Surface modified lithium-rich manganese-based positive electrode material as well as preparation method and application thereof

Abstract

The invention relates to a surface modified lithium-rich manganese-based positive electrode material as well as a preparation method and application thereof. The surface modified lithium-rich manganese-based positive electrode material comprises a lithium-rich manganese-based positive electrode material core layer and a metal sulfate / metal sulfite modified layer which is constructed on the surface of the core layer in situ in an amorphous form, preferably, the metal sulfurous acid is located on the inner layer of the modification layer, and the metal sulfate is located on the outer layer of the modification layer.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of solid-state battery positive electrode materials, and particularly relates to a surface-modified lithium-rich manganese-based positive electrode material and a preparation method and application thereof. BACKGROUND

[0002] It is of great significance to develop high-safety and high-specific-energy battery technology for new energy vehicles to improve their safety and cruising range, promote the large-scale application of new energy vehicles, and reduce carbon emissions. The all-solid-state battery uses non-flammable solid electrolyte to replace the traditional flammable organic electrolyte, making the battery have higher safety. At the same time, the excellent mechanical properties and chemical stability of the solid electrolyte can match the high-voltage positive electrode material and the metal lithium negative electrode, which is expected to further improve the energy density of the battery. At present, the solid electrolyte has achieved a lithium ion conductivity similar to that of the liquid electrolyte (for example: the lithium ion conductivity of sulfide electrolytes such as Li6PS5Cl and halide electrolytes such as Li3InCl6 can reach 10 -3 ~ 10 -2 S / cm). Among them, the improvement of the energy density of the battery depends more on the performance of the positive electrode material. Compared with the traditional ternary positive electrode material, the lithium-rich manganese-based positive electrode material has a higher theoretical specific capacity (> 250 mAh / g) due to its unique oxygen anion participating in the charge compensation mechanism, and becomes one of the ideal candidate materials for realizing high-energy-density batteries.

[0003] However, the application of lithium-rich manganese-based positive electrode materials to all-solid-state batteries still faces serious challenges, mainly including the following aspects: first, the lithium-rich manganese-based positive electrode material has a low electronic conductivity, resulting in a slow internal charge transport rate of the composite positive electrode. Compared with the traditional ternary positive electrode material, such as Li(Ni 0.5 Co 0.2 Mn 0.3 )O2, the electronic conductivity is ~ 10 - 3 Scm -1 , while the electronic conductivity of the lithium-rich manganese-based positive electrode material is only ~ 10 -8 Scm -1 ; second, the voltage window of the lithium-rich manganese-based positive electrode material is wide (2-4.8V vs Li), which exceeds the electrochemical window of most solid electrolytes, and new types of solid electrolytes need to be developed and the interface needs to be modified; third, the lithium-rich manganese-based positive electrode will generate oxygen during the charging process, and the generated oxygen will oxidize the surrounding electrolyte, resulting in the oxidation and inactivation of the electrolyte and the decrease of the lithium ion transport performance in the composite positive electrode; fourth, the oxygen evolution of the lithium-rich manganese-based positive electrode material will cause the collapse of the lithium-rich manganese structure, which not only worsens the charge transport performance of the lithium-rich manganese positive electrode, but also reduces the lithium ion sites that can be embedded back during the discharging process, resulting in the attenuation of the voltage and capacity.

[0004] The above problems seriously restrict the application of lithium-rich manganese-based positive electrode materials in full solid-state batteries, and the lithium-rich manganese-based materials need to be optimized to improve their performance. SUMMARY

[0005] In view of the above technical problems, the present application aims to provide a surface-modified lithium-rich manganese-based positive electrode material and a preparation method and application thereof.

[0006] In a first aspect, the present application provides a surface-modified lithium-rich manganese-based positive electrode material, which comprises a lithium-rich manganese-based positive electrode material core layer and a metal sulfate / metal sulfite modification layer in amorphous form constructed in situ on the surface of the core layer. Preferably, the metal sulfite is located in the inner layer of the modification layer, and the metal sulfate is located in the outer layer of the modification layer.

[0007] In a second aspect, the present application provides a preparation method of the above surface-modified lithium-rich manganese-based positive electrode material, which comprises the following steps: mixing a lithium-rich manganese-based positive electrode material with a metal sulfate, and then performing high-speed ball milling to amorphize the metal sulfate and construct a metal sulfate / metal sulfite mixed modification layer in situ on the surface of the lithium-rich manganese-based positive electrode material, thereby obtaining the surface-modified lithium-rich manganese-based positive electrode material.

[0008] Preferably, the lithium-rich manganese-based positive electrode material comprises a lithium-rich manganese-based oxide layered positive electrode material with a chemical composition of xLi2MnO3·(1-x)LiMO2, 0

[0009] Preferably, the particle size of the lithium-rich manganese-based positive electrode material is 1-100 um.

[0010] Preferably, the type of the metal sulfate comprises one of stannous sulfate, cerium sulfate, indium sulfate, zirconium sulfate, aluminum sulfate, iron sulfate and copper sulfate.

[0011] Preferably, the mass fraction of the lithium-rich manganese-based positive electrode material is 50-95% and the mass fraction of the metal sulfate is 5-50% based on the total mass of the lithium-rich manganese-based positive electrode material and the metal sulfate being 100%.

[0012] Preferably, the grinding balls of the high-speed ball milling are stainless steel grinding balls with a diameter distribution of 1-15 mm, a ball-to-material ratio of 10-40:1, and a rotation speed of 200-1000 rmp; the ball milling condition is 30 minutes of forward rotation, 5-10 minutes of pause, 30 minutes of reverse rotation, 10 minutes of pause, one cycle, and the total ball milling time is 1-100 h.

[0013] In a third aspect, the present application provides an application of the above-mentioned surface-modified lithium-rich manganese-based positive electrode material in a full solid-state battery.

[0014] Preferably, the full solid-state battery comprises the above-mentioned surface-modified lithium-rich manganese-based positive electrode material, a positive electrode film formed by mixing the positive electrode material with a solid electrolyte powder, a conductive carbon material and a binder, a solid electrolyte, and a negative electrode material.

[0015] Preferably, the solid electrolyte comprises one of a sulfide solid electrolyte and a halide solid electrolyte; the conductive carbon material comprises VGCF and Super P; and the negative electrode material comprises graphite, silicon-carbon, silicon dioxide, silicon alloy, metallic lithium or lithium alloy.

[0016] Advantages (1) The present application is based on the addition of a low-melting-point sulfate salt. The energy provided in the high-energy ball milling process is used to amorphize the low-melting-point sulfate salt and coat it on the surface of the lithium-rich manganese positive electrode particles. At the same time, electron transfer occurs between the sulfur ions in the sulfate salt and the transition metal manganese ions on the surface of the lithium-rich manganese positive electrode material. A sulfite is formed on the surface of the lithium-rich manganese particles. Part of the manganese ions on the surface of the lithium-rich manganese positive electrode material obtains a higher oxidation state. The outer electrons of the sulfur atom have more electrons. Experimental results show that the sulfur ions can compensate for the charge loss of the anion oxygen, thereby inhibiting the excessive oxidation of the anion oxygen on the surface of the lithium-rich manganese and slowing down the oxygen precipitation. In addition, the higher oxidation state of the manganese ions on the surface of the lithium-rich manganese positive electrode material can effectively inhibit the J-T effect and relieve the structural distortion, thereby effectively improving the structural stability of the lithium-rich manganese positive electrode material during the cycling process. (2) The present application improves the electrochemical performance and safety of the lithium-rich manganese-based positive electrode material by surface modification. The method is easy to operate, the principle is simple, and it is easy to scale up production. (3) The lithium-rich manganese-based positive electrode material modified by the method provided by the present application has high electronic conductivity on the surface of the positive electrode material. The obtained positive electrode material has good charge and discharge specific capacity, cycling and rate performance. The method has rich raw material sources, low cost and simple process, and has good industrial application value. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 XRD patterns of the positive electrode materials prepared in Examples 1-3 and Comparative Example 1; Figure 2 SEM images of the positive electrode material prepared in Example 1; Figure 3A XPS patterns of the positive electrode materials prepared in Example 1 and Comparative Example 1; Figure 4 TEM images of the positive electrode material prepared in Example 1; Figures 5-9The first cycle charge-discharge curves of the all-solid-state batteries prepared in Examples 1-3 and Comparative Examples 1-3, respectively, under the conditions of room temperature (25℃), voltage range 2-4.6V (vs. Li), and current density 0.1C; Figure 10 The first cycle dQ / dV curves of the positive electrode materials prepared in Examples 1 and Comparative Example 1 under the conditions of room temperature (25℃), voltage range 2-4.6V (vs. Li), and current density 0.1C; Figure 11 The cycle stability comparison chart of the positive electrode materials prepared in Examples 1 and Comparative Example 1; Figure 12 The rate capability comparison chart of the positive electrode materials prepared in Examples 1 and Comparative Example 1. DETAILED DESCRIPTION

[0018] The present application is further illustrated by the following examples, which should not be construed as limiting the present application.

[0019] Firstly, the present application provides 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 positive electrode material core layer and a metal sulfate / metal sulfite modification layer in amorphous form constructed in situ on the surface of the core layer; preferably, the metal sulfite is located in the inner layer of the modification layer and the metal sulfate is located in the outer layer of the modification layer.

[0020] Hereinafter, the preparation method of the surface-modified lithium-rich manganese-based positive electrode material provided by the present application is exemplarily described. The preparation method can comprise the following steps: mixing a lithium-rich manganese-based positive electrode material with a metal sulfate, and then performing high-speed ball milling to amorphize the metal sulfate and construct a metal sulfate / metal sulfite mixed modification layer in situ on the surface of the lithium-rich manganese-based positive electrode material, thereby obtaining the surface-modified lithium-rich manganese-based positive electrode material.

[0021] In some embodiments, the lithium-rich manganese-based positive electrode material can comprise a lithium-rich manganese-based oxide layered positive electrode material, and the chemical composition can be xLi2MnO3·(1-x)LiMO2, 0 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2.

[0022] In some embodiments, the particle size of the lithium-rich manganese-based positive electrode material can be 1-100 um.

[0023] In some embodiments, the metal sulfate can include one of stannous sulfate, cerium sulfate, indium sulfate, zirconium sulfate, aluminum sulfate, iron sulfate, and copper sulfate.

[0024] It should be noted that the present application selects a sulfate with a lower melting point (such as ≤600℃), thereby ensuring that the sulfate can be amorphized and effectively uniformly coated on the surface of the lithium-rich manganese positive electrode particles during high-energy ball milling, and improving the uniformity of the coating. In addition, the cations of the sulfate can play a synergistic role in stabilizing the surface oxygen structure of the lithium-rich manganese. For example, stannous sulfate, cerium sulfate, and indium sulfate all have a melting point below 600 degrees, and stannous ions, cerium ions, and indium ions can all form bonds with high-activity oxygen ions during charging and discharging, stabilize high-activity oxygen ions, inhibit the excessive oxidation and precipitation of surface layer oxygen ions, and effectively improve the stability of the surface oxygen structure of the lithium-rich manganese.

[0025] In some embodiments, the mass ratio of the lithium-rich manganese-based positive electrode material to the total mass of the lithium-rich manganese-based positive electrode material and the metal sulfate can be 50-95%, and the mass ratio of the metal sulfate can be 5-50%. If the amount of the metal sulfate is too large, it will introduce more non-active substances, which is not conducive to the charge transfer between the lithium-rich manganese positive electrodes; if the amount of the metal sulfate is too small, it will result in insufficient coating, and cannot achieve the desired effect.

[0026] In some embodiments, the mixing method of the lithium-rich manganese-based positive electrode material and the metal sulfate can include one of manual mixing in a mortar, low-speed ball milling mixing, and high-speed vortex mixing; preferably, the mixing is performed in an inert environment.

[0027] In some embodiments, the grinding balls of the high-speed ball mill can be stainless steel grinding balls with a diameter distribution of 1-15mm, the ball-to-material ratio can be 10-40:1, and the rotation speed can be 200-1000rmp; the ball milling conditions can be 30 minutes of forward rotation, 5-10 minutes of pause, 30 minutes of reverse rotation, and 10 minutes of pause for one cycle, and the total ball milling time can be 1-100h. If the ball milling speed is too high, it will cause serious damage to the structure of the lithium-rich manganese; if the ball milling speed is too low, it will be difficult to coat the sulfate on the surface of the lithium-rich manganese particles.

[0028] That is, the present application uniformly mixes the lithium-rich manganese-based positive electrode material and the sulfate, performs high-energy ball milling, uses the energy provided during high-energy ball milling to amorphize the low-melting-point sulfate and coat it on the surface of the lithium-rich manganese-based positive electrode material, and under the energy provided by high-energy ball milling, the amorphized sulfate and the lithium-rich manganese-based positive electrode material undergo electron transfer, forming a sulfate and a sulfite on the surface of the lithium-rich manganese-based positive electrode material, in-situ constructing a sulfate / sulfite layer, and part of the manganese valence in the lithium-rich manganese-based positive electrode material is raised, that is, the lithium-rich manganese-based positive electrode material is obtained after ball milling.

[0029] Further, in order to further stabilize the interface between the lithium-rich manganese and the solid electrolyte, the present application proposes a synergistic effect of anions and cations to jointly alleviate the interface degradation of the lithium-rich manganese and the solid electrolyte. In addition to the anion sulfur capable of compensating for the loss of electrons of the oxygen on the surface of the lithium-rich manganese, the introduced cations such as tin and cerium can also capture the precipitated oxygen, providing another guarantee layer for inhibiting the interface degradation, and further improving the interface stability.

[0030] In addition, the present application also provides an application of the above-mentioned surface-modified lithium-rich manganese-based positive electrode material in a full solid-state battery.

[0031] In some embodiments, the full solid-state battery can include the above-mentioned surface-modified lithium-rich manganese-based positive electrode material and a positive electrode film formed by mixing the same with a solid electrolyte powder, a conductive carbon material and a binder, a solid electrolyte, and a negative electrode material.

[0032] Among them, the solid electrolyte can include one of a sulfide solid electrolyte and a halide solid electrolyte; the conductive carbon material can include VGCF and Super P; and the negative electrode material can include graphite, silicon-carbon, silicon dioxide, silicon alloy, metallic lithium or lithium alloy.

[0033] The lithium-rich manganese-based ternary positive electrode material coated with a sulfate and a sulfite provided by the present application can effectively improve the charge-discharge specific capacity, the first cycle efficiency, the rate performance and the cycle stability of the lithium-rich manganese-based ternary positive electrode material in a full solid-state battery, and exhibits excellent electrochemical performance, thereby promoting the application of high-energy-density full solid-state batteries.

[0034] In some embodiments, the first cycle efficiency of the full solid-state battery under the condition of 25 DEG C, a voltage of 2-4.6 V (to lithium), and a current density of 0.1 C can reach 125.9%.

[0035] In summary, the basic principle of the present application is to use the energy provided in the high-energy ball milling process to amorphize the low-melting-point sulfate and coat it on the surface of the lithium-rich manganese positive electrode material, and the transition metal manganese element in the lithium-rich manganese and the S in the sulfate undergo charge transfer, so that in addition to the sulfate on the surface of the lithium-rich manganese particles, there is also a sulfite, and the partial valence of the manganese element on the surface of the lithium-rich manganese is increased, and the high valence of manganese is more conducive to alleviating the structural distortion caused by the J-T effect in the charge-discharge process of the lithium-rich manganese positive electrode material. Therefore, by in-situ coating a layer of sulfate / sulfite on the surface of the lithium-rich manganese-based positive electrode material, the charge-discharge specific capacity, the first cycle efficiency, the rate performance and the cycle stability of the lithium-rich manganese-based positive electrode material can be effectively improved.

[0036] The following further illustrates the embodiments in detail. It should also be understood that the following embodiments are only used to further illustrate the present application and cannot be understood as limiting the scope of the present application. Some non-essential improvements and adjustments made by those skilled in the art according to the above content of the present application all belong to the protection scope of the present application. The specific process parameters in the following examples are only one example in the appropriate range, i.e. those skilled in the art can make appropriate selection within the range according to the description herein, and are not limited to the specific values in the following examples. If not specifically indicated, the technical means used in the examples are the conventional means familiar to those skilled in the art.

[0037] Example 1

[0038] The preparation method of the surface-modified lithium-rich manganese-based positive electrode material and the all-solid-state battery provided by the present embodiment comprises the following steps: (1) In an argon glove box, 1.6 g of polycrystalline lithium-rich manganese positive electrode material and 0.4 g of stannous sulfate are weighed and uniformly mixed by manual grinding to form a uniform mixture; the uniform mixture is added to a 80 ml stainless steel ball mill tank, the ball-to-material ratio is 40:1, and after sealing, it is transferred to a ball mill for ball milling; the ball milling parameters are set as 30 minutes of forward rotation, 10 minutes of rest, 30 minutes of reverse rotation, and 10 minutes of rest, which is set as one cycle; the ball milling time is set as 30 h, and the ball milling speed is set as 800 rmp; after the ball milling is completed, the ball mill tank is transferred to the glove box, and the surface-modified lithium-rich manganese-based positive electrode material is separated; (2) In the glove box, the surface-modified lithium-rich manganese-based positive electrode material prepared in step (1) is ground and mixed with Li3InCl6 solid electrolyte and VGCF according to a ratio of 60:40:5 to obtain a composite positive electrode material; 2-3% of PTFE binder is added to the mortar, and the composite positive electrode film is formed by manual grinding; the composite positive electrode film is rolled into a thin composite positive electrode film on a glass plate, and is cut into a 10 m diameter disc; the disc is assembled with lithium phosphorus sulfur chloride (LPSC) solid electrolyte, lithium indium chloride (LIC) solid electrolyte and lithium indium alloy negative electrode to obtain an all-solid-state lithium battery; the battery is tested for charge and discharge at a rate of 0.1 C in the range of 2-4.6 V.

[0039] Example 2

[0040] The preparation method of the surface-modified lithium-rich manganese-based positive electrode material and the all-solid-state battery provided by the present embodiment refers to Example 1, and the main difference is: In step (1), the sulfate salt is cerium sulfate.

[0041] Example 3

[0042] The preparation method of the surface-modified lithium-rich manganese-based positive electrode material and the all-solid-state battery provided by the present embodiment refers to Example 1, and the main difference is: In step (1), the sulfate salt is indium sulfate.

[0043] Comparative Example 1

[0044] The preparation method of the lithium-rich manganese-based positive electrode material and the all-solid-state battery provided by the present comparative example refers to Example 1, and the main difference is that: In step (1), 2 g of the polycrystalline lithium-rich manganese-based positive electrode material is ground.

[0045] Comparative Example 2

[0046] The preparation method of the lithium-rich manganese-based positive electrode material and the all-solid-state battery provided by the present comparative example refers to Example 1, and the main difference is that: In step (1), 1.9 g of the polycrystalline lithium-rich manganese-based positive electrode material and 0.1 g of stannous sulfate are ground.

[0047] Comparative Example 3

[0048] The preparation method of the lithium-rich manganese-based positive electrode material and the all-solid-state battery provided by the present comparative example refers to Example 1, and the main difference is that: In step (1), 1.8 g of the polycrystalline lithium-rich manganese-based positive electrode material and 0.2 g of stannous sulfate are ground.

[0049] Figure 1 The XRD pattern of the positive electrode material prepared in Example 1-3 and Comparative Example 1. As can be seen from the figure, all the diffraction peaks are well matched with the typical hexagonal a-NaFeO2 structure (JCPDF card No. 01-089-4533, space group R-3m), which represents the main phase of the lithium-rich manganese-based positive electrode material. The lithium-rich manganese-based positive electrode material has a layered NaFeO2 structure and an R-3m space group, which is formed by LiO6 and MO6 octahedra. The main diffraction peaks of all samples are well matched with the JCPDF card with R-3m space group, indicating that the use of high-energy ball milling to provide energy and the low-melting-point sulfate salt for surface modification does not change the layered structure of the lithium-rich manganese-based positive electrode material, and it can be known that the coating layer on the surface of the lithium-rich manganese particle is amorphous structure.

[0050] Figure 2 The SEM pattern of the positive electrode material prepared in Example 1. As can be seen from the figure, the particle size of the lithium-rich manganese positive electrode material after surface modification by ball milling is reduced, and the secondary spherical particles (~ 15 um) are converted into primary particles (~ 500 nm).

[0051] Figure 3AB, C are tin sulfate, XPS spectra of the positive electrode material prepared in Example 1 and Comparative Example 1. As can be seen from the figure, in the Ols spectrum, Example 1 appears S-O bond at ~ 531.3 eV; in the S2p spectrum, Example 1 has peaks of SO4 2- and SO3 2- at 168.4 eV and 166.34 eV, respectively; in the Sn3d spectrum, there are peaks of Sn3d3 / 2 and Sn3d5 / 2 at 495.4 eV and 486.9 eV, respectively; in addition, the interval of Mn3s peaks changes from 5.8 eV to 5.6 eV, indicating that the Mn ions are partially oxidized and the valence state is increased; and the surface etching of Example 1 shows that SO3 2- exists under the surface, and SO4 2- exists mainly on the surface, indicating that the high-energy ball milling induces the chemical reaction of the lithium-rich manganese-based positive electrode material with tin sulfate, generating SO3 2- and manganese ions in a higher oxidation state on the surface of the lithium-rich manganese particles.

[0052] Figure 4 is a TEM image of the positive electrode material prepared in Example 1. As can be seen from the figure, there is a sulfite and sulfite coating layer of about ~ 5 nm on the surface of the lithium-rich manganese positive electrode particles after surface modification; in addition, after high-speed ball milling, part of the rock salt phase structure is also introduced into the inner surface of the lithium-rich manganese particles, and the rock salt phase is zero strain during charging and discharging, which is beneficial to improve the long cycle performance of the battery.

[0053] Figures 5-9 are the first cycle charge-discharge curves of the full solid-state batteries prepared in Examples 1-3 and Comparative Examples 1-3 at room temperature (25°C), voltage range 2-4.6 V (vs. lithium), and current density 0.1 C. As can be seen from the figure, the charge-discharge specific capacity of the surface-modified Example 1 is obviously improved compared with the unmodified Comparative Example 1, and a high first efficiency is also obtained, which increases from 76.07% to 98.74%. The improvement of the charge-discharge specific capacity benefits from the improvement of the stability of the positive electrode and electrolyte interface, and the higher first efficiency indicates the improvement of the redox reversibility of the anion oxygen of the lithium-rich manganese-based positive electrode; the positive electrode materials Example 2 and Example 3 after surface modification both exhibit higher charge-discharge specific capacity and first efficiency than the positive electrode material Comparative Example 1 without surface modification, the positive electrode material Comparative Example 2 with insufficient amount of tin sulfate modification, and the positive electrode material Comparative Example 3, fully indicating that the surface modification method of high-energy ball milling and low-melting-point sulfite reaction can significantly improve the stability of the positive electrode material.

[0054] Figure 10The first cycle dQ / dV curve of the positive electrode material prepared in Example 1 and Comparative Example 1 at room temperature (25°C), voltage range of 2-4.6V (vs. Li), current density of 0.1C. As can be seen from the figure, when charged to above 4.4V, Example 1 has a clear current peak at this point, indicating that charge compensation occurs in this voltage range, which corresponds to the charge compensation of anionic oxygen of the lithium-rich manganese-based positive electrode material, while Comparative Example 1 does not have a clear current peak in this voltage range, indicating that the charge compensation of anionic oxygen in Comparative Example 1, which should exist in this voltage range, has disappeared, indicating that the composite positive electrode of Comparative Example 1 has a serious charge transport blockage, which is most likely due to the deterioration of the positive electrode and electrolyte interface, forming a passivation layer that seriously hinders the charge transport at the interface, while the surface modification of Example 1 is coated with a layer of sulfate / sulfite, which effectively alleviates the degradation of the interface and improves the stability of the interface.

[0055] Figure 11 The cycle stability comparison chart of the positive electrode material prepared in Example 1 and Comparative Example 1. As can be seen from the figure, the cycle stability of the positive electrode material of Example 1 after surface modification has been significantly improved, fully indicating that the electrochemical stability of the positive electrode material after surface modification has been significantly improved.

[0056] Figure 12 The rate performance comparison chart of the positive electrode material prepared in Example 1 and Comparative Example 1. As can be seen from the figure, the rate performance of the positive electrode material of Example 1 after surface modification has been significantly improved compared to Comparative Example 1, fully indicating that the composite positive electrode side interface stability of the positive electrode material after surface modification has been significantly improved.

[0057] The above results show the effectiveness of the surface modification method of the lithium-rich manganese-based positive electrode material after high-energy ball milling and low-melting-point sulfate reaction, which can effectively improve the specific capacity, cycle stability and rate performance of the lithium-rich manganese-based positive electrode material.

[0058] Although the content of the present application has been described in detail through the above preferred embodiments, it should be recognized that the above description should not be considered as limiting the present application. After reading the above content, various modifications and alternatives of the present application will be apparent to those skilled in the art. Therefore, the scope of protection of the present application should be defined by the appended claims.

Claims

1. A surface-modified lithium-rich manganese-based positive electrode material, characterized in that, The surface-modified lithium-rich manganese-based positive electrode material comprises a lithium-rich manganese-based positive electrode material core layer and a metal sulfate / metal sulfite modification layer in amorphous form constructed in situ on the surface of the core layer. Preferably, the metal sulfite is located in the inner layer of the modification layer, and the metal sulfate is located in the outer layer of the modification layer.

2. A method of preparing the surface-modified lithium-rich manganese-based positive electrode material of claim 1, characterized in that, The preparation method comprises the following steps: mixing the lithium-rich manganese-based positive electrode material with a metal sulfate, and then performing high-speed ball milling to amorphize the metal sulfate and construct a metal sulfate / metal sulfite mixed modification layer in situ on the surface of the lithium-rich manganese-based positive electrode material, thereby obtaining the surface-modified lithium-rich manganese-based positive electrode material.

3. The production method according to claim 2, characterized by, The lithium-rich manganese-based positive electrode material comprises a lithium-rich manganese-based oxide layered positive electrode material with a chemical composition of xLi2MnO3·(1-x)LiMO2, 0 4. The production method according to claim 2 or 3, characterized by, The particle size of the lithium-rich manganese-based positive electrode material is 1-100 um.

5. The production method according to any one of claims 2 to 4, characterized by, The type of the metal sulfate comprises one of stannous sulfate, cerium sulfate, indium sulfate, zirconium sulfate, aluminum sulfate, iron sulfate, and copper sulfate.

6. The production method according to any one of claims 2 to 5, characterized by, The mass percentage of the lithium-rich manganese-based positive electrode material is 50-95% based on the total mass of the lithium-rich manganese-based positive electrode material and the metal sulfate, and the mass percentage of the metal sulfate is 5-50%.

7. The production method according to any one of claims 2 to 6, characterized by, The high-speed ball milling uses stainless steel ball mills with a diameter distribution of 1-15 mm, a ball-to-material ratio of 10-40:1, and a rotation speed of 200-1000 rmp; the ball milling condition is 30 minutes of forward rotation, 5-10 minutes of pause, 30 minutes of reverse rotation, and 10 minutes of pause for one cycle, and the total ball milling time is 1-100 h.

8. Use of the surface-modified lithium-rich manganese-based positive electrode material of claim 1 in a full solid-state battery.

9. Use according to claim 8, characterized in that, The full solid-state battery comprises the above surface-modified lithium-rich manganese-based positive electrode material, a positive electrode film formed by mixing the surface-modified lithium-rich manganese-based positive electrode material with a solid electrolyte powder, a conductive carbon material, and a binder, a solid electrolyte, and a negative electrode material.

10. Use according to claim 8 or 9, characterized in that, The solid electrolyte comprises one of a sulfide solid electrolyte and a halide solid electrolyte; the conductive carbon material comprises VGCF and Super P; and the negative electrode material comprises graphite, silicon-carbon, silicon dioxide, silicon alloy, metallic lithium, or lithium alloy.

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