characterized in that, The conductive agent includes conductive carbon black and carbon nanotubes.

3. The ternary single-crystal lithium-ion battery cathode material suitable for high voltage according to claim 2, characterized in that, The carbon nanotubes are nickel-coated multi-walled carbon nanotubes.

4. The ternary single-crystal lithium-ion battery cathode material suitable for high voltage according to claim 2, characterized in that, The mass ratio of the conductive carbon black to carbon nanotubes is (3:2)-(4:1).

5. The ternary single-crystal lithium-ion battery cathode material suitable for high voltage according to claim 1, characterized in that, The adhesive is polyvinylidene fluoride.

6. The ternary single-crystal lithium-ion battery cathode material suitable for high voltage according to claim 5, characterized in that, The average molecular weight of the polyvinylidene fluoride is 500,000 to 700,000.

7. The ternary single-crystal lithium-ion battery cathode material suitable for high voltage according to claim 1, characterized in that, The heat stabilizer is yttrium-stabilized zirconium oxide.

8. The ternary single-crystal lithium-ion battery cathode material suitable for high voltage according to claim 1, characterized in that, The modified LiNi 0.6 Mn 0.2 Co 0.2 The method for preparing O2 includes the following steps: Single-crystal LiNi 0.6 Mn 0.2 Co 0.2 O2 powder, lithium nitrate, lanthanum nitrate, zirconium oxychloride, and gallium nitrate are mixed in a solvent, and the pH is adjusted to deposit a precursor hydroxide layer. This layer is then sintered at high temperature in LiNi. 0.6 Mn 0.2 Co 0.2 Modified LiNi was obtained by forming a gallium-doped lithium lanthanum zirconium oxide coating on the O2 surface. 0.6 Mn 0.2 Co 0.2 O2.

9. A method for preparing a ternary single-crystal lithium-ion battery cathode material suitable for high voltage as described in claims 1-8, characterized in that, Includes the following steps: The modified LiNi 0.6 Mn 0.2 Co 0.2 O2, conductive agent and binder are mixed; N-methylpyrrolidone solvent is added and stirred to form a slurry; the slurry is coated on aluminum foil current collector, dried and rolled into a sheet.

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