Modified ternary positive electrode material and preparation method and application thereof
By preparing modified ternary cathode materials with interpenetrating network structures, the problems of lattice distortion and volume expansion of high-nickel ternary cathode materials were solved, achieving good cycle performance, rate performance and thermal stability, which are suitable for new energy vehicles and energy storage devices.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- GEM WUXI ENERGY MATERIAL CO LTD
- Filing Date
- 2026-04-28
- Publication Date
- 2026-06-09
AI Technical Summary
High-nickel ternary cathode materials are prone to lattice distortion and volume expansion during charge and discharge, resulting in poor cycle performance and rate performance, as well as insufficient thermal stability, posing safety hazards.
A lithium titanate precursor sol is formed by mixing a titanium source, a lithium source, and a solvent. This sol is then mixed with a ternary cathode material precursor and dried to form an interpenetrating network structure. A modified ternary cathode material is prepared by combining this with a programmed temperature sintering process. The lithium titanate heterophase and the ternary cathode material precursor form a stable bond through Ti-O-Ni chemical bonding.
It effectively suppresses lattice distortion and volume expansion during charging and discharging, provides a continuous lithium-ion transport channel, improves cycle stability and rate performance, and enhances thermal stability at high temperatures.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of lithium-ion battery materials technology, specifically to a modified ternary cathode material, its preparation method, and its application. Background Technology
[0002] High-nickel ternary cathode materials (NCA) have become core candidate materials for new energy vehicles, energy storage devices, and other fields due to their ultra-high specific capacity and excellent energy density. However, the high nickel content makes the material prone to lattice distortion and volume expansion during charge and discharge, leading to structural collapse; the surface-active Ni element is prone to redox side reactions with the electrolyte, causing metal ion dissolution and SEI film rupture, significantly reducing cycle stability; at the same time, the material has poor thermal stability and is prone to thermal decomposition at high temperatures, releasing oxygen and posing safety hazards. These problems seriously restrict its large-scale application.
[0003] To address the aforementioned bottlenecks, surface coating and elemental doping are commonly used modification methods. However, traditional surface coating uses single oxides such as Al2O3 and ZrO2 as coating agents, and the coating layer is mostly physically attached to the NCA matrix, resulting in limited improvement in the material's cycle stability and rate performance. Elemental doping modification faces significant challenges in precisely controlling the doping amount. Insufficient doping cannot effectively suppress NCA lattice distortion, while excessive doping leads to an increase in matrix lattice defects, resulting in reduced reversible capacity and deteriorated rate performance. Furthermore, doping modification cannot fundamentally improve the inherently poor thermal stability of high-nickel ternary cathode materials. Under high-temperature and high-voltage conditions, it can still exacerbate electrolyte decomposition and induce interfacial side reactions, leading to safety hazards such as gas generation, expansion, and decreased thermal stability. Therefore, a preparation method that can suppress lattice distortion and volume expansion is urgently needed to obtain a cathode material with excellent cycle performance, rate performance, and thermal stability. Summary of the Invention
[0004] This invention provides a modified ternary cathode material, its preparation method, and its application, to solve the problems in the prior art where ternary cathode materials are prone to lattice distortion and volume expansion, resulting in poor cycle performance and rate performance, and poor thermal stability due to easy thermal decomposition at high temperatures.
[0005] In a first aspect, the present invention provides a method for preparing a modified ternary cathode material, comprising the following steps: Step S1: The titanium source, lithium source and solvent are first mixed to obtain solution A. Solution A is then second mixed with a complexing agent to obtain lithium titanate precursor sol. Step S2: The ternary cathode material precursor and lithium titanate precursor sol are mixed for the third time and then dried to obtain the composite precursor. Step S3: Sinter the composite precursor to obtain the modified ternary cathode material.
[0006] In one optional embodiment, in step S1, the solid content of the lithium titanate precursor sol is 3%-8%.
[0007] In one alternative embodiment, the titanium source comprises tetrabutyl titanate and / or tetraisopropyl titanate.
[0008] In one alternative embodiment, the lithium source includes lithium hydroxide and / or lithium carbonate.
[0009] In one alternative embodiment, the solvent comprises water and an alcohol compound, preferably a mixture of water and ethanol.
[0010] In one optional embodiment, the volume ratio of water to alcohol compound is 1:0.8-1.2.
[0011] In one alternative embodiment, the complexing agent includes at least one of citric acid, tartaric acid, and ethylenediaminetetraacetic acid.
[0012] In one optional embodiment, the molar ratio of titanium in the titanium source to lithium in the lithium source is 1:1.8-2.2.
[0013] In one optional embodiment, the molar ratio of the complexing agent to titanium in the titanium source is 1:0.8-1.2.
[0014] In one optional embodiment, the concentration of the titanium source in the solvent is 0.05-0.2 mol / L.
[0015] In one alternative embodiment, the first mixing speed is 200-300 rpm and the time is 10-30 min.
[0016] In one optional embodiment, the temperature of the second mixing is 50-75°C, the rotation speed is 300-400 rpm, and the time is 30-60 min.
[0017] In one optional implementation, in step S2, the chemical formula of the ternary cathode material precursor is Ni. x Co y Al 1-x-y (OH)₂, where 0.8 ≤ x ≤ 0.95, 0.02 ≤ y ≤ 0.1, 0 <x+y<1。
[0018] In one optional embodiment, the preparation method of the ternary cathode material precursor includes the following steps: obtaining a mixed solution of nickel source, cobalt source, aluminum source and water, adding a precipitant to carry out a co-precipitation reaction, and drying the obtained product to obtain the ternary cathode material precursor.
[0019] In one optional embodiment, in the method for preparing the ternary cathode material precursor, the nickel source includes at least one of nickel sulfate, nickel acetate, and nickel nitrate.
[0020] In one alternative embodiment, the cobalt source includes at least one of cobalt sulfate, cobalt acetate, and cobalt nitrate.
[0021] In one optional embodiment, the aluminum source includes at least one of aluminum sulfate, aluminum nitrate, and sodium aluminate.
[0022] In one alternative embodiment, the precipitant includes at least one of sodium hydroxide, sodium carbonate, and sodium oxalate.
[0023] In one optional embodiment, the total molar concentration of nickel source, cobalt source and aluminum source in the mixed solution is 0.8-1.2 mol / L.
[0024] In one optional embodiment, the molar ratio of the total metal elements in the nickel source, cobalt source, and aluminum source to the precipitant is 1:1-2.
[0025] In one optional embodiment, the coprecipitation reaction is carried out at a temperature of 50-60°C, a rotation speed of 600-800 rpm, and a time of 12-24 h.
[0026] In one alternative embodiment, the coprecipitation reaction further includes the step of adjusting the pH of the system to 10.5-11.5 with an alkaline solution.
[0027] In one optional embodiment, the alkaline solution includes at least one of ammonia, sodium hydroxide, and potassium hydroxide.
[0028] In one optional embodiment, the drying temperature is 80-120°C and the time is 6-10 hours.
[0029] In one alternative implementation, the drying method is vacuum drying and / or forced air drying.
[0030] In one optional embodiment, the vacuum degree of the vacuum drying is -0.08 to -0.1 MPa.
[0031] In one alternative embodiment, the drying process further includes steps of pulverizing and sieving.
[0032] In one optional implementation, the sieving is performed through a 200-300 mesh sieve.
[0033] In one optional embodiment, in step S2, the mass ratio of the ternary cathode material precursor to the lithium titanate precursor sol is 10:0.5-2, preferably 10:0.8-1.2.
[0034] In one alternative implementation, the third mixing includes steps of ultrasonic dispersion and stirring.
[0035] In one optional embodiment, the ultrasonic dispersion power is 200-300W and the time is 25-40min.
[0036] In one optional embodiment, the stirring speed is 300-500 rpm and the stirring time is 60-90 min.
[0037] In one alternative implementation, the third mixing process further includes a drying step.
[0038] In one optional embodiment, the drying temperature is 100-150°C, the vacuum degree is -0.05~-0.1MPa, and the time is 7-11h.
[0039] In an optional embodiment, in step S3, the sintering operation is performed by raising the temperature from room temperature to 350-450°C at a heating rate of 4-7°C / min under an oxygen atmosphere and holding for 1.5-2.5 hours; then raising the temperature to 800-900°C at a heating rate of 3-5°C / min and holding for 8-12 hours; preferably, the sintering operation is performed by raising the temperature from room temperature to 350-450°C at a heating rate of 4-7°C / min and holding for 1.5-2.5 hours; then raising the temperature to 820-880°C at a heating rate of 3-5°C / min and holding for 9-11 hours.
[0040] In one alternative embodiment, the sintering process further includes steps of cooling, crushing, and sieving.
[0041] In one alternative embodiment, the cooling rate is 5-10°C / min.
[0042] In one alternative implementation, the sieving operation is to pass the material through a 300-500 mesh sieve.
[0043] Secondly, the present invention provides a modified ternary cathode material prepared by the above-mentioned method for preparing the modified ternary cathode material.
[0044] In one optional embodiment, the mass of the lithium titanate heterophase in the modified ternary cathode material accounts for 4.5-16.7% of the total mass of the modified ternary cathode material.
[0045] In one optional embodiment, the particle size D50 of the lithium titanate heterophase is 5-20 nm.
[0046] In this invention, a heterogeneous phase refers to a second phase in the cathode material that is fundamentally different from the cathode material precursor in terms of crystal structure and chemical composition. It can be dispersed on the surface and in the gaps between precursor particles to form an interpenetrating composite structure.
[0047] Thirdly, the present invention provides a positive electrode sheet, comprising: Positive current collector, and A positive electrode active material layer disposed on at least one side of the positive electrode current collector, the positive electrode active material layer comprising the above-mentioned modified ternary positive electrode material.
[0048] Fourthly, the present invention provides a secondary battery comprising the aforementioned positive electrode sheet. Fifthly, the present invention provides an electrical device comprising the aforementioned secondary battery.
[0049] The technical solution of this invention has the following advantages: 1. The present invention provides a method for preparing a modified ternary cathode material, comprising the following steps: S1 step: mixing a titanium source, a lithium source and a solvent to obtain solution A, and mixing solution A with a complexing agent to obtain a lithium titanate precursor sol; S2 step: mixing the ternary cathode material precursor and the lithium titanate precursor sol in a third step and then drying to obtain a composite precursor; S3 step: sintering the composite precursor to obtain the modified ternary cathode material. This invention first prepares a uniformly dispersed lithium titanate precursor sol through step S1, and then mixes the sol with a ternary cathode material precursor through step S2. This allows the lithium titanate precursor sol to fully penetrate the surface and interstices of the ternary cathode material precursor particles. Drying then avoids structural porosity caused by solvent residue, further ensuring the compactness of the composite precursor. Sintering then forms a lithium titanate heterophase in situ, which permeates the interstices of the ternary cathode material precursor particles. Simultaneously, due to the excellent compatibility between the lithium titanate crystal structure and the layered structure of the ternary cathode material precursor, the two can achieve stable bonding through Ti-O-Ni chemical bonding, ultimately resulting in... The modified ternary cathode material obtained forms an interpenetrating network heterogeneous composite structure. This structure has the dual functions of internal support and surface protection. It suppresses the lattice distortion and volume expansion of NCA during charging and discharging through the three-dimensional network structure. As a perovskite composite oxide, lithium titanate not only has high lithium-ion conductivity (superior to traditional alumina insulating coating agents) and can provide continuous lithium-ion transport channels to reduce interface resistance, but also has good thermal stability, which can effectively suppress the thermal decomposition of NCA at high temperatures. This effectively achieves a synergistic improvement in cycle performance, rate performance and thermal stability, giving the prepared modified ternary cathode material excellent electrochemical performance.
[0050] 2. The present invention provides a method for preparing a modified ternary cathode material. In step S2, the third mixing uses ultrasonic dispersion to break up the agglomeration of ternary cathode material precursor particles, and then stirring and mixing can promote the full interaction of the two-phase interface, ensuring that the lithium titanate heterophase is uniformly dispersed and the particle size is controlled within 5-20 nm. In step S3, a programmed temperature rise sintering process is used to achieve precise control through segmented temperature control. The temperature is raised from room temperature to 350-450℃ at a heating rate of 4-7℃ / min and held for 1.5-2.5h, which can completely remove organic residues such as complexing agents and avoid residual impurities from affecting the interface bonding. Subsequently, the temperature is raised to 800-900℃ at a heating rate of 3-5℃ / min and held for 8-12h, which can promote the full crystallization of the NCA matrix and the formation of the lithium titanate heterophase, and reduce lattice damage caused by thermal stress through slow heating. Finally, a cooling rate of 5-10℃ / min can avoid structural cracking caused by rapid cooling. This process can precisely control the content of lithium titanate heterophase in the modified ternary cathode material, ensuring a continuous and dense interpenetrating network structure, effectively guaranteeing the structural consistency of the material in mass production, avoiding performance differences caused by process fluctuations, and laying the foundation for large-scale industrial applications. 3. The present invention provides a modified ternary cathode material, which is prepared by the above-described method for preparing modified ternary cathode materials. This modified ternary cathode material has an NCA matrix and a lithium titanate hetero-interpenetrating network structure, which are firmly bonded together by Ti-O-Ni chemical bonds. This effectively suppresses lattice distortion and volume expansion of the NCA matrix during charging and discharging, while providing continuous lithium-ion transport channels and reducing interfacial resistance. Ultimately, this modified ternary cathode material possesses good cycle stability, excellent rate performance, and reliable thermal stability, making it suitable for high-performance battery applications. Detailed Implementation
[0051] The following embodiments are provided to better understand the present invention, but the following embodiments do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the scope of protection of the present invention.
[0052] Unless otherwise specified, all experimental steps or conditions in the examples were performed according to conventional experimental procedures and conditions in the art. Reagents or instruments whose manufacturers are not specified are all commercially available products.
[0053] The method for testing particle size D50 in this invention is as follows: A positive electrode material sample is added to ethanol and ultrasonically dispersed, then introduced into a laser particle size analyzer to test the particle size distribution. The instrument directly outputs the median particle size D50 of the volume distribution.
[0054] The method for testing solid content in this invention is as follows: Take 10g of sol and dry it at 120℃ to constant weight. The percentage of the solid mass after drying to the total mass is the solid content.
[0055] The method for determining the mass ratio of lithium titanate heterophase in this invention is as follows: accurately weigh 0.1g of sample, place it in a microwave digestion vessel, add 5mL of nitric acid and 2mL of hydrofluoric acid, seal, microwave digest until clear, and then cool to room temperature; then transfer the digestion solution to a 100mL volumetric flask, dilute to volume with ultrapure water and shake well to obtain the test solution.
[0056] Standard curve: A series of working solutions with concentrations of 0.5 mg / L, 1 mg / L, 5 mg / L, 10 mg / L, and 20 mg / L were prepared using titanium standard solutions. Inductively coupled plasma optical emission spectrometry (ICP-OES) was used for testing. The instrument parameters were set as follows: radio frequency power 1150 W, cooling gas (argon) flow rate 12 L / min, auxiliary gas flow rate 0.5 L / min, nebulizer flow rate 0.7 L / min, observation height 15 mm, titanium element analysis spectral line 334.941 nm, integration time 10 s. Under the above conditions, the titanium element emission intensity of each standard solution was tested, and a titanium concentration-intensity standard curve was plotted.
[0057] Sample testing: The test solution was tested using an inductively coupled plasma optical emission spectrometer (ICP-OES) under the conditions described above. The mass concentration (mg / L) of titanium was calculated from the standard curve. Since titanium is derived solely from the lithium titanate heterogeneous phase, the mass fraction of lithium titanate was calculated based on the molar ratio of titanium to lithium titanate (1:1), which represents the mass percentage of the lithium titanate heterogeneous phase.
[0058] Example 1 This embodiment provides a method for preparing a modified ternary cathode material, including the following steps: (1) Mix 0.88 mol nickel sulfate, 0.05 mol cobalt sulfate, 0.035 mol aluminum sulfate and deionized water to form a mixed solution and put it into a reaction vessel. The total molar concentration of nickel source, cobalt source and aluminum source in the mixed solution is 1 mol / L. Then, control the pH of the reaction solution to 11.0 with a 0.8% ammonia solution. Co-precipitation reaction is carried out at 55℃ and 700 rpm for 20 h with continuous stirring. After the reaction is completed, filter and wash with water to remove impurity ions. Place the product under vacuum drying at 100℃ and vacuum degree -0.09MPa for 8 h. After drying, pulverize and pass through a 250 mesh sieve to obtain the ternary cathode material precursor (molecular formula: Ni 0.88 Co 0.05 Al 0.07 (OH)2); (2) Weigh 0.01 mol tetrabutyl titanate and 0.02 mol lithium hydroxide, and dissolve them together in 100 mL of a mixed solvent of deionized water and ethanol in a volume ratio of 1:1. Stir at 250 rpm for 20 min until completely dissolved. Then add 0.01 mol citric acid as a complexing agent and place the system under constant temperature magnetic stirring at 350 rpm and 65 °C for 45 min to form a transparent lithium titanate precursor sol (solid content: 5.2%). (3) Take 10g of the ternary cathode material precursor obtained in step (1), add 1g of the lithium titanate precursor sol prepared in step (2), and ultrasonically disperse it for 35min at 250W power; after ultrasonication, magnetically stir it at 400rpm for 75min; after stirring, place the mixture at 120℃ and vacuum degree -0.09MPa for 9h to remove solvent and residual moisture, and obtain the composite precursor; (4) The above composite precursor was subjected to programmed temperature sintering in an oxygen atmosphere: first, the temperature was increased from room temperature to 400℃ at a rate of 5.5℃ / min and held at this temperature for 2 hours; then, the temperature was increased to 860℃ at a rate of 3.5℃ / min and held at this temperature for 10 hours; after sintering, the temperature was cooled at a cooling rate of 5℃ / min, and after cooling, the material was crushed and passed through a 400-mesh sieve to obtain the modified ternary cathode material, wherein the mass of the lithium titanate heterophase accounted for 9.1% of the total mass of the modified ternary cathode material, and the particle size D50 of the lithium titanate heterophase was 17nm.
[0059] Example 2 This embodiment provides a method for preparing a modified ternary cathode material, including the following steps: (1) 0.64 mol nickel acetate, 0.08 mol cobalt acetate, 0.027 mol aluminum nitrate and deionized water were mixed to form a mixed solution and placed in a reaction vessel. The total molar concentration of nickel source, cobalt source and aluminum source in the mixed solution was 0.8 mol / L. Then, the pH of the reaction solution was controlled to be 10.5 with a 0.8% ammonia solution. The co-precipitation reaction was carried out at 600 rpm for 24 h under constant stirring at 60 ℃. After the reaction was completed, the mixture was filtered and washed with water to remove impurity ions. The product was vacuum dried at 80 ℃ and vacuum degree -0.1 MPa for 10 h. After drying, it was pulverized and passed through a 200-mesh sieve to obtain the ternary cathode material precursor (molecular formula: Ni 0.8 Co 0.1 Al 0.1 (OH)2); (2) Weigh 0.01 mol tetraisopropyl titanate and 0.018 mol lithium carbonate, and dissolve them together in 50 mL of a mixed solvent of deionized water and ethanol in a volume ratio of 1:0.8. Stir at 200 rpm for 30 min until completely dissolved. Then add 0.012 mol tartaric acid as a complexing agent and place the system under constant temperature magnetic stirring at 400 rpm and 50 °C for 30 min to form a transparent lithium titanate precursor sol (solid content: 4.8%). (3) Take 10g of the ternary cathode material precursor obtained in step (1), add 0.8g of the lithium titanate precursor sol prepared in step (2), and ultrasonically disperse it for 25min at 300W power; after ultrasonication, magnetically stir it at 300rpm for 90min; after stirring, place the mixture in a vacuum dryer at 100℃ and vacuum degree -0.1MPa for 11h to remove solvent and residual moisture, and obtain the composite precursor; (4) The above composite precursor was subjected to programmed temperature sintering in an oxygen atmosphere: first, the temperature was increased from room temperature to 350°C at a rate of 4°C / min, and held at this temperature for 2.5h; then, the temperature was increased to 820°C at a rate of 3°C / min, and held at this temperature for 11h; after sintering, the temperature was cooled at a rate of 8°C / min, and after cooling, the material was crushed and passed through a 300-mesh sieve to obtain the modified ternary cathode material, wherein the mass of the lithium titanate heterophase accounted for 8.5% of the total mass of the modified ternary cathode material, and the particle size D50 of the lithium titanate heterophase was 15nm.
[0060] Example 3 This embodiment provides a method for preparing a modified ternary cathode material, including the following steps: (1) 1.14 mol nickel nitrate, 0.024 mol cobalt nitrate, 0.036 mol sodium aluminate and deionized water were mixed to form a mixed solution and placed in a reaction vessel. The total molar concentration of nickel source, cobalt source and aluminum source in the mixed solution was 1.2 mol / L. Then, 2 mol / L NaOH solution was added. The pH of the reaction solution was controlled to 11.5 with ammonia solution with a mass fraction of 0.8%. The co-precipitation reaction was carried out for 12 h with continuous stirring at 800 rpm at a temperature of 50℃. After the reaction was completed, the mixture was filtered and washed with water to remove impurity ions. The product was placed in a vacuum dryer at 120℃ and a vacuum degree of -0.08 MPa for 6 h. After drying, the product was pulverized and passed through a 300-mesh sieve to obtain the ternary cathode material precursor. (2) Weigh 0.01 mol tetrabutyl titanate and 0.022 mol lithium hydroxide, and dissolve them together in 200 mL of a mixed solvent of deionized water and ethanol in a volume ratio of 1:1.2. Stir at 300 rpm for 10 min until completely dissolved. Then add 0.008 mol citric acid as a complexing agent and place the system under constant temperature magnetic stirring at 300 rpm and 75 °C for 60 min to form a transparent lithium titanate precursor sol (solid content: 6.5%). (3) Take 10g of the ternary cathode material precursor obtained in step (1), add 1.2g of the lithium titanate precursor sol prepared in step (2), and ultrasonically disperse it for 25min at 200W power; after ultrasonication, magnetically stir it at 500rpm for 60min; after stirring, place the mixture in a vacuum dryer at 150℃ and vacuum degree -0.05MPa for 7h to remove solvent and residual moisture, and obtain the composite precursor; (4) The above composite precursor was subjected to programmed temperature sintering in an oxygen atmosphere: first, the temperature was increased from room temperature to 450°C at a rate of 7°C / min and held at this temperature for 1.5h; then, the temperature was increased to 880°C at a rate of 5°C / min and held at this temperature for 9h; after sintering, the temperature was cooled at a rate of 10°C / min, and after cooling, the material was crushed and passed through a 500-mesh sieve to obtain the modified ternary cathode material, wherein the mass of the lithium titanate heterophase accounted for 11.2% of the total mass of the modified ternary cathode material, and the particle size D50 of the lithium titanate heterophase was 18nm.
[0061] Comparative Example 1 This comparative example provides a method for preparing a ternary cathode material, including the following steps: Take the ternary cathode material precursor prepared in step (1) of Example 1, mix it evenly with the three metal elements nickel, cobalt and aluminum in the precursor and the lithium element in lithium carbonate at a molar ratio of 1:1.1 to obtain a mixture; then place the mixture in an oxygen atmosphere for programmed temperature sintering, the sintering program being the same as step (4) of Example 1; after sintering, cool it at a cooling rate of 5℃ / min, pulverize it after cooling and pass it through a 400-mesh sieve to obtain an unmodified ternary cathode material.
[0062] Comparative Example 2 This comparative example provides an alumina-coated ternary cathode material, which is basically the same as Example 1, except that step (2) is omitted and the lithium titanate precursor sol in step (3) is replaced with an alumina precursor sol (preparation method: weigh 0.18 mol aluminum isopropoxide, dissolve it in 100 mL of a mixed solvent of deionized water and ethanol in a volume ratio of 1:1, stir at 250 rpm until completely dissolved; then add 0.22 mol citric acid as a complexing agent, and place the system under constant temperature magnetic stirring at 350 rpm and 65°C for 45 min to form a transparent and uniform alumina precursor sol). The amount of alumina precursor sol added is controlled so that the alumina coating amount in the final ternary cathode material is 9.1 wt%, which is the same as the lithium titanate heterophase content in Example 1.
[0063] Comparative Example 3 This comparative example provides a method for preparing a ternary cathode material, including the following steps: 10g of the ternary cathode material precursor prepared in step (1) of Example 1 is taken and sintered with 0.036g of tetrabutyl titanate and 0.005g of lithium hydroxide under an oxygen atmosphere for programmed temperature sintering. The sintering program is the same as step (4) of Example 1. After sintering, the material is naturally cooled, pulverized and sieved through a 400-mesh sieve to obtain the ternary cathode material.
[0064] Experimental Example 1 1. The positive electrode materials obtained in each embodiment and comparative example are assembled into coin cells. The preparation method of the coin cells is as follows: (1) Preparation of positive electrode sheet: The positive electrode material, conductive agent acetylene black, and binder PVDF obtained in each example and comparative example were mixed in a mass ratio of 90:5:5. N-methylpyrrolidone (NMP) was used as solvent and the mixture was stirred in a vacuum mixer for 4 hours to form a uniform and viscous slurry. The slurry was uniformly coated onto an aluminum foil current collector with a thickness of 15 μm using an automatic coating machine. The coated electrode sheet was then placed in a vacuum oven at 80°C and dried for 12 hours. After that, it was compacted with a roller press and cut into round sheets with a diameter of 12 mm. The mass loading of the positive electrode material on each electrode sheet was precisely controlled to be 3 mg / cm³. 2 ; (2) Button cell assembly: All battery assembly steps were carried out in a glove box filled with high-purity argon (H2O<0.1ppm, O2<0.1ppm). Lithium metal sheet was used as the negative electrode, Celgard 2400 was used as the separator, and the electrolyte was 1mol / L LiPF6 solution (the solvent was a mixed solvent of ethylene carbonate, dimethyl carbonate and methyl ethyl carbonate in a volume ratio of 1:1:1). The negative electrode shell, negative electrode sheet (lithium sheet) were placed in sequence, the electrolyte was added, the separator was laid, the positive electrode sheet was placed, the electrolyte was added, the positive electrode shell was covered, and the sealing machine was used to press and seal the battery to obtain a button cell. The assembled battery was tested after standing for 12 hours.
[0065] 2. Perform performance tests on the button cells prepared above. 1) Charge / discharge test: The Blue Battery testing system was used to conduct tests within the voltage range of 2.8-4.3V. First, the initial charge / discharge was performed at 0.1C to obtain the initial coulombic efficiency; then, the cycle performance test (200 cycles) was performed at 0.5C to obtain the capacity retention rate after 200 cycles at 0.5C = discharge capacity after 200 cycles at 0.5C / discharge capacity in the first cycle × 100%.
[0066] 2) Rate performance test: The test was conducted at 25℃. The battery was charged at a constant current of 0.2C to 4V, then charged at a constant voltage to 0.05C, left to stand for 10 minutes, and then discharged at a constant current of 0.2C to 4V to obtain the 0.2C discharge capacity. Then, the battery was charged at 0.2C to 4V, then charged at a constant voltage to 0.05C, left to stand for 10 minutes, and then discharged at 5C to 3V to obtain the 5C discharge capacity. The 5C / 0.2C capacity retention rate was calculated as 5C discharge capacity / 0.2C discharge capacity × 100%.
[0067] 3. Thermal decomposition initiation temperature test Take 5 mg of each of the cathode material powders prepared in the examples and comparative examples, and use a simultaneous thermal analyzer (TG-DSC). Place the powder samples in an alumina crucible and heat them from room temperature to 800°C at a rate of 10°C / min under a nitrogen atmosphere (flow rate of 50 mL / min). The instrument's built-in software automatically reads the thermal decomposition initiation temperature. Perform three parallel tests and take the average value.
[0068] 4. Test Results Table 1 Electrochemical performance test results
[0069] As shown in Table 1, regarding cycle performance, after 200 cycles at 0.5C, the capacity retention of all embodiments was above 90%, especially Example 1, which achieved a capacity retention of 93.2%, far superior to the comparative example, indicating that the cathode material prepared by this invention has good cycle stability. Regarding rate performance, at a high rate of 5C, the capacity retention of all embodiments was above 84%, especially Example 1, which achieved a capacity retention of 87.5%, far superior to the comparative example, indicating that the cathode material prepared by this invention has good rate performance. Regarding thermal stability, compared to the comparative example, the cathode materials prepared in the embodiments have higher thermal decomposition onset temperatures, all above 295℃, indicating that the cathode material prepared by this invention has good thermal stability.
[0070] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.
Claims
1. A method for preparing a modified ternary cathode material, characterized in that, Includes the following steps: Step S1: The titanium source, lithium source and solvent are first mixed to obtain solution A. Solution A is then second mixed with a complexing agent to obtain lithium titanate precursor sol. Step S2: The ternary cathode material precursor and lithium titanate precursor sol are mixed for the third time and then dried to obtain the composite precursor. Step S3: Sinter the composite precursor to obtain the modified ternary cathode material.
2. The method for preparing the modified ternary cathode material according to claim 1, characterized in that, In step S1, the solid content of the lithium titanate precursor sol is 3%-8%; And / or, the titanium source includes tetrabutyl titanate and / or tetraisopropyl titanate; And / or, the lithium source includes lithium hydroxide and / or lithium carbonate; And / or, the solvent comprises water and alcohol compounds, preferably a mixture comprising water and ethanol; Optionally, the volume ratio of water to alcohol compound is 1:0.8-1.2; And / or, the complexing agent includes at least one of citric acid, tartaric acid, and ethylenediaminetetraacetic acid; And / or, the molar ratio of titanium in the titanium source to lithium in the lithium source is 1:1.8-2.2; And / or, the molar ratio of titanium in the complexing agent and the titanium source is 1:0.8-1.2; And / or, the concentration of the titanium source in the solvent is 0.05-0.2 mol / L; And / or, the first mixing speed is 200-300 rpm, and the time is 10-30 min; And / or, the temperature of the second mixing is 50-75°C, the rotation speed is 300-400 rpm, and the time is 30-60 min.
3. The method for preparing the modified ternary cathode material according to claim 1, characterized in that, In step S2, the chemical formula of the ternary cathode material precursor is Ni. x Co y Al 1-x-y (OH)₂, where 0.8 ≤ x ≤ 0.95, 0.02 ≤ y ≤ 0.1, 0 <x+y<1; And / or, the preparation method of the ternary cathode material precursor includes the following steps: obtaining a mixed solution of nickel source, cobalt source, aluminum source and water, adding a precipitant to carry out a co-precipitation reaction, and drying the obtained product to obtain the ternary cathode material precursor.
4. The method for preparing the modified ternary cathode material according to claim 3, characterized in that, In the preparation method of the ternary cathode material precursor, the nickel source includes at least one of nickel sulfate, nickel acetate, and nickel nitrate; And / or, the cobalt source includes at least one of cobalt sulfate, cobalt acetate, and cobalt nitrate; And / or, the aluminum source includes at least one of aluminum sulfate, aluminum nitrate, and sodium aluminate; And / or, the precipitant includes at least one of sodium hydroxide, sodium carbonate, and sodium oxalate; And / or, the total molar concentration of nickel source, cobalt source and aluminum source in the mixed solution is 0.8-1.2 mol / L; And / or, the molar ratio of total metal elements in the nickel source, cobalt source, and aluminum source to the precipitant is 1:1-2; And / or, the coprecipitation reaction is carried out at a temperature of 50-60℃, a rotation speed of 600-800 rpm, and a time of 12-24h; And / or, the coprecipitation reaction further includes the step of adjusting the pH of the system to 10.5-11.5 with an alkaline solution; Optionally, the alkaline solution includes at least one of ammonia, sodium hydroxide, and potassium hydroxide; And / or, the drying temperature is 80-120℃ and the time is 6-10h; And / or, the drying method is vacuum drying and / or forced air drying; Optionally, the vacuum degree of the vacuum drying is -0.08 to -0.1 MPa; And / or, the drying process may further include the steps of pulverizing and sieving; Optionally, the sieving is performed through a 200-300 mesh sieve.
5. The method for preparing the modified ternary cathode material according to claim 1, characterized in that, In step S2, the mass ratio of the ternary cathode material precursor to the lithium titanate precursor sol is 10:0.5-2, preferably 10:0.8-1.2; And / or, the third mixing includes the steps of ultrasonic dispersion and stirring; Optionally, the ultrasonic dispersion power is 200-300W and the time is 25-40min; Optionally, the stirring speed is 300-500 rpm and the time is 60-90 min; And / or, the third mixing process further includes a drying step; Optionally, the drying temperature is 100-150℃, the vacuum degree is -0.05~-0.1MPa, and the time is 7-11h; And / or, in step S3, the sintering operation is to raise the temperature from room temperature to 350-450°C at a heating rate of 4-7°C / min under an oxygen atmosphere, and hold at that temperature for 1.5-2.5 hours; then raise the temperature to 800-900°C at a heating rate of 3-5°C / min, and hold at that temperature for 8-12 hours; preferably, the sintering operation is to raise the temperature from room temperature to 350-450°C at a heating rate of 4-7°C / min, and hold at that temperature for 1.5-2.5 hours; then raise the temperature to 820-880°C at a heating rate of 3-5°C / min, and hold at that temperature for 9-11 hours; And / or, the sintering process further includes steps of cooling, crushing, and sieving; Optionally, the cooling rate is 5-10℃ / min; Optionally, the sieving operation is to pass the material through a 300-500 mesh sieve.
6. The modified ternary cathode material prepared by the method of any one of claims 1-5.
7. The modified ternary cathode material according to claim 6, characterized in that, In the modified ternary cathode material, the mass of the lithium titanate heterophase accounts for 4.5-16.7% of the total mass of the modified ternary cathode material; And / or, the particle size D50 of the lithium titanate heterophase is 5-20 nm.
8. A positive electrode sheet, characterized in that, include: Positive current collector, and A positive electrode active material layer disposed on at least one side of the positive electrode current collector, the positive electrode active material layer comprising the modified ternary positive electrode material as described in claim 6 or 7.
9. A secondary battery, characterized in that, Includes the positive electrode sheet as described in claim 8.
10. An electrical device, characterized in that, Includes the secondary battery as described in claim 9.