Preparation method of high-temperature resistant and long-life power-type coated modified lithium manganese oxide

Abstract

The present invention relates to the technical field of lithium-ion battery positive electrode materials, and discloses a preparation method of a high-temperature resistant and long-life power-type coated modified lithium manganate, comprising: step 1, mixing lithium carbonate and a manganese source and performing a roasting to obtain a lithium manganate primary product; step 2, preparing a ZrO2 coating solution; step 3, spraying and coating the lithium manganate primary product with a ZrO2 coating solution; carrying out a secondary roasting of the sprayed product to obtain a ZrO2-coated lithium manganate; step 4, preparing a Cr2O3 coating solution; step 5, spraying and coating the ZrO2-coated lithium manganate with a Cr2O3 coating solution, and roasting the sprayed product three times to obtain a lithium manganate positive electrode material with a ZrO2-Cr2O3 double coating layer. The preparation method of the present invention achieves the goal of improving the uniformity of coating distribution, effectively suppressing the dissolution of manganese in the positive electrode material, and improving the positive electrode material discharge specific capacity and high-temperature cycle retention rate.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion battery positive electrode materials, and in particular to a method for preparing high-temperature-resistant, long-life power-type coated modified lithium manganese oxide. Background Art

[0002] Lithium-ion batteries have become a new type of green power source due to their high energy density, high operating voltage, low self-discharge, and long cycle life. They are widely used in mobile phones, laptops, electric vehicles and other fields.

[0003] Lithium-ion battery cathode materials typically include lithium cobalt oxide, ternary materials, lithium manganese oxide, and lithium iron phosphate. Lithium manganese oxide offers broad application prospects in power batteries due to its high specific capacity (theoretical capacity of 148 mAh / g), high operating voltage, excellent safety, low cost, and environmental friendliness. However, LiMn2O4 suffers from particularly severe capacity fading during high-temperature cycling due to issues such as the Jahn-Tener effect, manganese dissolution, and electrolyte decomposition. Surface coating is currently widely used to mitigate capacity fading in LiMn2O4. Surface coating reduces the contact area between LiMn2O4 and the electrolyte, minimizing manganese ion dissolution. Furthermore, the surface coating effectively inhibits structural distortion, increases structural stability, and improves the cycling performance of the LiMn2O4 material. Zirconium dioxide is a commonly used coating modifier for lithium manganese oxide surfaces. However, due to its chemical inactivity, zirconium dioxide can reduce the specific discharge capacity of the modified material. Furthermore, coating inhomogeneity significantly impacts the performance of lithium battery cathode materials. Summary of the Invention

[0004] In view of the above problems, the technical problem to be solved by the present invention is to provide a preparation method of high-temperature resistant and long-life power-type coated modified lithium manganese oxide, improve the thermal stability and high-temperature cycle of the positive electrode material, and improve the discharge specific capacity.

[0005] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0006] A method for preparing a high-temperature resistant, long-life power-type coated modified lithium manganese oxide comprises the following steps:

[0007] Step 1: mixing lithium carbonate and a manganese source and then calcining them once, with a lithium-manganese molar ratio of 0.5-0.55, to obtain a primary product of lithium manganate;

[0008] Step 2, preparing a ZrO2 coating solution: dissolving tetrabutyl zirconate in anhydrous ethanol solution, adding 15% ammonia water to adjust the pH to 9-10, and stirring at 35-40°C for 2-3 hours to obtain a ZrO2 coating solution;

[0009] Step 3, spray coating the initial lithium manganate product with a ZrO2 coating solution; and calcining the sprayed product twice to obtain a ZrO2 coated lithium manganate material;

[0010] Step 4, preparing a Cr2O3 coating solution: dissolving tert-butyl chromate in anhydrous ethanol solution, adding 15% ammonia water to adjust the pH to 9-10, and stirring at 35-40°C for 2-3 hours to obtain a Cr2O3 coating solution;

[0011] Step 5: Spray-coat the ZrO2-coated lithium manganate material with a Cr2O3 coating solution, and calcine the sprayed product three times to obtain a lithium manganate positive electrode material with a ZrO2-Cr2O3 double coating layer.

[0012] Furthermore, the manganese source is composed of the following components in weight percentage: 5% MnO, 5% Mn2O3, 70%-80% Mn3O4, and 10%-20% MnO2.

[0013] Furthermore, the manganese source is spherical particles with D50=8-15 μm.

[0014] Furthermore, in step 1, the atmosphere for the first calcination is air, the calcination temperature is 750° C.-850° C., and the calcination time is 18-23 hours.

[0015] Furthermore, in step 2, the concentration of the ZrO2 coating solution is 10-20%.

[0016] Furthermore, in step 3, the atmosphere for the secondary calcination is air, the calcination temperature is 650° C.-750° C., and the calcination time is 12-16 hours.

[0017] Furthermore, in step 3, the coating amount of ZrO2 is 1-2% of the mass fraction of the initial lithium manganese oxide product.

[0018] Furthermore, in step 4, the concentration of the Cr2O3 coating solution is 10-20%.

[0019] Furthermore, in step 5, the atmosphere for the three calcinations is air, the calcination temperature is 550° C.-650° C., and the calcination time is 8-10 hours.

[0020] Furthermore, in step 5, the coating amount of Cr2O3 is 0.3-0.6% of the mass fraction of the initial lithium manganese oxide product.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention uses zirconium dioxide and chromium trioxide to perform double-layer coating on the lithium manganate positive electrode material. The nano-scale coating prevents the contact between the electrolyte and the lithium manganate material, inhibits the occurrence of Mn3+ disproportionation reaction, effectively improves the high-temperature electrochemical cycle performance of the lithium manganate material, and significantly improves the performance of the battery. Since zirconium dioxide has good thermal stability, the structural stability and thermal stability of the material are improved, and the cycle performance and thermal stability are effectively modified. However, zirconium dioxide has no electrochemical activity and reduces the discharge specific capacity of the modified material to a certain extent. Chromium trioxide has good electrochemical activity. The combination of the two can improve the electrical conductivity of the modified material, improve the charge and discharge specific capacity of the material, and has good rate performance and cycle performance.

[0023] By using ester compounds of zirconium and chromium metals as precursors, the polycondensation process is controlled by ammonia water in the ethanol phase, and a coating layer with uniform thickness at the nanometer level is synthesized through spray coating, which reduces the impact of the unevenness of the coating layer on the performance of the lithium battery positive electrode material. DETAILED DESCRIPTION

[0024] The specific implementation of the present invention is further described below with reference to the examples.

[0025] Example 1

[0026] A method for preparing a high-temperature resistant, long-life power-type coated modified lithium manganese oxide comprises the following steps:

[0027] Step 1: lithium carbonate and a manganese source are mixed and then calcined once, with a lithium-manganese molar ratio of 0.5, to obtain a primary lithium manganate; wherein the manganese source is composed of the following components in weight percentage: 5% MnO, 5% Mn2O3, 70% Mn3O4, and 20% MnO2; the manganese source is spherical particles with a D50 of 8-15 μm; the primary calcination atmosphere is air, the calcination temperature is 750°C, and the calcination time is 23 hours;

[0028] Step 2, preparing a ZrO2 coating solution: dissolving tetrabutyl zirconate in anhydrous ethanol solution, adding 15% ammonia water to adjust the pH to 9-10, stirring at 35-40°C for 2-3 hours to obtain a ZrO2 coating solution; wherein the concentration of the ZrO2 coating solution is 10%;

[0029] Step 3, spray coating the primary lithium manganate product with a ZrO2 coating solution for 1.5 hours; and performing a secondary roasting on the sprayed product to obtain a ZrO2-coated lithium manganate material; wherein the coating amount of ZrO2 is 1% of the mass fraction of the primary lithium manganate product, the secondary roasting atmosphere is air, the roasting temperature is 650°C, and the roasting time is 16 hours;

[0030] Step 4, preparing a Cr2O3 coating solution: dissolving tert-butyl chromate in anhydrous ethanol solution, adding 15% ammonia water to adjust the pH to 9-10, stirring at 35-40°C for 2-3 hours to obtain a Cr2O3 coating solution; wherein the concentration of the Cr2O3 coating solution is 10%;

[0031] Step 5: Spray-coating the ZrO2-coated lithium manganate material with a Cr2O3 coating solution for 1.5 hours, and calcining the sprayed product three times to produce a lithium manganate positive electrode material having a ZrO2-Cr2O3 double coating layer. The Cr2O3 coating amount is 0.6% by mass of the initial lithium manganate product, and the three calcinations are performed in air at a temperature of 550°C for 10 hours.

[0032] Example 2

[0033] Step 1: lithium carbonate and a manganese source are mixed and then calcined once, with a lithium-manganese molar ratio of 0.55, to obtain a primary product of lithium manganate; wherein the manganese source is composed of the following components in weight percentage: 5% MnO, 5% Mn2O3, 80% Mn3O4, and 10% MnO2; the manganese source is spherical particles with a D50 of 8-15 μm; the primary calcination atmosphere is air, the calcination temperature is 850°C, and the calcination time is 18 hours;

[0034] Step 2, preparing a ZrO2 coating solution: dissolving tetrabutyl zirconate in anhydrous ethanol solution, adding 15% ammonia water to adjust the pH to 9-10, stirring at 35-40°C for 2-3 hours to obtain a ZrO2 coating solution; wherein the concentration of the ZrO2 coating solution is 20%;

[0035] Step 3, spray coating the primary lithium manganate product with a ZrO2 coating solution for 1 hour; and performing a secondary calcination on the sprayed product to obtain a ZrO2-coated lithium manganate material; wherein the coating amount of ZrO2 is 1% of the mass fraction of the primary lithium manganate product, the secondary calcination atmosphere is air, the calcination temperature is 750°C, and the calcination time is 12 hours;

[0036] Step 4, preparing a Cr2O3 coating solution: dissolving tert-butyl chromate in anhydrous ethanol solution, adding 15% ammonia water to adjust the pH to 9-10, stirring at 35-40°C for 2-3 hours to obtain a Cr2O3 coating solution; wherein the concentration of the Cr2O3 coating solution is 20%;

[0037] Step 5: Spray-coating the ZrO2-coated lithium manganate material with a Cr2O3 coating solution for 1 hour, and calcining the sprayed product three times to produce a lithium manganate positive electrode material having a ZrO2-Cr2O3 double coating layer. The Cr2O3 coating amount is 0.6% by mass of the initial lithium manganate product, and the three calcinations are performed in air at a temperature of 650°C for 8 hours.

[0038] Example 3

[0039] Same as Example 1, except that:

[0040] The coating amount of ZrO2 is 2% of the mass fraction of the initial lithium manganese oxide.

[0041] Example 4

[0042] Same as Example 1, except that:

[0043] The coating amount of Cr2O3 is 1% of the mass fraction of the initial lithium manganate product.

[0044] Comparative Example 1

[0045] Same as Example 1, except that:

[0046] The coating amount of ZrO2 is 4% of the mass fraction of the initial lithium manganese oxide

[0047] Comparative Example 2

[0048] Same as Example 1, except that:

[0049] The coating amount of Cr2O3 is 2% of the mass fraction of the initial lithium manganese oxide.

[0050] Comparative Example 3

[0051] Same as Example 1, except that:

[0052] A lithium manganate positive electrode material containing only a ZrO2 coating layer.

[0053] Comparative Example 4

[0054] Same as Example 1, except that:

[0055] Lithium manganate positive electrode material containing only a Cr2O3 coating layer.

[0056] Comparative Example 5

[0057] Lithium carbonate and a manganese source are mixed and calcined in air at a calcination temperature of 750°C for 23 hours. The molar ratio of lithium to manganese is 0.5, and the manganese source is composed of the following components in weight percentage: 5% MnO, 5% Mn2O3, 70% Mn3O4, and 20% MnO2. The manganese source is spherical particles with a D50 of 8-15 μm to obtain an uncoated lithium manganate positive electrode material.

[0058] The lithium manganate positive electrode materials obtained in Examples 1-4 and Comparative Examples 1-5 were prepared into 1500mAh soft-pack lithium-ion batteries, and the rate performance and cycle performance at 1C and 5C rates at room temperature were tested, with a charge and discharge voltage of 3.0-4.2V.

[0059] Rate performance at different magnifications

[0060] 1C rate cycle 5C rate cycle First discharge specific capacity mAh / g First discharge specific capacity mAh / g Example 1 108.5 105.2 Example 2 108.2 104.8 Example 3 110.4 106.9 Example 4 110.9 107.3 Comparative Example 1 106.8 103.6 Comparative Example 2 107.1 103.1 Comparative Example 3 107.5 102.9 Comparative Example 4 107.2 102.5 Comparative Example 5 106.1 99.4

[0061] Cycling performance at different rates

[0062] After 2000 cycles at 1C rate at 25°C After 2000 cycles at 5C rate at 25℃ Discharge capacity mAh / g Discharge capacity mAh / g Example 1 97.5 94.6 Example 2 97.2 94.3 Example 3 99.4 96.2 Example 4 99.9 96.5 Comparative Example 1 96.1 93.2 Comparative Example 2 96.2 92.7 Comparative Example 3 96.2 92.6 Comparative Example 4 96.8 92.2 Comparative Example 5 95.4 90.6

[0063] The lithium manganate positive electrode materials obtained in the above Examples 1-4 and Comparative Examples 1-5 were prepared into 1500mAh soft-pack lithium ion batteries, and the discharge specific capacities of the first cycle and the 500th cycle were tested at a high temperature of 55°C, with a charge and discharge voltage of 3.0-4.2V.

[0064] Cycling performance at high temperature of 55°C

[0065] First cycle 500th cycle Discharge capacity mAh / g Discharge capacity retention rate Example 1 105.8 85.6% Example 2 105.5 86.4% Example 3 107.6 87.1% Example 4 108.1 87.4% Comparative Example 1 104.1 84.2% Comparative Example 2 104.4 83.5% Comparative Example 3 104.8 83.8% Comparative Example 4 104.5 83.6% Comparative Example 5 101.5 65.2%

[0066] The above data shows that when the ZrO2 coating amount is 1%, the low ZrO2 content has little effect on the electrochemical performance of lithium manganese oxide, and the rate performance of the two is relatively close to that of the uncoated lithium manganese oxide. When the ZrO2 coating amount is 2%, the specific capacity is significantly improved compared to the uncoated lithium manganese oxide positive electrode material. However, when the ZrO2 coating amount is increased to 4%, the specific capacity decreases at different rates.

[0067] When the ZrO2 coating amount is 1%, the low ZrO2 content has little effect on the electrochemical performance of lithium manganese oxide, and the rate performance of the two is close to that of the uncoated lithium manganese oxide. When the ZrO2 coating amount is 2%, the specific capacity is significantly improved compared to the uncoated lithium manganese oxide positive electrode material.

[0068] Moreover, when ZrO2 is coated alone or Cr2O3 is coated alone, the specific capacity at different rates is lower than that of the lithium manganate positive electrode material with a double coating layer of ZrO2-Cr2O3. This is because zirconium dioxide has no electrochemical activity, which reduces the charge and discharge specific capacity of the modified material to a certain extent, while chromium trioxide has good electrochemical activity, can improve the conductivity of the modified material, can inhibit the discharge process, and improve the charge and discharge specific capacity of the material.

[0069] Under high temperature conditions of 55°C, the ZrO2-Cr2O3 double-layer lithium manganese oxide positive electrode material can still maintain a discharge capacity retention rate of more than 85% after 500 cycles, and has good cycle stability.

[0070] The present invention uses zirconium dioxide and chromium trioxide to perform a double-layer coating on the lithium manganate positive electrode material, thereby improving the structural stability and thermal stability of the material and effectively improving the cycle performance and thermal stability. The nano-scale coating prevents the contact between the electrolyte and the lithium manganate material, inhibits the occurrence of Mn3+ disproportionation reaction, effectively improves the high-temperature electrochemical cycle performance of the lithium manganate material, and significantly improves the performance of the battery.

[0071] By using ester compounds of zirconium and chromium metals as precursors, the polycondensation process is controlled by ammonia water in the ethanol phase, and a coating layer with uniform thickness at the nanometer level is synthesized through spray coating, which reduces the impact of the unevenness of the coating layer on the performance of the lithium battery positive electrode material.

[0072] The above description is a detailed description of the preferred embodiments of the present invention, but the embodiments are not intended to limit the scope of the patent application of the present invention. Any equivalent changes or modifications completed under the technical spirit suggested by the present invention should be covered by the patent of the present invention.

Claims

1. A method for preparing high-temperature resistant and long-life power-type coated modified lithium manganese oxide, characterized in that: The following steps are included: Step 1: mixing lithium carbonate and a manganese source and then calcining them once, with a lithium-manganese molar ratio of 0.5-0.55, to obtain a primary product of lithium manganate; Step 2, preparing a ZrO2 coating solution: dissolving tetrabutyl zirconate in anhydrous ethanol solution, adding 15% ammonia water to adjust the pH to 9-10, and stirring at 35-40°C for 2-3 hours to obtain a ZrO2 coating solution; Step 3, spray coating the initial lithium manganate product with a ZrO2 coating solution for 1-1.5 hours; secondary calcining the sprayed product to obtain a ZrO2-coated lithium manganate material; the coating amount of ZrO2 is 1-2% by mass of the initial lithium manganate product; Step 4, preparing a Cr2O3 coating solution: dissolving tert-butyl chromate in anhydrous ethanol solution, adding 15% ammonia water to adjust the pH to 9-10, and stirring at 35-40°C for 2-3 hours to obtain a Cr2O3 coating solution; Step 5: Spray-coat the ZrO2-coated lithium manganate material with a Cr2O3 coating solution for 1-1.5 hours, and calcine the sprayed product three times to obtain a lithium manganate positive electrode material with a ZrO2-Cr2O3 double coating layer; the coating amount of Cr2O3 is 0.6-1% of the mass fraction of the initial lithium manganate product.

2. The method for preparing a high-temperature resistant, long-life power-type coated modified lithium manganate according to claim 1, characterized in that: The manganese source consists of the following components in weight percentage: 5% MnO, 5% Mn2O3, 70%-80% Mn3O4, and 10%-20% MnO2.

3. The method for preparing a high-temperature resistant, long-life power-type coated modified lithium manganate according to claim 2, characterized in that: The manganese source is spherical particles with a D50 of 8-15 μm.

4. The method for preparing a high-temperature resistant, long-life power-type coated modified lithium manganate according to claim 3, characterized in that: In step 1, the primary calcination atmosphere is air, the calcination temperature is 750° C.-850° C., and the calcination time is 18-23 hours.

5. The method for preparing a high-temperature resistant, long-life power-type coated modified lithium manganate according to claim 1, characterized in that: In step 2, the concentration of the ZrO2 coating solution is 10-20%.

6. The method for preparing a high-temperature resistant, long-life power-type coated modified lithium manganate according to claim 1, characterized in that: In step 3, the atmosphere for the secondary calcination is air, the calcination temperature is 650° C.-750° C., and the calcination time is 12-16 hours.

7. The method for preparing a high-temperature resistant, long-life power-type coated modified lithium manganate according to claim 1, characterized in that: In step 4, the concentration of the Cr2O3 coating solution is 10-20%.

8. The method for preparing a high-temperature resistant, long-life power-type coated modified lithium manganate according to claim 1, characterized in that: In step 5, the atmosphere for the three calcinations is air, the calcination temperature is 550° C.-650° C., and the calcination time is 8-10 hours.