Atmospheric pressure cold plasma modified lithium-rich manganese oxide positive electrode material and preparation method and application thereof

Abstract

The invention discloses an atmospheric pressure cold plasma modified lithium-rich manganese oxide positive electrode material as well as a preparation method and application thereof, and relates to the technical field of preparation of lithium ion battery positive electrode materials, the chemical formula of the material is Li1. 2Ni0. 132Co0. 172Mn0. 492 O2, the preparation method comprises the following steps: treating the lithium-rich manganese oxide positive electrode material by adopting plasma, and preparing the atmospheric pressure cold plasma modified lithium-rich manganese oxide positive electrode material. Through plasma discharge treatment, the content of oxygen vacancies on the lithium-rich manganese surface is increased, and the lithium-rich manganese oxide positive electrode material with high capacity, high rate and excellent cycle performance is obtained. The invention solves the problem of complex modification process of the existing lithium-manganese-rich positive electrode material.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion battery positive electrode material preparation, and in particular to an atmospheric pressure cold plasma modified lithium-rich manganese oxide positive electrode material and a preparation method and application thereof. Background Art

[0002] Lithium-ion batteries have become an indispensable secondary battery in the market due to their long service life, high energy density, and environmental friendliness. With the continuous development of energy storage technology, people's requirements for battery energy density are also increasing. Lithium-rich manganese cathode materials have a large theoretical capacity (>300mAh·g -1 ), high working voltage, and low cost, and are considered to be the most promising cathode material for high energy density lithium-ion batteries. However, at present, it faces key problems such as low initial Coulombic efficiency, capacity / voltage decay, poor rate performance, and poor cycle stability, which limit its large-scale application in lithium-ion batteries. Therefore, in order to accelerate its commercialization process, it is crucial to effectively solve the problems it faces.

[0003] When the lithium-rich manganese cathode material is charged to above 4.5V, the Li2MnO3 phase will be activated, and the capacity will be provided by anion redox, which will inevitably produce oxygen precipitation, leading to irreversible structural transformation, thus affecting the electrochemical performance. Therefore, the introduction of oxygen vacancies will stabilize the lattice oxygen on the surface of lithium-rich manganese, slow down the oxygen precipitation and play a role in stabilizing the structure. At present, the generation of oxygen vacancies is mainly produced by surface modification and sintering in a reducing atmosphere. In the patent specification with the publication number CN113410457A, the inventor discloses a preparation method for producing oxygen vacancies by heating a lithium-rich manganese-based layered positive electrode material with argon gas. The method can improve the rate performance and cycle stability of the lithium-rich manganese-based layered positive electrode material, and can inhibit the precipitation of transition metal ions and voltage decay in the lithium-rich manganese-based layered positive electrode material, and can reduce the precipitation of oxygen; in the patent specification with the publication number CN110828816A, the inventor discloses the use of a stirring method to introduce a reducing hydrazine hydrate material on the surface of the main material of the lithium-rich manganese-based positive electrode material. Compared with the same type of material without oxygen vacancies, the battery performance such as battery cycle stability and rate has been greatly improved. The above cases all belong to surface modification, but there are problems such as complex processing technology and even environmental damage, which need to be improved. Summary of the invention

[0004] In order to solve the above technical problems, the purpose of the present invention is to provide an atmospheric pressure cold plasma modified lithium-rich manganese oxide positive electrode material and a preparation method and application thereof, so as to solve the problem of complex modification process of existing lithium-rich manganese positive electrode materials.

[0005] The technical solution of the present invention to solve the above technical problems is as follows: Provide an atmospheric pressure cold plasma modified lithium-rich manganese oxide positive electrode material, the chemical formula of which is Li 1.2 Ni 0.132 Co 0.172 Mn 0.492 O2.

[0006] The beneficial effects of the present invention are as follows: the atmospheric pressure cold plasma modified lithium-rich manganese oxide positive electrode material of the present invention has high specific capacity, high rate performance and excellent cycle performance, low material cost, does not use any other chemical reagents, and only increases the content of oxygen vacancies by changing different discharge atmospheres, and after atmospheric pressure cold plasma treatment, the material (003) peak shifts to the left, so that the c-axis is enlarged, which is conducive to improving lithium ion diffusion. In addition, under the cold plasma modification of the reducing atmosphere, the valence state of Mn on the surface of the material is increased, which also plays a role in stabilizing the structure of the electrode material. Finally, the lithium-rich manganese oxide positive electrode material of the present invention has excellent electrochemical performance.

[0007] On the basis of the above technical solution, the present invention can also be improved as follows:

[0008] The present invention also provides a method for preparing the above atmospheric pressure cold plasma modified lithium-rich manganese oxide positive electrode material, comprising the following steps: treating the lithium-rich manganese oxide positive electrode material with plasma to obtain the atmospheric pressure cold plasma modified lithium-rich manganese oxide positive electrode material.

[0009] Furthermore, a mixed gas is used for discharge to generate plasma, and the mixed gas is a mixed gas of any one of H2, O2 and NH3 and Ar.

[0010] Furthermore, the mixed gas flow rate is 80-120 mL / min.

[0011] Furthermore, the mixed gas flow rate is 100 mL / min.

[0012] Furthermore, the discharge voltage is 13-19 kV, and the discharge frequency is 11.76-11.78 kHz.

[0013] Furthermore, the discharge voltage is 19 kV and the discharge frequency is 11.78 kHz.

[0014] Furthermore, the discharge time is 5-40 minutes.

[0015] Furthermore, the discharge time is 40 min.

[0016] Furthermore, the lithium-rich manganese oxide positive electrode material is placed in a coaxial dielectric barrier discharge reactor for plasma treatment.

[0017] Furthermore, the coaxial dielectric barrier discharge reactor has an inner diameter of 7 mm and an outer diameter of 10 mm.

[0018] Further, Ar is introduced to exhaust the air in the coaxial dielectric barrier discharge reactor, and then plasma treatment is performed.

[0019] Furthermore, the Ar flow rate is 80-120 mL / min, and the introduction time is 5-20 min.

[0020] Furthermore, the Ar flow rate was 100 mL / min, and the introduction time was 10 min.

[0021] Further, the lithium-rich manganese oxide positive electrode material is prepared by the following method:

[0022] (1) lithium acetate dihydrate, nickel acetate tetrahydrate, cobalt acetate tetrahydrate, manganese acetate tetrahydrate and citric acid monohydrate are mixed, added into deionized water, and stirred to prepare a precursor solution;

[0023] (2) The precursor solution obtained in step (1) is spray-dried and then heat-treated to obtain a lithium-rich manganese oxide positive electrode material.

[0024] Furthermore, in step (1), the molar ratio of lithium acetate dihydrate, nickel acetate tetrahydrate, cobalt acetate tetrahydrate and manganese acetate tetrahydrate is 1-1.5:0.1-0.2:0.1-0.2:0.49-0.6.

[0025] Furthermore, in step (1), the molar ratio of lithium acetate dihydrate, nickel acetate tetrahydrate, cobalt acetate tetrahydrate and manganese acetate tetrahydrate is 1-1.5:0.1-0.2:0.1-0.2:0.49-0.6, and lithium acetate dihydrate is additionally added in an amount of 3% by mole of the original lithium acetate dihydrate to compensate for the lithium loss during the heat treatment process.

[0026] Furthermore, in step (1), the molar ratio of lithium acetate dihydrate, nickel acetate tetrahydrate, cobalt acetate tetrahydrate and manganese acetate tetrahydrate is 1.2:0.132:0.172:0.492.

[0027] Furthermore, in step (1), the molar ratio of lithium acetate dihydrate, nickel acetate tetrahydrate, cobalt acetate tetrahydrate and manganese acetate tetrahydrate is 1.2:0.132:0.172:0.492, and lithium acetate dihydrate is additionally added in an amount of 3% by mole of the original lithium acetate dihydrate to compensate for the lithium loss during the heat treatment process.

[0028] Furthermore, in step (1), the total concentration of metal acetate in the precursor solution is 0.1-0.2 mol / L, and the concentration of citric acid monohydrate is 0.2-0.4 mol / L.

[0029] Furthermore, in step (1), the total concentration of metal acetate in the precursor solution is 0.15 mol / L, and the concentration of citric acid monohydrate is 0.3 mol / L.

[0030] Furthermore, in step (1), stirring is performed at 20-30° C. for 1-2 h.

[0031] Furthermore, in step (1), the stirring speed is 400-600 rpm.

[0032] Furthermore, in step (1), the stirring speed is 500 rpm.

[0033] Furthermore, in step (2), the inlet temperature of the spray drying is 200-250°C, the outlet temperature is 110-115°C, and the feed rate is 1-2 L / h.

[0034] Furthermore, in step (2), the inlet temperature of the spray drying is 230° C., the outlet temperature is 115° C., and the feed rate is 1 L / h.

[0035] Furthermore, in step (2), the temperature is raised to 900-1200° C. in an air atmosphere and kept at this temperature for 18-22 minutes to complete the heat treatment process.

[0036] Furthermore, in step (2), the temperature is raised to 1000° C. in an air atmosphere and kept at that temperature for 20 minutes to complete the heat treatment process.

[0037] Furthermore, the heating rate is 2-5°C / min.

[0038] Furthermore, the heating rate was 3°C / min.

[0039] The present invention also provides the use of the atmospheric pressure cold plasma modified lithium-rich manganese oxide positive electrode material in the preparation of lithium ion batteries.

[0040] The present invention has the following beneficial effects:

[0041] 1. Plasma is a new type of surface modification method with simple process. It can uniformly treat materials under fast, green and efficient conditions. It can interact with atoms on the surface of lithium-rich manganese oxide, causing the redistribution of surface electronic structure and inducing the generation of oxygen vacancies, which is beneficial to improving the electrochemical performance of lithium-rich manganese oxide positive electrode materials.

[0042] 2. The present invention does not need to introduce other reducing chemical reagents. Through plasma discharge treatment, the content of oxygen vacancies on the surface of lithium-rich manganese increases, which is beneficial to inhibit the precipitation of lattice oxygen under high voltage and improve structural stability; secondly, atmospheric pressure cold plasma modification causes the material (003) peak to shift to the left, expands the interlayer spacing of the (003) crystal plane, and is beneficial to the rapid transport of lithium ions; finally, after plasma treatment, the surface charge distribution is changed, so that the Mn valence state increases and the Ni valence state decreases, which not only stabilizes the structure but also improves the capacity contribution of transition metals. Finally, a lithium-rich manganese oxide positive electrode material with high capacity, high rate and excellent cycle performance is obtained.

[0043] 3. The preparation method of the lithium-rich manganese-based positive electrode material provided by the present invention has a simple synthesis process, a fast and efficient modification process, and can achieve uniform treatment by changing the plasma discharge atmosphere. It is low in cost, environmentally friendly, and conducive to large-scale production and application.

[0044] 4. By treating with atmospheric pressure plasma in different discharge atmospheres of O2:Ar, H2:Ar and NH3:Ar, the surface oxygen vacancy content of lithium-rich manganese oxide increased to 34.80%, 43.16% and 56.33% respectively compared with 27.76% of the unmodified one. The lithium-ion battery assembled with the LRO / NH3:Ar sample prepared by the method of the present invention has a capacity retention rate of up to 73.15% after 400 cycles at a current density of 200mA / g; after 297 cycles at a current density of 1000mA / g, the capacity retention rate is 80%, and after 500 cycles, the capacity retention rate is still 67.84%. The atmospheric pressure cold plasma modified lithium-rich manganese oxide positive electrode material of the present invention has electrochemical properties superior to most lithium-rich manganese-based positive electrode materials, and improves the performance and effect of lithium-ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 XRD diagrams of the positive electrode materials prepared in Examples 1-3 and Comparative Example 1;

[0046] Figure 2 The SEM images of the positive electrode materials obtained in Examples 1-3 and Comparative Example 1;

[0047] Figure 3 XPS O1s graphs of the positive electrode materials obtained in Examples 1-3 and Comparative Example 1;

[0048] Figure 4 XPS Mn2p diagrams of the positive electrode materials obtained in Examples 1-3 and Comparative Example 1;

[0049] Figure 5 XPS Ni2p diagram of the positive electrode materials obtained in Examples 1-3 and Comparative Example 1;

[0050] Figure 6 The first charge and discharge diagram of the positive electrode materials prepared in Examples 1-3 and Comparative Example 1;

[0051] Figure 7 The cycle performance of the positive electrode materials prepared for Examples 1-3 and Comparative Example 1 at a current density of 200 mA / g;

[0052] Figure 8 The rate performance diagram of the positive electrode materials prepared in Examples 1-3 and Comparative Example 1;

[0053] Fig. 9 The cycle performance of the positive electrode materials prepared for Examples 1-3 and Comparative Example 1 at a current density of 1000 mA / g. DETAILED DESCRIPTION

[0054] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples are only used to explain the present invention and are not used to limit the scope of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0055] Embodiment 1:

[0056] An atmospheric pressure cold plasma modified lithium-rich manganese oxide positive electrode material, the chemical formula of which is: Li 1.2 Ni 0.132 Co 0.172 Mn 0.492 O2.

[0057] An atmospheric pressure cold plasma modified lithium-rich manganese oxide positive electrode material, the preparation method of which comprises the following steps:

[0058] (1) lithium acetate dihydrate, nickel acetate tetrahydrate, cobalt acetate tetrahydrate, manganese acetate tetrahydrate and citric acid monohydrate were mixed, added into deionized water, and stirred at 25° C. and 500 rpm for 1 h to prepare a precursor solution;

[0059] The molar ratio of lithium acetate dihydrate, nickel acetate tetrahydrate, cobalt acetate tetrahydrate and manganese acetate tetrahydrate is 1.2:0.132:0.172:0.492, and lithium acetate dihydrate is additionally added in an amount of 3% of the original lithium acetate dihydrate to compensate for the lithium loss during the heat treatment process; the total concentration of metal acetate in the precursor solution is 0.15 mol / L, and the concentration of citric acid monohydrate is 0.3 mol / L;

[0060] (2) The precursor solution obtained in step (1) is sent to a spray dryer by a peristaltic pump, and spray dried at high temperature and high pressure, wherein the inlet temperature of the spray dryer is 230° C., the outlet temperature is 115° C., and the feed rate is 1 L / h; then placed in an alumina crucible (120 mm, 120 mm in width, and 50 mm in height), and the alumina crucible is placed in a box furnace, and heated to 1000° C. at a heating rate of 3° C. / min in an air atmosphere, and kept warm for 20 min to complete the heat treatment process, thereby obtaining a lithium-rich manganese oxide positive electrode material;

[0061] (3) The lithium-rich manganese oxide positive electrode material obtained in step (2) was placed in a coaxial dielectric barrier discharge reactor (inner diameter 7 mm, outer diameter 10 mm), Ar was introduced at a flow rate of 100 mL / min, and the Ar was introduced for 10 min. The air in the coaxial dielectric barrier discharge reactor was discharged and plasma treatment was performed. A mixed gas (H2 and Ar) with a flow rate of 100 mL / min was used for discharge to generate cold plasma. The discharge voltage was 19 kV, the discharge frequency was 11.78 kHz, and the discharge time was 40 min. An atmospheric pressure cold plasma modified lithium-rich manganese oxide positive electrode material (named LRO / H2:Ar) was obtained.

[0062] Embodiment 2:

[0063] An atmospheric pressure cold plasma modified lithium-rich manganese oxide positive electrode material, the chemical formula of which is: Li 1.2 Ni 0.132 Co 0.172 Mn 0.492 O2.

[0064] An atmospheric pressure cold plasma modified lithium-rich manganese oxide positive electrode material, the preparation method of which comprises the following steps:

[0065] In step (3), the mixed gas (O2 and Ar) is discharged to generate cold plasma, the discharge voltage is 13 kV, the discharge frequency is 11.76 kHz, and the discharge time is 10 min, to obtain an atmospheric pressure cold plasma modified lithium-rich manganese oxide positive electrode material (named LRO / O2:Ar). The rest is the same as in Example 1.

[0066] Embodiment 3:

[0067] An atmospheric pressure cold plasma modified lithium-rich manganese oxide positive electrode material, the chemical formula of which is: Li 1.2 Ni 0.132 Co 0.172 Mn 0.492 O2.

[0068] An atmospheric pressure cold plasma modified lithium-rich manganese oxide positive electrode material, the preparation method of which comprises the following steps:

[0069] In step (3), the mixed gas (NH3 and Ar) is discharged to generate cold plasma, the discharge voltage is 13 kV, the discharge frequency is 11.76 kHz, and the discharge time is 40 min, to obtain an atmospheric pressure cold plasma modified lithium-rich manganese oxide positive electrode material (named LRO / NH3:Ar). The rest is the same as in Example 1.

[0070] Embodiment 4:

[0071] An atmospheric pressure cold plasma modified lithium-rich manganese oxide positive electrode material, the chemical formula of which is: Li 1.2 Ni 0.132 Co 0.172 Mn 0.492 O2.

[0072] An atmospheric pressure cold plasma modified lithium-rich manganese oxide positive electrode material, the preparation method of which comprises the following steps:

[0073] (1) lithium acetate dihydrate, nickel acetate tetrahydrate, cobalt acetate tetrahydrate, manganese acetate tetrahydrate and citric acid monohydrate were mixed, added into deionized water, and stirred at 20° C. and 400 rpm for 2 h to prepare a precursor solution;

[0074] The molar ratio of lithium acetate dihydrate, nickel acetate tetrahydrate, cobalt acetate tetrahydrate and manganese acetate tetrahydrate is 1:0.1:0.1:0.49; lithium acetate dihydrate is additionally added in an amount of 3% of the original lithium acetate dihydrate to compensate for the lithium loss during the heat treatment process; the total concentration of metal acetate in the precursor solution is 0.1 mol / L, and the concentration of citric acid monohydrate is 0.2 mol / L;

[0075] (2) The precursor solution obtained in step (1) is sent to a spray dryer by a peristaltic pump, and spray dried at high temperature and high pressure, wherein the inlet temperature of the spray dryer is 200° C., the outlet temperature is 110° C., and the feed rate is 1.5 L / h; then placed in an alumina crucible (120 mm, 120 mm in width, and 50 mm in height), and the alumina crucible is placed in a box furnace, and heated to 900° C. at a heating rate of 2° C. / min in an air atmosphere, and kept warm for 22 min to complete the heat treatment process, thereby obtaining a lithium-rich manganese oxide positive electrode material;

[0076] (3) placing the lithium-rich manganese oxide positive electrode material obtained in step (2) in a coaxial dielectric barrier discharge reactor (inner diameter 7 mm, outer diameter 10 mm), introducing Ar at a flow rate of 80 mL / min for 20 min, exhausting the air in the coaxial dielectric barrier discharge reactor, performing plasma treatment, discharging with a mixed gas (O2 and Ar) at a flow rate of 80 mL / min to generate cold plasma, the discharge voltage is 13 kV, the discharge frequency is 11.76 kHz, and the discharge time is 5 min, thereby obtaining an atmospheric pressure cold plasma modified lithium-rich manganese oxide positive electrode material.

[0077] Embodiment 5:

[0078] An atmospheric pressure cold plasma modified lithium-rich manganese oxide positive electrode material, the chemical formula of which is: Li 1.2 Ni 0.132 Co 0.172 Mn 0.492 O2.

[0079] An atmospheric pressure cold plasma modified lithium-rich manganese oxide positive electrode material, the preparation method of which comprises the following steps:

[0080] (1) lithium acetate dihydrate, nickel acetate tetrahydrate, cobalt acetate tetrahydrate, manganese acetate tetrahydrate and citric acid monohydrate were mixed, added into deionized water, and stirred at 30° C. and 600 rpm for 1.5 h to prepare a precursor solution;

[0081] The molar ratio of lithium acetate dihydrate, nickel acetate tetrahydrate, cobalt acetate tetrahydrate and manganese acetate tetrahydrate is 1.5:0.2:0.2:0.6; lithium acetate dihydrate is additionally added in an amount of 3% by mole of the original lithium acetate dihydrate to compensate for the lithium loss during the heat treatment process; the total concentration of metal acetate in the precursor solution is 0.2 mol / L, and the concentration of citric acid monohydrate is 0.3 mol / L;

[0082] (2) The precursor solution obtained in step (1) is sent to a spray dryer by a peristaltic pump, and spray dried at high temperature and high pressure, wherein the inlet temperature of the spray dryer is 250° C., the outlet temperature is 115° C., and the feed rate is 2 L / h; then placed in an alumina crucible (120 mm, 120 mm in width, and 50 mm in height), and the alumina crucible is placed in a box furnace, and heated to 1200° C. at a heating rate of 5° C. / min in an air atmosphere, and kept warm for 18 min to complete the heat treatment process, thereby obtaining a lithium-rich manganese oxide positive electrode material;

[0083] (3) placing the lithium-rich manganese oxide positive electrode material obtained in step (2) in a coaxial dielectric barrier discharge reactor (inner diameter 7 mm, outer diameter 10 mm), introducing Ar at a flow rate of 120 mL / min for 5 min, exhausting the air in the coaxial dielectric barrier discharge reactor, and performing plasma treatment, using a mixed gas (NH3 and Ar) with a flow rate of 80-120 mL / min for discharge to generate cold plasma, with a discharge voltage of 15 kV, a discharge frequency of 11.77 kHz, and a discharge time of 40 min to obtain an atmospheric pressure cold plasma modified lithium-rich manganese oxide positive electrode material.

[0084] Comparative Example 1:

[0085] A lithium-rich manganese oxide positive electrode material, the chemical formula of which is: Li 1.2 Ni 0.132 Co 0.172 Mn 0.492 O2.

[0086] A lithium-rich manganese oxide positive electrode material, the preparation method of which comprises the following steps:

[0087] The steps excluding step (3) are the same as those in Example 1 to obtain a lithium-rich manganese oxide positive electrode material (named LRO).

[0088] Test example

[0089] 1. XRD test

[0090] The lithium-rich manganese-based positive electrode materials prepared in Examples 1-3 and Comparative Example 1 were subjected to XRD tests respectively to test the average structure of the lithium-rich manganese-based positive electrode materials. The results are shown in Figure 1 .

[0091] Depend on Figure 1 It can be seen that after plasma treatment, the peak positions of (003) of LRO / H2:Ar, LRO / O2:Ar, and LRO / NH3:Ar all shifted toward the low-angle direction, indicating that the c-axis interlayer spacing increased, which is beneficial to lithium ion transport.

[0092] 2. SEM test

[0093] The lithium-rich manganese-based positive electrode materials prepared in Examples 1-3 and Comparative Example 1 were subjected to SEM tests to test the surface morphology and average size of the lithium-rich manganese-based positive electrode materials. The results are shown in Figure 2 .

[0094] Depend on Figure 2It can be seen that there is no obvious change in morphology before and after atmospheric pressure cold plasma treatment, indicating that under different discharge atmospheres, the high-energy particles generated by the plasma bombard the surface of the lithium-rich manganese cathode material without causing damage to the particle morphology and size, and the original morphology of the material is retained. The particle size of the lithium-rich manganese-based cathode material before and after plasma treatment is 200-300nm.

[0095] 3. XPS test

[0096] The lithium-rich manganese-based positive electrode materials prepared in Examples 1-3 and Comparative Example 1 were subjected to XPS tests to test the surface structure of the lithium-rich manganese-based positive electrode materials. The results are shown in Figure 3-5 .

[0097] Depend on Figure 3-5 It can be seen that the oxygen vacancy content of the lithium-rich manganese-based positive electrode materials prepared in the embodiments of the present invention has increased, among which the increase in LRO / H2:Ar and LRO / NH3:Ar is more significant, and the increase in LRO / O2:Ar is less. This is because the ratio in the O2:Ar mixed discharge atmosphere is 1:4, and O2 accounts for a small proportion. In fact, Ar itself also has a certain reducing property and can generate oxygen vacancies, but the reduction strength is very different from that of H2 and NH3. Even if O2 is reducing, a small amount of oxygen vacancies will still be generated when it accounts for a small proportion. The increase in oxygen vacancies helps to stabilize the lattice oxygen on the surface of the material, inhibit the precipitation of lattice oxygen under high voltage, and improve the stability of the high-voltage crystal structure. At the same time, it was found that the valence state of Mn on the surface of the material increased after atmospheric pressure cold plasma treatment in a reducing atmosphere, which also played a role in stabilizing the structure.

[0098] 4. Electrochemical performance test

[0099] 1. Preparation of positive electrode sheet

[0100] The lithium-rich manganese-based positive electrode materials and Super P prepared in Examples 1-3 and Comparative Example 1 were weighed in a mass ratio of 8:1 and placed in a ball mill, tungsten carbide ball milling beads were added, the ball-to-material mass ratio in the ball mill was 100:1, and alcohol was added as a dispersant. After ball milling for 6 hours, the mixture was dried in a drying oven to obtain a mixture A;

[0101] Weigh 285 mg of mixture A and 1250 mg of 1.2% CMC solution, stir at room temperature for 2 h, ultrasonicate for 2 h, stir again for 2 h, coat on aluminum foil with a 0.15 μm scraper, dry in a vacuum drying oven at 110 ° C for 20 h, cut into electrodes with a diameter of 10 mm, and then transfer the cut electrodes to a vacuum oven at 115 ° C for 10 h for use.

[0102] 2. Assemble CR2025 stainless steel button battery

[0103] Using a metal lithium sheet as the negative electrode, 250 μL of LBC-3045I(G) commercial electrolyte was dripped into the battery. The CR2025 stainless steel button cell was assembled in a glove box filled with argon gas and with a moisture content of less than 0.01 ppm. The charge and discharge performance was tested after standing at 45°C for 40 hours.

[0104] CR2025 stainless steel button battery electrochemical performance test:

[0105] The battery made of the positive electrode material of Examples 1-3 and Comparative Example 1 was tested for cycle performance by constant current charge and discharge. The test temperature was 25°C, the voltage window was 2.0-4.8V, and the current density was 0.1C, 0.2C, 0.5C, 1C, 2C, 5C and 10C, respectively, where 1C = 200mA / g. The results are shown in Table 1. Figure 6-9 .

[0106] Depend on Figure 6 It can be seen that with the increase of oxygen vacancy content, the lithium-ion battery prepared by the lithium-rich manganese oxide positive electrode material LRO / O2:Ar in Example 2 of the present invention has a maximum first discharge specific capacity of 272.83 mAh / g at a current density of 20 mA / g.

[0107] Depend on Figure 7-8 It can be seen that the lithium-ion battery prepared by the lithium-rich manganese oxide positive electrode material LRO / NH3:Ar in Example 3 of the present invention has a capacity retention rate of up to 73.15% and a voltage retention rate of up to 80.44% after 400 cycles at a current density of 200mA / g. This is mainly because the increase in the oxygen vacancy content can stabilize the lattice oxygen and inhibit the irreversible release of oxygen, further increasing the Mn valence state, reducing the disproportionation reaction, stabilizing the framework structure of the overall material, and improving the cycle stability. The lithium-ion battery prepared by the lithium-rich manganese oxide positive electrode materials LRO / O2:Ar and LRO / NH3:Ar in the present invention maintains excellent rate performance in the rate performance tests of 0.1C, 0.2C, 0.5C, 1C, 2C, 5C and 10C.

[0108] Depend on Fig. 9It can be seen that due to the rich oxygen vacancies on the surface after plasma treatment and the increased interlayer spacing, the structural stability is improved and the rapid diffusion of lithium ions is promoted, so that the lithium-ion batteries obtained by preparing LRO / O2:Ar and LRO / NH3:Ar with the lithium-rich manganese oxide positive electrode material in the present invention still have a capacity of 145.29mAh / g and 147.98mAh / g even at an ultra-large current density of 1000mA / g, which are significantly higher than the capacity (131.37mAh / g) without plasma modification. Moreover, the lithium-ion battery assembled with the LRO / NH3:Ar sample has a capacity retention rate of 80% after 297 cycles, and a capacity retention rate of up to 67.84% after 500 cycles, showing excellent rate performance and long cycle stability.

[0109] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An atmospheric pressure cold plasma modified lithium-rich manganese oxide positive electrode material, characterized in that: Its chemical formula is Li 1.2 Ni 0.132 Co 0.172 Mn 0.492 O2.

2. The method for preparing the atmospheric pressure cold plasma modified lithium-rich manganese oxide positive electrode material according to claim 1, characterized in that: The method comprises the following steps: treating a lithium-rich manganese oxide positive electrode material with plasma to obtain an atmospheric pressure cold plasma modified lithium-rich manganese oxide positive electrode material.

3. The method for preparing the atmospheric pressure cold plasma modified lithium-rich manganese oxide positive electrode material according to claim 2, characterized in that: A mixed gas is used for discharge to generate plasma, wherein the mixed gas is a mixed gas of any one of H2, O2 and NH3 and Ar.

4. The method for preparing the atmospheric pressure cold plasma modified lithium-rich manganese oxide positive electrode material according to claim 2, characterized in that: The discharge voltage is 13-19kV and the discharge frequency is 11.76-11.78kHz.

5. The method for preparing the atmospheric pressure cold plasma modified lithium-rich manganese oxide positive electrode material according to claim 2, characterized in that: The lithium-rich manganese oxide positive electrode material is prepared by the following method: (1) lithium acetate dihydrate, nickel acetate tetrahydrate, cobalt acetate tetrahydrate, manganese acetate tetrahydrate and citric acid monohydrate are mixed, added into deionized water, and stirred to prepare a precursor solution; (2) The precursor solution obtained in step (1) is spray-dried and then heat-treated to obtain a lithium-rich manganese oxide positive electrode material.

6. The method for preparing the atmospheric pressure cold plasma modified lithium-rich manganese oxide positive electrode material according to claim 5, characterized in that: In step (1), the molar ratio of lithium acetate dihydrate, nickel acetate tetrahydrate, cobalt acetate tetrahydrate and manganese acetate tetrahydrate is 1-1.5:0.1-0.2:0.1-0.2:0.49-0.

6.

7. The method for preparing the atmospheric pressure cold plasma modified lithium-rich manganese oxide positive electrode material according to claim 5, characterized in that: In step (1), the total concentration of metal acetate in the precursor solution is 0.1-0.2 mol / L, and the concentration of citric acid monohydrate is 0.2-0.4 mol / L.

8. The method for preparing the atmospheric pressure cold plasma modified lithium-rich manganese oxide positive electrode material according to claim 5, characterized in that: In step (2), the inlet temperature of the spray drying is 200-250°C, the outlet temperature is 110-115°C, and the feed rate is 1-2L / h.

9. The method for preparing the atmospheric pressure cold plasma modified lithium-rich manganese oxide positive electrode material according to claim 5, characterized in that: In step (2), the temperature is raised to 900-1200° C. in an air atmosphere and kept at this temperature for 18-22 minutes to complete the heat treatment process.

10. Use of the atmospheric pressure cold plasma modified lithium-rich manganese oxide positive electrode material according to claim 1 in the preparation of lithium-ion batteries.

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