Preparation method of modified lithium cobalt oxide positive electrode material with high temperature stability

Abstract

The application provides a preparation method of a modified lithium cobaltate positive electrode material with high-temperature stability. First, nanoscale raw materials of cobalt salt and lithium salt are mixed uniformly to obtain a mixture, which is placed in an air atmosphere to be subjected to first calcination, and the particles after the calcination are crushed to obtain a lithium cobaltate positive electrode material; the lithium cobaltate positive electrode material is mixed with a titanium source to be subjected to second calcination, so as to obtain titanium element surface-modified lithium cobaltate; finally, the titanium element surface-modified lithium cobaltate is mixed with a strontium source and a manganese source to be subjected to third calcination, so that most of the surface-modified titanium element is converted into a titanium strontium manganese oxygen coating layer, but a small part of the titanium element still forms a gradient doping on the surface, and therefore a large-particle lithium cobaltate positive electrode material with double modification of doping and coating can be obtained. The obtained lithium cobaltate positive electrode material has the advantages of high capacity and good high-temperature cycle stability, and has the advantages of simple preparation process, high production efficiency, good product uniformity and suitability for large-scale production.

Description

Technical Field

[0001] This invention relates to the field of new energy battery materials technology, specifically to a method for preparing a modified lithium cobalt oxide cathode material with high-temperature stability. Background Technology

[0002] With rapid technological advancements, lithium-ion batteries have become the core power source for consumer electronics, electric vehicles, and large-scale energy storage. As a mainstream cathode material, lithium cobalt oxide (LiCoO2) has long dominated the 3C market due to its high specific capacity, stable discharge platform, and excellent cycle life. However, the ever-increasing demands of end-devices for energy density, fast charging capabilities, and adaptability to extreme environments have forced the industry to widely adopt a "large-size particle gradation" strategy to compact the electrode and increase capacity. Unfortunately, as particle size increases, the intrinsic defects of the material under high temperature and high voltage—lattice distortion, intensified phase transitions, and a surge in interfacial side reactions—are amplified exponentially, leading to a significant increase in cycle degradation and thermal runaway risks. Even more serious is the fact that large-particle lithium cobalt oxide decomposes and releases oxygen at high temperatures, further catalyzing electrolyte oxidation, creating a vicious cycle that simultaneously reduces safety and reliability. Therefore, how to enhance the high-temperature stability of large-particle lithium cobalt oxide without sacrificing specific capacity has become a crucial technological hurdle that next-generation high-energy-density batteries must overcome.

[0003] The current mainstream modification strategies for lithium cobalt oxide cathode materials can be summarized into three routes: bulk doping—introducing elements such as Al, Mg, Ti, P, and F to stabilize the crystal lattice and suppress phase transitions; surface coating—constructing inert layers such as oxides, phosphates, and fluorides to block electrolyte erosion; and process optimization—finely controlling the sintering curve and precursor morphology to improve crystal integrity. However, these strategies still have drawbacks: doping easily generates impurity phases, and it is difficult to balance the uniformity of the coating layer with high-temperature stability; the crystallization defects and excessively wide particle size distribution caused by the growth of large single-core particles force extremely stringent process windows, leading to increased yield and cost. In other words, existing solutions have not yet found the optimal solution within the "performance-cost-process feasibility" triangle constraint.

[0004] Looking to the future, there is an urgent need to develop a large-particle lithium cobalt oxide cathode material that combines high capacity, high-temperature stability, low cost, and ease of large-scale production. This has become a core challenge that the lithium-ion battery field urgently needs to overcome. Summary of the Invention

[0005] To address the technical problems existing in the prior art, this invention provides a method for preparing a modified lithium cobalt oxide cathode material with high-temperature stability. The method for preparing the modified lithium cobalt oxide cathode material of this invention changes the previous method of growing large single crystals from single nuclei, adopting a method of growing large particles from nanoparticles through multi-nuclei growth. This improves the crystallinity of the material, and the unique perovskite structure coating significantly enhances the cycle stability of the battery at high temperatures. The resulting lithium cobalt oxide cathode material has the advantages of high capacity and good high-temperature cycle stability. Furthermore, the preparation process is simple, production efficiency is high, product uniformity is good, and it is suitable for large-scale production.

[0006] The specific technical solution of the present invention is as follows: A method for preparing a modified lithium cobalt oxide cathode material with high-temperature stability, comprising the following steps:

[0007] (1) Mix the nano-sized raw materials cobalt salt and lithium salt evenly to obtain a mixture;

[0008] (2) After the mixture is made into particles, it is placed in an air atmosphere and calcined for the first time. The calcined particles are crushed to obtain lithium cobalt oxide cathode material with a diameter of 10-30 micrometers.

[0009] (3) The lithium cobalt oxide cathode material and the titanium source are mixed according to the molar ratio of Co in the lithium cobalt oxide cathode material to Ti in the titanium source being 1:(γ×δ), and the mixture is calcined for the second time to obtain titanium-modified lithium cobalt oxide, wherein 0<γ≤0.1, 0<δ≤1;

[0010] (4) The titanium-modified lithium cobalt oxide is mixed with strontium source and manganese source according to the molar ratio of Ti in the titanium-modified lithium cobalt oxide: Sr in the strontium source: Mn in the manganese source as δ: (1-δ): 1. Then, it is calcined for the third time. After the third calcination, most of the surface-modified titanium obtained in step (3) is transformed into titanium-strontium-manganese-oxygen coating layer, but a small part of titanium still forms gradient doping on the surface. Therefore, a large particle lithium cobalt oxide cathode material with doping and coating can be obtained.

[0011] Furthermore, in step (1), the lithium salt is at least one of lithium carbonate, lithium hydroxide, and lithium acetate, with a particle size of 5-10 nm; the cobalt source is at least one of cobalt sulfate, cobalt nitrate, cobalt chloride, cobalt acetate, and cobalt tetroxide, with a particle size of 5-10 nm.

[0012] Furthermore, the particle size of the particles produced in step (2) is 3-80 mesh; the crushing in step (2) is plow crushing with a frequency of 10-70 Hz.

[0013] Furthermore, the titanium source in step (3) is at least one of titanium dioxide, titanium monoxide, titanium trioxide, titanium tetrachloride, titanium trichloride, and titanium trifluoride.

[0014] Furthermore, in step (4), the strontium source is at least one of strontium carbonate, strontium nitrate, strontium oxide, strontium hydroxide, strontium chloride, strontium sulfate, strontium fluoride, strontium titanate, strontium chromate, and strontium peroxide; and the manganese source is at least one of manganese oxide, manganese hydroxide, manganese sulfate, manganese chloride, manganese carbonate, manganese trioxide, manganese dioxide, manganese fluoride, and manganese acetate.

[0015] Furthermore, the first calcination temperature is 800-1100℃, and the calcination time is 5-24h; the second calcination temperature is 300-500℃, and the calcination time is 0.5-3h; the third calcination temperature is 300-900℃, and the calcination time is 1-5h, with the calcination atmosphere being air, oxygen, nitrogen, or argon.

[0016] This invention also discloses a modified lithium cobalt oxide cathode material with the general molecular formula: LiCoO2@γTi δ Sr 1-δ MnO3, of which Ti δ Sr 1-δ MnO3 is the molecule of the coating material.

[0017] Compared with the prior art, the beneficial effects of the present invention are:

[0018] This invention proposes a disruptive strategy for preparing large particles: using highly active nanocrystals synthesized from nanoscale lithium and cobalt sources as "seeds," breaking through the path dependence of traditional single-core growth of large-particle raw materials. Traditional single-core methods are limited by poor crystallinity, narrow process windows, and difficulty in controlling particle size. This method, however, achieves "multi-core co-growth" through the synergistic assembly of multiple nanocrystals, significantly improving crystallinity, simplifying reaction conditions, and allowing for precise control of particle size distribution. Based on this, a perovskite-type coating layer is constructed in situ on the surface, enabling large particles to maintain a stable framework under high temperature and high voltage, thus endowing the lithium cobalt oxide cathode material with excellent layered structure, superior thermal stability, and reliable electrochemical performance, meeting the urgent needs of modern electronic devices for high-performance lithium-ion batteries. The lithium cobalt oxide cathode material of this invention maintains a capacity retention of 90% after 1000 cycles at high rate at room temperature. Under high load (13 mg / cm³), the capacity retention is also achieved. 2 At 45°C for 50 cycles, the capacity retention rate can reach 93% (see Table 1).

[0019] Compared to traditional preparation methods, the preparation process of this invention is simpler, significantly reduces production costs, and greatly improves production efficiency. Furthermore, the prepared product exhibits high homogeneity (sampling performance from various points in the same batch of synthesized material shows high consistency), making it highly suitable for large-scale production applications. In addition, the reaction raw materials used in this invention are readily available and low-cost, require no special protective measures during production, and the reaction conditions are easy to control. The prepared product not only yields a considerable amount but also demonstrates good reproducibility. Attached Figure Description

[0020] Figure 1 The image shows the XRD pattern of the uncoated lithium cobalt oxide cathode material prepared in Example 1 of this invention.

[0021] Figure 2 The image shows the XRD pattern of the unmodified lithium cobalt oxide cathode material prepared in Comparative Example 1.

[0022] Figure 3 This is a granulation diagram from Example 1 of the present invention;

[0023] Figure 4 The discharge specific capacity cycling comparison diagram of the modified lithium cobalt oxide cathode material prepared in Example 1 of the present invention and the unmodified lithium cobalt oxide cathode material prepared in Comparative Example 1 under the conditions of 25℃ 5C (1000mA / g) and 4.6V cutoff voltage is shown.

[0024] Figure 5 The modified lithium cobalt oxide cathode material prepared in Example 1 of this invention and the unmodified lithium cobalt oxide cathode material prepared in Comparative Example 1 are compared under high loading (13 mg / cm²). 2 A comparison of discharge specific capacity cycling under 45℃ 1C (200 mA / g) and 4.6V cutoff voltage conditions. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will now be clearly and completely described with reference to the accompanying drawings. Unless otherwise specified, the reagents, equipment, and materials described in the embodiments and comparative examples are all commercially available.

[0026] The testing methods for various properties of the modified lithium cobalt oxide cathode materials prepared in the examples and comparative examples are as follows: X-ray diffraction (XRD): The testing instrument was a Dandong Haoyuan XRD instrument, model DX-2700BH. The radiation source was CuKα, the tube voltage was set to 40kV, and the tube current was set to 30mA. During the scanning process, the scanning rate was controlled at 2° / min to ensure data accuracy. The scanning range of the 2θ angle was 10° to 80° to cover a wider range of material structure information.

[0027] Lithium-ion battery cycle performance testing: The lithium cobalt oxide cathode materials prepared in the examples and comparative examples were used to make cathode sheets, which were then assembled into lithium-ion batteries with a cathode sheet, separator, and electrolyte. The discharge specific capacity cycle and average voltage were then tested under 5C (400mA / g) and 4.6V cutoff voltage conditions. The specific steps were as follows: Lithium cobalt oxide cathode material, SP (conductive carbon black), PVDF (polyvinylidene fluoride), and an appropriate amount of NMP were prepared in a mass ratio of 9:0.5:0.5 and mixed together. The mixture was stirred on a magnetic stirrer until homogeneous. The prepared slurry was coated onto the electrode sheet and transferred to a vacuum drying oven for vacuum drying at 120℃ for 12 hours. The electrode sheet was cut into 12mm round pieces for battery assembly. In a glove box, the cathode shell, cathode sheet, separator, lithium sheet, and cathode shell were assembled in that order, using LiPF6 electrolyte. After assembly, a lithium-ion battery was obtained. This invention utilizes the LANHECT2001A charge / discharge instrument from Wuhan Lanbo Electronics Co., Ltd. to conduct constant current charge / discharge and cycle performance tests. At 45℃, under high load (13mg / cm³), the test was performed. 2 The test method for discharge specific capacity cycle performance under 1C discharge rate and 4.6V cutoff voltage conditions is the same as above.

[0028] The cobalt tetroxide, cobalt nitrate, cobalt acetate, cobalt sulfate, lithium acetate, lithium carbonate, and lithium hydroxide used in this embodiment are nanoscale raw materials with a particle size of 5-10 nm.

[0029] Example 1

[0030] This embodiment discloses a method for preparing a modified lithium cobalt oxide cathode material, including the following steps:

[0031] (1) Cobalt tetroxide and lithium carbonate were mixed evenly according to the molar ratio of Co in cobalt tetroxide to Li in lithium carbonate being 1:1.07;

[0032] (2) The mixture is made into particles with a particle size of 7 mesh (e.g. Figure 3 As shown in the figure), the particles are then calcined at 900°C for 10 hours in air atmosphere. The calcined particles are then crushed with a plow at 50 Hz to obtain large-particle (18-20 micrometers) lithium cobalt oxide cathode material.

[0033] (3) Mix large-particle lithium cobalt oxide cathode material with titanium dioxide at a molar ratio of Co in lithium cobalt oxide cathode material to Ti in titanium dioxide of 1:0.007; then calcine the uniformly mixed mixture at 500°C for 0.5 hours to obtain titanium dioxide surface-modified lithium cobalt oxide.

[0034] (4) The titanium-modified lithium cobalt oxide, strontium oxide and manganese oxide are mixed with each other according to the molar ratio of Ti in the titanium-modified lithium cobalt oxide, Sr in the strontium oxide and Mn in the manganese oxide being 0.7:0.3:1. The mixture is then calcined in air at 400°C for 4 hours to obtain the target product.

[0035] Example 2

[0036] This embodiment discloses a method for preparing a modified lithium cobalt oxide cathode material, including the following steps:

[0037] (1) Cobalt tetroxide and lithium hydroxide were mixed evenly according to the molar ratio of Co to Li in cobalt hydroxide as 1:1.04.

[0038] (2) The mixture is made into particles with a particle size of 20 mesh and calcined in air at 900°C for 12 hours. The calcined particles are crushed with a plow at 30 Hz to obtain large particles (13-15 micrometers) of lithium cobalt oxide cathode material.

[0039] (3) Mix large-particle lithium cobalt oxide cathode material with titanium monoxide at a molar ratio of Co in lithium cobalt oxide cathode material to Ti in titanium monoxide of 1:0.0045; then calcine the uniformly mixed mixture at 450°C for 1.5 hours to obtain titanium monoxide-modified lithium cobalt oxide.

[0040] (4) Titanium-modified lithium cobalt oxide is mixed with strontium carbonate and manganese hydroxide in a molar ratio of Ti in titanium-modified lithium cobalt oxide: Sr in strontium carbonate: Mn in manganese hydroxide of 0.9:0.1:1. The mixture is then calcined in air at 700°C for 2 hours to obtain the target product.

[0041] Example 3

[0042] This embodiment discloses a method for preparing a modified lithium cobalt oxide cathode material, including the following steps:

[0043] (1) Cobalt nitrate and lithium carbonate are mixed evenly according to the molar ratio of Co in cobalt nitrate to Li in lithium carbonate of 1:1.03;

[0044] (2) The mixture is made into particles with a particle size of 5 mesh and calcined in air at 1000°C for 8 hours. The calcined particles are crushed with a plow at 10 Hz to obtain large particles (20-22 micrometers) of lithium cobalt oxide cathode material.

[0045] (3) Mix large-particle lithium cobalt oxide cathode material with titanium trioxide at a molar ratio of Co in lithium cobalt oxide cathode material to Ti in titanium trioxide of 1:0.014; then calcine the uniformly mixed mixture at 400℃ for 1 hour to obtain lithium cobalt oxide modified with titanium trioxide surface.

[0046] (4) The titanium-modified lithium cobalt oxide is mixed with strontium nitrate and manganese chloride in a molar ratio of Ti in the titanium-modified lithium cobalt oxide: Sr in strontium nitrate: Mn in manganese chloride of 0.8:0.2:1. The mixture is then calcined at 550°C for 4 hours in an oxygen atmosphere to obtain the target product.

[0047] Example 4

[0048] This embodiment discloses a method for preparing a modified lithium cobalt oxide cathode material, including the following steps:

[0049] (1) Cobalt acetate and lithium hydroxide were mixed evenly according to the molar ratio of Co in cobalt acetate to Li in lithium hydroxide of 1:1.04;

[0050] (2) The mixture is made into particles with a particle size of 3 mesh and calcined in air at 920°C for 14 hours. The calcined particles are crushed with a plow at 60 Hz to obtain large particles (13-15 micrometers) of lithium cobalt oxide cathode material.

[0051] (3) Mix large-particle lithium cobalt oxide cathode material with titanium trifluoride according to the molar ratio of Co in lithium cobalt oxide cathode material to Ti in titanium trifluoride of 1:0.008; then calcine the uniformly mixed mixture at 350°C for 2 hours to obtain lithium cobalt oxide with titanium trifluoride surface modification.

[0052] (4) Titanium-modified lithium cobalt oxide is mixed with strontium hydroxide and manganese hydroxide according to the molar ratio of Ti in titanium-modified lithium cobalt oxide: Sr in strontium hydroxide: Mn in manganese hydroxide being 0.8:0.2:1. The mixture is then calcined at 500°C for 3 hours in a nitrogen atmosphere to obtain the target product.

[0053] Example 5

[0054] This embodiment discloses a method for preparing a modified lithium cobalt oxide cathode material, including the following steps:

[0055] (1) Cobalt acetate and lithium acetate are mixed evenly according to the molar ratio of Co in cobalt acetate to Li in lithium acetate of 1:1.02;

[0056] (2) The mixture is made into particles with a particle size of 15 mesh and calcined in air at 950°C for 12 hours. The calcined particles are crushed with a plow at 40 Hz to obtain large particles (10-13 micrometers) of lithium cobalt oxide cathode material.

[0057] (3) Large-particle lithium cobalt oxide cathode material was mixed with titanium trichloride at a molar ratio of Co to Ti in the lithium cobalt oxide cathode material of 1:0.016. The uniformly mixed material was then calcined at 400°C for 2 hours to obtain lithium cobalt oxide with titanium trichloride surface modification.

[0058] (4) The titanium-modified lithium cobalt oxide is mixed with strontium hydroxide and manganese hydroxide according to the molar ratio of Ti in the titanium-modified lithium cobalt oxide: Sr in strontium hydroxide: Mn in manganese hydroxide being 0.8:0.2:1. Then it is calcined in air at 800°C for 2 hours to obtain the target product.

[0059] Example 6

[0060] (1) Cobalt nitrate and lithium carbonate are mixed evenly according to the molar ratio of Co in cobalt nitrate to Li in lithium carbonate of 1:1.08;

[0061] (2) The mixture is made into particles with a particle size of 30 mesh and calcined in air at 950°C for 12 hours. The calcined particles are crushed with a plow at 40 Hz to obtain large particles (10-12 micrometers) of lithium cobalt oxide cathode material.

[0062] (3) Mix large-particle lithium cobalt oxide cathode material with titanium trioxide at a molar ratio of Co in lithium cobalt oxide cathode material to Ti in titanium trioxide of 1:0.027; then calcine the uniformly mixed mixture at 400℃ for 2 hours to obtain lithium cobalt oxide modified with titanium trioxide surface;

[0063] (4) The titanium-modified lithium cobalt oxide is mixed with strontium sulfate and manganese carbonate in a molar ratio of Ti in the titanium-modified lithium cobalt oxide: Sr in the strontium sulfate: Mn in the manganese carbonate of 0.9:0.1:1. The mixture is then calcined in air at 800°C for 2 hours to obtain the target product.

[0064] Example 7

[0065] This embodiment discloses a method for preparing a modified lithium cobalt oxide cathode material, including the following steps:

[0066] (1) Cobalt sulfate and lithium hydroxide are mixed evenly according to the molar ratio of Co in cobalt sulfate to Li in lithium hydroxide of 1:1.09;

[0067] (2) The mixture is made into particles with a particle size of 7 mesh and calcined in air at 950°C for 12 hours. The calcined particles are crushed with a plow at 20 Hz to obtain large particles (20-22 micrometers) of lithium cobalt oxide cathode material.

[0068] (3) Mix large-particle lithium cobalt oxide cathode material with titanium trioxide at a molar ratio of Co in lithium cobalt oxide cathode material to Ti in titanium trioxide of 1:0.016; then calcine the uniformly mixed mixture at 400℃ for 2 hours to obtain lithium cobalt oxide with titanium trioxide surface modification.

[0069] (4) The titanium-modified lithium cobalt oxide, strontium titanate, and manganese trioxide are mixed with each other according to the molar ratio of Ti in the titanium-modified lithium cobalt oxide, Sr in the strontium titanate, and Mn in the manganese trioxide being 0.8:0.2:1. The mixture is then calcined at 300°C for 3 hours in an argon atmosphere to obtain the target product.

[0070] Example 8

[0071] This embodiment discloses a method for preparing a modified lithium cobalt oxide cathode material, including the following steps:

[0072] (1) Cobalt tetroxide and lithium acetate were mixed evenly according to the molar ratio of Co to Li in lithium acetate being 1:1.1.

[0073] (2) The mixture is made into particles with a particle size of 9 mesh and calcined in air at 950°C for 12 hours. The calcined particles are crushed with a plow at 45 Hz to obtain large particles (19-21 micrometers) of lithium cobalt oxide cathode material.

[0074] (3) Mix large-particle lithium cobalt oxide cathode material with titanium tetrachloride at a molar ratio of Co:Ti in the lithium cobalt oxide cathode material of 1:0.016; then calcine the uniformly mixed mixture at 400°C for 2 hours to obtain lithium cobalt oxide with titanium tetrachloride surface modification.

[0075] (4) The titanium-modified lithium cobalt oxide, strontium peroxide, and manganese acetate were mixed in a molar ratio of Ti in the titanium-modified lithium cobalt oxide, Sr in the strontium peroxide, and Mn in the manganese acetate of 0.8:0.2:1. The mixture was then calcined at 500°C for 3 hours in an oxygen atmosphere to obtain the target product.

[0076] Comparative Example 1

[0077] This comparative example discloses a method for preparing a lithium cobalt oxide cathode material, including the following steps:

[0078] (1) Cobalt tetroxide and lithium carbonate were mixed evenly according to the molar ratio of Co in cobalt tetroxide to Li in lithium carbonate being 1:1.07;

[0079] (2) Sintering: The mixture is calcined in air at 900°C for 10 hours to obtain lithium cobalt oxide cathode material.

[0080] Comparative Example 2

[0081] The only difference between this comparative example and Example 1 is that step (4) is omitted; otherwise, they are exactly the same as Example 1.

[0082] Comparative Example 3

[0083] The only difference between this comparative example and Example 1 is that step (4) is performed first, followed by step (3), while everything else is exactly the same as Example 1.

[0084] Figure 1 The XRD pattern of the uncoated lithium cobalt oxide cathode material prepared in Example 1 of this invention is shown. Figure 2 This is the XRD pattern of the lithium cobalt oxide cathode material prepared in Comparative Example 1. From... Figure 1 As can be seen, no impurity peaks appeared in the XRD patterns of Example 1 and Comparative Example 1, indicating that both materials have high purity. However, the XRD diffraction peak intensity of the large-particle lithium cobalt oxide cathode material sintered after granulation in Example 1 is significantly higher than that of the ungranulated and sintered material in Comparative Example 1. This result indicates that the granulated and sintered lithium cobalt oxide cathode material has higher crystallinity and a more regular layered structure.

[0085] Figure 4 This paper presents a comparison of the discharge specific capacity cycle performance of the modified lithium cobalt oxide cathode material prepared in Example 1 of the present invention and the unmodified lithium cobalt oxide cathode material in Comparative Example 1 under the conditions of discharge rate at 25℃ and 5C (1000mA / g) and cutoff voltage of 4.6V. Figure 5 This demonstrates that these two materials exhibit high loading capacity (13 mg / cm³) at 45°C. 2 A comparison of discharge specific capacity cycle performance under 1C discharge rate and 4.6V cutoff voltage conditions. (This is achieved through comparison.) Figure 4 and Figure 5 It can be observed that the modified lithium cobalt oxide cathode material prepared by this invention exhibits significant optimization effects compared to the unmodified material in terms of increasing capacity, slowing down capacity decay, and suppressing structural degradation at high temperatures.

[0086] At 45°C, the various lithium cobalt oxide coin cells were tested under high load (13 mg / cm³). 2 The cycling performance at 1C rate was measured, and the capacity retention rate after 50 cycles was calculated. The test results are shown in Table 1.

[0087] Table 1. Preparation conditions and capacity retention after 50 cycles for Examples 1-8 and Comparative Examples 1-3

[0088]

[0089] As shown in Table 1, the positive electrode materials prepared using Examples 1-8 of the present invention all exhibit superior cycle stability. After 50 cycles, the capacity retention rate can be maintained within a favorable range of 85.8-93.5%.

[0090] Compared to Comparative Example 2, Example 2 doped the cathode material with a certain amount of Ti, which effectively stabilized the layered structure and prevented phase transition to some extent. Compared to the unmodified lithium cobalt oxide cathode material (Comparative Example 1), it improved cycle stability to a certain extent, with a 6.1% increase in capacity retention after 50 cycles (see Table 1). However, this method still has the following drawbacks: the surface-modified Ti reacts with LiPF6 in the electrolyte during cycling, leading to instability at the cathode-electrolyte interface and loss of Ti from the bulk phase. In contrast, Example 1 coated perovskite-structured titanium strontium manganese oxide onto Ti-doped LiCoO2, effectively suppressing interfacial side reactions and significantly improving the high-temperature cycling performance of the battery, maintaining a 93.5% capacity retention after 50 cycles.

[0091] Compared with Comparative Example 3, Example 1 formed a complete titanium-strontium-manganese oxide coating layer on the surface, which greatly improved the electrochemical characteristics of the coating layer. It not only did not affect the crystallinity of lithium cobalt oxide material, but also had high ionic conductivity, thus improving the overall cycle stability. In contrast, Comparative Example 3 did not form a complete coating layer. Under the same conditions, its internal crystal structure was affected by factors such as battery polarization and electrolyte degradation. As a result, the battery assembled in Example 3 had a shorter test life, and the capacity retention rate after 50 cycles decreased by 10.6% compared with Example 1.

Claims

1. A method for preparing a modified lithium cobalt oxide cathode material with high-temperature stability, characterized in that, Includes the following steps: (1) Mix the nano-sized raw material cobalt salt and lithium salt evenly to obtain a mixture; the lithium salt is at least one of lithium carbonate, lithium hydroxide, and lithium acetate, with a particle size of 5-10 nm; the cobalt source is at least one of cobalt sulfate, cobalt nitrate, cobalt chloride, cobalt acetate, and cobalt tetroxide, with a particle size of 5-10 nm; (2) After the mixture is made into particles, it is placed in an air atmosphere and calcined for the first time. The calcined particles are crushed to obtain lithium cobalt oxide cathode material with a diameter of 10-30 micrometers. (3) The lithium cobalt oxide cathode material and the titanium source are mixed according to the molar ratio of Co in the lithium cobalt oxide cathode material to Ti in the titanium source being 1:(γ×δ), and the mixture is calcined for the second time to obtain titanium-modified lithium cobalt oxide, wherein 0<γ≤0.1, 0<δ≤1; (4) The titanium-modified lithium cobalt oxide is mixed with strontium source and manganese source according to the molar ratio of Ti in the titanium-modified lithium cobalt oxide: Sr in the strontium source: Mn in the manganese source as δ: (1-δ):

1. Then, it is calcined for the third time. After the third calcination, most of the surface-modified titanium obtained in step (3) is transformed into titanium-strontium-manganese-oxygen coating layer, but a small part of titanium still forms gradient doping on the surface. Therefore, a large particle modified lithium cobalt oxide cathode material with doping and coating is obtained.

2. The preparation method according to claim 1, characterized in that, The particle size of the particles produced in step (2) is 3-80 mesh; the crushing in step (2) is plow crushing, and the frequency is 10-70HZ.

3. The preparation method according to claim 1, characterized in that, The titanium source in step (3) is at least one of titanium dioxide, titanium monoxide, titanium trioxide, titanium tetrachloride, titanium trichloride, and titanium trifluoride.

4. The preparation method according to claim 1, characterized in that, The strontium source in step (4) is at least one of strontium carbonate, strontium nitrate, strontium oxide, strontium hydroxide, strontium chloride, strontium sulfate, strontium fluoride, strontium titanate, strontium chromate, and strontium peroxide.

5. The preparation method according to claim 1, characterized in that, The manganese source in step (4) is at least one of manganese oxide, manganese hydroxide, manganese sulfate, manganese chloride, manganese carbonate, manganese trioxide, manganese dioxide, manganese fluoride, and manganese acetate.

6. The preparation method according to claim 1, characterized in that, The first calcination is carried out at a temperature of 800-1100℃ for 5-24 hours; the second calcination is carried out at a temperature of 300-500℃ for 0.5-3 hours.

7. The preparation method according to claim 1, characterized in that, The third calcination is carried out at a temperature of 300-900℃ for 1-5 hours, and the calcination atmosphere is air, oxygen, nitrogen or argon.

8. The modified lithium cobalt oxide cathode material obtained by the preparation method according to any one of claims 1-7, characterized in that, The general molecular formula is: LiCoO2@γTi δ Sr 1-δ MnO3, of which Ti δ Sr 1-δ MnO3 is the molecule of the coating material.

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