A modification method for lithium-rich manganese-based solid solution lithium-ion battery positive electrode material

Abstract

The present invention discloses a method for modifying a lithium-rich manganese-based solid solution lithium-ion battery positive electrode material. The method comprises mixing a lithium-rich manganese-based material and dopamine hydrochloride in a certain proportion to prepare a mixture, placing the mixture in a modification solution for preliminary modification, separating to obtain a modified solid, drying the solid to obtain a primary intermediate, calcining the primary intermediate to obtain a primary modified lithium-rich manganese-based solid solution lithium-ion battery positive electrode material, and then placing the primary modified lithium-rich manganese-based solid solution lithium-ion battery positive electrode material in acetic acid for full oxidation to passivate the surface of the primary modified lithium-rich manganese-based solid solution lithium-ion battery positive electrode material. The secondary intermediate is separated and dried to obtain a modified secondary intermediate, and after calcining the secondary intermediate, a layer of stable coating is formed on the surface of the primary modified lithium-rich manganese-based solid solution lithium-ion battery positive electrode material. The coating further stabilizes the lithium-rich manganese-based solid solution lithium-ion battery positive electrode material, thereby preventing the capacity and voltage of the material from rapidly declining during use.

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 modifying a lithium-rich manganese-based solid solution lithium ion battery positive electrode material. Background Art

[0002] With the widespread adoption of new energy vehicles and portable electronic devices, lithium-ion batteries, as highly efficient energy storage devices, have gradually become an important means of storing and converting electrical energy. Currently, the specific energy of the cathode material in lithium-ion battery systems largely determines the energy density, cycle life, and safety of the battery. Furthermore, cathode materials contribute significantly to the cost of the battery, exceeding 40%. Therefore, the development of low-cost, high-energy-density cathode materials is of great significance.

[0003] With the development of materials science, the use of lithium-rich manganese-based materials to prepare positive electrode materials for lithium-ion batteries has emerged. Lithium-rich manganese-based materials have the advantages of high energy density and relatively low cost. However, this material also has some usage defects during use. The lithium-rich layered structure in the lithium-rich manganese-based positive electrode material is unstable. During the battery charging and discharging process, transition metal ions will irreversibly migrate into the lithium ion layer, transforming the layered structure into a disordered structure such as spinel or rock salt phase, which will lead to rapid decay of the battery's capacitance and voltage. Therefore, it is necessary to improve the performance of existing lithium-rich manganese-based materials. Summary of the Invention

[0004] In order to overcome the deficiencies of the prior art, the present invention aims to provide a method for modifying a lithium-rich manganese-based solid solution lithium-ion battery positive electrode material to solve the problem of structural instability of the existing lithium-rich manganese-based material during use.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a method for modifying a lithium-rich manganese-based solid solution lithium-ion battery positive electrode material, which specifically comprises the following steps:

[0007] (1) Mixing a lithium-rich manganese-based cathode material and dopamine hydrochloride in proportion to form a mixture, and placing the mixture in a modification liquid for reaction to obtain a modified material system;

[0008] (2) performing solid-liquid separation on the modified material system described in (1), obtaining a solid in the modified material system, and drying the solid to obtain a primary intermediate;

[0009] (3) Calcining the primary intermediate to obtain a primary modified lithium-rich manganese-based solid solution lithium-ion battery cathode material;

[0010] (4) placing the primary modified lithium-rich manganese-based solid solution lithium-ion battery cathode material in acetic acid for mixed reaction to form a mixed oxidation system;

[0011] (5) solid-liquid separation of the mixed oxidation system described in (4), obtaining solids in the mixed oxidation system, and drying the solids to obtain a secondary intermediate;

[0012] (6) Calcination of the secondary intermediate yields a secondary modified lithium-rich manganese-based solid solution lithium-ion battery cathode material.

[0013] Furthermore, the mass ratio of the lithium-rich manganese-based material to dopamine hydrochloride in the mixture in step (1) is (6-20):(2-4).

[0014] Furthermore, the modification solution in step (1) is prepared by mixing water, lithium periodate, sodium periodate and buffer solution in a mass ratio of 1000: (1.5-2.5): 0.5: (6-8).

[0015] Furthermore, the buffer solution is sodium acetate.

[0016] Furthermore, the modified material system in step (1) is placed on a shaker for reaction, the shaker speed is set to 80-130 r / min, and the reaction time is 2-5 h.

[0017] Furthermore, in step (3), the calcination temperature of the primary solid is 900-1000°C, the heating rate during calcination is 5-10°C / min, and the calcination time is 8-12h.

[0018] Furthermore, in step (4), the mixing reaction time of the primary modified lithium-rich manganese-based solid solution lithium-ion battery positive electrode material and acetic acid is 10 to 40 minutes.

[0019] Furthermore, the concentration of acetic acid in step (4) is 0.2-1.5 mol / l.

[0020] Furthermore, in step (6), the temperature for calcining the secondary intermediate is 400-550°C, the heating rate during calcination is 5-10°C / min, and the calcination time is 30-60 min.

[0021] The present invention also provides a lithium-rich manganese-based solid solution lithium-ion battery positive electrode material, which is prepared by the above method.

[0022] A method for modifying a lithium-rich manganese-based solid solution lithium-ion battery positive electrode material specifically comprises the following steps:

[0023] (1) The lithium-rich manganese-based material and dopamine hydrochloride are mixed in proportion to form a mixture, and the mixture is placed in a modification liquid for reaction to obtain a modified material system;

[0024] (2) performing solid-liquid separation on the modified material system to obtain a solid in the modified material system, and drying and sintering the solid to obtain a primary intermediate;

[0025] (3) Calcining the primary intermediate to obtain a primary modified lithium-rich manganese-based solid solution lithium-ion battery cathode material;

[0026] (4) placing the obtained primary modified lithium-rich manganese-based solid solution lithium-ion battery cathode material in acetic acid for mixed reaction to form a mixed oxidation system;

[0027] (5) solid-liquid separation of the modified material system described in (4) to obtain solids in the mixed oxidation system, and drying the solids to obtain a secondary intermediate;

[0028] (6) Calcination of the secondary intermediate yields a secondary modified lithium-rich manganese-based solid solution lithium-ion battery cathode material.

[0029] Furthermore, the mass ratio of the lithium-rich manganese-based material to dopamine hydrochloride in the mixture in step (1) is (6-20):(2-4).

[0030] Furthermore, the modification solution in step (1) is prepared by mixing water, lithium periodate, sodium periodate and buffer solution in a mass ratio of 1000: (1.5-2.5): 0.5: (6-8).

[0031] Furthermore, the buffer solution is sodium acetate.

[0032] Furthermore, the modified material system in step (1) is placed on a shaker for reaction, the shaker speed is set to 80-130 r / min, and the reaction time is 2-5 h.

[0033] Furthermore, the sintering temperature in step (23) is 900-1000°C (450-600°C), the heating rate during sintering is 5-10°C / min, and the sintering time is 58-812h.

[0034] Furthermore, the intermediate is ground before calcination, and the ground product is calcined at 900-1000° C. for 8-12 hours.

[0035] Furthermore, after obtaining the primary modified lithium-rich manganese-based solid solution lithium battery positive electrode material, the primary modified lithium-rich manganese-based solid solution lithium battery positive electrode material is placed in acetic acid for mixed reaction to form a mixed oxidation system, solid-liquid separation is performed to obtain the solid in the mixed oxidation system, the solid is calcined at medium temperature, the temperature is raised and the solid is calcined again at high temperature, and after natural cooling, the secondary modified lithium-rich manganese-based solid solution lithium battery positive electrode material is obtained.

[0036] Furthermore, the concentration of acetic acid used in step (4) is 0.2-1.5 mol / l.

[0037] Furthermore, in step (4), the mixing reaction time of the primary modified lithium-rich manganese-based solid solution lithium-ion battery positive electrode material and acetic acid is 10 to 40 minutes.

[0038] Furthermore, the medium temperature of the calcined solid in step (6) is 400-550°C; the high temperature of the calcined solid is 600-800°C, the heating rate during calcination is 5-10°C / min, and the calcination time at the medium temperature and high temperature is 30-60 minutes.

[0039] The present invention also provides a lithium-rich manganese-based solid solution lithium-ion battery positive electrode material, which is prepared by the above method.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] The present invention prepares a mixture by mixing a lithium-rich manganese-based material and dopamine hydrochloride in proportion, and then placing the mixture in a modifying liquid for preliminary modification. The modifying liquid, which contains lithium periodate and sodium periodate as main raw materials, serves as an oxidant for the dopamine self-polymerization reaction, thereby improving the efficiency of the dopamine self-polymerization reaction and the uniformity and density of the polydopamine coated on the surface of the lithium-rich manganese-based material. During the subsequent calcination process, the polydopamine forms a well-connected conductive structure under the action of calcination. The modified solid is further separated, and the solid is calcined and dried to obtain a primary intermediate. The primary intermediate is calcined to obtain a primary modified lithium-rich manganese-based solid solution lithium-ion battery positive electrode material.

[0042] The first-level modified lithium-rich manganese-based solid solution lithium-ion battery positive electrode material is then placed in acetic acid for full oxidation to passivate the surface of the first-level modified lithium-rich manganese-based solid solution lithium-ion battery positive electrode material. Further solid-liquid separation and drying are performed to obtain a modified secondary intermediate. After calcining the secondary intermediate, a layer of stable coating is formed on the surface of the first-level modified lithium-rich manganese-based solid solution lithium-ion battery positive electrode material. The coating further stabilizes the lithium-rich manganese-based solid solution lithium-ion battery positive electrode material, thereby avoiding the rapid decline of the battery's capacitance and voltage during use, and effectively improving the performance of the lithium-rich manganese-based material. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 A schematic diagram of a process for modifying a lithium-rich manganese-based solid solution lithium-ion battery positive electrode material provided by the present invention

[0044] Figure 2 A comparison chart of the initial charge and discharge capacities of lithium-ion batteries prepared in the embodiments of the present invention and the comparative examples;

[0045] Figure 3 A comparison chart of the initial coulombic efficiency and capacity retention rate of lithium-ion batteries prepared in the embodiment of the present invention and the comparative example;

[0046] Figure 4 Comparison of rate performance of lithium-ion batteries made in the examples of the present invention and comparative examples. DETAILED DESCRIPTION

[0047] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention and the accompanying drawings. Example 1

[0048] The modification method of the lithium-rich manganese-based solid solution lithium-ion battery positive electrode material of this embodiment includes the following steps:

[0049] (1) Dissolve 6 g of sodium acetate in 1 L of water to obtain a buffer solution; add 2.5 g of lithium periodate and 0.5 g of sodium periodate to the buffer solution and stir until the solid is fully dissolved to obtain a modified solution. Pour all the modified solution into a reaction vessel and set aside.

[0050] (2) Place the reaction vessel containing the modified liquid on a shaker, then add 6 g of lithium-rich manganese-based material and 2 g of dopamine hydrochloride into the reaction vessel, turn on the shaker, and set the shaker speed at 80 r / min. After 5 hours, filter the material in the reaction vessel, wash, and dry to obtain the dopamine-coated lithium-rich manganese-based material (primary intermediate).

[0051] (3) The dopamine-coated lithium-rich manganese-based material was placed in a muffle furnace and heated to 900°C at a heating rate of 5°C / min under an argon atmosphere. The temperature was kept at this temperature for 8 hours and then cooled to room temperature to obtain a first-level modified lithium-rich manganese-based solid solution lithium-ion battery positive electrode material.

[0052] (4) 12 g of 1.5 mol / l acetic acid was added to the reaction vessel and placed on a shaker. Then 6 g of lithium-rich manganese-based material was added to the reaction vessel. The shaker was turned on at a speed of 80 r / min. After 10 minutes, the material in the reaction vessel was filtered, washed, and dried to obtain a secondary intermediate.

[0053] (5) The secondary intermediate is placed in a muffle furnace and heated to 400°C at a heating rate of 5°C / min under an argon atmosphere, kept at this temperature for 30 minutes, and cooled to room temperature to obtain a secondary modified lithium-rich manganese-based solid solution lithium-ion battery positive electrode material. Example 2

[0054] The modification method of the lithium-rich manganese-based solid solution lithium-ion battery positive electrode material of this embodiment includes the following steps:

[0055] (1) Dissolve 8 g of sodium acetate in 1 L of water to obtain a buffer solution; add 1.5 g of lithium periodate and 0.5 g of sodium periodate to the buffer solution and stir until the solid is fully dissolved to obtain a modified solution. Pour all the modified solution into a reaction vessel and set aside.

[0056] (2) Place the reaction vessel containing the modified liquid on a shaker, then add 20 g of lithium-rich manganese-based material and 4 g of dopamine hydrochloride into the reaction vessel, turn on the shaker, and set the shaker speed at 130 r / min. After 2 hours, filter the material in the reaction vessel, wash, and dry to obtain the dopamine-coated lithium-rich manganese-based material.

[0057] (3) The dopamine-coated lithium-rich manganese-based material was placed in a muffle furnace and heated to 1000°C at a heating rate of 10°C / min under an argon atmosphere. The temperature was kept at this temperature for 12 hours and then cooled to room temperature to obtain a first-level modified lithium-rich manganese-based solid solution lithium-ion battery positive electrode material.

[0058] (4) 35 g of 0.2 mol / l acetic acid was added to a reaction vessel and placed on a shaker. Then 20 g of lithium-rich manganese-based material was added to the reaction vessel. The shaker was turned on at a speed of 130 r / min. After 40 min, the material in the reaction vessel was filtered, washed, and dried to obtain a secondary intermediate.

[0059] (5) The secondary intermediate was placed in a muffle furnace and heated to 550°C at a heating rate of 10°C / min under an argon atmosphere, kept warm for 60 minutes, and cooled to room temperature to obtain a secondary modified lithium-rich manganese-based solid solution lithium-ion battery positive electrode material. Example 3

[0060] The modification method of the lithium-rich manganese-based solid solution lithium-ion battery positive electrode material of this embodiment includes the following steps:

[0061] (1) Dissolve 7 g of sodium acetate in 1 L of water to obtain a buffer solution; add 2 g of lithium periodate and 0.5 g of sodium periodate to the buffer solution and stir until the solid is fully dissolved to obtain a modified solution. Pour all the modified solution into a reaction vessel and set aside.

[0062] (2) Place the reaction vessel containing the modified liquid on a shaker, then add 15 g of lithium-rich manganese-based material and 3 g of dopamine hydrochloride into the reaction vessel, turn on the shaker, and set the shaker speed at 100 r / min. After 3 hours, filter the material in the reaction vessel, wash, and dry to obtain the dopamine-coated lithium-rich manganese-based material.

[0063] (3) The dopamine-coated lithium-rich manganese-based material was placed in a muffle furnace and heated to 920°C at a heating rate of 6°C / min under an argon atmosphere. The material was kept warm for 10 hours and then cooled to room temperature to obtain a first-level modified lithium-rich manganese-based solid solution lithium-ion battery positive electrode material.

[0064] (4) 45 g of 0.8 mol / l acetic acid was added to a reaction vessel and placed on a shaker. Then, 15 g of lithium-rich manganese-based material was added to the reaction vessel. The shaker was turned on at a speed of 100 r / min. After 20 minutes, the material in the reaction vessel was filtered, washed, and dried to obtain a secondary intermediate.

[0065] (5) The secondary intermediate was placed in a muffle furnace and heated to 450°C at a heating rate of 6°C / min under an argon atmosphere, kept at this temperature for 40 minutes, and cooled to room temperature to obtain a secondary modified lithium-rich manganese-based solid solution lithium-ion battery positive electrode material. Example 4

[0066] The modification method of the lithium-rich manganese-based solid solution lithium-ion battery positive electrode material of this embodiment includes the following steps:

[0067] (1) Dissolve 7 g of sodium acetate in 1 L of water to obtain a buffer solution; add 1.8 g of lithium periodate and 1 g of sodium periodate to the buffer solution and stir until the solid is fully dissolved to obtain a modified solution. Pour all the modified solution into a reaction vessel and set aside.

[0068] (2) Place the reaction vessel containing the modified liquid on a shaker, then add 10 g of lithium-rich manganese-based material and 2.5 g of dopamine hydrochloride into the reaction vessel, turn on the shaker, and set the shaker speed at 110 r / min. After 4 hours, filter the material in the reaction vessel, wash, and dry to obtain the dopamine-coated lithium-rich manganese-based material.

[0069] (3) The dopamine-coated lithium-rich manganese-based material was placed in a muffle furnace and heated to 950°C at a heating rate of 8°C / min under an argon atmosphere. The material was kept warm for 9 hours and then cooled to room temperature to obtain a first-level modified lithium-rich manganese-based solid solution lithium-ion battery positive electrode material.

[0070] (4) Add 20 g of 1.2 mol / l acetic acid into the reaction vessel and place it on a shaker. Then add 10 g of lithium-rich manganese-based material into the reaction vessel and start the shaker at a speed of 90 r / min. After 30 minutes, filter, wash, and dry the material in the reaction vessel to obtain a secondary intermediate.

[0071] (5) The secondary intermediate was placed in a muffle furnace, heated to 500°C at a heating rate of 10°C / min under an argon atmosphere, kept warm for 50 minutes, and cooled to room temperature to obtain a secondary modified lithium-rich manganese-based solid solution lithium-ion battery positive electrode material.

[0072] Comparative Example 1:

[0073] The difference between the modification method of the lithium-rich manganese-based solid solution lithium-ion battery positive electrode material of this comparative example and the modification method of the lithium-rich manganese-based solid solution lithium-ion battery positive electrode material of Example 1 is that the mass of lithium periodate in step (1) of this comparative example is 0, and the mass of sodium periodate is 3g.

[0074] Comparative Example 2:

[0075] The difference between the modification method of the lithium-rich manganese-based solid solution lithium-ion battery positive electrode material of this comparative example and the modification method of the lithium-rich manganese-based solid solution lithium-ion battery positive electrode material of Example 1 is that the mass of sodium periodate in step (1) of this comparative example is 0, and the mass of lithium periodate is 3g.

[0076] Comparative Example 3:

[0077] The difference between the modification method of the lithium-rich manganese-based solid solution lithium-ion battery positive electrode material of this comparative example and the modification method of the lithium-rich manganese-based solid solution lithium-ion battery positive electrode material of Example 1 is that the mass of lithium periodate in step (1) of this comparative example is 3 g.

[0078] Comparative Example 4:

[0079] The difference between the modification method of the lithium-rich manganese-based solid solution lithium-ion battery positive electrode material of this comparative example and the modification method of the lithium-rich manganese-based solid solution lithium-ion battery positive electrode material of Example 1 is that the mass of lithium periodate in step (1) of this comparative example is 1 g.

[0080] Comparative Example 5:

[0081] The difference between the modification method of the lithium-rich manganese-based solid solution lithium-ion battery positive electrode material of this comparative example and the modification method of the lithium-rich manganese-based solid solution lithium-ion battery positive electrode material of Example 1 is that the mass of dopamine hydrochloride in step (2) of this comparative example is 4 g.

[0082] Comparative Example 6:

[0083] The difference between the modification method of the lithium-rich manganese-based solid solution lithium-ion battery positive electrode material of this comparative example and the modification method of the lithium-rich manganese-based solid solution lithium-ion battery positive electrode material of Example 1 is that in step (3) of this comparative example, the dopamine-coated lithium-rich manganese-based material is placed in a muffle furnace and heated to 1000°C at a heating rate of 5°C / min under an argon atmosphere.

[0084] Comparative Example 7:

[0085] The difference between the modification method of the lithium-rich manganese-based solid solution lithium-ion battery positive electrode material of this comparative example and the modification method of the lithium-rich manganese-based solid solution lithium-ion battery positive electrode material of Example 1 is that the mass of acetic acid in step (4) of this comparative example is 18 g.

[0086] Comparative Example 8:

[0087] The difference between the modification method of the lithium-rich manganese-based solid solution lithium-ion battery positive electrode material of this comparative example and the modification method of the lithium-rich manganese-based solid solution lithium-ion battery positive electrode material of Example 1 is that in step (1) of this comparative example, sodium periodate is replaced by potassium periodate.

[0088] Comparative Example 9:

[0089] The difference between the modification method of the lithium-rich manganese-based solid solution lithium-ion battery positive electrode material of this comparative example and the modification method of the lithium-rich manganese-based solid solution lithium-ion battery positive electrode material of Example 1 is that in step (1) of this comparative example, lithium periodate is replaced by potassium periodate.

[0090] Application examples:

[0091] The modified lithium-rich manganese-based solid solution lithium-ion battery cathode materials obtained in Examples 1 to 3 and the comparative example were fabricated into lithium-ion batteries, and then battery performance was tested. The lithium-ion battery fabrication method is as follows: 0.1 g of the lithium-rich manganese-based solid solution lithium-ion battery cathode material, 0.01 g of acetylene black, 0.01 g of polyvinylidene fluoride, and an appropriate amount of N-methylpyrrolidone were mixed and uniformly coated on aluminum foil to obtain a cathode electrode sheet; then, in a vacuum glove box, a lithium metal sheet was used as the anode, a commercial PP film was used as the separator, and a 1 mol / L lithium hexafluorophosphate solution was used as the electrolyte (the solvent in the electrolyte was composed of ethylene carbonate and dimethyl carbonate in a volume ratio of 1:1), to assemble the lithium-ion battery. Then, the lithium-ion battery was subjected to the first charge and discharge performance test, rate performance and cycle performance test at room temperature using an electrochemical tester. The conditions for the first charge and discharge performance test were as follows: current density of 0.1C, charge and discharge voltage range of 2 to 4.8V; rate performance test was carried out at rates of 0.2C, 1C, 3C and 5C; cycle performance was characterized by the capacity retention rate after 800 cycles at a rate of 1C. The first charge and discharge performance, rate performance and cycle performance of the lithium-ion battery made from the lithium-rich manganese-based solid solution lithium-ion battery positive electrode material modified from each embodiment and comparative example are shown in Table 1-2. The first charge and discharge capacity comparison of the lithium-ion battery made from the lithium-rich manganese-based solid solution lithium-ion battery positive electrode material modified from each embodiment and comparative example is shown in Table 1-2. Figure 1 As shown in the comparison chart of the first coulombic efficiency and capacity retention rate Figure 2 As shown in the figure, the rate performance comparison is as follows Figure 3 shown.

[0092] Table 1: Initial charge and discharge performance and cycle performance of lithium-ion batteries made from the modified lithium-rich manganese-based solid solution lithium-ion battery cathode materials obtained in each embodiment and comparative example

[0093] cathode materials First discharge capacity (mAh / g) First coulombic efficiency (%) Capacity retention rate (%) Example 1 275.8 88.5 89.6 Example 2 278.4 88.9 90.3 Example 3 276.3 88.3 88.9 Comparative Example 1 245.6 81.6 69.3 Comparative Example 2 247.3 79.3 72.5 Comparative Example 3 251.8 83.5 74.1 Comparative Example 4 249.7 82.9 73.8 Comparative Example 5 252.9 85.7 75.6 Comparative Example 6 259.5 84.8 77.9 Comparative Example 7 253.8 85.1 76.8 Comparative Example 8 248.5 85.3 77.4 Comparative Example 9 249.3 84.6 76.1

[0094] Table 2: Rate performance of lithium-ion batteries made from the modified lithium-rich manganese-based solid solution lithium-ion battery positive electrode materials obtained in each embodiment and comparative example

[0095] cathode materials Capacity at 0.2C rate (mAh / g) Capacity at 1C rate (mAh / g) Capacity at 3C rate (mAh / g) Capacity at 5C rate (mAh / g) Example 1 267.3 249.7 221.4 192.7 Example 2 270.1 251.4 225.2 195.3 Example 3 268.4 248.6 223.2 191.8 Comparative Example 1 232.7 213.5 189.5 156.3 Comparative Example 2 236.2 215.2 190.4 159.6 Comparative Example 3 239.5 214.8 191.3 158.7 Comparative Example 4 234.1 210.7 188.6 154.9 Comparative Example 5 245.7 219.6 192.2 155.8 Comparative Example 6 247.2 221.4 195.1 161.4 Comparative Example 7 244.3 218.5 188.5 153.8 Comparative Example 8 245.1 219.3 189.6 157.1 Comparative Example 9 246.8 220.3 193.9 165.8

[0096] It can be seen from Tables 1 and 2 that, compared with using only lithium periodate or sodium periodate, the lithium-rich manganese-based solid solution lithium-ion battery positive electrode material prepared by using both lithium periodate and sodium periodate has better battery performance; and a ratio of lithium periodate to sodium periodate that is too large or too small is not conducive to improving the battery performance of the lithium-rich manganese-based solid solution lithium-ion battery positive electrode material; in addition, the calcination temperature also has a certain influence on the battery performance of the lithium-rich manganese-based solid solution lithium-ion battery positive electrode material. Too high a temperature will destroy the coating layer structure, and too low a temperature is not conducive to the formation of a graphitized structure.

Claims

1. A method for modifying a lithium-rich manganese-based solid solution lithium-ion battery positive electrode material, characterized in that: The specific steps include: (1) Mixing a lithium-rich manganese-based cathode material and dopamine hydrochloride in proportion to form a mixture, and placing the mixture in a modification liquid for reaction to obtain a modified material system; (2) performing solid-liquid separation on the modified material system described in (1), obtaining a solid in the modified material system, and drying the solid to obtain a primary intermediate; (3) Calcining the primary intermediate to obtain a primary modified lithium-rich manganese-based solid solution lithium-ion battery cathode material; (4) placing the primary modified lithium-rich manganese-based solid solution lithium-ion battery cathode material in acetic acid for mixed reaction to form a mixed oxidation system; (5) solid-liquid separation of the mixed oxidation system described in (4), obtaining solids in the mixed oxidation system, and drying the solids to obtain a secondary intermediate; (6) Calcining the secondary intermediate to obtain a secondary modified lithium-rich manganese-based solid solution lithium-ion battery cathode material; The modified solution in step (1) is prepared by mixing water, lithium periodate, sodium periodate and buffer solution in a mass ratio of 1000: (1.5-2.5): 0.5: (6-8); In step (3), the calcination temperature of the primary solid is 900-1000°C, the heating rate during calcination is 5-10°C / min, and the calcination time is 8-12h.

2. The method for modifying a lithium-rich manganese-based solid solution lithium-ion battery positive electrode material according to claim 1, wherein: The mass ratio of the lithium-rich manganese-based material to dopamine hydrochloride in the mixture in step (1) is (6-20):(2-4).

3. The method for modifying a lithium-rich manganese-based solid solution lithium-ion battery positive electrode material according to claim 2, wherein: The buffer solution is sodium acetate.

4. The method for modifying a lithium-rich manganese-based solid solution lithium-ion battery positive electrode material according to claim 3, wherein: In step (1), the modified material system is placed on a shaker for reaction, the shaker speed is set to 80-130 r / min, and the reaction time is 2-5 h.

5. The method for modifying a lithium-rich manganese-based solid solution lithium-ion battery positive electrode material according to claim 4, characterized in that: In step (4), the mixing reaction time of the primary modified lithium-rich manganese-based solid solution lithium-ion battery positive electrode material and acetic acid is 10 to 40 minutes.

6. The method for modifying a lithium-rich manganese-based solid solution lithium-ion battery positive electrode material according to claim 5, characterized in that: The concentration of acetic acid in step (4) is 0.2-1.5 mol / l.

7. The method for modifying a lithium-rich manganese-based solid solution lithium-ion battery positive electrode material according to claim 6, characterized in that: In step (6), the temperature for calcining the secondary intermediate is 400-550°C, the heating rate during calcination is 5-10°C / min, and the calcination time is 30-60 min.

8. A lithium-rich manganese-based solid solution lithium-ion battery positive electrode material, prepared by the method according to any one of claims 1 to 7.

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