A high-voltage high-rate lithium cobalt oxide cathode material and a preparation method thereof

Abstract

The application discloses a high-voltage high-rate lithium cobalt oxide positive electrode material, which comprises a lithium cobalt oxide base material and an oxide coating layer coated on the lithium cobalt oxide base material. a Tm 1‑a O2, wherein 0.99<=a<=0.999, Tm is at least two of Mg, Al, Ti, Sr and Zr; the chemical formula of the oxide coating layer is MO x , wherein M comprises at least five of Co, Al, Y, La, Zr, Ti and Sr, 1

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, and in particular to a high-voltage, high-rate lithium cobalt oxide cathode material and its preparation method. Background Technology

[0002] With the rapid development of portable electronic devices, electric vehicles, and other fields, increasingly higher demands are being placed on the energy density, rate performance, and cycle life of lithium-ion batteries. Lithium cobalt oxide (LiCoO2), as a classic cathode material, is widely used in various lithium-ion batteries due to its high theoretical capacity, good electronic conductivity, and processing performance. However, under high-voltage (e.g., exceeding 4.3V) charge-discharge conditions, the crystal structure of traditional lithium cobalt oxide cathode materials is prone to distortion, and cobalt ions easily dissolve from the crystal lattice and deposit on the negative electrode surface, leading to increased internal resistance and rapid capacity decay. Furthermore, its rate performance and high-temperature cycle stability are insufficient to meet the requirements of high-power devices and long-life applications. To address these issues, extensive research has been conducted in the industry, primarily employing two modification methods: elemental doping and surface coating. Regarding elemental doping, researchers have attempted to introduce single or a few metal elements such as Mg, Al, and Ti to replace some of the Co, thereby stabilizing the layered structure of lithium cobalt oxide and inhibiting cobalt ion dissolution. However, doping with a single or small number of elements often only improves performance in one aspect and cannot simultaneously achieve high capacity, high rate capability, and long cycle stability. For surface coating, Al₂O₃ is commonly used. 3、 ZrO2 and other single oxides are used as coating layers to prevent direct contact between the electrolyte and the substrate material, reducing cobalt ion dissolution. However, coating layers prepared by traditional methods (such as mechanical ball milling and sol-gel methods) suffer from poor uniformity and weak bonding with the substrate, making them prone to detachment during high-voltage charge-discharge processes, resulting in limited modification effects. Furthermore, single oxide coating layers typically have poor conductivity, affecting the rate performance of the battery. In addition, existing modification technologies struggle to simultaneously achieve high discharge specific capacity (e.g., 198 mAh / g at 0.1C), excellent rate performance (1C / 15C), and high capacity retention (95% after 100 cycles) under high voltage (3.0-4.55V) conditions. This fails to meet the current urgent demand for high energy density, high power density, and long lifespan lithium-ion batteries. Therefore, developing a lithium cobalt oxide cathode material and its preparation method that combines high voltage adaptability, high capacity output, high rate response, and long cycle stability has become a pressing technical problem in this field. Summary of the Invention

[0003] The purpose of this invention is to provide a high-voltage, high-rate lithium cobalt oxide cathode material and its preparation method, so as to solve the problem of insufficient capacity rate cycling performance of lithium cobalt oxide under high voltage.

[0004] The above technical object of the present invention is achieved through the following technical solutions:

[0005] A high-voltage and high-rate lithium cobalt oxide cathode material, comprising a lithium cobalt oxide matrix material and an oxide coating layer coated on the lithium cobalt oxide matrix material. The chemical formula of the lithium cobalt oxide matrix is LiCo a Tm 1-a O2, where 0.99 ≤ a ≤ 0.999, and Tm is at least two of Mg, Al, Ti, Sr, Zr; the chemical formula of the oxide coating layer is MO x where M includes at least five of Co, Al, Y, La, Zr, Ti, Sr, 1 < x < 2 and the total valence is zero.

[0006] In a preferred embodiment, the thickness of the oxide coating layer is 1 nm - 500 nm.

[0007] In a preferred embodiment, the oxide coating layer is a fluorine-doped modification layer, and the fluorine doping amount satisfies MO x F Y where y ≤ 0.1.

[0008] In a preferred embodiment, the material surface has a micro-nano porous structure with a pore diameter of 5 - 50 nm and a specific surface area ≥ 3.0 m² / g.

[0009] In a preferred embodiment, the cobalt source for preparing the lithium cobalt oxide matrix is an oxide or a carbonate, and the D50 of the cobalt source satisfies 3.5 μm ≤ D50 ≤ 6.5 μm.

[0010] In a preferred embodiment, the M source for preparing the oxide coating layer is a nano-oxide, and the D50 of the M source ≤ 2.0 μm.

[0011] A preparation method of a high-voltage and high-rate lithium cobalt oxide cathode material, comprising the following steps:

[0012] S1. Weigh and mix a lithium source, a cobalt source, and a Tm source in a stoichiometric ratio and then perform a first heat treatment to obtain a lithium cobalt oxide matrix LiCo a Tm 1-a O2, where 0.99 ≤ a ≤ 0.999; the lithium source is one or two of lithium carbonate and lithium hydroxide; the cobalt source is one or two of its oxides and carbonates, and the D50 of the cobalt source satisfies 3.5 μm ≤ D50 ≤ 6.5 μm; the Tm source is one or more of its oxides, hydroxides, and carbonates, and the Tm is at least two of Mg, Al, Ti, Sr, Zr;

[0013] S2. Mix the lithium cobalt oxide matrix material with MO xMix them in a designed mass ratio in a plasma ball mill to obtain a mixed powder material; the M source is a nano-oxide, and the D50 of the M source ≤ 2.0 μm, where M includes at least five of Co, Al, Y, La, Zr, Ti, Sr, 1 < x < 2 and the total valence is zero;

[0014] S3. Perform a second heat treatment on the mixed powder to obtain a lithium cobalt oxide cathode material with high voltage and high rate.

[0015] In a preferred embodiment, in S1, the heat preservation temperature of the first heat treatment is 950°C - 1000°C, the heat preservation time is 7 - 10 hours, the heating rate is 3 - 5°C / min, and the sintering atmosphere is air; in S3, the heat preservation temperature of the second heat treatment is 750°C - 850°C, the heat preservation time is 5 - 8 hours, the heating rate is 3 - 5°C / min, and the sintering atmosphere is air.

[0016] In a preferred embodiment, in S2, the plasma ball milling uses a two-way gas mixing system to supply a two-component pulsed gas source. The main gas source is 95 - 98 vol% compressed air, and the auxiliary gas source is 2 - 5 vol% fluorine-containing gas. The fluorine-containing gas is CF4 or SF6. The on-off frequency of the auxiliary gas source is controlled by a pulse valve to be 5 - 10 Hz; during the ball milling process, the exhaust gas flow rate is 100 ml / min - 300 ml / min, the ball milling speed is 500 - 960 rpm, and the ball milling time is 10 - 30 min.

[0017] In a preferred embodiment, the discharge parameters of the plasma ball milling in S2 are dynamically adjusted in gradients. Within the same ball milling stage, in the first 1 / 3 of the time, the discharge current is 1.8 - 2.0 A and the duty cycle is 30%, and in the last 2 / 3 of the time, the discharge current is 1.2 - 1.5 A and the duty cycle is 60%.

[0018] Compared with the prior art, the Tm in the present invention is a multi-element doping structure of at least two of Mg, Al, Ti, Sr, Zr. Due to the characteristic of the Tm element matching the Co ion radius, it can be uniformly incorporated into the lithium cobalt oxide lattice to form a stable layered crystal structure, effectively inhibiting the lattice distortion and cobalt ion dissolution phenomena during high-voltage charge and discharge - both retaining the high electrochemical active sites of the lithium cobalt oxide matrix (the a value is close to 1 to ensure the capacity basis), and adjusting the lattice field strength through the synergistic effect of multi-element doping, reducing the ion migration energy barrier, and enhancing the Li + conduction efficiency; at the same time, the introduction of the Tm element can enhance the Co - O bond binding strength, reduce the deintercalation of oxygen under high voltage, and avoid capacity attenuation caused by structural collapse. And the oxide coating layer MO coated on the surface of the matrix xHigh-entropy oxide system (M contains at least five of Co, Al, Y, La, Zr, Ti, Sr, 1 < x < 2 and the total valence is zero). The high-entropy effect of multi-metal elements enables it to form a thermodynamically stable homogeneous phase structure with uniform chemical potential distribution, which can effectively block the direct contact between the electrolyte and the matrix material, inhibit the erosion of the matrix by the decomposition products of the electrolyte (such as HF), and at the same time avoid the defects of poor conductivity and weak bonding with the matrix in a single oxide coating layer; the oxygen content design of 1 < x < 2 and the constraint of zero total valence ensure the electrical neutrality and structural integrity of the coating layer, which will neither hinder Li + transport due to charge accumulation, nor can it improve the electronic conductivity and mechanical stability of the coating layer through the synergistic effect of multi-metal elements, reducing the risk of coating layer shedding during charge and discharge cycles. The multi-element doping of the matrix and the high-entropy oxide coating layer form a synergistic effect of "internal lattice stability - external interface protection", which not only ensures the structural integrity of the material under high voltage conditions, but also optimizes the electron and ion transport kinetics, enabling the material to have high-capacity output, excellent rate response and long cycle stability, meeting the application requirements of high-energy density and high-power density lithium-ion batteries.

[0019] The preparation method of a high-voltage and high-rate lithium cobalt oxide cathode material of the present invention selects one or two of lithium carbonate and lithium hydroxide as the lithium source, and its reaction activity adapts to the synthesis requirements of the lithium cobalt oxide matrix, and can fully react with the cobalt source and the Tm source during heat treatment, ensuring the uniform doping of lithium element and the integrity of the crystal lattice; the cobalt source is selected as an oxide or carbonate and D50 is controlled at 3.5μm ≤ D50 ≤ 6.5μm, which ensures the chemical stability of the raw materials, avoids the introduction of impurities, and through appropriate particle size design, ensures the uniformity of powder mixing, improves the ion diffusion efficiency during sintering, and promotes the formation of a dense and highly crystalline matrix; the Tm source adopts one or more of oxides, hydroxides, carbonates, and Tm is at least two of Mg, Al, Ti, Sr, Zr. The multi-form Tm source can adapt to different heat treatment reaction paths, ensuring that the Tm element is uniformly incorporated into the lithium cobalt oxide lattice and playing the synergistic effect of multi-element doping on structural stability.

[0020] In S2, a nano-oxide with D50 ≤ 2.0μm is used as the M source, and M contains at least five of Co, Al, Y, La, Zr, Ti, Sr. The nano-scale particle size makes the M source have a high specific surface area and reaction activity, which can achieve fine and uniform mixing with the lithium cobalt oxide matrix in a planetary ball mill, avoiding coating defects caused by agglomeration. The multi-element M source provides the material basis for the formation of the high-entropy oxide coating layer; the high-energy mixing method of planetary ball milling further strengthens the interfacial bonding between the matrix and the coating layer raw materials, laying the foundation for the formation of a firm coating structure in subsequent heat treatment.

[0021] The second heat treatment in S3 can promote MO xIt fully reacts and crystallizes on the surface of the substrate to form an oxide coating layer with stable structure and tight bonding with the substrate, while solidifying the doping and modification effect of the substrate. Through the coordinated cooperation of raw material selection, particle size control, multi-component design and step-by-step heat treatment in the whole preparation process, the lattice stability of the lithium cobaltate substrate and the uniform density of the oxide coating layer are ensured, and finally the improvement of high capacity, high rate and long cycle stability of the material under high voltage is achieved.

[0022] Under the settings of the present invention, under the test conditions: voltage range 3.0 - 4.55V; tested at room temperature of 25°C, the discharge specific capacity at 0.1C: 198 mAh / g, rate performance 1C / 15C, and the capacity retention rate after 100 cycles of 1C / 1C charge and discharge at 45°C is 95%. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a finished product electron microscope image of a high-voltage and high-rate lithium cobaltate cathode material according to the present invention, and an obvious island structure can be seen in the figure.

[0024] Figure 2 It is an electron microscope image of a high-voltage and high-rate lithium cobaltate cathode material after being mixed in a plasma ball mill.

[0025] Figure 3 It is an electron microscope image of a high-voltage and high-rate lithium cobaltate cathode material after being mixed in a high-speed mixer.

[0026] Figure 4 It is a high-temperature cycle retention rate graph. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] The present invention will be further described in detail below with reference to the accompanying drawings.

[0028] This specific embodiment is only an explanation of the present invention, and it is not a limitation of the present invention. Those skilled in the art can make modifications without creative contributions to this embodiment after reading this specification, but as long as they are within the scope of the claims of the present invention, they are protected by the patent law.

[0029] Embodiment 1

[0030] A high-voltage and high-rate lithium cobaltate cathode material, comprising a lithium cobaltate matrix material and an oxide coating layer coated on the lithium cobaltate matrix material. The chemical formula of the lithium cobaltate matrix is LiCo a Tm 1-a O2, where 0.99 ≤ a ≤ 0.999, and Tm is at least two of Mg, Al, Ti, Sr, Zr; the chemical formula of the oxide coating layer is MO x , where M contains at least five of Co, Al, Y, La, Zr, Ti, Sr, 1 < x < 2 and the total valence is zero.

[0031] In the above settings, Tm is a multi-doped structure of at least two of Mg, Al, Ti, Sr, and Zr. Due to the characteristic of the Tm element matching the Co ion radius, it can be uniformly incorporated into the lithium cobaltate lattice to form a stable layered crystal structure, effectively suppressing the lattice distortion and cobalt ion dissolution during high-voltage charge and discharge. This not only retains the high electrochemical active sites of the lithium cobaltate matrix (the a value is close to 1 to ensure the capacity basis), but also adjusts the lattice field strength through the synergistic effect of multi-doped elements, reduces the ion migration energy barrier, and improves the Li + conduction efficiency. At the same time, the introduction of the Tm element can enhance the Co-O bond binding strength, reduce the oxygen deintercalation at high voltage, and avoid the capacity attenuation caused by structural collapse. The oxide coating layer MO x (M includes at least five of Co, Al, Y, La, Zr, Ti, and Sr, 1 < x < 2 and the total valence is zero) of the high-entropy oxide system. The high-entropy effect of multi-metal elements enables it to form a thermodynamically stable homogeneous phase structure with uniform chemical potential distribution, which can effectively block the direct contact between the electrolyte and the matrix material, inhibit the erosion of the matrix by the electrolyte decomposition products (such as HF), and at the same time avoid the defects of poor conductivity and weak binding to the matrix of a single oxide coating layer. The oxygen content design of 1 < x < 2 and the constraint of the total valence of zero ensure the electrical neutrality and structural integrity of the coating layer, which will neither hinder Li + transport due to charge accumulation, nor can it improve the electronic conductivity and mechanical stability of the coating layer through the synergistic effect of multi-metal elements, reducing the risk of coating layer shedding during charge and discharge cycles. The multi-doping of the matrix and the high-entropy oxide coating layer form a synergistic effect of "internal lattice stability - external interface protection", which not only ensures the structural integrity of the material under high-voltage conditions, but also optimizes the electron and ion transport kinetics, enabling the material to have both high-capacity output, excellent rate response and long cycle stability, meeting the application requirements of high-energy density and high-power density lithium-ion batteries.

[0032] In this embodiment, the thickness of the oxide coating layer is 1 nm - 500 nm.

[0033] In this embodiment, the oxide coating layer is a fluorine-doped modification layer, and the fluorine doping amount satisfies MO x F Y , where y ≤ 0.1. The fluorine doping amount is controlled within the appropriate range of y ≤ 0.1, which can not only form a dense fluorine-doped modification layer by replacing part of O - with F 2- , significantly improving the electrolyte erosion resistance of the oxide coating layer and inhibiting the corrosion of the matrix by HF at high voltage, but also avoiding the destruction of the coating layer crystal structure and ion transport channels by excessive F - .

[0034] The material surface possesses a micro-nano porous structure with pore sizes of 5-50 nm and a specific surface area ≥3.0 m² / g. This 5-50 nm micro-nano porous structure combined with a specific surface area ≥3.0 m² / g significantly increases the contact area between the material and the electrolyte, shortening the Li-terminal compression time. + The diffusion path enhances ion transport efficiency; at the same time, it reserves space for volume expansion, suppresses structural collapse, and synergistically enhances the material's high-rate discharge capability and long-cycle stability.

[0035] The cobalt source used to prepare the lithium cobalt oxide matrix is ​​an oxide or carbonate, and the D50 of the cobalt source satisfies 3.5μm≤D50≤6.5μm. The selection of oxide or carbonate cobalt sources ensures chemical stability suitable for the heat treatment process, allowing for sufficient reaction to generate a high-purity lithium cobalt oxide matrix. The particle size of 3.5μm≤D50≤6.5μm ensures uniform powder mixing and sintering density, improving the integrity of the matrix's crystal structure.

[0036] The M source used to prepare the oxide coating is a nano-oxide with a D50 ≤ 2.0 μm. The selection of a nano-oxide with a D50 ≤ 2.0 μm as the M source ensures fine particles and good dispersibility, allowing for thorough contact and mixing with the lithium cobalt oxide matrix to form a uniform and dense oxide coating, thus avoiding coating defects caused by agglomeration. Simultaneously, it reduces uneven coating thickness, ensuring smooth ion transport channels.

[0037] In this embodiment, the lithium cobalt oxide matrix material and MO x The design mass ratio is: the content of the coating layer accounts for 0.2%-0.9% of the matrix mass.

[0038] See Figures 1 to 4 , Figure 1 and Figure 2 The image presented shows electron micrographs of the finished cathode material and the mixture after being mixed in a plasma ball mill. Figure 3 The electron microscope images of the mixture after mixing using a high-speed mixer are presented. Figure 2 and Figure 3 The comparison shows that the materials present different forms. Figure 4 The high-temperature cycling retention rate graph is presented. Comparative Example 1 is the blank control group without a coating layer, and Comparative Example 2 is the coating control group of the high-temperature mixing equipment. It can be seen that the retention rate of the cathode material using this scheme is significantly higher than that of the comparative example.

[0039] Example 2

[0040] A method for preparing a high-voltage, high-rate lithium cobalt oxide cathode material, used to fabricate the high-voltage, high-rate lithium cobalt oxide cathode material described in Example 1, includes the following steps:

[0041] S1. After weighing and mixing the lithium source, cobalt source, and Tm source according to the stoichiometric ratio, perform a first heat treatment to obtain lithium cobalt oxide-based LiCo. aTm 1-a O2, where 0.99 ≤ a ≤ 0.999; the lithium source is one or both of lithium carbonate and lithium hydroxide; the cobalt source is one or both of its oxide and carbonate, and the D50 of the cobalt source satisfies 3.5 μm ≤ D50 ≤ 6.5 μm; the Tm source is one or more of its oxide, hydroxide, and carbonate, and Tm is at least two of Mg, Al, Ti, Sr, and Zr;

[0042] S2. Mix the lithium cobaltate matrix material with MO x and add them to a planetary ball mill according to the designed mass ratio to obtain a mixed powder material; the M source is a nano-oxide, and the D50 of the M source ≤ 2.0 μm, where M contains at least five of Co, Al, Y, La, Zr, Ti, and Sr, 1 < x < 2 and the total valence is zero;

[0043] S3. Perform a second heat treatment on the mixed powder to obtain a high-voltage and high-rate lithium cobaltate cathode material.

[0044] By selecting one or both of lithium carbonate and lithium hydroxide as the lithium source, its reaction activity adapts to the synthesis requirements of the lithium cobaltate matrix, can fully react with the cobalt source and the Tm source during the heat treatment process, ensuring the uniform doping of lithium elements and the integrity of the crystal lattice; the cobalt source is selected as an oxide or carbonate and the D50 is controlled within 3.5 μm ≤ D50 ≤ 6.5 μm, which ensures the chemical stability of the raw materials, avoids the introduction of impurities, and through the appropriate particle size design, ensures the uniform mixing of the powder, improves the ion diffusion efficiency during the sintering process, and promotes the formation of a dense and highly crystalline matrix; the Tm source is one or more of an oxide, hydroxide, and carbonate, and Tm is at least two of Mg, Al, Ti, Sr, and Zr. The multi-form Tm source can adapt to different heat treatment reaction paths, ensuring that the Tm element is uniformly incorporated into the lithium cobaltate lattice and exerting the synergistic effect of multi-element doping on structural stability.

[0045] In S2, a nano-oxide with D50 ≤ 2.0 μm is used as the M source, and M contains at least five of Co, Al, Y, La, Zr, Ti, and Sr. The nano-scale particle size gives the M source a high specific surface area and reaction activity, enabling fine and uniform mixing with the lithium cobaltate matrix in a planetary ball mill, avoiding coating defects caused by agglomeration. The multi-element M source provides the material basis for the formation of a high-entropy oxide coating layer; the high-energy mixing method of planetary ball milling further strengthens the interfacial bonding between the matrix and the coating layer raw materials, laying the foundation for the formation of a firm coating structure during subsequent heat treatment.

[0046] The second heat treatment in S3 can promote MO xReact and crystallize sufficiently on the surface of the matrix to form an oxide coating layer with stable structure and strong bonding with the matrix, while solidifying the doping modification effect of the matrix. Through the coordinated cooperation of raw material selection, particle size control, multi-component design and step-by-step heat treatment in the whole preparation process, the lattice stability of the lithium cobaltate matrix and the uniform density of the oxide coating layer are ensured, and finally the improvement of high capacity, high rate and long cycle stability of the material under high voltage is achieved.

[0047] In this embodiment, the holding temperature of the first heat treatment in S1 is 950 °C - 1000 °C, the holding time is 7 - 10 hours, the heating rate is 3 - 5 °C / min, and the sintering atmosphere is air; the holding temperature of the second heat treatment in S3 is 750 °C - 850 °C, the holding time is 5 - 8 hours, the heating rate is 3 - 5 °C / min, and the sintering atmosphere is air.

[0048] The first heat treatment in S1 adopts a high temperature of 950 °C - 1000 °C, a long holding time of 7 - 10 hours and a slow heating rate of 3 - 5 °C / min, combined with an air oxidation atmosphere, which can not only provide sufficient thermodynamic conditions for the sufficient reaction of the lithium source, cobalt source and Tm source, promote ion cross-phase diffusion, ensure the uniform incorporation of Tm element into the lithium cobaltate lattice, form a layered matrix with complete crystallization and dense structure, and avoid lattice defects and segregation of doping elements caused by insufficient reaction; but also reduce the lattice stress caused by sudden temperature change through the slow heating rate, prevent crack generation, and at the same time the air atmosphere can maintain the stable valence state of Co 3+ to ensure the integrity of the layered structure of the matrix. The second heat treatment in S3 selects a medium temperature range of 750 °C - 850 °C and a holding time of 5 - 8 hours, combined with the same slow heating rate and air atmosphere, which not only avoids the lattice distortion of the matrix caused by high temperature or the overreaction of the coating layer and the matrix, but also promotes the sufficient crystallization of MO x on the surface of the matrix to form a high-entropy oxide coating layer with uniform density and strong interfacial bonding with the matrix. At the same time, the uniform distribution of multi-metal elements in the coating layer is ensured through an appropriate holding time, and the oxygen content and electrical neutrality of 1 < x < 2 are maintained; the consistent heating rate and air atmosphere of the two heat treatments form process synergy, which not only ensures the high crystallinity and doping uniformity of the matrix, but also guarantees the structural stability and interfacial compatibility of the coating layer, effectively avoiding problems such as lattice defects, element segregation, and coating layer peeling that may occur during the heat treatment process.

[0049] In this embodiment, the plasma ball mill in S2 uses a dual-path gas mixing system to supply a two-component pulsed gas source. The main gas source is 95-98 vol% compressed air, and the auxiliary gas source is 2-5 vol% fluorine-containing gas, which is CF4 or SF6. The on / off frequency of the auxiliary gas source is controlled by a pulse valve to be 5-10 Hz. During the ball milling process, the exhaust flow rate is 100 ml / min-300 ml / min, the ball milling speed is 500-960 rpm, and the ball milling time is 10-30 min.

[0050] The S2 plasma ball mill employs a dual-path gas mixing system to supply a two-component pulsed gas source. The main gas source, 95-98 vol% compressed air, maintains the oxidizing atmosphere during the ball milling process, ensuring the proper interaction between the lithium cobalt oxide substrate and MO. x The oxide phase of the raw material is stable, avoiding lattice defects caused by the reduction reaction; a 2-5 vol% CF4 or SF6 fluorine-containing auxiliary gas source is supplied alternately through a 5-10 Hz pulse on / off frequency, which can precisely control the amount of F introduced, avoiding excessive fluorine from damaging the material structure, and also ensure that F... + The particles, carried by the airflow, alternately act on the material surface, providing a uniform elemental basis for subsequent fluorine doping modification, interfacial bonding strengthening, and the formation of micro- and nano-porous structures. An exhaust flow rate of 100 ml / min-300 ml / min can promptly remove volatile byproducts (such as fluorides) generated during ball milling, preventing impurities from accumulating on the powder surface and maintaining stable gas composition within the chamber. A ball milling speed of 500-960 rpm paired with a ball milling time of 10-30 min provides sufficient collision energy to promote fine and uniform mixing of the lithium cobalt oxide matrix and the nano-M source, breaking up particle agglomeration, while avoiding particle breakage or lattice distortion caused by excessive ball milling. The synergistic effect of the above parameters ensures that the composition and intensity of high-energy particles remain uniform and stable during plasma ball milling. This not only enhances the interfacial bonding activity between the matrix and the coating material, but also provides a key guarantee for the formation of a uniform, dense, and firmly bonded fluorine-doped high-entropy oxide coating and micro-nano porous structure through precise control of the action mode and mixing degree of the fluorine element. This effectively improves the interfacial stability, mass transfer efficiency, and chemical corrosion resistance of the material.

[0051] The discharge parameters of the S2 plasma ball mill are dynamically adjusted according to the gradient. In the same ball milling stage, the discharge current is 1.8-2.0A and the duty cycle is 30% for the first 1 / 3 of the time, and the discharge current is 1.2-1.5A and the duty cycle is 60% for the second 2 / 3 of the time.

[0052] In S2 plasma ball milling, the discharge parameters are dynamically adjusted using a gradient. During the first third of the milling stage, a high current of 1.8-2.0 A combined with a low duty cycle of 30% is used to instantaneously generate high-energy-density plasma, releasing O2. + F +High-energy particles violently bombard the lithium cobalt oxide matrix and MO x At the interface of the coating material, the original surface chemical bonds are broken and a large number of dangling bonds are formed, creating active conditions for the subsequent formation of quaternary chemical bonds at the interface. In the latter two-thirds of the time, a low current of 1.2-1.5 A and a high duty cycle of 60% are switched to generate a medium-energy-density, long-duration plasma. This avoids excessive damage to the material lattice by high-energy particles and allows for the formation of a plasma through the continuous presence of F... + Particles achieve selective etching, precisely removing low-valence metal oxides from the material surface and generating volatile fluorides, thereby forming a micro / nano porous structure, while simultaneously promoting the partial deposition of fluorides. + O in particle replacement coating layer 2- Fluorine doping modification was completed. This gradient discharge design, characterized by "high-energy short pulse → medium-energy long duration," synergizes with the dual-component pulsed gas source. It activates interfacial bonding through high energy in the initial stage and completes porous structure construction and fluorine doping through gentle and continuous energy input in the later stage. This effectively avoids the problems of weak interfacial bonding, porous structure collapse, or uneven fluorine doping that often occur with single discharge parameters. Ultimately, it simultaneously strengthens the interfacial bonding strength and Li... + Conductivity and chemical corrosion resistance.

[0053] In this embodiment, the lithium cobalt oxide matrix material and MO x The design mass ratio is: the content of the coating layer accounts for 0.2%-0.9% of the matrix mass.

[0054] See Figures 1 to 4 , Figure 1 and Figure 2 The image presented shows electron micrographs of the finished cathode material and the mixture after being mixed in a plasma ball mill. Figure 3 The electron microscope images of the mixture after mixing using a high-speed mixer are presented. Figure 2 and Figure 3 The comparison shows that the materials present different forms. Figure 4 The high-temperature cycling retention rate graph is presented. Comparative Example 1 is the blank control group without a coating layer, and Comparative Example 2 is the coating control group of the high-temperature mixing equipment. It can be seen that the retention rate of the cathode material using this scheme is significantly higher than that of the comparative example.

[0055] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. Unless otherwise specified, an element defined by the phrase "comprising..." or "including..." does not exclude the presence of additional elements in the process, method, article, or terminal device that includes said element. Additionally, in this document, "greater than," "less than," "exceeding," etc., are understood to exclude the stated number; "above," "below," "within," etc., are understood to include the stated number.

[0056] The above description of the embodiments is provided to facilitate understanding and use of the present invention by those skilled in the art. It is obvious to those skilled in the art that various modifications can be easily made to the embodiments, and the general principles described herein can be applied to other embodiments without creative effort. Therefore, the present invention is not limited to the above embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the protection scope of the present invention.

Claims

1. A high-voltage high-rate lithium cobalt oxide cathode material, characterized in that, A lithium cobalt oxide-based material comprising a lithium cobalt oxide base material and an oxide coating layer coated on the lithium cobalt oxide base material, the lithium cobalt oxide base material having a chemical formula of LiCoaTm1-aO2, wherein 0.99≤a≤0.999, Tm is at least two of Mg, Al, Ti, Sr, and Zr; the oxide coating layer having a chemical formula of MOx x , wherein M comprises at least five of Co, Al, Y, La, Zr, Ti, and Sr, 1 x x Y , wherein y≤0.1; Prepared by the following steps: S1, a lithium source, a cobalt source, a Tm source are mixed according to the chemical stoichiometric ratio, and then subjected to first heat treatment to obtain a cobalt acid lithium matrix LiCoaTm1-aO2, wherein 0.99≤a≤0.999; the lithium source is one or both of lithium carbonate and lithium hydroxide; the cobalt source is one or both of its oxide and carbonate, and the D50 of the cobalt source satisfies 3.5μm≤D50≤6.5μm; the Tm source is one or more of its oxide, hydroxide, and carbonate, and the Tm is at least two of Mg, Al, Ti, Sr, and Zr; S2, the cobalt acid lithium matrix material and MOx are mixed in a plasma ball mill according to the designed mass ratio to obtain a mixed powder material; the M source is a nano-oxide, and the D50 of the M source is ≤2.0μm, wherein M contains at least five of Co, Al, Y, La, Zr, Ti, and Sr, 1<x<2 and the total valence is zero; S3, the mixed powder is subjected to second heat treatment to obtain a high-voltage high-rate cobalt acid lithium positive electrode material; In S2, the double-component pulse type gas sources are supplied by a double-path gas mixing system in the plasma ball milling, the main gas source is 95-98vol% compressed air, and the auxiliary gas source is 2-5vol% fluorine-containing gas, the fluorine-containing gas is CF4 or SF6, the on-off frequency of the auxiliary gas source is controlled by a pulse valve at 5-10Hz; the exhaust flow rate during ball milling is 100ml / min-300ml / min, the ball milling speed is 500-960rpm, and the ball milling time is 10-30min; In S2, the discharge parameters of the plasma ball milling are dynamically adjusted according to the gradient, in the same ball milling stage, the discharge current is 1.8-2.0A and the duty cycle is 30% in the first 1 / 3 time, and the discharge current is 1.2-1.5A and the duty cycle is 60% in the last 2 / 3 time.

2. The high-voltage high-rate LiCoO4 cathode material of claim 1, wherein, The thickness of the oxide coating layer is 1nm-500nm.

3. The high-voltage high-rate LiCoO4 cathode material of claim 1, wherein, The material surface has a micro-nano porous structure with a pore size of 5-50nm, and the specific surface area is ≥3.0m² / g.

4. The high-voltage high-rate LiCoO2 cathode material of claim 1, wherein, The cobalt source for preparing the cobalt acid lithium matrix is an oxide or a carbonate, and the D50 of the cobalt source satisfies 3.5μm≤D50≤6.5μm.

5. The high-voltage high-rate LiCoO2 cathode material of claim 1, wherein, The M source for preparing the oxide coating layer is a nano-oxide, and the D50 of the M source is ≤2.0μm.

6. A method for preparing a high-voltage high-rate lithium cobalt oxide cathode material, characterized in that, Comprising the following steps: S1, a lithium source, a cobalt source, and a Tm source are mixed according to a stoichiometric ratio, and then subjected to first heat treatment to obtain a cobalt acid lithium-based material LiCoaTm1-aO2, wherein 0.99≤a≤0.999; the lithium source is one or both of lithium carbonate and lithium hydroxide; the cobalt source is one or both of an oxide and a carbonate of cobalt, and the D50 of the cobalt source satisfies 3.5μm≤D50≤6.5μm; and the Tm source is one or more of an oxide, a hydroxide, and a carbonate of Tm, and the Tm is at least two of Mg, Al, Ti, Sr, and Zr; S2, the cobalt acid lithium-based material is mixed with MOx in a designed mass ratio in a plasma ball mill to obtain a mixed powder material; the M source is a nano-oxide, and the D50 of the M source satisfies D50≤2.0μm, wherein M includes at least five of Co, Al, Y, La, Zr, Ti, and Sr, 1<x<2, and the total valence is zero; S3, the mixed powder is subjected to second heat treatment to obtain a high-voltage high-rate cobalt acid lithium positive electrode material; In S2, a double-component pulse gas source is supplied by a double-path gas mixing system in the plasma ball mill, the main gas source is 95-98vol% compressed air, and the auxiliary gas source is 2-5vol% fluorine-containing gas, the fluorine-containing gas is CF4 or SF6, the on-off frequency of the auxiliary gas source is controlled by a pulse valve at 5-10Hz, the exhaust flow rate during ball milling is 100ml / min-300ml / min, the ball milling speed is 500-960rpm, and the ball milling time is 10-30min; In S2, the discharge parameters of the plasma ball mill are dynamically adjusted according to a gradient, in the same ball milling stage, the discharge current is 1.8-2.0A and the duty cycle is 30% in the first 1 / 3 time, and the discharge current is 1.2-1.5A and the duty cycle is 60% in the last 2 / 3 time.

7. The method for preparing a high-voltage, high-rate lithium cobalt oxide cathode material according to claim 6, characterized in that, In S1, the holding temperature of the first heat treatment is 950-1000℃, the holding time is 7-10 hours, the heating rate is 3-5℃ / min, and the sintering atmosphere is air; in S3, the holding temperature of the second heat treatment is 750-850℃, the holding time is 5-8 hours, the heating rate is 3-5℃ / min, and the sintering atmosphere is air.

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