Preparation method of high-stable high-nickel positive electrode material
By optimizing the preparation process of high-nickel cathode materials through a multi-step sintering strategy, the stability and electrochemical performance problems of high-nickel cathode materials in the existing technology have been solved, realizing the preparation of high-stability and low-cost high-nickel cathode materials and improving electrochemical performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ZHEJIANG UNIV
- Filing Date
- 2026-01-23
- Publication Date
- 2026-05-29
AI Technical Summary
Existing high-nickel cathode materials face problems such as cation mixing, grain boundary microcracks, bulk structure deterioration, and interfacial side reactions in practical applications, leading to electrochemical performance degradation and accelerated capacity decay. Traditional methods are costly and complicated, and cannot meet the ultra-high capacity requirements of the market.
By employing a multi-stage sintering (MSS) strategy, while maintaining the hexagonal layered structure, the introduction of lithium salts or dopants is reduced by controlling sintering process parameters and precursor preparation, thereby optimizing the orderliness of the cation structure and preparing a high-stability, high-nickel cathode material.
This achievement enables higher cation ordering and lower lithium-nickel mixing, improves the electrochemical performance of high-nickel cathode materials, reduces production costs, and provides a new approach for industrialization.
Smart Images
Figure CN122102226A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of lithium-ion battery cathode material technology, specifically relating to a method for preparing a highly stable high-nickel cathode material. Background Technology
[0002] The continued consumption of fossil fuels has brought severe challenges such as environmental pollution and exacerbated the greenhouse effect, driving an increasingly urgent global demand for new energy storage technologies. Lithium-ion batteries, due to their high energy density, ease of use, and environmental friendliness, have become a research hotspot in the energy storage field. Among high-performance cathode materials, high-nickel cathode material LiNi... x Co y Mn 1-x-y O2 (NCM, with a nickel content of x ≥ 0.8) is considered an important candidate material for next-generation power batteries due to its high specific capacity, good cycle performance, and relatively reasonable cost. However, this type of material still faces many challenges in practical applications, such as cation mixing, grain boundary microcracks, bulk structure deterioration, and interfacial side reactions. These factors together lead to a decrease in the stability of the material bulk and interface, which in turn causes electrochemical performance degradation and accelerated capacity decay.
[0003] Traditional high-nickel cathode material LiNi x Co y Mn 1-x-y O2 is typically synthesized using a single or double high-temperature solid-state sintering method. Multi-step sintering methods often require the addition of lithium salts or other dopants in subsequent sintering processes. For example, patent CN115710023B discloses a method for preparing high-nickel cathode materials for lithium-ion batteries. This method involves mixing a high-nickel cathode material precursor, lithium salt, phosphorus-containing additives, and metal oxide additives, and then using a gradient sintering method, first sintering at a low temperature and then at a high temperature. Specifically, the temperature is increased to 650–780°C at a heating rate of 1–3°C / min while maintaining a pressure of -10 to -5 Pa, and held for 4–10 hours at a pressure of 50–200 Pa. Then, the temperature is increased to 750–850°C at a heating rate of 0.5–2°C / min while maintaining a pressure of -10 to -5 Pa, and held for 4–10 hours at a pressure of 5–50 Pa. Assembling this cathode material into coin cells for testing reduced reversible capacity loss, achieving a final coin cell capacity of 209.8 mAh / g@0.1C. However, its cycle stability still falls short of real-world requirements. In addition, methods such as elemental doping, surface coating, single-crystal structure modification, and electrode-electrolyte interface modification are used to optimize the intrinsic and surface structures of high-nickel cathode materials, effectively improving their electrochemical performance. However, these methods involve numerous doping and coating modification elements, complex steps, and high raw material costs, still failing to meet the ultra-high capacity demands of the market. Summary of the Invention
[0004] The purpose of this invention is to provide a method for preparing highly stable high-nickel cathode materials. Addressing the shortcomings of existing technologies, a multi-stage sintering strategy (MSS) is proposed to improve the orderliness of the cation structure while maintaining the hexagonal layered structure. This multi-stage sintering strategy differs from traditional sintering methods by eliminating the need for additional lithium salts or dopants. This reduces the number of sintering steps and lowers production costs, while simultaneously enabling the preparation of high-nickel cathode materials with higher cation orderliness and lower lithium-nickel mixing, thus exhibiting better electrochemical performance. Furthermore, this method effectively enhances the electrochemical performance of high-nickel cathode materials, providing a new approach for the industrialization of high-nickel cathode material synthesis.
[0005] To solve the above-mentioned technical problems, the following technical solution is adopted.
[0006] A method for preparing a highly stable high-nickel cathode material includes the following steps.
[0007] (1) Preparation of metal salt solution: Mix the raw materials for preparing high nickel cathode precursor, including nickel source, cobalt source, manganese source metal salt, with deionized water to prepare metal salt solution.
[0008] (2) Co-precipitation preparation of high nickel cathode material precursor: The metal salt solution, alkali solution and complexing agent are added to the reaction vessel by metering pump and the pH is controlled to be 10-11 during the reaction process. The reaction time is 10-15h. After the reaction is completed, the high nickel cathode precursor is obtained by centrifugation, washing and drying.
[0009] (3) Mixing: Mix the high-nickel cathode precursor and lithium salt evenly in a ball mill.
[0010] (4) Solid-state sintering: The mixed material from step (3) is placed in a tube furnace through which oxygen is introduced, and high-nickel cathode material is obtained through multi-step sintering.
[0011] After optimization, in step (1), before mixing, deionized water needs to be purged with excess argon gas to reduce the oxygen content in the liquid.
[0012] After optimization, in step (1), the nickel source is selected from any one or at least a combination of two of nickel sulfate, nickel nitrate, or nickel chloride; the cobalt source is selected from any one or at least a combination of two of cobalt sulfate, cobalt nitrate, cobalt carbonate, or cobalt chloride; and the manganese source is selected from any one or at least a combination of two of manganese carbonate, manganese acetate, manganese sulfate, or manganese chloride.
[0013] After optimization, in step (2), the alkaline solution is selected as sodium hydroxide, and the complexing agent is selected as ammonia monohydrate.
[0014] After optimization, in step (2), the concentration of ammonia monohydrate is N, and the addition flow rate of ammonia monohydrate is controlled at 100-1000 mL / h; the concentration of sodium hydroxide is 2N, and the addition flow rate of alkali solution is controlled at 200-1000 mL / h.
[0015] After optimization, in step (2), nitrogen gas is continuously introduced during the synthesis process to prevent oxidation from occurring during the reaction. The nitrogen gas flow rate is 3000-4000 mL / min.
[0016] After optimization, in step (2), the gas flow rate and stirring rate need to be controlled during the reaction process to obtain a high-nickel cathode precursor with uniform particle size as much as possible, and to make its particle size distribution 2-6μm.
[0017] After optimization, in step (3), the lithium salt is lithium hydroxide, lithium hydroxide monohydrate or lithium carbonate, the ball milling speed is 200-800 rpm and the ball milling time is 10-60 min.
[0018] After optimization, step (4) is a three-step sintering process.
[0019] First step sintering: At room temperature, heat to 450-500℃ at a heating rate of 2-3℃ / min, hold at this temperature for 2.5-3 hours, then heat to 550-650℃ at a heating rate of 2-3℃ / min, hold at this temperature for 5-6 hours, then heat to 700-800℃ at a heating rate of 2-3℃ / min, hold at this temperature for 12-15 hours, then cool to 550-650℃ at a cooling rate of 2-3℃ / min, and cool to room temperature with the furnace.
[0020] The second step is sintering: the temperature is increased to 650-700℃ at room temperature at a heating rate of 2-3℃ / min, held at this temperature for 5-6 hours, and then cooled to 450-500℃ at a cooling rate of 2-3℃ / min, and then cooled to room temperature in the furnace.
[0021] The third step is sintering: the temperature is increased to 300-320℃ at room temperature at a heating rate of 2-3℃ / min, held at this temperature for 5-6 hours, and then cooled to 200-220℃ at a cooling rate of 2-3℃ / min. Finally, the material is cooled to room temperature in the furnace to obtain the high-nickel cathode material.
[0022] The high-nickel cathode material prepared by the above method has the following general formula: LiNi x Co y Mn 1-x-y O2, where 0.9≤x≤0.99, 0.01≤y≤0.1.
[0023] Furthermore, the high-nickel cathode material prepared by this invention can be used to make cathode sheets and applied to electrochemical devices.
[0024] The above technical solution has the following beneficial effects.
[0025] This invention obtains a high-nickel cathode precursor with relatively uniform size and morphology by controlling and optimizing key process parameters (synthesis pH, concentration of ammonia and sodium hydroxide, and N2 flow rate) during the preparation of the high-nickel precursor. A high-nickel cathode material with a lower lithium-nickel mixing ratio is obtained by controlling the sintering process. Compared with other high-nickel cathode materials with the same nickel content, it achieves greater capacity and stability advantages. Attached Figure Description
[0026] The invention will now be further described with reference to the accompanying drawings.
[0027] Figure 1 The image shows the SEM image of the precursor prepared in Example 1.
[0028] Figure 2 The image shows a SEM image of the cathode material prepared in Example 1.
[0029] Figure 3 The image shows the XRD pattern of the cathode material prepared in Example 1.
[0030] Figure 4 The diagram shows the electrochemical cycling performance of the cathode material prepared in Example 1.
[0031] Figure 5 SEM image of the cathode material prepared for Comparative Example 1.
[0032] Figure 6 The image shows the XRD pattern of the cathode material prepared in Comparative Example 1.
[0033] Figure 7 The diagram shows the electrochemical cycling performance of the cathode material prepared in Comparative Example 1. Detailed Implementation
[0034] This invention aims to propose a multi-stage sintering (MSS) strategy that improves the orderliness of the cation structure while maintaining the hexagonal layered structure. Unlike traditional sintering methods, this multi-stage sintering strategy does not require the introduction of additional lithium salts or dopants, reducing sintering steps and production costs. Simultaneously, it can prepare high-nickel cathode materials with higher cation orderliness and lower lithium-nickel mixing, thus exhibiting better electrochemical performance. Furthermore, this method can effectively improve the electrochemical performance of high-nickel cathode materials, providing a new approach for the industrialization of high-nickel cathode material synthesis.
[0035] The present invention will be further described below with reference to specific embodiments.
[0036] Raw materials and sources: transition metal salts were from Sinopharm Chemical Reagent Co., Ltd.; lithium source was from Aladdin Reagent (Shanghai) Co., Ltd.
[0037] Test methods: SEM images were taken using a Hitachi SU-70 field emission scanning electron microscope at magnifications of 1k-10k. Electrochemical performance tests were conducted using coin cell half-cells, following the standard GB / T37201-2018. The test voltage range was 2.7-4.3V. The initial charge-discharge capacity test conditions were: a controlled test temperature of 25℃, a charge-discharge cutoff voltage of 2.7-4.3V, and a charge-discharge rate of 0.1C. Cycling test conditions were: two cycles of 0.1C charge-discharge activation, followed by 100 cycles of 1C charge-1C discharge. Example 1
[0038] High-nickel cathode precursor Ni 0.9 Co 0.05 Mn 0.05 Preparation of (OH)2.
[0039] Step 1: Prepare metal salt solution: Argon gas is passed through deionized water at room temperature for 2 hours. Then, nickel sulfate, cobalt sulfate and manganese sulfate are dissolved in deionized water in a ratio of 0.9:0.05:0.05 to obtain a mixed salt solution.
[0040] Step 2: Co-precipitation preparation of high-nickel cathode precursor: 1 mol / L mixed salt solution, 2 mol / L sodium hydroxide solution and 2 mol / L ammonia solution were added to the reaction vessel using a metering pump. The flow rate of the ammonia solution was controlled at 500 mL / h, and the flow rate of the sodium hydroxide solution was controlled at 400 mL / h. The pH of the reaction was controlled at 11 using a pH meter, and the reaction time was 15 h. Nitrogen gas was introduced at a flow rate of 4000 mL / min during the synthesis process. After the precursor volume particle size distribution grew to 4 μm, it was centrifuged, washed and dried to obtain the high-nickel cathode precursor.
[0041] High-nickel cathode material LiNi 0.9 Co 0.05 Mn 0.05 O2 preparation.
[0042] Step 3: Mixing: Mix the high-nickel cathode material precursor and lithium hydroxide evenly in a ball mill at a speed of 500 rpm for 20 min.
[0043] Step 4: Solid-state sintering: The mixed material is placed in a tube furnace with oxygen introduced, and high-nickel cathode material is obtained through multi-step sintering. Specifically: Step 1 sintering: The temperature is increased to 480℃ (temperature 1) at room temperature at a heating rate of 3℃ / min, held at temperature 1 for 2.5h, then increased to 590℃ (temperature 2) at a heating rate of 3℃ / min, held at temperature 2 for 6h, then increased to 750℃ (temperature 3) at a heating rate of 2℃ / min, held at temperature 3 for 15h, and then decreased to 590℃ (temperature 2) at a cooling rate of 2℃ / min, and cooled to room temperature with the furnace; Step 2 sintering The process is as follows: At room temperature, the temperature is increased to 680℃ (temperature 4) at a heating rate of 3℃ / min, held at this temperature 4 for 6 hours, and then decreased to 500℃ (temperature 5) at a cooling rate of 2℃ / min, and then cooled to room temperature in the furnace. The third sintering step is as follows: At room temperature, the temperature is increased to 300℃ (temperature 6) at a heating rate of 3℃ / min, held at this temperature 6 for 6 hours, and then decreased to 200℃ (temperature 7) at a cooling rate of 2℃ / min, and finally cooled to room temperature in the furnace to obtain the cathode material. Example 2
[0044] High-nickel cathode precursor Ni 0.92 Co 0.04 Mn 0.04 Preparation of (OH)2.
[0045] Step 1: Prepare metal salt solution: Argon gas is passed through deionized water at room temperature for 2 hours. Then, nickel sulfate, cobalt sulfate and manganese sulfate are dissolved in deionized water in a ratio of 0.92:0.04:0.04 to obtain a mixed salt solution.
[0046] Step 2: Precipitation preparation of high-nickel cathode precursor: 1 mol / L mixed salt solution, 2 mol / L sodium hydroxide solution and 2 mol / L ammonia solution were added to the reaction vessel using a metering pump. The flow rate of the ammonia solution was controlled at 500 mL / h, and the flow rate of the sodium hydroxide solution was controlled at 400 mL / h. The pH of the reaction was controlled at 11 using a pH meter, and the reaction time was 15 h. Nitrogen gas was introduced at a flow rate of 4000 mL / min during the synthesis process. After the precursor volume particle size distribution grew to 4 μm, it was centrifuged, washed and dried to obtain the high-nickel cathode precursor.
[0047] High-nickel cathode material LiNi 0.92 Co 0.04 Mn 0.04 O2 preparation.
[0048] Step 3: Mixing: Mix the high-nickel cathode precursor and lithium hydroxide evenly in a ball mill at a speed of 500 rpm for 20 min.
[0049] Step 4: Solid-state sintering: The mixed material is placed in a tube furnace with oxygen introduced, and high-nickel cathode material is obtained through multi-step sintering. Specifically: First step sintering: The temperature is increased to 480℃ (temperature 1) at room temperature at a heating rate of 2℃ / min, held at temperature 1 for 2.5h, then increased to 580℃ (temperature 2) at a heating rate of 2℃ / min, held at temperature 2 for 6h, then increased to 730℃ (temperature 3) at a heating rate of 2℃ / min, held at temperature 3 for 15h, and then decreased to 580℃ (temperature 2) at a cooling rate of 2℃ / min, and cooled to room temperature with the furnace; Second step sintering The process is as follows: At room temperature, the temperature is increased to 700℃ (temperature 4) at a heating rate of 2℃ / min, held at this temperature 4 for 6 hours, and then decreased to 500℃ (temperature 5) at a cooling rate of 2℃ / min, and then cooled to room temperature in the furnace; The third sintering step is as follows: At room temperature, the temperature is increased to 310℃ (temperature 6) at a heating rate of 2℃ / min, held at this temperature 6 for 6 hours, and then decreased to 200℃ (temperature 7) at a cooling rate of 2℃ / min, and finally cooled to room temperature in the furnace to obtain the cathode material. Example 3
[0050] High-nickel cathode precursor Ni 0.95 Co 0.025 Mn 0.025 Preparation of (OH)2.
[0051] Step 1: Prepare metal salt solution: Argon gas is passed through deionized water at room temperature for 2 hours. Then, nickel sulfate, cobalt sulfate and manganese sulfate are dissolved in deionized water in a ratio of 0.9:0.025:0.025 to obtain a mixed salt solution.
[0052] Step 2: Co-precipitation preparation of high-nickel cathode precursor: 1 mol / L mixed salt solution, 2 mol / L sodium hydroxide solution and 2 mol / L ammonia solution were added to the reaction vessel using a metering pump. The flow rate of the ammonia solution was controlled at 500 mL / h, and the flow rate of the sodium hydroxide solution was controlled at 400 mL / h. The pH of the reaction was controlled at 11 using a pH meter, and the reaction time was 15 h. Nitrogen gas was introduced at a flow rate of 4000 mL / min during the synthesis process. After the precursor volume particle size distribution grew to 4 μm, it was centrifuged, washed and dried to obtain the high-nickel cathode precursor.
[0053] High-nickel cathode material LiNi 0.95 Co 0.025 Mn 0.025 O2 preparation.
[0054] Step 3: Mixing: Mix the high-nickel cathode precursor and lithium hydroxide evenly in a ball mill at a speed of 500 rpm for 20 min.
[0055] Step 4: Solid-state sintering: The mixed material is placed in a tube furnace with oxygen introduced, and high-nickel cathode material is obtained through multi-step sintering. Specifically: Step 1 sintering: The temperature is increased to 450℃ (temperature 1) at room temperature at a heating rate of 3℃ / min, held at temperature 1 for 2.5h, then increased to 550℃ (temperature 2) at a heating rate of 3℃ / min, held at temperature 2 for 6h, then increased to 700℃ (temperature 3) at a heating rate of 3℃ / min, held at temperature 3 for 15h, and then decreased to 550℃ (temperature 2) at a cooling rate of 3℃ / min, and cooled to room temperature with the furnace; Step 2 sintering The process is as follows: At room temperature, the temperature is increased to 650℃ (temperature 4) at a heating rate of 3℃ / min, held at this temperature 4 for 6 hours, and then decreased to 500℃ (temperature 5) at a cooling rate of 3℃ / min, and then cooled to room temperature in the furnace. The third sintering step is as follows: At room temperature, the temperature is increased to 300℃ (temperature 6) at a heating rate of 3℃ / min, held at this temperature 6 for 6 hours, and then decreased to 200℃ (temperature 7) at a cooling rate of 3℃ / min, and finally cooled to room temperature in the furnace to obtain the cathode material.
[0056] Comparative Example 1.
[0057] High-nickel cathode precursor Ni 0.9 Co 0.05 Mn 0.05 Preparation of (OH)2.
[0058] Step 1: Prepare metal salt solution: Argon gas is passed through deionized water at room temperature for 2 hours. Then, nickel sulfate, cobalt sulfate and manganese sulfate are dissolved in deionized water in a ratio of 0.9:0.05:0.05 to obtain a mixed salt solution.
[0059] Step 2: Co-precipitation preparation of high-nickel cathode precursor: 1 mol / L mixed salt solution, 2 mol / L sodium hydroxide solution and 2 mol / L ammonia solution were added to the reaction vessel using a metering pump. The flow rate of the ammonia solution was controlled at 500 mL / h, and the flow rate of the sodium hydroxide solution was controlled at 400 mL / h. The pH of the reaction was controlled at 11 using a pH meter, and the reaction time was 15 h. Nitrogen gas was introduced at a flow rate of 4000 mL / min during the synthesis process. After the precursor volume particle size distribution grew to 4 μm, it was centrifuged, washed and dried to obtain the high-nickel cathode precursor.
[0060] High-nickel cathode material LiNi 0.9 Co 0.05 Mn 0.05 O2 preparation.
[0061] Step 3: Mixing: Mix the high-nickel cathode precursor and lithium hydroxide evenly in a ball mill at a speed of 500 rpm for 20 min.
[0062] Step 4: Solid-state sintering: The mixed material is placed in a tube furnace with oxygen introduced, and high-nickel cathode material is obtained by one-step sintering. Specifically, the temperature is increased to 750°C at room temperature at a heating rate of 5°C / min, held at this temperature for 15 hours, and then cooled to room temperature in the furnace to obtain the cathode material.
[0063] Comparative Example 2.
[0064] High-nickel cathode precursor Ni 0.9 Co 0.05 Mn 0.05 Preparation of (OH)2.
[0065] Step 1: Prepare metal salt solution: Argon gas is passed through deionized water at room temperature for 2 hours. Then, nickel sulfate, cobalt sulfate and manganese sulfate are dissolved in deionized water in a ratio of 0.9:0.05:0.05 to obtain a mixed salt solution.
[0066] Step 2: Co-precipitation preparation of high-nickel cathode precursor: 1 mol / L mixed salt solution, 2 mol / L sodium hydroxide solution and 2 mol / L ammonia solution were added to the reaction vessel using a metering pump. The flow rate of the ammonia solution was controlled at 500 mL / h, and the flow rate of the sodium hydroxide solution was controlled at 400 mL / h. The pH of the reaction was controlled at 11 using a pH meter, and the reaction time was 15 h. Nitrogen gas was introduced at a flow rate of 4000 mL / min during the synthesis process. After the precursor volume particle size distribution grew to 4 μm, it was centrifuged, washed and dried to obtain the high-nickel cathode precursor.
[0067] High-nickel cathode material LiNi 0.9 Co 0.05 Mn 0.05 O2 preparation.
[0068] Step 3: Mixing: Mix the high-nickel cathode precursor and lithium hydroxide evenly in a ball mill at a speed of 500 rpm for 20 min.
[0069] Step 4: Solid-state sintering: The mixed material is placed in a tube furnace with oxygen introduced, and high-nickel cathode material is obtained by one-step sintering. Specifically: the temperature is increased to 500℃ (temperature 1) at room temperature at a heating rate of 5℃ / min, held at temperature 1 for 6 hours, then increased to 750℃ (temperature 2) at a heating rate of 5℃ / min, held at temperature 2 for 15 hours, and then cooled to room temperature in the furnace to obtain the cathode material.
[0070] Comparative Example 3.
[0071] High-nickel cathode precursor Ni 0.9 Co 0.05 Mn 0.05Preparation of (OH)2.
[0072] Step 1: Prepare metal salt solution: Argon gas is passed through deionized water at room temperature for 2 hours. Then, nickel sulfate, cobalt sulfate and manganese sulfate are dissolved in deionized water in a ratio of 0.9:0.05:0.05 to obtain a mixed salt solution.
[0073] Step 2: Co-precipitation preparation of high-nickel cathode precursor: 1 mol / L mixed salt solution, 2 mol / L sodium hydroxide solution and 2 mol / L ammonia solution were added to the reaction vessel using a metering pump. The flow rate of the ammonia solution was controlled at 500 mL / h, and the flow rate of the sodium hydroxide solution was controlled at 400 mL / h. The pH of the reaction was controlled at 11 using a pH meter, and the reaction time was 15 h. Nitrogen gas was introduced at a flow rate of 4000 mL / min during the synthesis process. After the precursor volume particle size distribution grew to 4 μm, it was centrifuged, washed and dried to obtain the high-nickel cathode precursor.
[0074] High-nickel cathode material LiNi 0.9 Co 0.05 Mn 0.05 O2 preparation.
[0075] Step 3: Mixing: Mix the high-nickel cathode precursor and lithium hydroxide evenly in a ball mill at a speed of 500 rpm for 20 min.
[0076] Step 4: Solid-state sintering: The mixed material is placed in a tube furnace with oxygen introduced, and high-nickel cathode material is obtained by one-step sintering. The temperature is increased to 500℃ (temperature 1) at room temperature at a heating rate of 3℃ / min, and held at this temperature 1 for 2.5h. Then, the temperature is increased to 600℃ (temperature 2) at a heating rate of 3℃ / min, and held at this temperature 2 for 6h. Then, the temperature is increased to 750℃ (temperature 3) at a heating rate of 2℃ / min, and held at this temperature 3 for 15h. The cathode material is then cooled to room temperature with the furnace to obtain the cathode material.
[0077] The precursors and cathode materials obtained in Examples 1-3 and Comparative Examples 1-3 were subjected to SEM and XRD tests. The SEM images of the precursors are shown below. Figure 1 As shown, the SEM images of Example 1 and Comparative Example 1 are as follows: Figure 2 and Figure 5 As shown, the XRD pattern is as follows Figure 3 and Figure 6 As shown in Table 1, the XRD parameters are presented in the table.
[0078] Table 1 project (003) / (104) Peak intensity ratio Li / Ni mixing degree Rwp Example 1 1.24 2.56% 5.52% Example 2 1.26 2.78% 4.78% Example 3 1.25 2.62% 4.63% Comparative Example 1 1.03 6.56% 5.18% Comparative Example 2 1.20 3.78% 4.94% Comparative Example 3 1.22 3.66% 4.67% The positive electrode materials obtained in Examples 1-3 and Comparative Examples 1-3 were subjected to steps such as homogenization, coating, and cutting to obtain corresponding positive electrode sheets, which were then assembled into coin cells for testing. The electrochemical cycle performance graphs of Example 1 and Comparative Example 1 are shown below. Figure 4 and Figure 7 As shown in Table 2, the electrochemical performance is as follows.
[0079] Table 2 project 1C initial discharge specific capacity [mAh g⁻¹] Discharge specific capacity after 100 cycles [mAh g⁻¹] Cycle retention rate % after 100 cycles Example 1 187.2 170.1 90.9 Example 2 195.3 170.9 87.5 Example 3 201.5 172.1 85.4 Comparative Example 1 171.6 112.6 65.6 Comparative Example 2 180.1 145.3 80.7 Comparative Example 3 182.2 152.5 83.7 Lithium-nickel hybridization for Li + The diffusion coefficient and the cycling stability of the material are significantly affected. This invention obtains high-nickel cathode materials with less lithium-nickel mixing by controlling the sintering process of the high-nickel cathode (Examples 1-3). Compared with other high-nickel cathode materials (Comparative Examples 1-3), higher capacity can be obtained, and the capacity retention rate is high after 100 cycles.
[0080] Compared with Example 1, Comparative Example 1 lacks a 450-500℃ heat preservation process during the synthesis of the cathode material, and the reaction time between the precursor and the lithium source is short. Therefore, its layered structure growth is poor. Specifically, its (003) / (104) peak intensity ratio is 1.03, which is much smaller than the theoretically required 1.2. The material has low capacity, poor rate performance, and fast capacity decay.
[0081] Compared to Example 1, Comparative Example 2 exhibits an excessively rapid heating rate during cathode material synthesis, resulting in a large internal temperature gradient and thermal stress that easily leads to cracking, thereby inducing an increase in intrinsic micro-defects. Furthermore, the cathode material, which undergoes only a simple single sintering process, has a higher lithium-nickel mixing ratio, lower capacity, poor rate performance, and rapid capacity decay.
[0082] Compared to Example 1, Comparative Example 3 lacks annealing and multiple sintering during the synthesis of the cathode material. The moderate low-temperature calcination in the three sintering processes of Example 1 can achieve densification of the material and reduce its porosity. Therefore, Comparative Example 3 has a lower capacity and faster capacity decay.
[0083] The above are merely specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent substitutions, or modifications made based on the present invention to solve essentially the same technical problems and achieve essentially the same technical effects are all covered within the protection scope of the present invention.
Claims
1. A method for preparing a highly stable high-nickel cathode material, characterized in that... Includes the following steps: (1) Preparation of metal salt solution: Mix the raw materials for preparing the high-nickel cathode precursor, including nickel source, cobalt source, and manganese source metal salts, with deionized water to prepare a metal salt solution; (2) Co-precipitation preparation of high-nickel cathode material precursor: The metal salt solution, alkali solution and complexing agent are added to the reaction vessel by metering pump and the pH is controlled to be 10-11 during the reaction process by pH meter. The reaction time is 10-15h. After the reaction is completed, the high-nickel cathode precursor is obtained by centrifugation, washing and drying. (3) Mixing: Mix the high-nickel cathode precursor and lithium salt evenly in a ball mill; (4) Solid-state sintering: The mixed material from step (3) is placed in a tube furnace through which oxygen is introduced, and high-nickel cathode material is obtained through multi-step sintering.
2. The method for preparing a highly stable high-nickel cathode material according to claim 1, characterized in that: In step (1), before mixing, excess argon gas needs to be introduced into the deionized water to reduce the oxygen content in the liquid.
3. The method for preparing a highly stable high-nickel cathode material according to claim 1, characterized in that: In step (1), the nickel source is selected from any one or at least a combination of two of nickel sulfate, nickel nitrate, or nickel chloride; the cobalt source is selected from any one or at least a combination of two of cobalt sulfate, cobalt nitrate, cobalt carbonate, or cobalt chloride; and the manganese source is selected from any one or at least a combination of two of manganese carbonate, manganese acetate, manganese sulfate, or manganese chloride.
4. The method for preparing a highly stable high-nickel cathode material according to claim 1, characterized in that: In step (2), sodium hydroxide is selected as the alkali solution and ammonia monohydrate is selected as the complexing agent.
5. The method for preparing a highly stable high-nickel cathode material according to claim 4, characterized in that: In step (2), the concentration of ammonia monohydrate is N, and the addition flow rate of ammonia monohydrate is controlled at 100-1000 mL / h; the concentration of sodium hydroxide is 2N, and the addition flow rate of alkali solution is controlled at 200-1000 mL / h.
6. The method for preparing a highly stable high-nickel cathode material according to claim 1, characterized in that: In step (2), nitrogen gas is continuously introduced during the synthesis process to prevent oxidation from occurring during the reaction. The nitrogen gas flow rate is 3000-4000 mL / min.
7. The method for preparing a highly stable high-nickel cathode material according to claim 1, characterized in that: In step (2), the particle size distribution of the high-nickel cathode precursor is controlled to be 2-6 μm.
8. The method for preparing a highly stable high-nickel cathode material according to claim 1, characterized in that: In step (3), the lithium salt is lithium hydroxide, lithium hydroxide monohydrate, or lithium carbonate, the ball milling speed is 200-800 rpm, and the ball milling time is 10-60 min.
9. The method for preparing a highly stable high-nickel cathode material according to claim 1, characterized in that: In step (4), the sintering process is a three-step sintering method: First step sintering: At room temperature, heat to 450-500℃ at a heating rate of 2-3℃ / min, hold at this temperature for 2.5-3h, then heat to 550-650℃ at a heating rate of 2-3℃ / min, hold at this temperature for 5-6h, then heat to 700-800℃ at a heating rate of 2-3℃ / min, hold at this temperature for 12-15h, then cool to 550-650℃ at a cooling rate of 2-3℃ / min, and cool to room temperature in the furnace. The second step of sintering: At room temperature, the temperature is increased to 650-700℃ at a heating rate of 2-3℃ / min, held at this temperature for 5-6 hours, and then cooled to 450-500℃ at a cooling rate of 2-3℃ / min, and then cooled to room temperature in the furnace. The third step is sintering: the temperature is increased to 300-320℃ at room temperature at a heating rate of 2-3℃ / min, held at this temperature for 5-6 hours, and then cooled to 200-220℃ at a cooling rate of 2-3℃ / min. Finally, the material is cooled to room temperature in the furnace to obtain the high-nickel cathode material.
10. The high-nickel cathode material prepared by the method according to claim 1, characterized in that: This high-nickel cathode material has the following general formula: LiNi x Co y Mn 1-x-y O2, where 0.8≤x≤0.99, 0.01≤y≤0.2.