Oxygen vacancy surface doped manganese-based lithium supplement agent and preparation method and application thereof

Abstract

The invention provides an oxygen vacancy surface doped manganese-based lithium supplement agent and a preparation method and application thereof, and belongs to the field of lithium ion battery lithium supplement materials. The plasma treatment method is adopted to treat the manganese-based lithium supplementing agent, controllable construction of oxygen vacancy concentration, depth and gradient distribution on the surface of the manganese-based lithium supplementing agent is achieved by regulating and controlling gas types, plasma power, treatment temperature and treatment time, surface oxygen evolution and surface side reaction are inhibited through controllable oxygen vacancy surface doping, and the surface oxygen vacancy concentration, depth and gradient distribution of the surface of the manganese-based lithium supplementing agent are improved. The surface stability of the lithium supplementing agent is improved; the preparation method provided by the invention is simple and low in cost, can effectively improve the physical and chemical properties of the manganese-based lithium supplement agent, and has important application prospects in lithium ion batteries.

Description

Technical Field

[0001] The present invention relates to the field of lithium-ion battery lithium-replenishing materials, and in particular to an oxygen vacancy surface doped manganese-based lithium-replenishing agent, and a preparation method and application thereof. Background Art

[0002] Lithium-ion batteries have been widely used in consumer electronics, electric vehicles, mobile energy storage and other fields, promoting the development of related fields. At present, new fields and new industries based on high-performance lithium-ion batteries are booming, including drones / electric aircraft, robots, and large-scale intelligent energy storage, which are expected to form a new industrial blue ocean. These applications have put forward higher requirements on the performance of lithium-ion batteries, including energy density, cycle life and safety. Therefore, it is urgent to develop key materials and key strategies that can significantly improve the electrochemical performance of lithium-ion batteries.

[0003] Among many solutions, lithium replenishment is an effective strategy. By adding lithium replenishers to the battery system, the irreversible lithium ion loss of lithium-ion batteries during formation and operation can be replenished, especially the lithium ions consumed by the formation of the solid-electrolyte interface (SEI) at the negative electrode can be compensated. Therefore, on the one hand, the energy density of the battery can be improved, and on the other hand, the cycle life of the battery can be improved. Lithium replenishment strategies can be divided into negative electrode lithium replenishment and positive electrode lithium replenishment. Negative electrode lithium replenishment often uses lithium metal foil, lithium powder or electrochemical lithium replenishment, which has the disadvantages of difficult control of lithium replenishment amount, unsafe process and high cost. In comparison, positive electrode lithium replenishment can be added with positive electrode lithium replenishers during the homogenization process of positive electrode preparation. Positive electrode lithium replenishers are compounds with high lithium content. Accurate lithium replenishment can be achieved by adjusting the amount of positive electrode lithium replenishers added. It is easy to operate, highly safe, and low cost. It has important application prospects and broad market potential.

[0004] Among many lithium supplements, the composite lithium manganese oxide xLi6MnO4·(1-x)LiMnO2 (0.3≤x≤1) formed by anti-fluorite Li6MnO4 and layered LiMnO2 has outstanding advantages such as high first-cycle charging capacity (>600mAh / g), low first-cycle discharge capacity (<100mAh / g), low cost and environmental friendliness, and is a positive electrode lithium supplement with important advantages. However, this manganese-based lithium supplement still has many problems, including severe gas production, large electrochemical polarization and significant surface side reactions, which seriously affect the electrochemical performance of the battery. Therefore, how to solve the problems of severe gas production, large electrochemical polarization and significant surface side reactions of manganese-based lithium supplements, and improve the air stability and electrochemical performance of manganese-based lithium supplements, has become a technical problem to be solved in this field. Summary of the invention

[0005] The purpose of the present invention is to provide an oxygen vacancy surface doped manganese-based lithium supplement agent and a preparation method and application thereof. The oxygen vacancy surface doping strategy provided by the present invention effectively improves the air stability and electrochemical performance of the manganese-based lithium supplement agent, and the interfacial oxygen precipitation and interfacial side reactions are significantly inhibited, thereby reducing the electrochemical polarization.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing an oxygen vacancy surface doped manganese-based lithium supplement agent, comprising: performing plasma treatment on the manganese-based lithium supplement agent to obtain the oxygen vacancy surface doped manganese-based lithium supplement agent;

[0008] The atmosphere of the plasma treatment includes any one or more of N2, Ar, H2, NH3, He, O2 and CH4, the pressure of the plasma treatment is 1 to 1000 Pa, the temperature of the plasma treatment is 25 to 600°C, and the time of the plasma treatment is 0.1 to 120 min.

[0009] Preferably, the chemical formula of the manganese-based oxide lithium supplement is xLi6MnO4·(1-x)LiMnO2, wherein x is 0.3-1.

[0010] Preferably, the atmosphere of the plasma treatment is a mixed atmosphere of Ar and H2, and the volume ratio of Ar to H2 in the mixed atmosphere of Ar and H2 is (90-95):(5-10).

[0011] Preferably, the pressure of the plasma treatment is 10-100 Pa.

[0012] Preferably, the temperature of the plasma treatment is 25-300°C.

[0013] Preferably, the plasma treatment time is 20 to 60 minutes.

[0014] Preferably, the power of the plasma treatment is 10-1000W.

[0015] The present invention provides an oxygen vacancy surface doped manganese-based lithium supplement agent prepared by the preparation method described in the above technical scheme.

[0016] The present invention provides the use of the oxygen vacancy surface doped manganese-based lithium supplement agent described in the above technical solution in a lithium ion battery.

[0017] Preferably, the application method is to mix the oxygen vacancy surface doped manganese-based lithium replenisher with the positive electrode material, then prepare it into a positive electrode plate, and finally assemble the positive electrode plate into a lithium battery; the amount of the oxygen vacancy surface doped manganese-based lithium replenisher is 0.1 to 10% of the mass of the positive electrode material.

[0018] The present invention provides a method for preparing a manganese-based lithium supplement agent doped with oxygen vacancies on the surface, comprising: subjecting the manganese-based lithium supplement agent to plasma treatment to obtain a manganese-based lithium supplement agent doped with oxygen vacancies on the surface; the atmosphere of the plasma treatment comprises any one or more of N2, Ar, H2, NH3, He, O2 and CH4, the pressure of the plasma treatment is 1 to 1000 Pa, the temperature of the plasma treatment is 25 to 600° C., and the time of the plasma treatment is 0.1 to 120 min. The present invention uses a plasma treatment method to treat the manganese-based lithium supplement agent, and by regulating the gas type, plasma power, treatment temperature and treatment time, the controllable construction of the oxygen vacancy concentration, depth and gradient distribution on the surface of the manganese-based lithium supplement agent is achieved, and the surface oxygen precipitation and surface side reactions are inhibited by controllable oxygen vacancy surface doping, thereby improving the surface stability of the lithium supplement agent; the preparation method provided by the present invention is simple and low in cost, and can effectively improve the physicochemical properties of the manganese-based lithium supplement agent, and has important application prospects in lithium-ion batteries. The results of the embodiments show that the surface oxygen vacancy concentration of the manganese-based lithium supplement agent doped with oxygen vacancies provided by the present invention is 5-35%, the oxygen vacancy depth is 3-30nm, and the oxygen vacancies are distributed in a surface gradient; the discharge voltage of a 100mAh-level lithium ion soft-pack battery prepared using the manganese-based lithium supplement agent doped with oxygen vacancies is 2-4.8V, the first-cycle charging capacity is 837mAh / g, the first-cycle discharge capacity is 60mAh / g, and the corresponding first-cycle coulomb efficiency is 7.2%; the manganese-based lithium supplement agent doped with oxygen vacancies is placed for one month to prepare a 100mAh-level lithium ion soft-pack battery, the discharge voltage is 2-4.8V, the first-cycle charging capacity is 798mAh / g, the first-cycle discharge capacity is 54mAh / g, and the corresponding first-cycle coulomb efficiency is 6.8%. The electrochemical properties of the two are very close, and the charging capacity can be effectively exerted, indicating that the oxygen vacancy surface doping method of the present invention effectively improves the air stability of the manganese-based lithium supplement agent, and the interfacial oxygen precipitation and interfacial side reactions are significantly inhibited. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A flow chart of the preparation method of the oxygen vacancy surface doped manganese-based lithium supplement agent provided by the present invention;

[0020] Figure 2 The charge and discharge curves of the 100mAh lithium-ion soft-pack batteries prepared in Application Examples 1 and 2 of the present invention. DETAILED DESCRIPTION

[0021] The present invention provides a method for preparing an oxygen vacancy surface doped manganese-based lithium supplement agent, comprising: performing plasma treatment on the manganese-based lithium supplement agent to obtain the oxygen vacancy surface doped manganese-based lithium supplement agent;

[0022] The atmosphere of the plasma treatment includes any one or more of N2, Ar, H2, NH3, He, O2 and CH4, the pressure of the plasma treatment is 1 to 1000 Pa, the temperature of the plasma treatment is 25 to 600°C, and the time of the plasma treatment is 0.1 to 120 min.

[0023] In the present invention, the chemical formula of the manganese-based lithium supplement is preferably xLi6MnO4·(1-x)LiMnO2; the x is 0.3-1, preferably 0.4-0.9, more preferably 0.5-0.8, and further preferably 0.6-0.7; the crystal structure of the manganese-based lithium supplement is preferably a composite structure formed by anti-fluorite Li6MnO4 and layered LiMnO2; the particle size of the lithium-rich manganese-based positive electrode material is preferably 0.2-20 μm. The present invention does not specifically limit the specific source of the manganese-based lithium supplement, and it can be prepared using a commercial product well known to those skilled in the art or a preparation method well known to those skilled in the art.

[0024] In the present invention, the plasma treatment is preferably performed in a plasma treatment instrument. The present invention has no particular limitation on the specific model and source of the plasma treatment instrument, and any plasma treatment instrument well known to those skilled in the art can be used.

[0025] In the present invention, the atmosphere of the plasma treatment includes any one or more of N2, Ar, H2, NH3, He, O2 and CH4, preferably a mixed atmosphere of Ar and H2; the volume ratio of Ar and H2 in the mixed atmosphere of Ar and H2 is preferably (90-95): (5-10), more preferably 95: 5. The present invention can increase the oxygen vacancy concentration on the surface of the manganese-based lithium supplement agent by controlling the atmosphere of the plasma treatment.

[0026] In the present invention, the pressure of the plasma treatment is 1-1000 Pa. The present invention can increase the oxygen vacancy depth on the surface of the manganese-based lithium supplement agent by controlling the atmosphere of the plasma treatment.

[0027] As an embodiment of the present invention, the pressure of the plasma treatment can be 1Pa, 5Pa, 10Pa, 20Pa, 50Pa, 80Pa, 100Pa, 150Pa, 200Pa, 300Pa, 400Pa, 500Pa, 600Pa, 700Pa, 800Pa, 900Pa or 1000Pa.

[0028] In the present invention, the temperature of the plasma treatment is 25-600° C. The present invention can control the oxygen vacancy concentration on the surface of the manganese-based lithium supplement agent by controlling the temperature of the plasma treatment.

[0029] As an embodiment of the present invention, the temperature of the plasma treatment may be 25°C, 50°C, 100°C, 150°C, 200°C, 250°C, 300°C, 350°C, 400°C, 450°C, 500°C, 550°C or 600°C.

[0030] In the present invention, the plasma treatment time is 0.1 to 120 minutes. By controlling the plasma treatment time, the present invention can control the oxygen vacancy depth on the surface of the manganese-based lithium supplement agent.

[0031] As an embodiment of the present invention, the plasma treatment time can be 0.1 min, 1 min, 5 min, 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, 100 min, 110 min or 120 min.

[0032] In the present invention, the power of the plasma treatment is preferably 10 to 1000 W. The present invention can ensure that the temperature of the plasma treatment is within a desired range by controlling the power of the plasma treatment, thereby further controlling the oxygen vacancy depth on the surface of the manganese-based lithium supplement agent.

[0033] As an embodiment of the present invention, the power of the plasma treatment can be 10W, 20W, 50W, 100W, 150W, 200W, 250W, 300W, 350W, 400W, 450W, 500W, 550W, 600W, 650W, 700W, 750W, 800W, 850W, 900W, 950W or 1000W.

[0034] In the present invention, the manganese-based lithium supplement agent is preferably rotated during the plasma treatment. The present invention has no special limitation on the rotation speed, which can be set according to the technical common sense of those skilled in the art. The present invention can make the manganese-based lithium supplement agent be treated more uniformly by rotating the manganese-based lithium supplement agent during the plasma treatment.

[0035] The present invention uses a plasma treatment method to treat a manganese-based lithium supplement agent. By adjusting the gas type, plasma power, treatment temperature and treatment time, the controllable construction of oxygen vacancy concentration, depth and gradient distribution on the surface of the manganese-based lithium supplement agent is achieved. Through controllable oxygen vacancy surface doping, surface oxygen precipitation and surface side reactions are suppressed, thereby improving the surface stability of the lithium supplement agent.

[0036] The flow chart of the preparation method of the oxygen vacancy surface doped manganese-based lithium supplement agent provided by the present invention is as follows Figure 1 As shown. Figure 1It can be seen that the preparation method provided by the present invention is simple and low-cost, and can effectively improve the physical and chemical properties of the manganese-based lithium supplement, and has important application prospects in lithium-ion batteries.

[0037] The present invention also provides an oxygen vacancy surface doped manganese-based lithium supplement agent prepared by the preparation method described in the above technical solution.

[0038] In the present invention, the oxygen vacancy surface doped manganese-based lithium supplement agent is preferably doped with oxygen vacancies; the surface oxygen vacancy concentration of the oxygen vacancy surface doped manganese-based lithium supplement agent is preferably 0.01-30%; the oxygen vacancy depth of the oxygen vacancy surface doped manganese-based lithium supplement agent is preferably 1-50nm; the oxygen vacancies of the oxygen vacancy surface doped manganese-based lithium supplement agent preferably present a gradient distribution that decreases from the surface to the inside.

[0039] The present invention also provides the use of the manganese-based lithium supplement agent doped on the surface of oxygen vacancies described in the above technical solution in a lithium ion battery.

[0040] In the present invention, the application method is preferably to mix the oxygen vacancy surface doped with a manganese-based lithium supplementer and a positive electrode material, and then prepare a positive electrode sheet, and finally assemble the positive electrode sheet into a lithium battery.

[0041] In the present invention, the positive electrode material preferably includes any one or more of lithium iron phosphate, lithium manganese iron phosphate, ternary layered oxide and lithium-rich layered oxide.

[0042] In the present invention, the amount of the manganese-based lithium supplement agent doped on the surface of the oxygen vacancies is preferably 0.1 to 10% of the mass of the positive electrode material.

[0043] In the present invention, the amount of the manganese-based lithium supplement agent doped on the oxygen vacancy surface can be 0.1%, 0.2%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10% of the mass of the positive electrode material.

[0044] The present invention has no special limitation on the specific operation of assembling the positive electrode plate into a lithium battery, and a lithium battery assembling method well known to those skilled in the art can be used.

[0045] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0046] Example 1

[0047] A method for preparing an oxygen vacancy surface doped manganese-based lithium supplement agent is as follows:

[0048] (1) placing a manganese-based lithium supplementer into a sample bottle, then placing the sample bottle into a chamber of a plasma treatment instrument, then introducing a plasma treatment atmosphere into the chamber and evacuating the chamber to a desired plasma treatment pressure; the chemical formula of the manganese-based lithium supplementer is xLi6MnO4·(1-x)LiMnO2, where x is 0.5; the crystal structure of the manganese-based lithium supplementer is a composite structure formed by anti-fluorite Li6MnO4 and layered LiMnO2; the particle size of the lithium-rich manganese-based positive electrode material is 0.2 to 20 μm; the plasma treatment atmosphere is a mixed atmosphere of Ar and H2, wherein the volume ratio of Ar to H2 is 95:5, and the plasma treatment pressure is 10 Pa;

[0049] (2) turning on the plasma treatment instrument in step (1), making the temperature of the chamber of the plasma treatment instrument reach the plasma treatment temperature of 25° C., rotating the sample bottle at the same time, then controlling the power of the plasma treatment to 100 W, and performing plasma treatment on the manganese-based lithium supplement for 20 minutes, and finally turning off the plasma treatment instrument, introducing air into the chamber to restore atmospheric pressure, opening the chamber to collect the solid material, and obtaining the oxygen vacancy surface doped manganese-based lithium supplement.

[0050] The XPS depth analysis test was performed on the oxygen vacancy surface doped manganese-based lithium replenisher prepared in Example 1. The results showed that the surface oxygen vacancy concentration of the oxygen vacancy surface doped manganese-based lithium replenisher was 20%, the oxygen vacancy depth was 25nm, and the oxygen vacancies were distributed in a surface gradient.

[0051] Example 2

[0052] A method for preparing an oxygen vacancy surface doped manganese-based lithium supplement agent is as follows:

[0053] (1) placing a manganese-based lithium supplementer into a sample bottle, then placing the sample bottle into a chamber of a plasma treatment instrument, then introducing a plasma treatment atmosphere into the chamber and evacuating the chamber to a desired plasma treatment pressure; the chemical formula of the manganese-based lithium supplementer is xLi6MnO4·(1-x)LiMnO2, where x is 0.5; the crystal structure of the manganese-based lithium supplementer is a composite structure formed by anti-fluorite Li6MnO4 and layered LiMnO2; the particle size of the lithium-rich manganese-based positive electrode material is 0.2 to 20 μm; the plasma treatment atmosphere is a mixed atmosphere of Ar and H2, wherein the volume ratio of Ar to H2 is 95:5, and the plasma treatment pressure is 10 Pa;

[0054] (2) turning on the plasma treatment instrument in step (1), making the temperature of the chamber of the plasma treatment instrument reach the plasma treatment temperature of 25° C., rotating the sample bottle at the same time, then controlling the power of the plasma treatment to 100 W, and performing plasma treatment on the manganese-based lithium supplement for 5 minutes, and finally turning off the plasma treatment instrument, introducing air into the chamber to restore atmospheric pressure, opening the chamber to collect the solid material, and obtaining an oxygen vacancy surface-doped manganese-based lithium supplement.

[0055] The XPS depth analysis test was performed on the oxygen vacancy surface doped manganese-based lithium replenisher prepared in Example 2. The results showed that the surface oxygen vacancy concentration of the oxygen vacancy surface doped manganese-based lithium replenisher was 10%, the oxygen vacancy depth was 10nm, and the oxygen vacancies were distributed in a surface gradient.

[0056] Example 3

[0057] A method for preparing an oxygen vacancy surface doped manganese-based lithium supplement agent is as follows:

[0058] (1) placing a manganese-based lithium supplement agent in a sample bottle, then placing the sample bottle in a chamber of a plasma treatment instrument, then introducing a plasma treatment atmosphere into the chamber and evacuating the chamber to a desired plasma treatment pressure; the chemical formula of the manganese-based lithium supplement agent is xLi6MnO4·(1-x)LiMnO2, where x is 0.5; the crystal structure of the manganese-based lithium supplement agent is a composite structure formed by anti-fluorite Li6MnO4 and layered LiMnO2; the particle size of the lithium-rich manganese-based positive electrode material is 0.2 to 20 μm; the plasma treatment atmosphere is Ar, and the plasma treatment pressure is 100 Pa;

[0059] (2) turning on the plasma treatment instrument in step (1), raising the temperature of the chamber of the plasma treatment instrument to 100° C., a plasma treatment temperature, at a heating rate of 1° C. / min, while rotating the sample bottle, then controlling the plasma treatment power to 100 W, subjecting the manganese-based lithium supplement to plasma treatment for 5 min, and finally turning off the plasma treatment instrument, introducing air into the chamber to restore atmospheric pressure, opening the chamber to collect the solid material, and obtaining an oxygen vacancy surface-doped manganese-based lithium supplement.

[0060] The XPS depth analysis test was performed on the oxygen vacancy surface doped manganese-based lithium replenisher prepared in Example 3. The results showed that the surface oxygen vacancy concentration of the oxygen vacancy surface doped manganese-based lithium replenisher was 30%, the oxygen vacancy depth was 30nm, and the oxygen vacancies were distributed in a surface gradient.

[0061] Example 4

[0062] A method for preparing an oxygen vacancy surface doped manganese-based lithium supplement agent is as follows:

[0063] (1) placing a manganese-based lithium supplement agent in a sample bottle, then placing the sample bottle in a chamber of a plasma treatment instrument, then introducing a plasma treatment atmosphere into the chamber and evacuating the chamber to a desired plasma treatment pressure; the chemical formula of the manganese-based lithium supplement agent is xLi6MnO4·(1-x)LiMnO2, where x is 0.5; the crystal structure of the manganese-based lithium supplement agent is a composite structure formed by anti-fluorite Li6MnO4 and layered LiMnO2; the particle size of the lithium-rich manganese-based positive electrode material is 0.2 to 20 μm; the plasma treatment atmosphere is N2, and the plasma treatment pressure is 20 Pa;

[0064] (2) turning on the plasma treatment instrument in step (1), raising the temperature of the chamber of the plasma treatment instrument to a plasma treatment temperature of 50° C. at a heating rate of 1° C. / min, rotating the sample bottle at the same time, then controlling the power of the plasma treatment to 20 W, subjecting the manganese-based lithium supplement to plasma treatment for 5 minutes, and finally turning off the plasma treatment instrument, introducing air into the chamber to restore atmospheric pressure, opening the chamber to collect the solid material, and obtaining an oxygen vacancy surface-doped manganese-based lithium supplement.

[0065] The XPS depth analysis test was performed on the oxygen vacancy surface doped manganese-based lithium replenisher prepared in Example 4. The results showed that the surface oxygen vacancy concentration of the oxygen vacancy surface doped manganese-based lithium replenisher was 5%, the oxygen vacancy depth was 5nm, and the oxygen vacancies were distributed in a surface gradient.

[0066] Example 5

[0067] A method for preparing an oxygen vacancy surface doped manganese-based lithium supplement agent is as follows:

[0068] (1) placing a manganese-based lithium supplement agent in a sample bottle, then placing the sample bottle in a chamber of a plasma treatment instrument, then introducing a plasma treatment atmosphere into the chamber and evacuating the chamber to a desired plasma treatment pressure; the chemical formula of the manganese-based lithium supplement agent is xLi6MnO4·(1-x)LiMnO2, where x is 0.5; the crystal structure of the manganese-based lithium supplement agent is a composite structure formed by anti-fluorite Li6MnO4 and layered LiMnO2; the particle size of the lithium-rich manganese-based positive electrode material is 0.2 to 20 μm; the plasma treatment atmosphere is H2, and the plasma treatment pressure is 20 Pa;

[0069] (2) turning on the plasma treatment instrument in step (1), raising the temperature of the chamber of the plasma treatment instrument to a plasma treatment temperature of 80° C. at a heating rate of 1° C. / min, rotating the sample bottle at the same time, then controlling the power of the plasma treatment to 5 W, subjecting the manganese-based lithium supplement to plasma treatment for 1 min, and finally turning off the plasma treatment instrument, introducing air into the chamber to restore atmospheric pressure, opening the chamber to collect the solid material, and obtaining an oxygen vacancy surface-doped manganese-based lithium supplement.

[0070] The XPS depth analysis test was performed on the oxygen vacancy surface doped manganese-based lithium replenisher prepared in Example 5. The results showed that the surface oxygen vacancy concentration of the oxygen vacancy surface doped manganese-based lithium replenisher was 6%, the oxygen vacancy depth was 3nm, and the oxygen vacancies were distributed in a surface gradient.

[0071] Example 6

[0072] A method for preparing an oxygen vacancy surface doped manganese-based lithium supplement agent is as follows:

[0073] (1) placing a manganese-based lithium supplementer into a sample bottle, then placing the sample bottle into a chamber of a plasma treatment instrument, then introducing a plasma treatment atmosphere into the chamber and evacuating the chamber to a desired plasma treatment pressure; the chemical formula of the manganese-based lithium supplementer is xLi6MnO4·(1-x)LiMnO2, where x is 0.5; the crystal structure of the manganese-based lithium supplementer is a composite structure formed by anti-fluorite Li6MnO4 and layered LiMnO2; the particle size of the lithium-rich manganese-based positive electrode material is 0.2 to 20 μm; the plasma treatment atmosphere is CH4, and the plasma treatment pressure is 20 Pa;

[0074] (2) turning on the plasma treatment instrument in step (1), raising the temperature of the chamber of the plasma treatment instrument to 300° C., a plasma treatment temperature, at a heating rate of 2° C. / min, while rotating the sample bottle, then controlling the power of the plasma treatment to 5 W, subjecting the manganese-based lithium supplement to plasma treatment for 10 min, and finally turning off the plasma treatment instrument, introducing air into the chamber to restore atmospheric pressure, opening the chamber to collect the solid material, and obtaining an oxygen vacancy surface-doped manganese-based lithium supplement.

[0075] The XPS depth analysis test was performed on the oxygen vacancy surface doped manganese-based lithium replenisher prepared in Example 6. The results showed that the surface oxygen vacancy concentration of the oxygen vacancy surface doped manganese-based lithium replenisher was 25%, the oxygen vacancy depth was 30nm, and the oxygen vacancies were distributed in a surface gradient.

[0076] Example 7

[0077] A method for preparing an oxygen vacancy surface doped manganese-based lithium supplement agent is as follows:

[0078] (1) placing a manganese-based lithium supplement agent in a sample bottle, then placing the sample bottle in a chamber of a plasma treatment instrument, then introducing a plasma treatment atmosphere into the chamber and evacuating the chamber to a desired plasma treatment pressure; the chemical formula of the manganese-based lithium supplement agent is xLi6MnO4·(1-x)LiMnO2, where x is 0.5; the crystal structure of the manganese-based lithium supplement agent is a composite structure formed by anti-fluorite Li6MnO4 and layered LiMnO2; the particle size of the lithium-rich manganese-based positive electrode material is 0.2 to 20 μm; the plasma treatment atmosphere is CH4, and the plasma treatment pressure is 30 Pa;

[0079] (2) turning on the plasma treatment instrument in step (1), raising the temperature of the chamber of the plasma treatment instrument to 300° C., a plasma treatment temperature, at a heating rate of 2° C. / min, while rotating the sample bottle, then controlling the plasma treatment power to 50 W, subjecting the manganese-based lithium supplement to plasma treatment for 10 min, and finally turning off the plasma treatment instrument, introducing air into the chamber to restore atmospheric pressure, and opening the chamber to collect the solid material to obtain an oxygen vacancy surface-doped manganese-based lithium supplement.

[0080] The XPS depth analysis test was performed on the oxygen vacancy surface doped manganese-based lithium replenisher prepared in Example 7. The results showed that the surface oxygen vacancy concentration of the oxygen vacancy surface doped manganese-based lithium replenisher was 35%, the oxygen vacancy depth was 30nm, and the oxygen vacancies were distributed in a surface gradient.

[0081] The oxygen vacancy surface doped manganese-based lithium replenishing agents prepared in Examples 1 to 7 were analyzed. By comparing Example 1 and Example 2, it can be seen that when the plasma treatment time was changed from 20 min to 5 min, the surface oxygen vacancy concentration and oxygen vacancy depth of the oxygen vacancy surface doped manganese-based lithium replenishing agent both showed a downward trend, but the oxygen vacancies were all distributed in a surface gradient, indicating that by controlling the plasma treatment time, the surface oxygen vacancy concentration and oxygen vacancy depth of the oxygen vacancy surface doped manganese-based lithium replenishing agent can be regulated; by comparing Example 2 and Example 3, it can be seen that when the pressure and temperature of the plasma treatment were increased, the surface oxygen vacancy concentration and oxygen vacancy depth of the oxygen vacancy surface doped manganese-based lithium replenishing agent were significantly improved. Improved, indicating that controlling the pressure and temperature of plasma treatment can regulate the surface oxygen vacancy concentration and oxygen vacancy depth of the manganese-based lithium supplement agent doped on the oxygen vacancy surface; through the comparison of Examples 4 to 5, it can be seen that under the condition that the pressure and time of plasma treatment remain unchanged, the higher the temperature of plasma treatment, the higher the oxygen vacancy concentration, and the higher the power of plasma treatment, the higher the oxygen vacancy depth; in Examples 6 to 7, by appropriately increasing the pressure and power of plasma treatment while other conditions remain unchanged, the surface oxygen vacancy concentration of the manganese-based lithium supplement agent doped on the oxygen vacancy surface is improved, while the oxygen vacancy depth does not change, indicating that controlling the pressure and power of plasma treatment can regulate the surface oxygen vacancy concentration of the manganese-based lithium supplement agent doped on the oxygen vacancy surface. It can be seen from Examples 1 to 7 that the present invention can achieve controllable construction of oxygen vacancy concentration, depth and gradient distribution on the surface of manganese-based lithium supplement agent by regulating gas type, plasma power, treatment temperature and treatment time.

[0082] Application Example 1

[0083] The oxygen vacancy surface prepared in Example 1 was doped with a manganese-based lithium supplement agent to prepare a 100 mAh lithium-ion soft-pack battery, and the specific steps were as follows:

[0084] 1) The oxygen vacancy surface doped manganese-based lithium supplement agent and lithium iron phosphate positive electrode material are homogenized by a homogenizer, and the solvent is NMP to obtain a positive electrode slurry with a solid content of 50wt.%, and then the positive electrode slurry is coated on the aluminum current collector by a coating machine to obtain a positive electrode sheet, and the surface density of the positive electrode sheet is 20mg / cm 2 ; The amount of manganese-based lithium supplement agent doped on the oxygen vacancy surface is 2% of the mass of the lithium iron phosphate positive electrode material;

[0085] 2) Assembling the positive electrode sheet obtained in step 1) and the graphite negative electrode sheet into a 100 mAh lithium-ion soft-pack battery with an N / P ratio of 1.1, and then performing liquid injection, formation and testing in sequence.

[0086] Application Example 2

[0087] The oxygen vacancy surface doped manganese-based lithium supplement agent prepared in Example 1 was placed in an air environment at room temperature for one month, and then prepared into a 100mAh lithium-ion soft-pack battery. The preparation method was the same as that in Application Example 1.

[0088] The performance of the 100mAh lithium-ion soft-pack battery provided in Example 1 and Application Example 2 was tested at a test voltage of 2 to 4.8V. The results were as follows: Figure 1 As shown in Table 1:

[0089] Table 1 Performance of 100mAh lithium-ion soft-pack batteries prepared in Application Example 1 and Application Example 2

[0090] performance First cycle charging capacity mAh / g First cycle discharge capacity mAh / g Corresponding first-cycle coulomb efficiency / % Application Example 1 837 60 7.2 Application Example 2 798 54 6.8

[0091] It can be seen from Table 1 that the electrochemical performance of the newly prepared oxygen vacancy surface doped manganese-based lithium supplementer is very similar to that of the oxygen vacancy surface doped manganese-based lithium supplementer after being placed for one month, and the charge specific capacity can be effectively exerted, indicating that the oxygen vacancy surface doping strategy effectively improves the air stability of the manganese-based lithium supplementer, and the interfacial oxygen precipitation and interfacial side reactions are significantly inhibited.

[0092] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing an oxygen vacancy surface doped manganese-based lithium supplement agent, comprising: Plasma treatment is performed on the manganese-based lithium supplement agent to obtain an oxygen vacancy surface-doped manganese-based lithium supplement agent; The atmosphere of the plasma treatment includes any one or more of N2, Ar, H2, NH3, He, O2 and CH4, the pressure of the plasma treatment is 1 to 1000 Pa, the temperature of the plasma treatment is 25 to 600°C, and the time of the plasma treatment is 0.1 to 120 min.

2. The preparation method according to claim 1, characterized in that: The chemical formula of the manganese-based oxide lithium supplement is xLi6MnO4·(1-x)LiMnO2, wherein x is 0.3-1.

3. The preparation method according to claim 1, characterized in that: The atmosphere of the plasma treatment is a mixed atmosphere of Ar and H2, and the volume ratio of Ar to H2 in the mixed atmosphere of Ar and H2 is (90-95): (5-10).

4. The preparation method according to claim 1, characterized in that: The pressure of the plasma treatment is 10-100 Pa.

5. The preparation method according to claim 1, characterized in that: The temperature of the plasma treatment is 25-300°C.

6. The preparation method according to claim 1, characterized in that: The plasma treatment time is 20 to 60 minutes.

7. The preparation method according to claim 1, characterized in that: The power of the plasma treatment is 10-1000W.

8. The oxygen vacancy surface doped manganese-based lithium supplement agent prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the oxygen vacancy surface doped manganese-based lithium supplement agent according to claim 8 in lithium ion batteries.

10. The use according to claim 9, characterized in that: The application method is to mix the manganese-based lithium replenisher doped on the oxygen vacancy surface with the positive electrode material, then prepare the positive electrode plate, and finally assemble the positive electrode plate into a lithium battery; the amount of the manganese-based lithium replenisher doped on the oxygen vacancy surface is 0.1 to 10% of the mass of the positive electrode material.

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