A method for preparing and synthesizing lithium titanate material for lithium ion batteries

Abstract

The present invention provides a preparation and synthesis method of lithium titanate material for lithium ion batteries, the main steps of which are: S1, mixing a lithium source, a titanium source and water, and stirring evenly; then spray drying until the moisture content of the material is below 5%; S2, sintering the material obtained in S1 once; S3, wet ball milling the calcined dry material, using water as a solvent and zirconium balls as a ball milling medium, grinding to obtain a nano slurry; S4, spray drying the nano slurry again to obtain a spherical material, performing a secondary sintering, and finally drying and removing water, controlling the water content of the material to be less than 200ppm, to obtain a lithium titanate material for lithium ion batteries. The lithium titanate material provided by the present invention has a smooth appearance, and through low-temperature sintering, has the advantages of improving material compaction, saving electrolyte, reducing electrolyte side reaction consumption, and improving battery cycle performance.

Description

Technical Field

[0001] The invention belongs to the technical field of negative electrode materials, and specifically relates to a method for preparing and synthesizing lithium titanate materials for lithium ion batteries. Background Art

[0002] In the context of the country's vigorous advocacy of the development of new energy and related industries, lithium titanate has become a research hotspot for negative electrode materials of new lithium-ion batteries due to its excellent safety, ultra-long cycle performance, fast charge and discharge, and ultra-wide high / low temperature performance, and its application prospects are constantly expanding.

[0003] At present, the main methods for preparing lithium titanate include solid phase reaction method, sol-gel method and hydrothermal ion exchange synthesis method. The high-temperature solid phase synthesis method has a simple preparation process, low equipment requirements, and few reaction influencing factors. It is the easiest to achieve industrial mass production, but its particle size is large, generally at the micron level; powder materials are difficult to mix, and the uniformity of raw material mixing is limited; the heat treatment temperature is high and the energy consumption is large. The lithium titanate prepared by the sol-gel method has high purity, controllable particle size and can achieve nano-materialization, but the preparation cycle is long and there are many factors affecting the preparation process. The hydrothermal ion exchange synthesis method is simple to operate, the synthesis temperature is low, the reaction conditions are variable and controllable, the product composition is uniform and the particle size is controllable, but the large-scale high temperature and high pressure reactor required for the preparation process is difficult to design and manufacture, the cost is high and it is difficult to maintain. Summary of the invention

[0004] The present invention provides a method for preparing a lithium titanate material for a lithium ion battery. The prepared lithium titanate material has a smooth surface and has the advantages of improving material compaction, saving electrolyte, reducing electrolyte side reaction consumption, and improving battery cycle performance.

[0005] The technical solution of the present invention is a method for preparing and synthesizing lithium titanate material for lithium ion batteries, comprising the following steps:

[0006] S1. Mix the lithium source, titanium source and water and stir them evenly; then spray dry them until the moisture content of the materials is below 5%;

[0007] S2, sintering the material obtained in S1;

[0008] S3, wet ball milling the calcined dry material, using water as solvent and zirconium oxide balls as ball milling media, to obtain nano slurry;

[0009] The nano-slurry obtained in S4 and S3 is spray-dried again to obtain a spherical material, which is then sintered for a second time and finally vacuum-dried at 120-180° C. to remove water, control the water content of the material to be less than 200 ppm, and obtain lithium titanate material for lithium-ion batteries.

[0010] Furthermore, the lithium source is one or a mixture of LiOH·H2O, lithium carbonate, lithium acetate, the titanium source is TiO2·2H2O, and the mass ratio of the lithium source, the titanium source and water is 2-3:6-8:20-25.

[0011] Furthermore, after the lithium source, titanium source and water in S1 are mixed, the solid content is 20-40%, and the mixture is stirred continuously for 4-10 hours.

[0012] Furthermore, during the drying in S1, air at 200 to 300°C is used for drying.

[0013] Furthermore, the sintering temperature in S2 is 300-500° C., and the sintering time is 10-18 hours.

[0014] Furthermore, after water is added to the dry material in S3, the solid content is 15-30%.

[0015] Furthermore, the diameter of the zirconium balls in S3 is 0.25-0.4 mm, and the ball milling is performed for 25-35 hours; the specific surface area after ball milling is 90-110 m 2 / g, the particle size of the material is D 10 60~90nm, D 50 250-300nm, D 90 400~600nm, D 99 650~800nm.

[0016] Furthermore, during the spray drying in S4, the temperature is 200-300° C.; the material is dried until the water content is less than 7%.

[0017] Furthermore, in S4, the sintering temperature is 300°C to 500°C, and the sintering time is 8 to 15 hours.

[0018] The present invention also relates to a lithium titanate material for lithium ion batteries prepared by the method, and application of the lithium titanate material as a negative electrode material for lithium ion batteries.

[0019] The present invention has the following beneficial effects:

[0020] The present invention uses a lithium source, a titanium source and water as raw materials, undergoes a spray drying and calcination, then performs ball milling, and then performs a second spray drying and calcination. The prepared lithium titanate material has a smooth surface, has the advantages of improving material compaction, saving electrolyte, reducing electrolyte side reaction consumption, and improving battery cycle performance.

[0021] The present invention is spray-dried and calcined twice in succession, and the calcination is all carried out at low temperature, so as to avoid the formation of high-temperature macropores and reduce side reactions. Under the condition of ensuring a certain charge and discharge rate, the cycle performance of the material can be significantly improved. DETAILED DESCRIPTION

[0022] The embodiments of the present invention will be described in detail below with reference to examples, but those skilled in the art will appreciate that the following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention.

[0023] Embodiment 1:

[0024] A method for preparing and synthesizing lithium titanate material for lithium ion batteries, the specific steps are:

[0025] Raw material mixing process (DT): In a stainless steel outer shell and 1-2 mm lining enamel reaction vessel, add 3 kg of LiOH·H2O, 8 kg of anatase TiO2·2H2O, and 20 kg of solvent H2O, with a solid content of 35%, and stir continuously for 6 hours.

[0026] Primary spray drying step (SD1): 300°C air is introduced into the spray dryer to reduce the moisture content of the mixed raw materials to less than 5%.

[0027] Primary calcination (CA): The spray-dried mixture is calcined at a high temperature of 300°C for 12 hours. During this process, a chemical reaction occurs to generate lithium titanate material with a phase purity of 97%, which is consistent with the lithium titanate crystal. If the Ti equivalent is too much in this process, a rutile phase will appear, and if the Li equivalent is too much, Li2TiO3 lithium metatitanate will be generated.

[0028] Wet ball milling (BM): transfer the calcined dry material to a ball mill, add H2O as solvent, control the solid content at 20%, the diameter of the zirconium ball is 0.3mm, ball milling for 30h (basically it can be formed in 17h), the specific surface area is 98m 2 / g, the particle size of the material is D 10 80nm, D 50 276nm, D 90 500nm, D 99 700nm.

[0029] Secondary spray drying (SD2): The wet ball-milled slurry was spray-dried again at a drying temperature of 280°C. During this process, the water content was dried to 7%. The material was spherical after spray drying.

[0030] Secondary sintering (Huike, HK): calcined at 300℃ for 1h in a muffle furnace, the grains are more complete and the repair is perfected, sintered at 300℃ for 10h, 405 plate, 4Kg / plate.

[0031] Drying and dehydration (WM): The water content of the material is less than 200ppm under 150℃ and 100Pa vacuum, which takes 22h (18h heating + 4h cooling).

[0032] Packaging: Packaging environment 1% humidity.

[0033] Example 2: In the raw material mixing step, the lithium source is lithium carbonate, the titanium source is TiO2·2H2O, the mass ratio of the lithium source, the titanium source and water is 2:7:23, and the remaining steps and parameters are the same as in Example 1.

[0034] Example 3: In the raw material mixing process, 2.5 kg of LiOH·H2O, 7.5 kg of anatase TiO2·2H2O, and 24 kg of solvent H2O were added, and stirring was continued for 8 hours; the remaining steps and parameters were the same as in Example 1.

[0035] Example 4: Primary spray drying process (SD1): Air at 200-220° C. is introduced into the spray dryer to reduce the moisture content of the mixed raw materials to 4%; the remaining steps and parameters are the same as in Example 1.

[0036] Example 5: During the first calcination process, the calcination temperature is 450-500°C and the time is 10 hours; the remaining steps and parameters are the same as in Example 1.

[0037] Example 6: During the secondary calcination process, the calcination temperature is 450-500°C and the time is 8 hours; the remaining steps and parameters are the same as in Example 1.

[0038] Comparative Example 1: During the first calcination process, the calcination temperature is 700° C. and the time is 4 h; during the second calcination process, the calcination temperature is 800° C. and the time is 3 h; the remaining steps and parameters are the same as in Example 1.

[0039] Comparative Example 2: During the first calcination process, the calcination temperature is 450-500° C. and the time is 10 h; during the second calcination process, the calcination temperature is 800° C. and the time is 3 h; the remaining steps and parameters are the same as in Example 1.

[0040] Comparative Example 3: During the first calcination process, the calcination temperature is 800°C and the time is 3 hours; during the second calcination process, the calcination temperature is 450±10°C and the time is 12 hours; the remaining steps and parameters are the same as in Example 1.

[0041] The lithium titanate materials obtained in Examples 1 to 6 and Comparative Examples 1 to 3 were used to prepare batteries, wherein the ratio of lithium titanate: SP: PVDF was 94%: 3%: 3%; the performance of the prepared batteries was tested, as shown in the following table.

[0042] Table 1

[0043]

[0044] The lithium titanate material prepared by the solution provided by the present invention is used for battery preparation, which can greatly increase the number of cycles while ensuring that the discharge rate is equivalent to or slightly lower than that of the traditional method.

Claims

1. A method for preparing and synthesizing lithium titanate material for lithium ion batteries, characterized in that: The following steps are involved: S1. Mix the lithium source, titanium source and water and stir evenly; then spray dry until the moisture content of the material is below 5%; S2, sintering the material obtained in S1 once, with the sintering temperature being 300-500°C; S3, wet ball milling the calcined dry material, using water as solvent and zirconium oxide balls as ball milling media, to obtain nano slurry; The nano-slurry obtained in S4 and S3 is spray-dried again to obtain a spherical material, which is then sintered for the second time at a sintering temperature of 300°C to 500°C. Finally, it is vacuum-dried at 120°C to 180°C to remove water, and the water content of the material is controlled to be less than 200ppm to obtain a lithium titanate material for lithium-ion batteries.

2. The method for preparing and synthesizing lithium titanate material for lithium ion batteries according to claim 1, characterized in that: The lithium source is one or a mixture of LiOH·H2O, lithium carbonate, and lithium acetate, the titanium source is TiO2·2H2O, and the mass ratio of the lithium source, the titanium source, and water is 2-3:6-8:20-25.

3. The method for preparing and synthesizing lithium titanate material for lithium ion battery according to claim 2, characterized in that: After the lithium source, titanium source and water in S1 are mixed, the solid content is 20-40%, and stirring is continued for 4-10 hours.

4. The method for preparing and synthesizing lithium titanate material for lithium ion battery according to claim 1, characterized in that: When drying in S1, air at 200-300°C is used for drying.

5. The method for preparing and synthesizing lithium titanate material for lithium ion battery according to claim 1, characterized in that: The sintering time in S2 is 10~18h.

6. The method for preparing and synthesizing lithium titanate material for lithium ion battery according to claim 1, characterized in that: After adding water to the dry material in S3, the solid content is between 15% and 30%.

7. The method for preparing and synthesizing lithium titanate material for lithium ion battery according to claim 1, characterized in that: The diameter of zirconium balls in S3 is 0.25-0.4 mm, and the ball milling time is 25-35 hours. The specific surface area after ball milling is 90-110 m 2 / g, the particle size of the material is D 10 60~90nm, D 50 250-300nm, D 90 400~600nm, D 99 650~800nm.

8. The method for preparing and synthesizing lithium titanate material for lithium ion battery according to claim 1, characterized in that: During spray drying in S4, the temperature is 200-300°C; the material is dried until the water content is less than 7%.

9. The method for preparing and synthesizing lithium titanate material for lithium ion battery according to claim 1, characterized in that: The sintering time in S4 is 8~15h.

10. A lithium titanate material for lithium ion batteries prepared by the method according to any one of claims 1 to 9, which is a negative electrode material for lithium ion batteries.

Images