Lithium-rich manganese-based positive electrode material with superlattice characteristic, preparation method of lithium-rich manganese-based positive electrode material and lithium ion battery

Abstract

The invention relates to the technical field of lithium ion batteries, in particular to a lithium-rich manganese-based positive electrode material with superlattice characteristics, a preparation method of the lithium-rich manganese-based positive electrode material and a lithium ion battery. In an X-ray diffraction pattern of the lithium-rich manganese-based positive electrode material with the superlattice characteristic, a superlattice peak of Li2MnO3 is shown at a Bragg angle of 20.7 degrees + / -0.3 degrees; the intensity of the superlattice peak is more than four times of the background intensity. By controlling sintering conditions, regulation and control on the degree of order of lithium ions in a metal layer in the lithium-rich manganese-based positive electrode material are realized, the lithium-rich manganese-based positive electrode material with the superlattice characteristic is prepared, and the Bragg angle of the lithium-rich manganese-based positive electrode material is a ratio gt of peak intensity I1 of a first diffraction peak of a lithium-rich phase near 20.7 degrees to intensity I2 improved by background intensity before and after the diffraction peak; and 4, the superlattice characteristic enhances the structural stability of the lithium-rich manganese-based positive electrode material in the cycle process, and improves the electrochemical performance, especially the cycle stability under a high-voltage condition.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and in particular to a superlattice characteristic lithium-rich manganese-based positive electrode material, a preparation method thereof, and a lithium-ion battery. Background Art

[0002] With growing global energy demand and increasingly stringent environmental regulations, lithium-ion batteries (Li-ion batteries) are attracting significant attention as efficient and clean energy storage technologies. Lithium-rich manganese-based cathode materials, due to their high capacity (>250 mAh / g), low cost, and excellent thermal stability, have become a research hotspot for next-generation high-energy-density batteries. However, practical applications of these materials still face challenges such as poor cycling stability.

[0003] In recent years, researchers have developed a variety of modification strategies (such as element doping, surface coating, nanostructure design, and single crystallization) to optimize the electrochemical performance of lithium-rich manganese-based materials. However, these methods only provide limited control over the surface and bulk of the materials. While they can partially suppress capacity decay, they struggle to address the underlying structural stability issues. Notably, the arrangement of lithium ions within the metal layer (manifested as superlattice peaks in X-ray diffraction) has a significant impact on electrochemical performance, yet this critical factor has long been overlooked and remains challenging to control.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] In order to solve the above problems in the prior art, the present invention provides a superlattice characteristic lithium-rich manganese-based positive electrode material, a preparation method thereof, and a lithium-ion battery.

[0006] Based on this, the present invention has the following technical solutions: In the first aspect, the present invention provides a superlattice characteristic lithium-manganese-rich positive electrode material, in which the X-ray diffraction pattern of the superlattice characteristic lithium-manganese-rich positive electrode material presents a superlattice peak of Li2MnO3 at a Bragg angle of 20.7°±0.3°; the intensity of the superlattice peak is more than 4 times the background intensity.

[0007] The lithium-rich manganese-based positive electrode material with superlattice characteristics prepared by the present invention can significantly enhance the structural stability of the material during the cycle process and improve the electrochemical performance of the material, especially the cycle performance under high voltage conditions, by controlling the order of the lithium ion arrangement of the metal layer in the material, that is, the superlattice peak characteristics in X-ray diffraction.

[0008] In the present invention, in the X-ray diffraction pattern of the superlattice characteristic lithium-rich manganese-based positive electrode material obtained by an XRD instrument with Cu K α as the incident light source, the ratio of the peak intensity I1 of the first diffraction peak of the lithium-rich phase at a Bragg angle near 20.7°±0.3° to the intensity I2 of the increased background intensity before and after the above diffraction peak is greater than 4.

[0009] According to a superlattice characteristic lithium manganese-rich positive electrode material provided by the present invention, the superlattice peak corresponds to the (020) crystal plane of Li2MnO3 and belongs to the C2 / m space group.

[0010] In the present invention, the first diffraction peak of the lithium-rich phase at a Bragg angle of around 20.7°±0.3° corresponds to the (020) crystal plane of Li2MnO3, belongs to the C2 / m space group, and corresponds to the order of lithium ions in the metal layer; the increased background intensity before and after the above-mentioned diffraction peak corresponds to the disorder of lithium ions in the metal layer; the ratio of the peak intensity I1 of the above-mentioned diffraction peak to the increased background intensity I2 before and after the peak corresponds to the order of lithium ions in the metal layer; a ratio of intensity I1 to intensity I2 greater than 4 corresponds to a higher order of lithium ions in the metal layer of the lithium-rich manganese-based positive electrode material, a stronger structural stability of the lithium-rich manganese-based positive electrode material, and a better cycle stability of the lithium-rich manganese-based positive electrode material.

[0011] According to the present invention, a superlattice characteristic lithium-rich manganese-based positive electrode material is provided. The chemical formula of the superlattice characteristic lithium-rich manganese-based positive electrode material is xLi2MnO3·yLi a TMO b zLiTM'O2, where: 0 <x<1,0≤y<1,0<z<1,a> 1, b>2, TM is one or more ions with a valence greater than or equal to positive tetravalence, and TM' is one or more ions with an average valence of positive trivalence.

[0012] In the present invention, the characteristic peak of the superlattice characteristic lithium-rich manganese-based positive electrode material comes from Li2MnO3. The above-mentioned Li2MnO3 can form a solid solution with a lithium-rich material having a metal valence greater than or equal to four excluding lithium ions and a layered oxide positive electrode material having an average metal valence of positive trivalent excluding lithium ions.

[0013] According to a superlattice characteristic lithium-rich manganese-based positive electrode material provided by the present invention, the metal source includes TM and / or TM', TM is one or more of titanium, zirconium, tin, ruthenium, iridium, niobium, molybdenum, tungsten, tantalum, and antimony; and / or, TM' is one or more of nickel, cobalt, manganese, copper, magnesium, zinc, boron, beryllium, aluminum, gallium, vanadium, chromium, iron, lanthanum, titanium, zirconium, tin, ruthenium, iridium, niobium, molybdenum, tungsten, tantalum, and antimony.

[0014] In the present invention, one or more of the above TM elements can form a lithium-rich material, and one or more of the above TM′ elements can form a layered oxide positive electrode material.

[0015] Preferably, the TM' is one or more of nickel, cobalt, manganese, magnesium, aluminum, titanium, copper and zirconium; and TM is one or more of zirconium, tin, ruthenium, niobium, molybdenum and tungsten.

[0016] According to the present invention, a superlattice-characterized lithium-rich manganese-based cathode material may have a coating material on its surface. Preferably, the coating material comprises one or more of an oxide, a fluoride, a lithium-containing oxide, and a lithium-containing fluoride. The coating element comprises one or more of nickel, cobalt, manganese, copper, magnesium, zinc, boron, aluminum, gallium, vanadium, chromium, iron, lanthanum, titanium, zirconium, tin, ruthenium, iridium, niobium, molybdenum, tungsten, tantalum, and antimony. In the present invention, the coating layer can reduce surface degradation of the cathode material.

[0017] In a second aspect, the present invention provides a method for preparing the superlattice characteristic lithium-rich manganese-based positive electrode material, comprising: obtaining a metal salt precursor by a co-precipitation method; then pre-sintering the metal salt precursor at 300°C~900°C to obtain an oxide precursor; mixing raw materials including the oxide precursor and a lithium source, and performing a first sintering and a second sintering in sequence.

[0018] In the present invention, the pre-sintering temperature can be any temperature value among 300°C, 400°C, 500°C, 600°C, 700°C, 800°C, and 900°C, or a numerical range with any two of the above temperature values ​​as endpoints.

[0019] The present invention finds that by controlling the pre-sintering of the metal source and combining it with the subsequent first and second sintering, the arrangement of lithium ions in the transition metal layer of the lithium-rich manganese-based positive electrode material can be adjusted, and the ratio of the peak intensity I1 of the first diffraction peak of the lithium-rich phase at a Bragg angle near 20.7° to the intensity I2 of the increased background intensity before and after the above diffraction peak can be controlled. The molten salt can play a role in dispersing the crystals, so that the product can be transformed from polycrystalline to single crystal.

[0020] Among them, the mass ratio of the molten salt to the oxide precursor is A, 0≤ A<1000; if molten salt is contained in the sintering process, the sintered product is washed, filtered and dried to obtain a superlattice characteristic lithium-rich manganese-based positive electrode material.

[0021] According to a method for preparing a superlattice characteristic lithium-rich manganese-based positive electrode material provided by the present invention, the metal salt precursor is heated to 300-900°C at a heating rate of 2°C / min-20°C / min and kept warm for 5h-10h, and then cooled to room temperature.

[0022] According to a method for preparing a superlattice characteristic lithium-rich manganese-based positive electrode material provided by the present invention, the temperature of the first sintering is 250°C~700°C, and the holding time is 2h~8h; the temperature of the second sintering is 800°C~1200°C, and the holding time is 4h~20h.

[0023] According to the present invention, a method for preparing a superlattice characteristic lithium-rich manganese-based positive electrode material comprises the following steps: S1: mixing a metal salt solution, a complexing agent, and a precipitant to perform a coprecipitation reaction. After the reaction is completed, the product is washed, filtered, and dried in sequence to obtain a metal salt precursor; S2: heating the metal salt precursor to 300-900° C. at a heating rate of 2° C. / min-20° C. / min and keeping the temperature for 5-10 hours, and then cooling to room temperature to obtain an oxide precursor; S3: Mixing the raw materials including the oxide precursor and the lithium source, performing a first sintering at 250° C. to 700° C. and keeping the temperature for 2 h to 8 h; then performing a second sintering at 800° C. to 1200° C. and keeping the temperature for 4 h to 20 h.

[0024] Preferably, the method for preparing the superlattice characteristic lithium-rich manganese-based positive electrode material comprises the following steps: S1: mixing a metal salt solution, a complexing agent, and a precipitant to perform a coprecipitation reaction. After the reaction is completed, the product is washed, filtered, and dried in sequence to obtain a metal salt precursor; S2: heating the metal salt precursor to 300-900° C. at a heating rate of 2° C. / min-20° C. / min and keeping the temperature for 5-10 hours, and then cooling to room temperature to obtain an oxide precursor; S3: Mix the oxide precursor, lithium source and other raw materials, perform a first sintering at 250°C~700°C, and keep warm for 2h~8h; then perform a second sintering at 800°C~1200°C, and keep warm for 4h~20h; the other raw materials include molten salt and / or coating material.

[0025] As a preferred embodiment of the present invention, the preparation method of the superlattice characteristic lithium-rich manganese-based positive electrode material can adopt any of the following methods: Method 1: S1: mixing a metal salt solution, a complexing agent, and a precipitant to perform a coprecipitation reaction. After the reaction is completed, the product is washed, filtered, and dried in sequence to obtain a metal salt precursor; S2: heating the metal salt precursor to 300-600° C. at a heating rate of 2° C. / min-20° C. / min and keeping the temperature for 5-10 hours, and then cooling to room temperature to obtain an oxide precursor; S3: mixing the oxide precursor and the lithium source, performing a first sintering at 250° C. to 700° C., and keeping the temperature for 2 h to 8 h; and then performing a second sintering at 800° C. to 1200° C., and keeping the temperature for 4 h to 20 h.

[0026] Method 2: S1: mixing a metal salt solution, a complexing agent, and a precipitant to perform a coprecipitation reaction. After the reaction is completed, the product is washed, filtered, and dried in sequence to obtain a metal salt precursor; S2: heating the metal salt precursor to 300-600° C. at a heating rate of 2° C. / min-20° C. / min and keeping the temperature for 5-10 hours, and then cooling to room temperature to obtain an oxide precursor; S3: The oxide precursor, lithium source and molten salt are mixed, and first sintered at 250° C. to 700° C. and kept warm for 2 h to 8 h; then a second sintered at 800° C. to 1200° C. and kept warm for 4 h to 20 h.

[0027] Method 3: S1: mixing a metal salt solution, a complexing agent, and a precipitant to perform a coprecipitation reaction. After the reaction is completed, the product is washed, filtered, and dried in sequence to obtain a metal salt precursor; S2: heating the metal salt precursor to 300-900° C. at a heating rate of 3° C. / min-10° C. / min and keeping the temperature for 5-10 hours, and then cooling to room temperature to obtain an oxide precursor; S3: The oxide precursor, lithium source and coating material are mixed, and first sintered at 250° C. to 700° C. for 2 h to 8 h; then sintered at 800° C. to 1200° C. for 4 h to 20 h.

[0028] Method 4: S1: mixing a metal salt solution, a complexing agent, and a precipitant to perform a coprecipitation reaction. After the reaction is completed, the product is washed, filtered, and dried in sequence to obtain a metal salt precursor; S2: heating the metal salt precursor to 300-900° C. at a heating rate of 2° C. / min-20° C. / min and keeping the temperature for 5-10 hours, and then cooling to room temperature to obtain an oxide precursor; S3: The oxide precursor, lithium source, molten salt and coating material are mixed, and first sintered at 250° C. to 700° C. and kept warm for 2 h to 8 h; then second sintered at 800° C. to 1200° C. and kept warm for 4 h to 20 h.

[0029] In the present invention, the metal source includes one or more of metal oxides, metal hydroxides, metal carbonates, metal oxalates, metal nitrates, and metal acetates; the lithium source includes one or more of lithium hydroxide, lithium carbonate, lithium nitrate, lithium oxalate, and lithium acetate; the coating material includes one or more of oxides, fluorides, lithium-containing oxides, and lithium-containing fluorides; the molten salt includes one or more of lithium sulfate, potassium sulfate, lithium nitrate, lithium chloride, potassium chloride, and cesium chloride; it can also be other metal sources, lithium sources, molten salts, and coating materials commonly used in the art, and the specific selection is not limited here.

[0030] In the present invention, both the metal source and the coating material can be obtained by a co-precipitation method.

[0031] In the present invention, the metal source, lithium source, coating material, and molten salt can be mixed by dry mixing or wet mixing. Dry mixing and wet mixing can achieve different degrees of mixing of the metal source, lithium source, coating material, and molten salt.

[0032] Preferably, the complexing agent includes ammonia water, and the precipitating agent includes one or more of sodium hydroxide, sodium carbonate, sodium bicarbonate and sodium oxalate.

[0033] Among them, those skilled in the art can determine the dosage relationship of the complexing agent, precipitant and metal salt, as well as the dosage relationship of the metal source, lithium source and coating material according to needs, and no specific limitation is made here.

[0034] Preferably, for example, the complexing agent is used in an amount of 1% to 100% of the metal salt, the precipitant is used in an excess of 0% to 50% based on the standard stoichiometric ratio of the metal salt, the metal source, the lithium source, and the metal source are used in an excess of 0% to 100% based on the standard stoichiometric ratio, and the coating material is used in a ratio of 0.1% to 10% based on the standard stoichiometric ratio of the metal source.

[0035] In a third aspect, the present invention provides a lithium-ion battery comprising the superlattice characteristic lithium-rich manganese-based positive electrode material.

[0036] Based on this, the technical solution of the present invention has the following beneficial effects: The present invention achieves regulation of the order of lithium ions in the metal layer of the lithium-rich manganese-based positive electrode material by controlling the sintering conditions, and prepares a lithium-rich manganese-based positive electrode material with superlattice characteristics. This is manifested in that in an X-ray diffraction pattern obtained by an XRD instrument using Cu K α as an incident light source, the ratio of the peak intensity I1 of the first diffraction peak of the lithium-rich phase at a Bragg angle of approximately 20.7° to the intensity I2 of the increased background intensity before and after the above diffraction peak is greater than 4. The superlattice characteristics enhance the structural stability of the lithium-rich manganese-based positive electrode material during the cycle process and improve the electrochemical properties, especially the cycle stability under high voltage conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions in the present invention or the prior art, a brief introduction is given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0038] Figure 1 This is the XRD diagram of the superlattice characteristic lithium-manganese-based positive electrode material in Example 1 provided by the present invention.

[0039] Figure 2 This is the XRD pattern of the superlattice characteristic lithium-manganese-based positive electrode material in Example 2 provided by the present invention.

[0040] Figure 3 This is the XRD pattern of the superlattice characteristic lithium-manganese-based positive electrode material in Example 3 provided by the present invention.

[0041] Figure 4 This is the XRD pattern of the superlattice characteristic lithium-manganese-based positive electrode material in Example 4 provided by the present invention.

[0042] Figure 5 This is the XRD pattern of the lithium-rich manganese-based positive electrode material in Comparative Example 1. DETAILED DESCRIPTION

[0043] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0044] Unless otherwise specified, the various raw materials used in the examples and comparative examples are commercially available conventional raw materials, and the technical means used are conventional means well known to those skilled in the art.

[0045] Example 1 This embodiment provides a superlattice characteristic lithium-rich manganese-based positive electrode material, and the preparation method thereof includes: (1) According to the Mn:Ni molar ratio of 0.75:0.25, weigh the corresponding mass of manganese sulfate monohydrate and nickel sulfate hexahydrate, dissolve them in deionized water, and prepare a metal salt solution with a concentration of 2 mol / L. At the same time, weigh sodium carbonate and dissolve it in water to prepare a sodium carbonate solution with a concentration of 2 mol / L, and add ammonia water with a concentration of 1 mol / L as a precipitant, stir evenly, and obtain a precipitant solution. Under the condition of stirring speed of 300 rpm, the metal salt solution and precipitant solution are slowly added dropwise to a certain amount of deionized water. The drop rate of the metal salt solution is controlled to 0.2L / h, and the drop rate of the precipitant solution is adjusted to maintain the pH value of the system at 12. The coprecipitation reaction is carried out at 50 ° C for 24 hours. After the reaction is completed, the product is washed, filtered and dried to finally obtain the positive electrode material carbonate precursor Mn 0.75 Ni 0.25 CO3.

[0046] (2) The positive electrode material carbonate precursor obtained in step (1) is placed in a muffle furnace and heated at a heating rate of 5°C / min to the precursor sintering temperature of 400°C and kept at this temperature for 6 hours. The oxide precursor Mn is then obtained by cooling the furnace to room temperature. 0.75 Ni 0.25 O 1.75 .

[0047] (3) The metal source cathode material oxide precursor Mn obtained in step (2) 0.75 Ni 0.25 O 1.75 The mixture was thoroughly mixed with lithium hydroxide and molten potassium chloride in a molar ratio of 0.8:1.2:8 by dry ball milling and placed in a crucible. The mixture was calcined at a first sintering temperature of 550°C for 6 hours, and then sintered at a second sintering temperature of 900°C for 12 hours. After cooling to room temperature, the mixture was washed, filtered, and dried. The product is 0.5Li2MnO3·0.5LiNi 0.5 Mn 0.5 O2.

[0048] The product was analyzed by XRD and showed to have the crystal structure of R-3m space group α-NaFeO2 with O3 phase. Figure 1 , which is characterized by, in an X-ray diffraction pattern obtained by an XRD instrument using Cu K α as an incident light source, a ratio of the peak intensity I1 of the first diffraction peak of the lithium-rich phase at a Bragg angle near 20.7° to the intensity I2 of the increased background intensity before and after the above diffraction peak is 7.4.

[0049] Example 2 This embodiment provides a superlattice characteristic lithium-rich manganese-based positive electrode material. The difference between its preparation method and that of embodiment 1 is that the second sintering temperature in step (3) is 950°C, and the product is 0.5Li2MnO3·0.5LiNi 0.5 Mn 0.5 O2, the ratio of the peak intensity I1 of the first diffraction peak of the lithium-rich phase to the increased intensity I2 of the background intensity before and after the diffraction peak is 9.5 ( Figure 2 ).

[0050] Example 3 This embodiment provides a superlattice characteristic lithium-rich manganese-based positive electrode material. The difference between its preparation method and that of embodiment 1 is that the second sintering temperature in step (3) is 1000°C, and the product is 0.5Li2MnO3·0.5LiNi 0.5 Mn 0.5 O2, the ratio of the peak intensity I1 of the first diffraction peak of the lithium-rich phase to the increased intensity I2 of the background intensity before and after the diffraction peak is 13.2 ( Figure 3 ).

[0051] Example 4 This embodiment provides a superlattice characteristic lithium-rich manganese-based positive electrode material. The difference between its preparation method and that of embodiment 1 is that the second sintering temperature in step (3) is 1050°C, and the product is 0.5Li2MnO3·0.5LiNi 0.5 Mn 0.5 O2, the ratio of the peak intensity I1 of the first diffraction peak of the lithium-rich phase to the increased intensity I2 of the background intensity before and after the diffraction peak is 43.6 ( Figure 4 ).

[0052] Example 5 This embodiment provides a superlattice characteristic lithium-rich manganese-based positive electrode material. The difference between its preparation method and that of embodiment 1 is that: the metal salt in step (1) is prepared according to the molar ratio of Mn:Ni:Co of 0.54:0.13:0.13, and the corresponding masses of manganese sulfate monohydrate, nickel sulfate hexahydrate, and cobalt sulfate heptahydrate are weighed, and the product is 0.5Li2MnO3·0.5LiCo 0.33 Ni 0.33 Mn 0.34 O2, the ratio of the peak intensity I1 of the first diffraction peak of the lithium-rich phase to the increased intensity I2 of the background intensity before and after the above diffraction peak is 6.0.

[0053] Example 6 This embodiment provides a superlattice characteristic lithium-rich manganese-based positive electrode material. The difference between its preparation method and that of embodiment 1 is that: the metal salt in step (1) is weighed according to the molar ratio of Mn:Ni of 0.66:0.34, and the corresponding mass of manganese sulfate monohydrate and nickel sulfate hexahydrate is obtained. The product is 0.34Li2MnO3·0.66LiNi 0.5 Mn 0.5 O2, the ratio of the peak intensity I1 of the first diffraction peak of the lithium-rich phase to the increased intensity I2 of the background intensity before and after the above diffraction peak is 7.1.

[0054] Example 7 This embodiment provides a superlattice characteristic lithium-rich manganese-based positive electrode material. The difference between its preparation method and that of Example 1 is that: in step (3), oxide Al2O3 is added, wherein the molar ratio of Al to (Mn+Ni) is 0.02:0.8, and the product is 0.5Li2MnO3·0.5LiNi 0.48 Mn 0.48 Al 0.04 O2, the ratio of the peak intensity I1 of the first diffraction peak of the lithium-rich phase to the increased intensity I2 of the background intensity before and after the above diffraction peak is 6.1.

[0055] Example 8 This embodiment provides a superlattice characteristic lithium-rich manganese-based positive electrode material. The difference between its preparation method and that of Example 1 is that: in step (3), oxides MgO and TiO2 are added, wherein the molar ratio of Mg, Ti and (Mn + Ni) is 0.01:0.01:0.8, and the product is 0.5Li2MnO3·0.5LiNi 0.48 Mn 0.48 Mg 0.02 Ti 0.02 O2, the ratio of the peak intensity I1 of the first diffraction peak of the lithium-rich phase to the increased intensity I2 of the background intensity before and after the above diffraction peak is 6.3.

[0056] Example 9 This embodiment provides a superlattice characteristic lithium-rich manganese-based positive electrode material. The difference between its preparation method and that of Example 1 is that: in step (3), oxide SnO2 is added, wherein the molar ratio of Sn to (Mn+Ni) is 0.02:0.8, and the product is 0.5Li2MnO3·0.02Li2SnO3·0.5LiNi 0.5 Mn 0.5 O2, the ratio of the peak intensity I1 of the first diffraction peak of the lithium-rich phase to the increased intensity I2 of the background intensity before and after the above diffraction peak is 7.4.

[0057] Example 10 This embodiment provides a superlattice characteristic lithium-rich manganese-based positive electrode material. The difference between its preparation method and that of Example 1 is that: in step (3), oxide WO3 is added, wherein the molar ratio of W to (Mn+Ni) is 0.02:0.8, and the product is 0.5Li2MnO3·0.02Li2WO4·0.5LiNi 0.5 Mn 0.5 O2, the ratio of the peak intensity I1 of the first diffraction peak of the lithium-rich phase to the increased intensity I2 of the background intensity before and after the above diffraction peak is 6.8.

[0058] Example 11 This embodiment provides a superlattice characteristic lithium-rich manganese-based positive electrode material. The difference between its preparation method and that of Example 1 is that: in step (3), oxide RuO2 is added, wherein the molar ratio of Ru to (Mn+Ni) is 0.4:0.8, and the product is 0.5Li2MnO3·0.5Li2RuO3·0.5LiNi 0.5 Mn 0.5 O2, the ratio of the peak intensity I1 of the first diffraction peak of the lithium-rich phase to the increased intensity I2 of the background intensity before and after the above diffraction peak is 7.5.

[0059] Example 12 This embodiment provides a superlattice characteristic lithium-rich manganese-based positive electrode material. The difference between its preparation method and that of embodiment 1 is that in step (3), the lithium source is LiNO3 and LiOH, and the molar ratio thereof is 0.5:0.5, and the product is 0.5Li2MnO3·0.5LiNi 0.5 Mn 0.5 O2, the ratio of the peak intensity I1 of the first diffraction peak of the lithium-rich phase to the intensity I2 of the increased background intensity before and after the above diffraction peak is 8.3.

[0060] Example 13 This embodiment provides a superlattice characteristic lithium-rich manganese-based positive electrode material. The difference between its preparation method and that of embodiment 1 is that in step (3), the lithium source is Li2CO3, and the product is 0.5Li2MnO3·0.5LiNi 0.5 Mn 0.5 O2, the ratio of the peak intensity I1 of the first diffraction peak of the lithium-rich phase to the increased intensity I2 of the background intensity before and after the above diffraction peak is 6.4.

[0061] Example 14 This embodiment provides a superlattice characteristic lithium-rich manganese-based positive electrode material. The difference between its preparation method and that of Example 1 is that the molar ratio of molten salt to metal in step (3) is 0.8:1, and the product is 0.5Li2MnO3·0.5LiNi 0.5 Mn 0.5O2, the ratio of the peak intensity I1 of the first diffraction peak of the lithium-rich phase to the increased intensity I2 of the background intensity before and after the above diffraction peak is 8.0.

[0062] Example 15 This embodiment provides a superlattice characteristic lithium-rich manganese-based positive electrode material. The difference between its preparation method and that of Example 1 is that the molar ratio of molten salt to metal in step (3) is 0.8:32, and the product is 0.5Li2MnO3·0.5LiNi 0.5 Mn 0.5 O2, the ratio of the peak intensity I1 of the first diffraction peak of the lithium-rich phase to the increased intensity I2 of the background intensity before and after the above diffraction peak is 6.5.

[0063] Example 16 This embodiment provides a superlattice characteristic lithium-rich manganese-based positive electrode material. The difference between its preparation method and that of Example 1 is that in step (3), the molten salt is LiCl, and the product is 0.5Li2MnO3·0.5LiNi 0.5 Mn 0.5 O2, the ratio of the peak intensity I1 of the first diffraction peak of the lithium-rich phase to the increased intensity I2 of the background intensity before and after the above diffraction peak is 6.9.

[0064] Example 17 This embodiment provides a superlattice characteristic lithium-rich manganese-based positive electrode material. The difference between its preparation method and that of embodiment 1 is that in step (3), the molten salt is CsCl, and the product is 0.5Li2MnO3·0.5LiNi 0.5 Mn 0.5 O2, the ratio of the peak intensity I1 of the first diffraction peak of the lithium-rich phase to the increased intensity I2 of the background intensity before and after the above diffraction peak is 7.5.

[0065] Example 18 This embodiment provides a superlattice characteristic lithium-rich manganese-based positive electrode material. The difference between its preparation method and that of embodiment 1 is that in step (3), the molten salt is LiCl and KCl, the molar ratio of which is 1:1, and the product is 0.5Li2MnO3·0.5LiNi 0.5 Mn 0.5 O2, the ratio of the peak intensity I1 of the first diffraction peak of the lithium-rich phase to the increased intensity I2 of the background intensity before and after the above diffraction peak is 7.1.

[0066] Example 19 This embodiment provides a superlattice characteristic lithium-rich manganese-based positive electrode material. The difference between its preparation method and that of embodiment 1 is that no molten salt is used in step (3), and the product is 0.5Li2MnO3·0.5LiNi 0.5 Mn 0.5O2, the ratio of the peak intensity I1 of the first diffraction peak of the lithium-rich phase to the increased intensity I2 of the background intensity before and after the above diffraction peak is 7.0.

[0067] Example 20 This embodiment provides a superlattice characteristic lithium-rich manganese-based positive electrode material. The difference between its preparation method and that of Example 1 is that: in step (3), oxide ZnO is added, wherein the molar ratio of Zn to (Mn + Ni) is 0.02:0.8, and the product is 0.5Li2MnO3·0.5LiNi 0.5 Mn 0.5 O2, the surface coating layer is ZnO, and the ratio of the peak intensity I1 of the first diffraction peak of the lithium-rich phase to the increased intensity I2 of the background intensity before and after the above diffraction peak is 6.4.

[0068] Example 21 This embodiment provides a superlattice characteristic lithium-rich manganese-based positive electrode material. The difference between its preparation method and that of embodiment 1 is that: in step (3), fluoride Li2ZrF6 is added, wherein the molar ratio of Zr to (Mn+Ni) is 0.02:0.8, and the product is 0.5Li2MnO3·0.5LiNi 0.5 Mn 0.5 O2, the surface coating layer is Li2ZrF6, and the ratio of the peak intensity I1 of the first diffraction peak of the lithium-rich phase to the intensity I2 of the increased background intensity before and after the above diffraction peak is 6.9.

[0069] Example 22 This embodiment provides a superlattice characteristic lithium-rich manganese-based positive electrode material. The difference between its preparation method and that of Example 1 is that: in step (3), non-metallic oxide B2O3 is added, wherein the molar ratio of B to (Mn+Ni) is 0.02:0.8, and the product is 0.5Li2MnO3·0.5LiNi 0.5 Mn 0.5 O2, the surface coating layer is B2O3, and the ratio of the peak intensity I1 of the first diffraction peak of the lithium-rich phase to the increased intensity I2 of the background intensity before and after the above diffraction peak is 7.9.

[0070] Comparative Example 1 This comparative example provides a superlattice characteristic lithium-rich manganese-based positive electrode material. The difference between its preparation method and that of Example 1 is that the metal source in step (3) is the metal carbonate precursor in step (1), and the product is 0.5Li2MnO3·0.5LiNi 0.5 Mn 0.5 O2, the ratio of the peak intensity I1 of the first diffraction peak of the lithium-rich phase to the increased intensity I2 of the background intensity before and after the diffraction peak is 3.7 ( Figure 5 ).

[0071] Comparative Example 2 This comparative example provides a superlattice characteristic lithium-rich manganese-based positive electrode material, and its preparation method is different from that of Example 1 in that it does not include step (2).

[0072] Test example The superlattice characteristic lithium-rich manganese-based positive electrode material prepared in the embodiment and the comparative example, the conductive material acetylene black, the binder polyvinylidene fluoride and N-methylpyrrolidone were mixed to form a slurry, which was evenly coated on the surface of an aluminum foil to obtain a positive electrode plate; then, a metal lithium plate was used as a negative electrode plate, and an ethylene carbonate (EC) and dimethyl carbonate (DMC) solution containing 1 mol / L lithium hexafluorophosphate (the volume ratio of EC to DMC being 1:1) was used as an electrolyte, and the batteries were assembled in a glove box to obtain a lithium-ion battery.

[0073] The assembled lithium-ion battery was tested for cycle performance using an electrochemical test device at a test temperature of 30°C and a current density of 0.1C (1C = 200 mAg -1 ), with a charge and discharge voltage range of 2-4.8V. It was charged to 4.8V at a constant current density of 0.1C, then charged at 4.8V for 3h, and then discharged to 2.0V at a current density of 0.1C. The discharge capacity was 252mAh / g at the 10th week and 252mAh / g at the 100th week, with a capacity retention rate of 100% after 100 weeks. The results are shown in Table 1.

[0074] Table 1

[0075] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A superlattice characteristic lithium-rich manganese-based positive electrode material, characterized in that: In the X-ray diffraction pattern of the superlattice-characteristic lithium-manganese-based positive electrode material, a superlattice peak of Li2MnO3 is presented at a Bragg angle of 20.7°±0.3°; the intensity of the superlattice peak is more than 4 times the background intensity.

2. The superlattice characteristic lithium-rich manganese-based positive electrode material according to claim 1, characterized in that: The superlattice peak corresponds to the (020) crystal plane of Li2MnO3 and belongs to the C2 / m space group.

3. The superlattice characteristic lithium-rich manganese-based positive electrode material according to claim 1, characterized in that: The chemical formula of the superlattice characteristic lithium-rich manganese-based positive electrode material is xLi2MnO3·yLi a TMO b zLiTM'O2, where: 0 <x<1,0≤y<1,0<z<1,a> 1, b>2, TM is one or more ions with a valence greater than or equal to positive tetravalence, and TM' is one or more ions with an average valence of positive trivalence.

4. The superlattice characteristic lithium-rich manganese-based positive electrode material according to claim 3, characterized in that: TM is one or more of titanium, zirconium, tin, ruthenium, iridium, niobium, molybdenum, tungsten, tantalum, and antimony; and / or TM' is one or more of nickel, cobalt, manganese, copper, magnesium, zinc, boron, beryllium, aluminum, gallium, vanadium, chromium, iron, lanthanum, titanium, zirconium, tin, ruthenium, iridium, niobium, molybdenum, tungsten, tantalum, and antimony.

5. The superlattice characteristic lithium-rich manganese-based positive electrode material according to claim 3, characterized in that: The surface of the superlattice characteristic lithium-rich manganese-based positive electrode material has a coating material; preferably, the coating material includes one or more of oxides, fluorides, lithium-containing oxides, and lithium-containing fluorides; the coating elements include one or more of nickel, cobalt, manganese, copper, magnesium, zinc, boron, aluminum, gallium, vanadium, chromium, iron, lanthanum, titanium, zirconium, tin, ruthenium, iridium, niobium, molybdenum, tungsten, tantalum, and antimony.

6. The method for preparing the superlattice characteristic lithium-rich manganese-based positive electrode material according to any one of claims 1 to 5, characterized in that: include: A metal salt precursor is obtained by a coprecipitation method; the metal salt precursor is then pre-sintered at 300°C to 900°C to obtain an oxide precursor; raw materials including the oxide precursor and a lithium source are mixed, and a first sintering and a second sintering are performed in sequence.

7. The method for preparing a superlattice characteristic lithium-rich manganese-based positive electrode material according to claim 6, characterized in that: The metal salt precursor is heated to 300° C. to 900° C. at a heating rate of 2° C. / min to 20° C. / min and kept at this temperature for 3 h to 10 h, and then cooled to room temperature.

8. The method for preparing a superlattice characteristic lithium-rich manganese-based positive electrode material according to claim 6, characterized in that: The temperature of the first sintering is 250° C. to 700° C., and the holding time is 2 hours to 8 hours; the temperature of the second sintering is 800° C. to 1200° C., and the holding time is 4 hours to 20 hours.

9. The method for preparing a superlattice characteristic lithium-rich manganese-based positive electrode material according to claim 6, characterized in that: The following steps are involved: S1: mixing a metal salt solution, a complexing agent, and a precipitant to perform a coprecipitation reaction. After the reaction is completed, the product is washed, filtered, and dried in sequence to obtain a metal salt precursor; S2: heating the metal salt precursor to 300° C. to 900° C. at a heating rate of 2° C. / min to 20° C. / min and keeping the temperature for 3 h to 10 h, and then cooling to room temperature to obtain an oxide precursor; S3: mixing the raw materials including the oxide precursor and the lithium source, performing a first sintering at 250° C. to 700° C. and keeping the temperature for 2 h to 8 h; then performing a second sintering at 800° C. to 1200° C. and keeping the temperature for 4 h to 20 h; Preferably, the preparation method comprises the following steps: S1: mixing a metal salt solution, a complexing agent, and a precipitant to perform a coprecipitation reaction. After the reaction is completed, the product is washed, filtered, and dried in sequence to obtain a metal salt precursor; S2: heating the metal salt precursor to 300-900° C. at a heating rate of 2° C. / min-20° C. / min and keeping the temperature for 3 h-10 h, and then cooling to room temperature to obtain an oxide precursor; S3: Mix the oxide precursor, lithium source and other raw materials, perform a first sintering at 250°C~700°C, and keep warm for 2h~8h; then perform a second sintering at 800°C~1200°C, and keep warm for 4h~20h; the other raw materials include molten salt and / or coating material.

10. A lithium ion battery, characterized in that: The invention comprises the superlattice characteristic lithium-manganese-rich positive electrode material according to any one of claims 1 to 5 or the superlattice characteristic lithium-manganese-rich positive electrode material prepared by the preparation method according to any one of claims 6 to 9.

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