Modified ternary positive electrode material as well as preparation method and application thereof
By using the bridge between trimethylolpropane and aluminum terephthalate on the ternary positive electrode material to form a high-temperature carbonized cladding and LiAlO2 coating, the problem of poor circulation performance of ternary positive electrode material in lithium-ion batteries is solved. , achieving better discharge specific capacity and cycling performance.
Patent Information
- Application Number
- CN202411208693.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-30
- Publication Date
- 2024-12-10
AI Technical Summary
The existing ternary positive electrode materials have capacity attenuation and poor circulation performance during the circulation of lithium-ion batteries. Traditional doping or coating methods cannot effectively improve the discharge specific capacity and first effect.
By dissolving trimethylolpropane in an alkaline buffer solution and mixing with the ternary positive electrode material, sonication and stirring, and then mixing with aluminum terephthalate to dry and sinter, forming a high-temperature carbonized coating and achieving Al ion doping , a tight LiAlO2 coating is formed to achieve uniform doping and coating.
The discharge specific capacity and cyclic performance of the ternary positive electrode material are significantly improved, surface degradation is suppressed, and good electrochemical performance is provided.
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Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of battery materials, and in particular relates to a modified ternary positive electrode material and a preparation method and application thereof. Background Art
[0002] In the new energy era, with the rapid development of new energy vehicles, the market has put forward higher requirements for lithium-ion batteries, among which the positive electrode material plays a decisive role in the electrochemical performance of lithium-ion batteries. Ternary positive electrode materials are considered to be one of the ideal candidate materials for current and future power batteries due to their advantages such as low cost, environmental friendliness, and reversible capacity. However, lithium-ion batteries prepared with ternary positive electrode materials will experience obvious capacity decay during the cycle process and show poor cycle performance. In the exploration of the past few years, researchers have improved the capacity of lithium-ion batteries during the cycle process and improved the cycle performance through doping and coating. However, traditional doping or coating is mainly mixed by high-speed mixers, which can only achieve superficial doping or coating, resulting in limited improvement in its discharge specific capacity, first efficiency and cycle performance. Summary of the invention
[0003] Therefore, the technical problem to be solved by the present invention is to overcome the defects of the existing ternary positive electrode materials in terms of limited improvement in discharge specific capacity, first efficiency and cycle performance, thereby providing a modified ternary positive electrode material and its preparation method and application.
[0004] The present invention provides a method for preparing a modified ternary positive electrode material, comprising the following steps:
[0005] 1) dissolving trimethylolpropane in an alkaline buffer solution to form a pretreatment solution, mixing the pretreatment solution and the ternary cathode material, ultrasonically treating, stirring, separating the solid, and obtaining the ternary cathode material pretreated with trimethylolpropane;
[0006] 2) The ternary cathode material pretreated with trimethylolpropane obtained in step 1), an organic solvent and aluminum terephthalate are mixed, dried, and then sintered in an inactive atmosphere to obtain the modified ternary cathode material.
[0007] Preferably, the mass concentration of trimethylolpropane in the pretreatment solution in step 1) is 2-5 g / L;
[0008] The alkaline buffer solution in step 1) is selected from a boric acid-borax buffer solution;
[0009] The total molar concentration of boric acid and borax in the boric acid-borax buffer solution is 0.1-0.3M;
[0010] The pH of the boric acid-borax buffer solution is 8.0-9.0.
[0011] Preferably, the ultrasonic treatment power in step 1) is 20kHz-40kHz, and the ultrasonic treatment time is 1-2h;
[0012] The stirring speed is 500-1200r / min, and the stirring time is 3-5h;
[0013] In the mixed solution formed by mixing the pretreatment solution and the ternary positive electrode material in step 1), the mass concentration of the ternary positive electrode material is 5-10 g / L.
[0014] Optionally, the separation of the solid further includes washing and drying steps;
[0015] The present invention does not impose any specific limitation on drying, and the water in the separated solid may be evaporated. For example, vacuum drying may be performed at 50-80°C.
[0016] Preferably, in step 2), the ternary positive electrode material pretreated with trimethylolpropane and part of the organic solvent are mixed to form solution A, aluminum terephthalate is mixed with the remaining part of the organic solvent to form solution B, and then solution B is added to solution A, the organic solvent is heated to evaporate, and then sintered in an inactive atmosphere to obtain the modified ternary positive electrode material.
[0017] The organic solvent of the present invention includes the above-mentioned part of organic solvent and the above-mentioned remaining part of organic solvent.
[0018] Preferably, the mass concentration of the ternary cathode material pretreated with trimethylolpropane in the solution A is 0.1-0.7 g / mL;
[0019] The mass concentration of aluminum terephthalate in the solution B is 0.001-0.19 g / mL;
[0020] The sintering temperature is 600-800°C and the sintering time is 6-10h;
[0021] The inactive atmosphere is a nitrogen atmosphere or an argon atmosphere.
[0022] Preferably, the chemical formula of the ternary cathode material in step 1) is Li f Ni x Co y Mn z O2, and 1.01≤f≤1.08, 0.7≤x≤0.9, 0.01≤y≤0.2, 0.01≤z≤0.2, x+y+z=1.
[0023] Preferably, the method for preparing the ternary positive electrode material in step 1) comprises the following steps:
[0024] The lithium source and the precursor are mixed and calcined to obtain the ternary positive electrode material.
[0025] Preferably, the lithium source is selected from at least one of lithium hydroxide and lithium carbonate;
[0026] The chemical formula of the precursor is Ni x Co y Mn z (OH)2, and 0.7≤x≤0.9, 0.01≤y≤0.2, 0.01≤z≤0.2, x+y+z=1;
[0027] The calcination temperature is 400-600° C., and the calcination time is 4-6 hours.
[0028] The aluminum terephthalate described in the present invention is MIL-53 (Al), CAS No.: 654061-20-8.
[0029] The present invention provides a modified ternary positive electrode material, which is prepared by the above-mentioned method for preparing the modified ternary positive electrode material.
[0030] The present invention also provides an application of the modified ternary positive electrode material described above in a lithium ion battery.
[0031] The technical solution of the present invention has the following advantages:
[0032] 1. The preparation method of the modified ternary cathode material provided by the present invention comprises the following steps: 1) dissolving trimethylolpropane in an alkaline buffer solution to form a pretreatment solution, mixing the pretreatment solution and the ternary cathode material, ultrasonically treating, stirring, separating the solid, and obtaining the ternary cathode material pretreated with trimethylolpropane; 2) mixing the ternary cathode material pretreated with trimethylolpropane obtained in step 1), an organic solvent and aluminum terephthalate, drying, and sintering to obtain the modified ternary cathode material. The present invention uses the pretreatment solution prepared by trimethylolpropane to ultrasonically and stir the ternary cathode material. After the treatment, the trimethylolpropane will be anchored on the surface of the ternary cathode material, and then the anchored trimethylolpropane and aluminum terephthalate will have a bridging effect between specific ligand groups, so that aluminum terephthalate is closely attached to the surface of the ternary cathode material and evenly distributed. Aluminum terephthalate is used as an organic Al source, and can provide a carbon source as a conductive layer while providing an Al source. After sintering, a high-temperature carbonized coating layer is formed in an integrated manner, and part of the Al ions are doped into the bulk phase, and part of the Al forms a tight LiAlO2 coating on the surface of the ternary material, achieving carbon surface coating and bulk phase doping in one step. The modified ternary positive electrode material prepared by the specific preparation method of the present invention achieves specific doping and coating, has a stable structure, can inhibit surface degradation, and provides good discharge specific capacity, first efficiency and cycle performance.
[0033] 2. The preparation method of the modified ternary positive electrode material provided by the present invention can achieve uniform doping and coating regardless of whether the particles of the positive electrode material are large or small, or whether the particles of large and small positive electrode materials are mixed, which effectively solves the problem that the dopants are attracted by small particles with larger specific surface area, resulting in uneven doping and easy formation of island-like aggregation. DETAILED DESCRIPTION
[0034] The following examples are provided for a better understanding of the present invention, but are not intended to limit the best mode of implementation, nor to limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.
[0035] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.
[0036] Example 1
[0037] This embodiment provides a method for preparing a modified ternary positive electrode material, comprising the following steps:
[0038] 1) Weigh lithium hydroxide and precursor Ni according to the stoichiometric ratio 0.88 Co 0.04 Mn 0.08 (OH)2 was mixed and calcined at 400℃ for 5h to obtain the ternary positive electrode material Li 1.04 Ni 0.88 Co 0.04 Mn 0.08 O2, dissolving trimethylolpropane in a boric acid-borax buffer solution to form a pretreatment solution, wherein the mass concentration of trimethylolpropane in the pretreatment solution is 2 g / L, and the total molar concentration of boric acid and borax in the boric acid-borax buffer solution is 0.1 M; the pH of the boric acid-borax buffer solution is 8.0, and then mixing the pretreatment solution and the ternary cathode material to form a mixed solution, wherein the mass concentration of the ternary cathode material in the mixed solution is 10 g / L, ultrasonically treating at a power of 20 kHz for 1 hour, and then stirring at a speed of 700 r / min for 4 hours, separating the solid by centrifugation, washing, and vacuum drying at 60°C to obtain the ternary cathode material pretreated with trimethylolpropane;
[0039] 2) 5 g of the ternary positive electrode material pretreated with trimethylolpropane obtained in step 1) and 16 mL of isopropanol were mixed to form solution A, 0.2 g of aluminum terephthalate was mixed with 4 mL of isopropanol to form solution B, and then solution B was added dropwise to solution A, and then heated to evaporate the isopropanol, and sintered at 700° C. in a nitrogen atmosphere for 10 h to obtain the modified ternary positive electrode material.
[0040] Example 2
[0041] This embodiment provides a method for preparing a modified ternary positive electrode material, which is different from Example 1 only in that 0.4 g of aluminum terephthalate is mixed with 4 mL of isopropanol to form solution B.
[0042] Example 3
[0043] This embodiment provides a method for preparing a modified ternary positive electrode material, which is different from Embodiment 1 only in that 0.6 g of aluminum terephthalate is mixed with 4 mL of isopropanol to form solution B.
[0044] Example 4
[0045] This embodiment provides a method for preparing a modified ternary positive electrode material, comprising the following steps:
[0046] 1) Weigh lithium hydroxide and precursor Ni according to the stoichiometric ratio 0.88 Co 0.04 Mn 0.08 (OH)2 was mixed and calcined at 400℃ for 5h to obtain the ternary positive electrode material Li 1.04 Ni 0.88 Co 0.04 Mn 0.08 O2, dissolving trimethylolpropane in a boric acid-borax buffer solution to form a pretreatment solution, wherein the mass concentration of trimethylolpropane in the pretreatment solution is 5 g / L, and the total molar concentration of boric acid and borax in the boric acid-borax buffer solution is 0.3 M; the pH of the boric acid-borax buffer solution is 8.0, and then mixing the pretreatment solution and the ternary cathode material to form a mixed solution, wherein the mass concentration of the ternary cathode material in the mixed solution is 10 g / L, ultrasonically treating at a power of 20 kHz for 1 hour, and then stirring at a speed of 700 r / min for 4 hours, centrifuging to separate the solid, washing, and vacuum drying at 60°C to obtain the ternary cathode material pretreated with trimethylolpropane;
[0047] 2) 5 g of the ternary positive electrode material pretreated with trimethylolpropane obtained in step 1) was mixed with 16 mL of isopropanol to form a solution A, 0.04 g of aluminum terephthalate was mixed with 4 mL of isopropanol to form a solution B, and then solution B was added dropwise to solution A, and then heated to evaporate the isopropanol, and sintered at 700° C. in a nitrogen atmosphere for 10 h to obtain the modified ternary positive electrode material.
[0048] Example 5
[0049] This embodiment provides a method for preparing a modified ternary positive electrode material, comprising the following steps:
[0050] 1) Weigh lithium hydroxide and precursor Ni according to the stoichiometric ratio 0.88 Co 0.04 Mn 0.08 (OH)2 was mixed and calcined at 400℃ for 5h to obtain the ternary positive electrode material Li 1.04 Ni 0.88 Co 0.04 Mn 0.08 O2, dissolving trimethylolpropane in a boric acid-borax buffer solution to form a pretreatment solution, wherein the mass concentration of trimethylolpropane in the pretreatment solution is 2 g / L, and the total molar concentration of boric acid and borax in the boric acid-borax buffer solution is 0.1 M; the pH of the boric acid-borax buffer solution is 8.0, and then mixing the pretreatment solution and the ternary cathode material to form a mixed solution, wherein the mass concentration of the ternary cathode material in the mixed solution is 5 g / L, ultrasonically treating at a power of 20 kHz for 1 hour, and then stirring at a speed of 1000 r / min for 4 hours, separating the solid by centrifugation, washing, and vacuum drying at 60°C to obtain the ternary cathode material pretreated with trimethylolpropane;
[0051] 2) 5 g of the ternary positive electrode material pretreated with trimethylolpropane obtained in step 1) and 16 mL of isopropanol were mixed to form solution A, 0.2 g of aluminum terephthalate was mixed with 4 mL of isopropanol to form solution B, and then solution B was added dropwise to solution A, and then the isopropanol was heated to evaporate, and sintered at 800° C. in a nitrogen atmosphere for 6 h to obtain the modified ternary positive electrode material.
[0052] Comparative Example 1
[0053] This comparative example provides a method for preparing a modified ternary positive electrode material, comprising the following steps:
[0054] 1) Weigh lithium hydroxide and precursor Ni according to the stoichiometric ratio 0.88 Co 0.04 Mn 0.08 (OH)2 was mixed and calcined at 400℃ for 5h to obtain the ternary positive electrode material Li 1.04 Ni 0.88 Co 0.04 Mn 0.08O2, dissolving trimethylolpropane in a boric acid-borax buffer solution to form a pretreatment solution, wherein the mass concentration of trimethylolpropane in the pretreatment solution is 2 g / L, and the total molar concentration of boric acid and borax in the boric acid-borax buffer solution is 0.1 M; the pH of the boric acid-borax buffer solution is 8.0, and then mixing the pretreatment solution and the ternary cathode material to form a mixed solution, wherein the mass concentration of the ternary cathode material in the mixed solution is 10 g / L, ultrasonically treating at a power of 20 kHz for 1 hour, and then stirring at a speed of 700 r / min for 4 hours, separating the solid by centrifugation, washing, and vacuum drying at 60°C to obtain the ternary cathode material pretreated with trimethylolpropane;
[0055] 2) The trimethylolpropane pretreated ternary cathode material obtained in step 2 (1) was mixed with 16 mL of isopropanol to form a solution A, 0.2 g of aluminum oxide was mixed with 4 mL of isopropanol to form a solution B, and then solution B was added dropwise to solution A, and then the isopropanol was heated to evaporate, and sintered at 700 ° C in a nitrogen atmosphere for 10 hours to obtain the modified ternary cathode material.
[0056] Comparative Example 2
[0057] This comparative example provides a method for preparing a modified ternary positive electrode material, comprising the following steps:
[0058] 1) Weigh lithium hydroxide and precursor Ni according to the stoichiometric ratio 0.88 Co 0.04 Mn 0.08 (OH)2 was mixed and calcined at 400℃ for 5h to obtain the ternary positive electrode material Li 1.04 Ni 0.88 Co 0.04 Mn 0.08 O2, prepare a boric acid-borax buffer solution, the total molar concentration of boric acid and borax in the boric acid-borax buffer solution is 0.1M; the pH of the boric acid-borax buffer solution is 8.0, then mix the boric acid-borax buffer solution and the ternary positive electrode material to form a mixed solution, the mass concentration of the ternary positive electrode material in the mixed solution is 10g / L, ultrasonically treat at a power of 20kHz for 1h, then stir at a speed of 700r / min for 4h, centrifuge to separate the solid, wash, and vacuum dry at 60°C to obtain a pretreated ternary positive electrode material;
[0059] 2) The pretreated ternary positive electrode material obtained in step 2 (1) was mixed with 16 mL of isopropanol to form solution A, 0.2 g of aluminum terephthalate was mixed with 4 mL of isopropanol to form solution B, and then solution B was added dropwise to solution A, and then heated to evaporate the isopropanol, and sintered at 700° C. in a nitrogen atmosphere for 10 h to obtain the modified ternary positive electrode material.
[0060] Comparative Example 3
[0061] This comparative example provides a method for preparing a modified ternary positive electrode material, which differs from Example 1 in that in step 2), sintering is performed at 700° C. in an oxygen atmosphere for 10 h.
[0062] Test Case
[0063] The modified ternary positive electrode materials prepared in Examples 1-5 and Comparative Examples 1-3 were used as the positive electrode main materials to prepare positive electrode plates. N-methylpyrrolidone was used as a dispersant. The positive electrode main material: carbon black: polyvinylidene fluoride (PVDF): dispersant were mixed at a mass ratio of 95:2.5:2.5:120 to prepare positive electrode slurry. The positive electrode slurry was evenly coated on aluminum foil and dried in an oven at 80°C for 2h to obtain positive electrode plates. The coating surface density of the positive electrode plates was 10mg / cm 2 Using metallic lithium as the negative electrode, glass fiber as the separator, and 1 mol / L LiPF6 ethylene carbonate (EC) / dimethyl carbonate (DMC) solution as the electrolyte (the volume ratio of EC and DMC is 1:1), in an argon atmosphere of a glove box, the positive electrode, negative electrode, separator, electrolyte, gasket and spring are placed in a button cell to assemble a CR2032 button cell.
[0064] The button cell was placed in a Xinwei test cabinet (CT 4008 5V10mA80CH) for electrical performance testing. Test conditions: test temperature 25°C, when the constant voltage cutoff current is 0.03mA, it means charging is finished, button cell cycle voltage 2.5-4.3V, charge and discharge at 0.1C for 1 cycle, test the first charge specific capacity and the first discharge specific capacity, and calculate the first efficiency, first efficiency = and first discharge specific capacity / first charge specific capacity * 100%, then charge and discharge for 50 cycles at 0.5C rate, test the cycle capacity retention rate after 50 cycles, the test results are shown in Table 1.
[0065] Table 1
[0066]
[0067] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.
Claims
1. A method for preparing a modified ternary cathode material, characterized in that: The following steps are involved: 1) dissolving trimethylolpropane in an alkaline buffer solution to form a pretreatment solution, mixing the pretreatment solution and the ternary cathode material, ultrasonically treating, stirring, separating the solid, and obtaining the ternary cathode material pretreated with trimethylolpropane; 2) The ternary cathode material pretreated with trimethylolpropane obtained in step 1), an organic solvent and aluminum terephthalate are mixed, dried, and then sintered in an inactive atmosphere to obtain the modified ternary cathode material.
2. The method for preparing the modified ternary positive electrode material according to claim 1, characterized in that: The mass concentration of trimethylolpropane in the pretreatment solution in step 1) is 2-5 g / L; The alkaline buffer solution in step 1) is selected from a boric acid-borax buffer solution; The total molar concentration of boric acid and borax in the boric acid-borax buffer solution is 0.1-0.3M; The pH of the boric acid-borax buffer solution is 8.0-9.
0.
3. The method for preparing the modified ternary positive electrode material according to claim 1 or 2, characterized in that: The ultrasonic treatment power in step 1) is 20kHz-40kHz, and the ultrasonic treatment time is 1-2h; The stirring speed is 500-1200r / min, and the stirring time is 3-5h; In the mixed solution formed by mixing the pretreatment solution and the ternary positive electrode material in step 1), the mass concentration of the ternary positive electrode material is 5-10 g / L.
4. The method for preparing the modified ternary cathode material according to any one of claims 1 to 3, characterized in that: In step 2), the ternary positive electrode material pretreated with trimethylolpropane and part of the organic solvent are mixed to form solution A, aluminum terephthalate is mixed with the remaining organic solvent to form solution B, and then solution B is added to solution A, the organic solvent is heated to evaporate, and then sintered in an inactive atmosphere to obtain the modified ternary positive electrode material.
5. The method for preparing the modified ternary cathode material according to any one of claims 1 to 3, characterized in that: The mass concentration of the ternary cathode material pretreated with trimethylolpropane in the solution A is 0.1-0.7 g / mL; The mass concentration of aluminum terephthalate in the solution B is 0.001-0.19 g / mL; The sintering temperature is 600-800°C and the sintering time is 6-10h; The inactive atmosphere is a nitrogen atmosphere or an argon atmosphere.
6. The method for preparing the modified ternary cathode material according to any one of claims 1 to 3, characterized in that: The chemical formula of the ternary cathode material in step 1) is Li f Ni x Co y Mn z O2, and 1.01≤f≤1.08, 0.7≤x≤0.9, 0.01≤y≤0.2, 0.01≤z≤0.2, x+y+z=1.
7. The method for preparing the modified ternary cathode material according to any one of claims 1 to 4, characterized in that: The method for preparing the ternary positive electrode material in step 1) comprises the following steps: The lithium source and the precursor are mixed and calcined to obtain the ternary positive electrode material.
8. The method for preparing the modified ternary cathode material according to claim 7, characterized in that: The lithium source is selected from at least one of lithium hydroxide and lithium carbonate; The chemical formula of the precursor is Ni x Co y Mn z (OH)2, and 0.7≤x≤0.9, 0.01≤y≤0.2, 0.01≤z≤0.2, x+y+z=1; The calcination temperature is 400-600° C., and the calcination time is 4-6 hours.
9. A modified ternary cathode material, characterized in that: The modified ternary positive electrode material is prepared by the preparation method of any one of claims 1 to 8.
10. Use of the modified ternary cathode material according to claim 9 in lithium-ion batteries.