Surface-modified lithium-rich manganese-based positive electrode material, preparation method and lithium ion battery

Abstract

The application relates to a surface-modified lithium-rich manganese-based positive electrode material, a preparation method and a lithium ion battery, which comprises the following steps: uniformly mixing a lithium-rich manganese-based precursor, a lithium source and a metal oxide required by a garnet solid electrolyte to obtain a mixture; performing gradient temperature calcination on the mixture in an oxidizing atmosphere to obtain a surface-modified lithium-rich manganese-based positive electrode material; the surface-modified lithium-rich manganese-based positive electrode material comprises a lithium-rich manganese-based material, a disordered spinel self-protection layer coated on the surface of the lithium-rich manganese-based material and a garnet solid electrolyte coated on the surface of the disordered spinel self-protection layer; the gradient temperature calcination comprises the following steps: first, performing calcination at a nucleation temperature of the lithium-rich manganese-based material, and then, performing calcination at a nucleation temperature of the garnet solid electrolyte after temperature rising. The application can solve the problems of low first coulomb efficiency and poor rate performance of the lithium-rich manganese-based positive electrode material in the prior art.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion batteries, in particular to a surface-modified lithium-rich manganese-based positive electrode material, a preparation method and a lithium ion battery. BACKGROUND

[0002] The range anxiety of new energy vehicles is an important factor limiting the large-scale promotion of new energy vehicles. Compared with the negative electrode material, the specific capacity of the positive electrode material is lower, which is one of the important factors that lithium ion batteries are difficult to obtain high energy density and hinder their further development. Therefore, researching and improving the specific capacity of the positive electrode material is the key to the development of lithium ion batteries. However, the traditional positive electrode materials, such as LiCoO2, LiFePO4 and LiTMO2 (TM is two or more of Ni, Co and Mn), etc., due to their low electrochemical capacity, the actual capacity is generally lower than 200 mAh / g, which limits their application in the next generation of high energy density lithium ion batteries. Therefore, developing positive electrode materials with high energy density is still a great challenge. The theoretical specific capacity of lithium-rich manganese-based positive electrode material xLi2MnO3·(1-x)LiMO2 (wherein M = Mn, Ni, Co, 0 < x < 1) is as high as 300 mAh / g, which is one of the most potential materials for preparing power battery with energy density exceeding 400 Wh / kg, and is expected to significantly improve the cruising range of new energy vehicles. However, lithium-rich manganese-based positive electrode materials face some challenges during electrochemical cycling, including low first coulombic efficiency, poor rate performance and other problems, which greatly hinder the commercialization progress of lithium-rich manganese-based positive electrode materials.

[0003] The low first coulombic efficiency of lithium-rich manganese-based positive electrode material produces a large amount of irreversible capacity, which reduces the actual energy density of the battery. During the first charge-discharge cycle, when the charging voltage reaches 4.5 V, Li + is extracted from Li2MnO3, while the oxygen anion is oxidized (O 2- → O2 2- ) to achieve charge compensation. The irreversible release of lattice oxygen leads to the generation of oxygen vacancies, which reduces the migration barrier of transition metal ions, promotes the migration of transition metal cations from the transition metal layer to the Li layer, and thus causes irreversible changes in the surface structure, making the extracted Li unable to re-embed in the structure. At the same time, after the activation of Li2MnO3 in the first cycle, the lithium-rich manganese-based positive electrode material produces inert Mn 4+ , which reduces the conductivity of the material; in addition, the poor kinetics of the material itself also leads to poor rate performance. Therefore, the low first coulombic efficiency and poor rate performance are two very key factors hindering the practical application of lithium-rich manganese-based positive electrode materials.

[0004] Currently, surface modification, doping and other means are mainly used to solve the application problems of lithium-rich manganese-based positive electrode materials.

[0005] For example, in some related technologies, LiNi a Mn 2-a O2(0<a≤1) is coated on the precursor of the lithium-rich manganese-based positive electrode material, and then a lithium-mixing sintering is performed to obtain the lithium-rich manganese-based positive electrode material coated on the surface. Although this method improves the cycle performance of the lithium-rich manganese-based material, it does not greatly improve the initial coulombic efficiency.

[0006] For example, in some related technologies, a gas lithium removal agent or a solid lithium removal agent is used to remove part of Li2O from Li2MnO3 in the lithium-rich manganese-based positive electrode material, which can improve the initial coulombic efficiency of the material. However, after using the gas lithium removal agent or the solid lithium removal agent, the recovery of harmful gas is involved, which increases the cost in industrial production.

[0007] For example, in some related technologies, a persulfate or a sulfate oxidizing agent is used to pretreat the surface of the lithium-rich manganese-based material to remove a small amount of lithium ions in advance, thereby improving the initial coulombic efficiency of the lithium-rich manganese-based material. However, the cycle performance of the material is not improved.

[0008] For example, in some related technologies, a fluorine-doped lithium-rich manganese-based precursor is prepared by a precipitation reaction to realize uniform doping of fluorine, inhibit the structural transformation of the material surface during the cycle process, and improve the voltage attenuation of the lithium-rich manganese-based positive electrode material. However, this method has little effect on improving the initial coulombic efficiency. SUMMARY

[0009] Embodiments of the present application provide a surface-modified lithium-rich manganese-based positive electrode material, a preparation method and a lithium ion battery to solve the problems of low initial coulombic efficiency and poor rate performance of the lithium-rich manganese-based positive electrode material in related technologies.

[0010] In a first aspect, a preparation method of a surface-modified lithium-rich manganese-based positive electrode material is provided, which includes:

[0011] Mixing a lithium-rich manganese-based precursor, a lithium source and metal oxides required for a garnet-type solid electrolyte to obtain a mixture;

[0012] Performing gradient temperature calcination on the mixture in an oxidizing atmosphere to obtain the surface-modified lithium-rich manganese-based positive electrode material;

[0013] The gradient temperature calcination includes: first calcining at a nucleation temperature of the lithium-rich manganese-based material, and then calcining at a nucleation temperature of the garnet-type solid electrolyte.

[0014] In some embodiments, the calcination at the nucleation temperature of the lithium-rich manganese-based material includes: calcining at 700-900℃ for 8-12h;

[0015] Calcination at the nucleation temperature of the garnet-type solid electrolyte includes: calcining at 900-1000° C. for 4-6 hours.

[0016] In some embodiments, before calcining at the nucleation temperature of the lithium-rich manganese-based material, the gradient temperature calcination further comprises: calcining at 400-600° C. for 4-8 hours.

[0017] In some embodiments, the mass fraction of the metal oxide is 1%-10% of the lithium-rich manganese-based precursor.

[0018] In some embodiments, the garnet-type solid electrolyte includes LLZO electrolyte Li7La3Zr2O 12 LLZAO electrolyte Li 6.23 La3Zr2A l 0.25 O 12 and LLZTO electrolyte Li 6.24 La3Zr 1.4 Ta 0.6 O 12 One or more of the .

[0019] In some embodiments, the metal oxide includes a lanthanum source and a zirconium source.

[0020] In some embodiments, the lanthanum source is selected from at least one of lanthanum oxide, lanthanum nitrate, and lanthanum acetate.

[0021] In some embodiments, the zirconium source is selected from at least one of zirconium oxide, zirconium nitrate, and zirconium acetate.

[0022] In some embodiments, the lithium source is selected from at least one of lithium carbonate, lithium hydroxide, lithium nitrate, lithium acetate, and lithium phosphate.

[0023] In some embodiments, the lithium-rich manganese-based precursor, the lithium source, and the metal oxide required for the garnet-type solid electrolyte are mixed to obtain a mixture, specifically comprising:

[0024] The metal oxides required for the garnet-type solid electrolyte are added into a ball milling jar, and a grinding aid is added for ball milling;

[0025] The lithium-rich manganese-based precursor is then added to a ball mill, ball milled, mixed evenly, and dried to obtain a modified lithium-rich manganese-based precursor;

[0026] The modified lithium-rich manganese-based precursor is evenly mixed with a lithium source to obtain a mixture.

[0027] In some embodiments, the grinding aid is selected from at least one of methanol, ethanol, propanol, isopropanol, and N-methylpyrrolidone.

[0028] In some embodiments, the molar ratio of the total amount of transition metal elements in the lithium-rich manganese-based precursor to the lithium element in the lithium source is 1:(1.3-1.8).

[0029] In some embodiments, the preparation step of the lithium-rich manganese-based precursor comprises:

[0030] mixing a soluble nickel source, a soluble cobalt source, a soluble manganese source, and deionized water to obtain a metal salt solution;

[0031] adding to the alkali solution to perform a co-precipitation reaction, and then washing and drying to obtain the lithium-rich manganese-based precursor.

[0032] In some embodiments, the soluble nickel source is at least one selected from the group consisting of nickel sulfate and hydrates thereof, nickel nitrate and hydrates thereof, nickel carbonate and hydrates thereof, and nickel oxide and hydrates thereof.

[0033] In some embodiments, the soluble cobalt source is at least one selected from the group consisting of cobalt sulfate and hydrates thereof, cobalt nitrate and hydrates thereof, cobalt carbonate and hydrates thereof, and cobalt oxide and hydrates thereof.

[0034] In some embodiments, the soluble manganese source is at least one selected from the group consisting of manganese sulfate and hydrates thereof, manganese nitrate and hydrates thereof, manganese carbonate and hydrates thereof, and manganese oxide and hydrates thereof.

[0035] In some embodiments, the alkali solution is a mixed alkali solution comprising a carbonate and ammonia water.

[0036] In some embodiments, the mixed alkali solution of the carbonate and ammonia water has a carbonate concentration of 3-12 mol / L and an NH3 concentration of 1-5 mol / L.

[0037] In some embodiments, the carbonate is at least one selected from the group consisting of sodium carbonate, potassium carbonate, and sodium bicarbonate.

[0038] In some embodiments, the molar ratio of the manganese element in the soluble manganese source, the cobalt element in the soluble cobalt source, and the nickel element in the soluble nickel source is x:y:z, wherein 0

[0039] In some embodiments, the co-precipitation reaction is performed in a continuous stirred tank reactor at a temperature of 40-60°C, a pH value of the reaction solution of 7.5-8.0, and a stirring speed of 200-400 rpm.

[0040] The washing process comprises washing 2-4 times with deionized water and then washing 2-4 times with ethanol.

[0041] The drying condition is a temperature of 80-120°C and vacuum drying for 12-24 h.

[0042] In a second aspect, a surface-modified lithium-rich manganese-based positive electrode material is provided, which includes a lithium-rich manganese-based material, a disordered spinel self-protecting layer coated on the surface of the lithium-rich manganese-based material, and a garnet solid-state electrolyte coated on the surface of the disordered spinel self-protecting layer.

[0043] In a third aspect, a positive electrode sheet is provided, which includes the surface-modified lithium-rich manganese-based positive electrode material as described above.

[0044] In a fourth aspect, a lithium ion battery is provided, which includes the positive electrode sheet as described above.

[0045] The technical solutions provided in the present application have the following beneficial effects:

[0046] The present application provides a surface-modified lithium-rich manganese-based positive electrode material, a preparation method and a lithium ion battery. The present application uses a lithium-rich manganese-based precursor as a raw material, fully mixes the lithium-rich manganese-based precursor with a lithium source and metal oxides required for the synthesis of a garnet solid-state electrolyte, and then sintering in an oxidizing atmosphere. The conventional synthesis method of the garnet solid-state electrolyte is similar to that of the lithium-rich manganese-based positive electrode material, and the sintering reaction is carried out at a high temperature. The difference is that the temperature required for the synthesis of the garnet solid-state electrolyte is higher than that required for the synthesis of the lithium-rich manganese-based positive electrode material. Therefore, the present application takes advantage of the different nucleation temperatures of the lithium-rich manganese-based positive electrode material and the garnet solid-state electrolyte, and the characteristic that the garnet solid-state electrolyte can combine with lithium released from the surface phase of the lithium-rich manganese-based positive electrode material during the synthesis process, to prepare a double-coated layer with an inner layer of a disordered spinel self-protecting layer and an outer layer of a garnet solid-state electrolyte. When the garnet solid-state electrolyte generates a nucleation reaction, it will rob lithium required for the synthesis on the surface of the lithium-rich manganese-based positive electrode material, which leads to a lithium-deficient environment for the lithium-rich manganese-based positive electrode material during the synthesis process. Therefore, a layer of disordered spinel self-protecting layer is formed on the surface of the lithium-rich manganese-based material, which can stabilize the material surface, reduce the release of oxygen, and enhance the oxygen framework on the material surface, stabilize the lattice oxygen, thereby improving the initial coulombic efficiency and rate performance.

[0047] As a fast ion conductor, the garnet solid-state electrolyte is generated in situ on the outer surface of the disordered spinel self-protecting layer. On the one hand, it has high ionic conductivity, which can improve the lithium ion transmission efficiency of the surface-modified lithium-rich manganese-based positive electrode material, thereby improving the charge and discharge rate of the battery. On the other hand, the garnet solid-state electrolyte is relatively stable, and when coated on the surface of the lithium-rich manganese-based material, it can act as a physical barrier layer to reduce the interfacial side reactions between the lithium-rich manganese-based material and the external electrolyte, thereby improving the cycle performance. BRIEF DESCRIPTION OF DRAWINGS

[0048] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0049] Figure 1 A flow chart of a method for preparing a surface-modified lithium-rich manganese-based positive electrode material provided in an embodiment of the present application;

[0050] Figure 2 A schematic cross-sectional view of a surface-modified lithium-rich manganese-based positive electrode material provided in an embodiment of the present application;

[0051] Figure 3 0.1C / 0.1C charge-discharge curves of the lithium-rich manganese-based positive electrode materials in Example 5 and Comparative Example 1 of the present application;

[0052] Figure 4 This is a rate diagram of 0.1C charging, 0.2C, 0.33C, 0.5C, 1C, 2C, 3C, and 0.33C discharge of the lithium-rich manganese-based positive electrode material in Example 5 and Comparative Example 1 of the present application;

[0053] Figure 5 This is a 1C charge-discharge cycle diagram of the lithium-rich manganese-based positive electrode material in Example 5 and Comparative Example 1 of the present application.

[0054] In the figure: 1. Lithium-rich manganese-based material; 2. Disordered spinel self-protection layer; 3. Garnet-type solid electrolyte. DETAILED DESCRIPTION

[0055] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0056] See also Figure 1 As shown, the embodiment of the present application provides a method for preparing a surface-modified lithium-rich manganese-based positive electrode material, which includes the following steps:

[0057] 101: A lithium-rich manganese-based precursor, a lithium source, and a metal oxide required for a garnet-type solid electrolyte are mixed to obtain a mixture.

[0058] 102: performing gradient temperature calcination on the mixture in an oxidizing atmosphere to obtain the surface-modified lithium-rich manganese-based positive electrode material; wherein the surface-modified lithium-rich manganese-based positive electrode material comprises a lithium-rich manganese-based material, a disordered spinel self-protection layer coated on the surface of the lithium-rich manganese-based material, and a garnet solid-state electrolyte coated on the surface of the disordered spinel self-protection layer; and the gradient temperature calcination comprises: first calcining at the nucleation temperature of the lithium-rich manganese-based material, and then calcining at the nucleation temperature of the garnet solid-state electrolyte.

[0059] The lithium-rich manganese-based precursor is mixed with a lithium source and metal oxides required for the garnet solid-state electrolyte, and then sintered in an oxidizing atmosphere. The conventional synthesis method of the garnet solid-state electrolyte is similar to that of the lithium-rich manganese-based positive electrode material, and the sintering reaction is performed at a high temperature. The difference is that the synthesis of the garnet solid-state electrolyte requires a higher temperature (i.e., the nucleation temperature) than the synthesis of the lithium-rich manganese-based positive electrode material. Therefore, the present application takes advantage of the different nucleation temperatures of the lithium-rich manganese-based positive electrode material and the garnet solid-state electrolyte, and the characteristic that the lithium-rich manganese-based positive electrode material can combine with lithium released from the surface phase of the lithium-rich manganese-based positive electrode material at a high temperature during the synthesis of the garnet solid-state electrolyte, to prepare a double-coated layer with a disordered spinel self-protection layer as the inner layer and a garnet solid-state electrolyte as the outer layer, as shown in the surface-modified lithium-rich manganese-based positive electrode material. Figure 2 As a core-shell structure, the surface-modified lithium-rich manganese-based positive electrode material has a lithium-rich manganese-based material 1 in the inside, a disordered spinel self-protection layer 2 in the middle, and a garnet solid-state electrolyte 3 on the outside. When the garnet solid-state electrolyte generates a nucleation reaction, it will rob lithium required for the synthesis on the surface of the lithium-rich manganese-based positive electrode material, which leads to a lithium-deficient environment for the lithium-rich manganese-based positive electrode material during the synthesis. Therefore, a layer of disordered spinel self-protection layer is formed on the surface of the lithium-rich manganese-based material, which can stabilize the material surface, reduce the release of oxygen, and enhance the oxygen framework on the material surface, stabilize the lattice oxygen, thereby improving the first coulombic efficiency and rate performance.

[0060] The garnet solid-state electrolyte, as a fast ion conductor, is generated in situ on the outer surface of the disordered spinel self-protection layer. On the one hand, it has a high ionic conductivity, which can improve the lithium ion transmission efficiency of the surface-modified lithium-rich manganese-based positive electrode material, thereby improving the charge and discharge rate of the battery. On the other hand, the garnet solid-state electrolyte is relatively stable, and when coated on the surface of the lithium-rich manganese-based material, it can act as a physical barrier layer to reduce the interfacial side reactions between the lithium-rich manganese-based material and the external electrolyte, thereby improving the cycle performance.

[0061] In addition, the gradient high-temperature solid-phase synthesis method adopted by the present application is compatible with the existing production process, does not require additional processes, and the preparation method is simple, which is conducive to large-scale production.

[0062] The temperature gradient calcination is performed at a temperature gradient of 3-8℃ / min. The nucleation temperature of the lithium-rich manganese-based material is 700-900℃, and the nucleation temperature of the garnet solid-state electrolyte is 900-1000℃.

[0063] That is, in the temperature gradient calcination process, the lithium-rich manganese-based positive electrode material is first synthesized at a temperature of 700-900℃, and then the garnet solid-state electrolyte is synthesized by increasing the temperature to 900-1000℃ at a temperature gradient of 3-8℃ / min. The lithium near the surface of the lithium-rich manganese-based positive electrode material is easily lost, and an inner layer of disordered spinel self-protection layer and an outer layer of garnet solid-state electrolyte are formed on the surface of the lithium-rich manganese-based positive electrode material due to the lack of lithium.

[0064] The temperature gradient calcination is performed at a temperature gradient of 3-8℃ / min. The nucleation temperature of the lithium-rich manganese-based material is 700-900℃, and the nucleation temperature of the garnet solid-state electrolyte is 900-1000℃.

[0065] The oxidation atmosphere is air or oxygen.

[0066] Further, before the calcination at the nucleation temperature of the lithium-rich manganese-based material, the temperature gradient calcination further includes calcination at 400-600℃ for 4-8h. The purpose of this low-temperature sintering step is to remove moisture and volatile substances to prevent the generation of gas during subsequent high-temperature sintering, which affects the structure and performance of the material; pre-sintering helps the precursor and lithium source to undergo preliminary solid-phase reaction to form the desired crystal structure; promotes the uniformity of the material; and reduces the subsequent high-temperature sintering time.

[0067] In step 101, the garnet solid-state electrolyte includes an LLZO electrolyte Li7La3Zr2O 12 , an LLZAO electrolyte Li 6.23 La3Zr2Al 0.25 O 12and LLZTO electrolyte Li 6.24 La3Zr 1.4 Ta 0.6 O 12 and one or more of the following:

[0068] It can be seen that the metal oxide of the garnet solid-state electrolyte at least includes a lanthanum source and a zirconium source.

[0069] For example, when the LLZO electrolyte Li7La3Zr2O 12 , the metal oxide includes a lanthanum source and a zirconium source.

[0070] For example, when the LLZAO electrolyte Li 6.23 La3Zr2Al 0.25 O 12 , the metal oxide not only includes a lanthanum source and a zirconium source, but also includes an aluminum source, such as aluminum oxide.

[0071] For example, when the LLZTO electrolyte Li 6.24 La3Zr 1.4 Ta 0.6 O 12 , the metal oxide not only includes a lanthanum source and a zirconium source, but also includes a tantalum source, such as di tantalum pentoxide.

[0072] When the materials are mixed, the mass fraction of the metal oxide is 1%-10% of the lithium-rich manganese-based precursor.

[0073] For example, when the garnet solid-state electrolyte is the LLZO electrolyte Li7La3Zr2O 12 , the metal oxide includes a lanthanum source and a zirconium source. When the materials are mixed, the lanthanum source and the zirconium source are taken in a molar ratio of 3:2, and the total mass of the lanthanum source and the zirconium source is 1%-10% of the lithium-rich manganese-based precursor.

[0074] The lanthanum source is selected from at least one of lanthanum oxide, lanthanum nitrate, and lanthanum acetate.

[0075] The zirconium source is selected from at least one of zirconium oxide, zirconium nitrate, and zirconium acetate.

[0076] The above step 101 mixes the lithium-rich manganese-based precursor, the lithium source, and the metal oxide required for the garnet solid-state electrolyte to obtain a mixture, and specifically includes the following steps:

[0077] 201: Add the metal oxide required for the garnet solid-state electrolyte to the ball mill tank, and add a grinding aid to perform ball milling.

[0078] In step 201, the grinding aid is selected from at least one of methanol, ethanol, propanol, isopropanol, and N-methylpyrrolidone. The rotation speed of the ball milling process is 300-600 rpm.

[0079] 202: The lithium-rich manganese-based precursor is then added to a ball mill, ball milled, mixed evenly, and dried to obtain a modified lithium-rich manganese-based precursor.

[0080] In step 202, the rotation speed of the ball milling process is 300-500 rpm.

[0081] The drying conditions are: vacuum drying at a temperature of 100-120°C for 6-20 hours.

[0082] 203: The modified lithium-rich manganese-based precursor is mixed evenly with a lithium source to obtain a mixture.

[0083] In step 203, the molar ratio of the total amount of transition metal elements in the lithium-rich manganese-based precursor to the lithium element in the lithium source is 1:(1.3-1.8). The transition metal elements in the lithium-rich manganese-based precursor include nickel, manganese and cobalt.

[0084] In the above step 101, the steps of preparing the lithium-rich manganese-based precursor include:

[0085] 301: Evenly mix a soluble nickel source, a soluble cobalt source, a soluble manganese source and deionized water to obtain a metal salt solution.

[0086] In step 301, the soluble nickel source is selected from at least one of nickel sulfate and its hydrate, nickel nitrate and its hydrate, nickel carbonate and its hydrate, and nickel oxide and its hydrate.

[0087] The soluble cobalt source is selected from at least one of cobalt sulfate and its hydrate, cobalt nitrate and its hydrate, cobalt carbonate and its hydrate, and cobalt oxide and its hydrate.

[0088] The soluble manganese source is at least one selected from manganese sulfate and its hydrate, manganese nitrate and its hydrate, manganese carbonate and its hydrate, and manganese oxide and its hydrate.

[0089] The molar ratio of the manganese element in the soluble manganese source, the cobalt element in the soluble cobalt source and the nickel element in the soluble nickel source is x:y:z, wherein 0<x<7, 0≤y<2, 0<z<4.

[0090] For example, when the molar ratio of manganese:cobalt:nickel is 0.675:0.1625:0.1625, the disordered spinel self-protective layer obtained is Li 1.2-x Ni 0.13+x Co 0.13 Mn 0.54 O2,0 <x<0.1。

[0091] By changing the proportion of transition metal elements in the lithium-rich manganese-based precursor, the composition of the disordered spinel self-protecting layer can be adjusted.

[0092] 302: added to the alkali solution again to perform a co-precipitation reaction, and after washing and drying, a lithium-rich manganese-based precursor was obtained.

[0093] In step 302, the alkali solution is a mixed alkali solution containing a carbonate and ammonia.

[0094] In the mixed alkali solution of the carbonate and ammonia, the concentration of the carbonate is 3-12 mol / L, and the concentration of NH3 is 1-5 mol / L.

[0095] The carbonate is at least one of sodium carbonate, potassium carbonate, or sodium bicarbonate.

[0096] The co-precipitation reaction is performed in a continuous stirred tank reactor, at a temperature of 40-60°C, a pH value of the reaction solution of 7.5-8.0, and a stirring speed of 200-400 rpm.

[0097] The washing process is: first washed 2-4 times with deionized water, and then washed 2-4 times with ethanol to prevent residual excess carbonate and ammonia.

[0098] The drying conditions are: a temperature of 80-120°C, and vacuum drying for 12-24 h.

[0099] The application also provides a surface-modified lithium-rich manganese-based positive electrode material, which comprises a lithium-rich manganese-based material, a disordered spinel self-protecting layer coated on the surface of the lithium-rich manganese-based material, and a garnet solid-state electrolyte coated on the surface of the disordered spinel self-protecting layer. It can be understood that it can be prepared by using any of the above-mentioned preparation methods of the surface-modified lithium-rich manganese-based positive electrode material.

[0100] The application also provides a positive electrode sheet comprising the surface-modified lithium-rich manganese-based positive electrode material as described above.

[0101] The application also provides a lithium ion battery comprising the positive electrode sheet as described above.

[0102] The application is described in detail below through several embodiments.

[0103] Embodiment 1

[0104] Step (1), MnSO4.H2O, CoSO4.7H2O and NiSO4.6H2O were dissolved in 3 L of deionized water with a molar ratio of 0.675:0.1625:0.1625 of manganese element, cobalt element and nickel element, and stirred uniformly to form a metal salt solution, which was pumped into a continuous stirred tank reactor (CSTR) at a speed of 100 ml / h. 6 mol of anhydrous sodium carbonate was weighed and prepared into 3 L of solution as a precipitant, and 0.3 mol / L of ammonia was added as a complexing agent. The pH value of the CSTR was adjusted to about 7.75. After the reaction was completed, filtration, washing and drying were performed to obtain a lithium-rich manganese-based precursor (Ni 1 / 6 Co 1 / 6 Mn 4 / 6 CO3).

[0105] Step (2), La2O3 and ZrO2 corresponding to 1% mass fraction of the surface modified lithium-rich manganese-based positive electrode material were added to the ball mill tank at a molar ratio of 3:2 of lanthanum element and zirconium element, and an appropriate amount of ethanol was added, and ball milling was performed at a speed of 500 r / min for 4 h. The lithium-rich manganese-based precursor obtained in step (1) was added to the ball mill tank, and ball milling was performed at a speed of 400 r / min for 5 h, and after mixing uniformly, drying was performed to obtain a modified lithium-rich manganese-based precursor.

[0106] Step (3), the modified lithium-rich manganese-based precursor obtained in step (2) and Li2CO3 were added to the ball mill tank at a molar ratio of 1:1.5 of transition metal element and lithium element, and ball milling was performed at a speed of 400 r / min for 4 h, and after mixing uniformly, it was placed in a muffle furnace, and heated to 500℃ at a heating rate of 5℃ / min in an air atmosphere, and kept for 5 h, and then heated to 850℃ at a heating rate of 5℃ / min, and kept for 10 h, and finally heated to 900℃ at a heating rate of 5℃ / min, and kept for 5 h, to prepare a surface modified lithium-rich manganese-based positive electrode material.

[0107] Example 2

[0108] Step (1) is the same as example 1.

[0109] Step (2), La2O3 and ZrO2 corresponding to 3% mass fraction of the surface modified lithium-rich manganese-based positive electrode material were added to the ball mill tank at a molar ratio of 3:2 of lanthanum element and zirconium element, and an appropriate amount of ethanol was added, and ball milling was performed at a speed of 500 r / min for 4 h. The lithium-rich manganese-based precursor obtained in step (1) was added to the ball mill tank, and ball milling was performed at a speed of 400 r / min for 5 h, and after mixing uniformly, drying was performed to obtain a modified lithium-rich manganese-based precursor.

[0110] Step (3), the modified lithium-rich manganese-based precursor obtained in step (2) and Li2CO3 are added into a ball mill jar in a molar ratio of transition metal element to lithium element of 1:1.5, ball-milled at a speed of 400 r / min for 4 h, uniformly mixed, and then placed in a muffle furnace, heated to 500 ℃ at a heating rate of 5 ℃ / min under an air atmosphere, kept for 5 h, heated to 850 ℃ at a heating rate of 5 ℃ / min, kept for 10 h, and finally heated to 900 ℃ at a heating rate of 5 ℃ / min, kept for 5 h, to prepare the surface-modified lithium-rich manganese-based positive electrode material.

[0111] Example 3

[0112] Step (1) is the same as that in Example 1.

[0113] Step (2), La2O3 and ZrO2 corresponding to 5% mass fraction of the surface-modified lithium-rich manganese-based positive electrode material are added into a ball mill jar in a molar ratio of lanthanum element to zirconium element of 3:2, and an appropriate amount of ethanol is added, and ball-milled at a speed of 500 r / min for 4 h. The lithium-rich manganese-based precursor obtained in step (1) is added into the ball mill jar, ball-milled at a speed of 400 r / min for 5 h, uniformly mixed, and dried to obtain the modified lithium-rich manganese-based precursor.

[0114] Step (3), the modified lithium-rich manganese-based precursor obtained in step (2) and Li2CO3 are added into a ball mill jar in a molar ratio of transition metal element to lithium element of 1:1.5, ball-milled at a speed of 400 r / min for 4 h, uniformly mixed, and then placed in a muffle furnace, heated to 500 ℃ at a heating rate of 5 ℃ / min under an air atmosphere, kept for 5 h, heated to 850 ℃ at a heating rate of 5 ℃ / min, kept for 10 h, and finally heated to 900 ℃ at a heating rate of 5 ℃ / min, kept for 5 h, to prepare the surface-modified lithium-rich manganese-based positive electrode material.

[0115] Example 4

[0116] Step (1) is the same as that in Example 1.

[0117] Step (2), La2O3 and ZrO2 corresponding to 1% mass fraction of the surface-modified lithium-rich manganese-based positive electrode material are added into a ball mill jar in a molar ratio of lanthanum element to zirconium element of 3:2, and an appropriate amount of ethanol is added, and ball-milled at a speed of 500 r / min for 4 h. The lithium-rich manganese-based precursor obtained in step (1) is added into the ball mill jar, ball-milled at a speed of 400 r / min for 5 h, uniformly mixed, and dried to obtain the modified lithium-rich manganese-based precursor.

[0118] Step (3), the modified lithium-rich manganese-based precursor obtained in step (2) and Li2CO3 are added into a ball mill jar in a molar ratio of transition metal element to lithium element of 1:1.5, ball-milled at a rotating speed of 400 r / min for 4 h, uniformly mixed, and then placed in a muffle furnace, heated to 500 ℃ at a heating rate of 5 ℃ / min under an air atmosphere, kept for 5 h, heated to 850 ℃ at a heating rate of 5 ℃ / min, kept for 10 h, and finally heated to 950 ℃ at a heating rate of 5 ℃ / min, kept for 5 h, to prepare the surface-modified lithium-rich manganese-based positive electrode material.

[0119] Example 5

[0120] Step (1) is the same as that in Example 1.

[0121] Step (2), La2O3 and ZrO2 corresponding to 5% mass fraction of the surface-modified lithium-rich manganese-based positive electrode material are added into a ball mill jar in a molar ratio of lanthanum element to zirconium element of 3:2, and an appropriate amount of ethanol is added, and ball-milled at a rotating speed of 500 r / min for 4 h. Then the lithium-rich manganese-based precursor obtained in step (1) is added into the ball mill jar, ball-milled at a rotating speed of 400 r / min for 5 h, uniformly mixed, and dried to obtain the modified lithium-rich manganese-based precursor.

[0122] Step (3), the modified lithium-rich manganese-based precursor obtained in step (2) and Li2CO3 are added into a ball mill jar in a molar ratio of transition metal element to lithium element of 1:1.5, ball-milled at a rotating speed of 400 r / min for 4 h, uniformly mixed, and then placed in a muffle furnace, heated to 500 ℃ at a heating rate of 5 ℃ / min under an air atmosphere, kept for 5 h, heated to 850 ℃ at a heating rate of 5 ℃ / min, kept for 10 h, and finally heated to 950 ℃ at a heating rate of 5 ℃ / min, kept for 5 h, to prepare the surface-modified lithium-rich manganese-based positive electrode material.

[0123] Example 6

[0124] Step (1) is the same as that in Example 1.

[0125] Step (2), La2O3 and ZrO2 corresponding to 5% mass fraction of the surface-modified lithium-rich manganese-based positive electrode material are added into a ball mill jar in a molar ratio of lanthanum element to zirconium element of 3:2, and an appropriate amount of ethanol is added, and ball-milled at a rotating speed of 500 r / min for 4 h. Then the lithium-rich manganese-based precursor obtained in step (1) is added into the ball mill jar, ball-milled at a rotating speed of 400 r / min for 5 h, uniformly mixed, and dried to obtain the modified lithium-rich manganese-based precursor.

[0126] Step (3), the modified lithium-rich manganese-based precursor obtained in step (2) and Li2CO3 are added into a ball mill jar in a molar ratio of transition metal element to lithium element of 1:1.5, ball-milled at a rotating speed of 400 r / min for 4 h, uniformly mixed, and then placed in a muffle furnace, heated to 500 ℃ at a heating rate of 5 ℃ / min under an air atmosphere, kept for 5 h, heated to 850 ℃ at a heating rate of 5 ℃ / min, kept for 10 h, and finally heated to 950 ℃ at a heating rate of 5 ℃ / min, kept for 5 h, to prepare the surface-modified lithium-rich manganese-based positive electrode material.

[0127] Example 7

[0128] Step (1) is the same as that in Example 1.

[0129] Step (2), La2O3 and ZrO2 corresponding to 1% mass fraction of the surface-modified lithium-rich manganese-based positive electrode material are added into a ball mill jar in a molar ratio of lanthanum element to zirconium element of 3:2, and an appropriate amount of ethanol is added, and ball-milled at a rotating speed of 500 r / min for 4 h. Then the lithium-rich manganese-based precursor obtained in step (1) is added into the ball mill jar, ball-milled at a rotating speed of 400 r / min for 5 h, uniformly mixed, and dried to obtain the modified lithium-rich manganese-based precursor.

[0130] Step (3), the modified lithium-rich manganese-based precursor obtained in step (2) and Li2CO3 are added into a ball mill jar in a molar ratio of transition metal element to lithium element of 1:1.5, ball-milled at a rotating speed of 400 r / min for 4 h, uniformly mixed, and then placed in a muffle furnace, heated to 500 ℃ at a heating rate of 5 ℃ / min under an air atmosphere, kept for 5 h, heated to 850 ℃ at a heating rate of 5 ℃ / min, kept for 10 h, and finally heated to 1000 ℃ at a heating rate of 5 ℃ / min, kept for 5 h, to prepare the surface-modified lithium-rich manganese-based positive electrode material.

[0131] Example 8

[0132] Step (1) is the same as that in Example 1.

[0133] Step (2), La2O3 and ZrO2 corresponding to 3% mass fraction of the surface-modified lithium-rich manganese-based positive electrode material are added into a ball mill jar in a molar ratio of lanthanum element to zirconium element of 3:2, and an appropriate amount of ethanol is added, and ball-milled at a rotating speed of 500 r / min for 4 h. Then the lithium-rich manganese-based precursor obtained in step (1) is added into the ball mill jar, ball-milled at a rotating speed of 400 r / min for 5 h, uniformly mixed, and dried to obtain the modified lithium-rich manganese-based precursor.

[0134] Step (3), adding the modified lithium-rich manganese-based precursor obtained in step (2) and Li2CO3 in a molar ratio of transition metal element to lithium element of 1:1.5 into a ball mill, ball milling at a speed of 400r / min for 4h, mixing evenly, and then placing in a muffle furnace, heating to 500℃ at a heating rate of 5℃ / min in an air atmosphere and keeping warm for 5h, then heating to 850℃ at 5℃ / min and keeping warm for 10h, and finally heating to 1000℃ at 5℃ / min and keeping warm for 5h to prepare a surface-modified lithium-rich manganese-based positive electrode material.

[0135] Example 9

[0136] Step (1) is the same as in Example 1.

[0137] Step (2): La2O3 and ZrO2 equivalent to 5% by mass of the surface-modified lithium-rich manganese-based positive electrode material are added to a ball mill according to a molar ratio of lanthanum to zirconium of 3:2, and an appropriate amount of ethanol is added. The mixture is ball milled at a speed of 500 r / min for 4 hours. The lithium-rich manganese-based precursor obtained in step (1) is then added to the ball mill, ball milled at a speed of 400 r / min for 5 hours, mixed evenly, and dried to obtain a modified lithium-rich manganese-based precursor.

[0138] Step (3), adding the modified lithium-rich manganese-based precursor obtained in step (2) and Li2CO3 in a molar ratio of transition metal element to lithium element of 1:1.5 into a ball mill, ball milling at a speed of 400r / min for 4h, mixing evenly, and then placing in a muffle furnace, heating to 500℃ at a heating rate of 5℃ / min in an air atmosphere and keeping warm for 5h, then heating to 850℃ at 5℃ / min and keeping warm for 10h, and finally heating to 1000℃ at 5℃ / min and keeping warm for 5h to prepare a surface-modified lithium-rich manganese-based positive electrode material.

[0139] Comparative Example 1

[0140] Step (1) is the same as in Example 1.

[0141] Step (2), the lithium-rich manganese-based precursor obtained in step (1) and Li2CO3 are added to a ball mill according to a molar ratio of transition metal element to lithium element of 1:1.5, ball milled at a speed of 400r / min for 4h, mixed evenly, and then placed in a muffle furnace, heated to 500℃ at a heating rate of 5℃ / min in an air atmosphere and kept warm for 5h, and then heated to 850℃ at a heating rate of 5℃ / min and kept warm for 10h, to prepare a lithium-rich manganese-based positive electrode material Li without surface modification. 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2.

[0142] Comparative Example 2

[0143] Step (1) is the same as in Example 1.

[0144] Step (2), the lithium-rich manganese-based precursor obtained in step (1) and Li2CO3 are added to a ball mill according to a molar ratio of transition metal element to lithium element of 1:1.5, ball milled at a speed of 400r / min for 4h, mixed evenly, and then placed in a muffle furnace, heated to 500℃ at a heating rate of 5℃ / min in an air atmosphere for 5h, then heated to 850℃ at 5℃ / min for 10h, and finally heated to 900℃ at 5℃ / min for 5h to prepare a lithium-rich manganese-based positive electrode material Li only sintered by gradient sintering 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2.

[0145] Comparative Example 3

[0146] Step (1) is the same as in Example 1.

[0147] Step (2): Li7La3Zr2O equivalent to 3% by mass of lithium-rich manganese-based positive electrode material 12 Add to a ball mill, add an appropriate amount of ethanol, and ball mill at a speed of 500 r / min for 4 hours. Then add the lithium-rich manganese-based precursor obtained in step (1) to the ball mill, ball mill at a speed of 400 r / min for 5 hours, mix well, and then dry to obtain a modified lithium-rich manganese-based precursor.

[0148] Step (3), adding the modified lithium-rich manganese-based precursor obtained in step (2) and Li2CO3 in a ratio of transition metal element to lithium element of 1:1.5 into a ball mill, milling at a speed of 400r / min for 4h, mixing evenly, and then placing in a muffle furnace, heating to 500℃ at a heating rate of 5℃ / min in an air atmosphere for 5h, and then heating to 850℃ at a heating rate of 5℃ / min for 10h, to prepare a coating only with Li7La3Zr2O 12 Lithium-rich manganese-based positive electrode materials.

[0149] Testing and analysis of electrical properties

[0150] The lithium-rich manganese-based positive electrode materials obtained in the above examples and comparative examples were respectively weighed with a conductive agent (acetylene black) and a binder (polyvinylidene fluoride) in a mass ratio of 80:10:10, and then an appropriate amount of NMP (N-methylpyrrolidone) was added and mixed evenly. The prepared slurry was evenly coated on an aluminum foil and placed in an 80°C vacuum drying oven to dry for 12 hours. After drying, the cut pieces were taken out and rolled, and the pressed electrode pieces were placed in a 120°C vacuum drying oven for 8 hours to obtain the lithium-rich manganese-based positive electrode electrode pieces of the present invention.

[0151] The button cell was prepared in a glove box with oxygen content and water content less than 0.01 ppm, assembled according to the structure of R2032 button cell, the negative electrode was metal lithium, the separator was Celgard 2400 porous polyethylene separator, and the electrolyte was EC-based and PC-based electrolyte.

[0152] 0.1C charge-discharge was carried out at a temperature of 25°C and a voltage interval of 2.0-4.6V; 0.1C charging was carried out at a temperature of 25°C and a voltage interval of 2.0-4.6V, followed by 0.2C, 0.33C, 0.5C, 1C, 2C, 3C, 0.33C discharging for rate test; 1C charge-discharge was carried out at a temperature of 25°C and a voltage interval of 2.0-4.6V for 100 cycles.

[0153] wherein, under the test conditions of a test temperature of 25°C, a current density of 0.1C (1C=220mAh / g), and a charge-discharge voltage of 2.0-4.6V, Figure 3 The charge-discharge curve comparison chart of Example 5 and Comparative Example 1 is shown in Figure 1. The initial specific discharge capacity of Example 5 is 263.5mAh / g, and the initial efficiency is 93.64%; while the initial specific discharge capacity of Comparative Example 1 is 242.38mAh / g, and the initial efficiency is 78.45%.

[0154] Figure 4 The rate performance comparison chart of Example 5 and Comparative Example 1 is shown in Figure 2. The discharge capacities of Example 5 at a charge rate of 0.1C and discharge rates of 0.2C, 0.33C, 0.5C, 1C, 2C, 3C, 0.33C are 262.92mAh / g, 259.0mAh / g, 247.91mAh / g, 234.63mAh / g, 221.93mAh / g, 209.72mAh / g, 252.17mAh / g, respectively; while the discharge capacities of Comparative Example 1 at a charge rate of 0.1C and discharge rates of 0.2C, 0.33C, 0.5C, 1C, 2C, 3C, 0.33C are 243.96mAh / g, 237.22mAh / g, 225.26mAh / g, 208.08mAh / g, 187.63mAh / g, 164.76mAh / g, 228.88mAh / g, respectively.

[0155] Figure 5 The cycle performance comparison chart of Example 5 and Comparative Example 1 is shown in Figure 3. The capacity retention rate of Example 5 at a 1C rate for 100 cycles is 92.85%; while that of Comparative Example 1 is 75.63%. The test results of all examples and comparative examples are as follows:

[0156] Table 1: Test results of button cell

[0157]

[0158] As can be seen from Table 1, the initial coulombic efficiency and the initial discharge capacity of Examples 1-9 are obviously higher than those of Comparative Examples 1-3, the discharge capacity of Examples 1-9 at a current density of 3C is obviously higher than that of Comparative Examples 1-3, and the 100-week capacity retention rate of Examples 1-9 is obviously higher than that of Comparative Examples 1-3. This fully demonstrates that the inner layer disordered spinel self-protection layer-outer layer Li7La3Zr2O 12 The double-coated layer of the garnet-type solid-state electrolyte can obviously improve the electrochemical performance of the lithium-rich manganese-based positive electrode.

[0159] The above description is merely that of specific embodiments of the application, to enable those skilled in the art to understand or implement the application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a surface-modified lithium-rich manganese-based positive electrode material, characterized by, It comprises: mixing the lithium-rich manganese-based precursor, the lithium source and the metal oxide required by the garnet solid electrolyte to obtain a mixture; gradient temperature calcining the mixture under an oxidizing atmosphere to obtain a surface-modified lithium-rich manganese-based positive electrode material; The gradient temperature calcining comprises: first calcining at the nucleation temperature of the lithium-rich manganese-based material, and then calcining at the nucleation temperature of the garnet solid electrolyte. The calcining at the nucleation temperature of the lithium-rich manganese-based material comprises: calcining at 700-900℃ for 8-12h. The calcining at the nucleation temperature of the garnet solid electrolyte comprises: calcining at 900-1000℃ for 4-6h.

2. The method of producing a surface-modified lithium-rich manganese-based positive electrode material according to claim 1, wherein Before the calcining at the nucleation temperature of the lithium-rich manganese-based material, the gradient temperature calcining further comprises: calcining at 400-600℃ for 4-8h.

3. The method of producing a surface-modified lithium-rich manganese-based positive electrode material according to claim 1, characterized by: The mass fraction of the metal oxide is 1%-10% of the lithium-rich manganese-based precursor.

4. The method of producing a surface-modified lithium-rich manganese-based positive electrode material according to claim 1, characterized by: The garnet solid state electrolyte includes one or more of LLZO electrolyte Li7La3Zr2O 12 LLZAO electrolyte Li 6.23 La3Zr2Al 0.25 O 12 and LLZTO electrolyte Li 6.24 La3Zr 1.4 Ta 0.6 O 12 .

5. The method of producing a surface-modified lithium-rich manganese-based positive electrode material according to claim 1, characterized by: The metal oxide comprises a lanthanum source and a zirconium source.

6. The method of producing a surface-modified lithium-rich manganese-based positive electrode material according to claim 5, characterized by: The lanthanum source is selected from at least one of lanthanum oxide, lanthanum nitrate and lanthanum acetate.

7. The method of producing a surface-modified lithium-rich manganese-based positive electrode material according to claim 5, characterized by: The zirconium source is selected from at least one of zirconium oxide, zirconium nitrate and zirconium acetate.

8. The method of producing a surface-modified lithium-rich manganese-based positive electrode material according to claim 1, characterized by: The lithium source is selected from at least one of lithium carbonate, lithium hydroxide, lithium nitrate, lithium acetate and lithium phosphate.

9. The method of producing a surface-modified lithium-rich manganese-based positive electrode material according to claim 1, wherein Mixing the lithium-rich manganese-based precursor, the lithium source and the metal oxide required by the garnet solid electrolyte to obtain a mixture, specifically comprising: adding the metal oxide required by the garnet solid electrolyte into a ball mill tank and adding a grinding aid for ball milling; then adding the lithium-rich manganese-based precursor into the ball mill tank for ball milling, and after uniform mixing, drying to obtain a modified lithium-rich manganese-based precursor; mixing the modified lithium-rich manganese-based precursor with the lithium source to obtain a mixture.

10. The method of producing a surface-modified lithium-rich manganese-based positive electrode material according to claim 9, characterized by: The grinding aid is selected from at least one of methanol, ethanol, propanol, isopropanol and N-methyl pyrrolidone.

11. The method of producing a surface-modified lithium-rich manganese-based positive electrode material according to claim 9, characterized by: The molar ratio of the total amount of transition metal elements in the lithium-rich manganese-based precursor to lithium elements in the lithium source is 1:(1.3-1.8).

12. The method of producing a surface-modified lithium-rich manganese-based positive electrode material according to claim 1, wherein The preparation steps of the lithium-rich manganese-based precursor comprise: mixing a soluble nickel source, a soluble cobalt source, a soluble manganese source and deionized water to obtain a metal salt solution; then adding into an alkali solution for co-precipitation reaction, and after washing and drying, obtaining the lithium-rich manganese-based precursor.

13. The method of producing a surface-modified lithium-rich manganese-based positive electrode material according to claim 12, characterized by: The soluble nickel source is selected from at least one of nickel sulfate and its hydrate, nickel nitrate and its hydrate, nickel carbonate and its hydrate, and nickel oxide and its hydrate.

14. The method of producing a surface-modified lithium-rich manganese-based cathode material according to claim 12, wherein: The soluble cobalt source is selected from at least one of cobalt sulfate and its hydrate, cobalt nitrate and its hydrate, cobalt carbonate and its hydrate, and cobalt oxide and its hydrate.

15. The method of producing a surface-modified lithium-rich manganese-based cathode material according to claim 12, wherein: The soluble manganese source is selected from at least one of manganese sulfate and its hydrate, manganese nitrate and its hydrate, manganese carbonate and its hydrate, and manganese oxide and its hydrate.

16. The method of producing a surface-modified lithium-rich manganese-based cathode material according to claim 12, wherein: The alkali solution is a mixed alkali solution containing carbonate and ammonia water.

17. The method of producing a surface-modified lithium-rich manganese-based positive electrode material according to claim 16, characterized by: The concentration of the carbonate in the mixed alkali solution of carbonate and ammonia water is 3-12mol / L, and the concentration of NH3 is 1-5mol / L.

18. The method of producing a surface-modified lithium-rich manganese-based cathode material according to claim 16, wherein: The carbonate is at least one of sodium carbonate, potassium carbonate or sodium bicarbonate.

19. The method of producing a surface-modified lithium-rich manganese-based cathode material according to claim 12, wherein: The molar ratio of manganese elements in the soluble manganese source, cobalt elements in the soluble cobalt source and nickel elements in the soluble nickel source is x:y:z, wherein 0 20. The method for preparing the surface-modified lithium-rich manganese-based positive electrode material of claim 12, wherein: the co-precipitation reaction is carried out in a continuous stirred tank reactor at a temperature of 40-60℃, a pH value of the reaction solution of 7.5-8.0, and a stirring speed of 200-400 rpm; the washing process is: first washing 2-4 times with deionized water, and then washing 2-4 times with ethanol; the drying condition is: a temperature of 80-120℃ and vacuum drying for 12-24 h.

21. A surface-modified lithium-rich manganese-based positive electrode material, characterized by: The lithium battery is prepared by using the method for preparing the surface-modified lithium-rich manganese-based positive electrode material according to any one of claims 1 to 20, and the surface-modified lithium-rich manganese-based positive electrode material comprises a lithium-rich manganese-based material, a disordered spinel self-protection layer coated on the surface of the lithium-rich manganese-based material, and a garnet solid-state electrolyte coated on the surface of the disordered spinel self-protection layer.

22. A positive electrode sheet characterized by comprising: The lithium battery comprises the surface-modified lithium-rich manganese-based positive electrode material according to claim 21.

23. A lithium-ion battery, characterized by, The lithium battery comprises the positive electrode sheet according to claim 22.

Images