CN114665086A - A kind of lithium-rich manganese-based cathode material and preparation method thereof - Google Patents

Abstract

The invention provides a lithium-rich manganese-based positive electrode material and a preparation method thereof. The preparation method comprises: adding nickel acetate, cobalt acetate and manganese acetate together with a predetermined amount of precipitant In a solvent, a solvothermal reaction is carried out to prepare a precursor material; the precursor material is pre-calcined, and a pre-calcined product is obtained after cooling; the lithium salt compound and the magnesium salt compound and the pre-calcined product are mixed uniformly and then calcined to obtain a The lithium-rich manganese-based cathode material is obtained. The preparation method provided by the invention adopts a solvothermal method to synthesize a lithium-rich manganese-based precursor material with a complete spherical structure and good dispersibility, and also uses magnesium acetate as a magnesium source for doping modification, thereby improving the stability of the material. At the same time, the material produces a porous structure, which can shorten the migration path of lithium ions and provide more channels for the transport of lithium ions, thereby helping to improve the electrochemical performance of the material.

Description

A kind of lithium-rich manganese-based cathode material and preparation method thereof

technical field

The invention belongs to the technical field of lithium ion battery electrode materials, and particularly relates to a lithium-rich manganese-based positive electrode material and a preparation method thereof.

Background technique

Lithium-ion batteries are widely used in portable devices such as mobile phones and notebooks, medical equipment, power tools, etc. due to their high voltage, high specific energy, long cycle life, good safety performance, wide operating temperature range, and environmental friendliness. In recent years, the application scope of lithium-ion batteries has also expanded to energy transportation (electric vehicles, hybrid vehicles, etc.), smart grids, new energy storage (solar energy, wind energy) and other new fields. performance puts forward higher requirements. Lithium-ion batteries include positive and negative electrode materials, electrolytes, separators and other important components. As a key factor affecting the electrochemical performance, safety, and cost of the entire battery, the development of positive electrode materials has received extensive attention from the scientific community. At present, the commonly used cathode materials for lithium ion batteries mainly include layered LiCoO ₂ , LiMnO ₂ , LiNiO ₂ , LiNixCoyMn1-x-yO ₂ , spinel structure LiMn ₂ O ₄ and olivine structure LiFePO ₄ . Unfortunately, these cathode materials almost all reach the limit of their usable specific capacity (120-200 mAh·g ^-1 ), so the research and development of cathode materials with high specific capacity is imminent. Lithium-rich manganese-based cathode material xLi ₂ MnO ₃ ·(1-x)LiMO ₂ (M=Ni, Co, Mn), or can be expressed as Li _1+x M _1-x O ₂ (M=Ni, Co, Mn) ), which has attracted extensive attention of scientific researchers because of its high capacity under high voltage. However, a large number of studies have shown that the first excessive delithiation of the material during the charge-discharge process at high voltage will destroy the surface lattice structure of the material, thereby affecting its electrochemical properties, such as poor cycle stability and rate performance. Therefore, improving the structural stability of the lithium-rich manganese-based material xLi ₂ MnO ₃ ·(1-x)LiMO ₂ (M=Ni, Co, Mn) and improving its electrochemical performance are the key issues to be solved at present. At present, the commonly used methods to improve the structural stability of lithium-rich manganese-based cathode materials mainly include doping, coating, and the combination of the two methods, etc. However, these modification methods have not achieved the expected modification effect. Protects the positive electrode material particles from erosion from the electrolyte, but does not contribute to the inherent structural stability of the material; doping will cause uneven doping, often with segregation, elements will aggregate to the surface, and no pores will be generated. The structure does not contribute to the migration of lithium ions. In many synthesis methods of precursors of lithium-rich manganese-based cathode materials xLi ₂ MnO ₃ ·(1-x)LiMO ₂ (M=Ni, Co, Mn), ammonia water is used as pH adjuster and transition metal chelator, The co-precipitation method with water as solvent is a commonly used method in the field of material synthesis. In the process of synthesizing lithium-rich manganese-based cathode materials using this method, the volatilization of ammonia water will cause environmental pollution and seriously endanger human health. In addition, the materials synthesized by this method have serious agglomeration, poor dispersibility, and low first coulomb efficiency. The spherical structure is incomplete and hinders the transport of Li ⁺ , and the structural stability is poor, which leads to the deterioration of its electrochemical properties such as capacity and cycle stability, and affects the electrochemical performance of the material.

SUMMARY OF THE INVENTION

In view of the deficiencies existing in the prior art, the present invention provides a lithium-rich manganese-based positive electrode material and a preparation method thereof, so as to solve the environmental problems generated in the synthesis process of the existing lithium-rich manganese-based positive electrode material synthesis method and the synthetic rich Lithium-manganese-based cathode materials have problems such as incomplete spherical structure, poor dispersion, poor structural stability, and deterioration of electrochemical performance.

In order to achieve the above object, one aspect of the present invention provides a method for preparing a lithium-rich manganese-based positive electrode material, comprising:

S110, adding nickel acetate, cobalt acetate and manganese acetate together with a predetermined amount of precipitant into a solvent to carry out a solvothermal reaction to prepare a precursor material;

S120, calcining the precursor material, and obtaining a calcined product after cooling;

S130 , mixing the lithium salt compound and the magnesium salt compound with the calcined product uniformly, and then calcining to obtain the lithium-rich manganese-based cathode material.

Preferably, the step S110 specifically includes:

Dissolving nickel acetate, cobalt acetate and manganese acetate in a solvent according to a predetermined molar ratio, and stirring until completely dissolved to obtain a first mixed solution;

adding a predetermined amount of precipitant to the first mixed solution and dissolving and mixing to obtain a second mixed solution;

The second mixed solution is placed in a reactor to perform a solvothermal reaction, and after the reaction is completed, cooling is performed to obtain the precursor material.

Further preferably, the predetermined molar ratio is set according to the requirement that the molecular formula of the precursor material is Mn _0.54 Ni _0.13 Co _0.13 (CO ₃ ) _0.8 .

Further preferably, the precipitating agent is urea.

Further preferably, the reaction temperature of the solvothermal reaction is 160°C to 180°C, and the reaction time is 10h to 24h.

Preferably, in the step S120, the temperature of the pre-burning is 450° C.˜550° C., and the time of the pre-burning is 6 h˜10 h.

Preferably, the step S130 specifically includes:

Mixing the lithium salt compound and the magnesium salt compound with the calcined product uniformly according to a predetermined reaction ratio to obtain a mixed material;

The mixed material is heated to a predetermined temperature in an air atmosphere and then calcined to obtain the porous lithium-rich manganese-based cathode material;

Further preferably, the predetermined temperature is 850°C to 950°C, and the calcination time is 10h to 12h.

Further preferably, the lithium salt compound is lithium carbonate, and the magnesium salt compound is magnesium acetate.

Further preferably, the molecular formula of the lithium-rich manganese-based cathode material is Li _1.2 [Mn _0.54 Ni _0.13 Co _0.13 ] _{1- x} Mg _x O ₂ , wherein x=0.01-0.05; the predetermined reaction ratio is based on the The molecular formula of the lithium-rich manganese-based cathode material is set according to the requirements of Li _1.2 [Mn _0.54 Ni _0.13 Co _0.13 ] _1-x Mg _x O ₂ .

Another aspect of the present invention provides a lithium-rich manganese-based cathode material prepared by the above preparation method.

Beneficial effects: The lithium-rich manganese-based positive electrode material and the preparation method thereof provided in the embodiment of the present invention use a solvent with dispersibility and adopt a solvothermal method to synthesize the precursor of the lithium-rich manganese-based positive electrode material with complete spherical structure and good dispersibility It is beneficial to improve the agglomeration problem in the synthesis process; in addition, the present invention also uses magnesium acetate as a magnesium source to dope and modify the lithium-rich manganese-based positive electrode material, so as to improve the stability of the material and make the lithium-rich material more stable. The manganese-based cathode material produces a porous structure, which is conducive to the diffusion of lithium ions, which can shorten the migration path of lithium ions and provide more channels for the transport of lithium ions, which is beneficial to improve the electrochemical performance of the material; in addition, The preparation method does not generate harmful substances in the preparation process, thereby avoiding environmental pollution and endangering human health.

Description of drawings

The above and other aspects, features and advantages of embodiments of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings, in which:

Fig. 1 is the flow chart of the preparation method of the lithium-rich manganese-based positive electrode material provided by the embodiment of the present invention;

2 is a scanning diagram of the precursor material provided in Example 1 of the present invention;

3 is a scanning cross-sectional view of the lithium-rich manganese-based positive electrode material after doping modification provided in Example 3 of the present invention;

Fig. 4 is the cycle performance diagram of correspondingly obtained lithium-rich manganese-based positive electrode materials obtained by adding different contents of magnesium acetate for doping modification provided in Examples 2-4 of the present invention;

5 is a scanning cross-sectional view of the lithium-rich manganese-based positive electrode material provided by Comparative Example 1 of the present invention that is not subjected to doping modification;

Figure 6(a) is a scanning diagram of the lithium-rich manganese-based positive electrode material provided by Comparative Example 1 of the present invention without being modified by doping;

FIG. 6( b ) is a scanning diagram of the lithium-rich manganese-based cathode material after doping modification provided in Example 3 of the present invention.

Detailed ways

Hereinafter, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as limited to the specific embodiments set forth herein. Rather, these embodiments are provided to explain the principles of the invention and its practical application, to thereby enable others skilled in the art to understand the invention for various embodiments and with various modifications as are suited to the particular intended use.

As used herein, the term "including" and variations thereof represent open-ended terms meaning "including but not limited to". The terms "based on", "depending on" and the like mean "based at least in part on", "based at least in part on". The terms "one embodiment" and "an embodiment" mean "at least one embodiment." The term "another embodiment" means "at least one other embodiment." The terms "first", "second", etc. may refer to different or the same objects. Other definitions, whether explicit or implicit, may be included below. The definition of a term is consistent throughout the specification unless the context clearly dictates otherwise.

As described in the background art, the existing method for synthesizing lithium-rich manganese-based cathode materials mainly adopts co-precipitation method, which easily leads to environmental pollution during the synthesis process. In addition, the materials synthesized by this method have serious agglomeration, poor dispersibility and spherical structure. It is incomplete and hinders the transport of lithium ions and has poor structural stability, which leads to the deterioration of its electrochemical properties such as capacity and cycle stability, and affects the electrochemical performance of the material. Therefore, in order to solve many technical problems existing in the lithium-rich manganese-based positive electrode material in the prior art, a lithium-rich manganese-based positive electrode material and a preparation method thereof are provided according to the embodiments of the present invention.

The lithium-rich manganese-based positive electrode material and the preparation method thereof according to the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a flowchart of the preparation method of the lithium-rich manganese-based positive electrode material according to the embodiment of the present invention.

Referring to FIG. 1 , in step S110 , nickel acetate, cobalt acetate and manganese acetate are added to a solvent together with a predetermined amount of precipitant to perform a solvothermal reaction to prepare a precursor material.

Preferably, the step S110 specifically includes:

Dissolving nickel acetate, cobalt acetate and manganese acetate in a solvent according to a predetermined molar ratio, and stirring until completely dissolved to obtain a first mixed solution;

adding a predetermined amount of precipitant to the first mixed solution and dissolving and mixing to obtain a second mixed solution;

The second mixed solution is placed in a reaction kettle containing a polytetrafluoroethylene liner to perform a solvothermal reaction, and after the reaction is completed, cooling is performed to obtain the precursor material.

Further preferably, the predetermined molar ratio is set according to the requirement that the molecular formula of the precursor material is Mn _0.54 Ni _0.13 Co _0.13 (CO ₃ ) _0.8 ; that is, the nickel acetate, the cobalt acetic acid The molar ratio of the salt to the manganese acetate was 0.13:0.13:0.54.

Further preferably, the solvent includes water, ethylene glycol and ethanol, and the solvent should have dispersibility to disperse and dissolve the nickel acetate, cobalt acetate and manganese acetate, And no other impurity ions are introduced; in addition, the solvent is added in such an amount that the total concentration of the nickel metal ions, cobalt metal ions and manganese metal ions in the first mixed solution is 0.5 mol/L.

Further preferably, the precipitant is urea, and the amount of substances added to the precipitant is equal to the sum of the amounts of the nickel metal ions, cobalt metal ions and manganese metal ions in the first mixed solution.

Further preferably, the reaction temperature of the solvothermal reaction is 160°C to 180°C, and the reaction time is 10h to 24h.

The precipitating agent has both N element and C element. During the solvothermal reaction process, under the reaction conditions of high temperature and high pressure, the precipitating agent can complex the three elements of nickel, cobalt and manganese together for co-coagulation. precipitation, thereby forming the precursor material.

The present invention uses a solvent with dispersibility, and adopts a solvothermal method to synthesize the precursor material of the lithium-rich manganese-based positive electrode material. The obtained precursor material has a complete spherical structure and good dispersibility, which is beneficial to improving the lithium-rich manganese-based positive electrode material. Agglomeration problems during synthesis.

In step S120, the precursor material is calcined, and a calcined product is obtained after cooling.

Preferably, the temperature of the pre-sintering is 450° C.˜550° C., and the time of the pre-sintering is 6 h˜10 h.

In step S130, the lithium salt compound and the magnesium salt compound are uniformly mixed with the calcined product and then calcined to obtain the lithium-rich manganese-based cathode material.

Preferably, the step S130 specifically includes:

Mixing the lithium salt compound and the magnesium salt compound with the calcined product uniformly according to a predetermined reaction ratio to obtain a mixed material;

The mixed material is heated to a predetermined temperature in an air atmosphere and then calcined to obtain the porous lithium-rich manganese-based positive electrode material.

Further preferably, the predetermined temperature is 850°C to 950°C, and the calcination time is 10h to 12h.

Further preferably, the lithium salt compound is lithium carbonate, and the magnesium salt compound is magnesium acetate.

Preferably, the molecular formula of the lithium-rich manganese-based cathode material is Li _1.2 [Mn _0.54 Ni _0.13 Co _0.13 ] _1-x Mg _x O ₂ , where x=0.01-0.05; the predetermined reaction ratio is based on the rich The molecular formula of the lithium-manganese-based cathode material is set according to the requirements of Li _1.2 [Mn _0.54 Ni _0.13 Co _0.13 ] _1-x Mg _x O ₂ .

Further preferably, the value of x is 0.01, or 0.03, or 0.05.

Wherein, since the volatilization of lithium ions will result in the loss of lithium ions in the process of high temperature calcination, the addition amount of the lithium carbonate should be in excess of 5% by mole.

In the present invention, magnesium acetate is used as the magnesium source, and the lithium-rich manganese-based positive electrode material is doped and modified during the preparation process. Because magnesium acetate contains more elements of C and H, it is different from the pre-fired precursor material and the Carbon dioxide, water vapor, etc. will be released in the process of high temperature calcination in air atmosphere after the lithium carbonate compound is mixed, resulting in a porous structure of the lithium-rich manganese-based material, which is conducive to the diffusion of lithium ions and shortens the migration of lithium ions. It provides more channels for the transport of lithium ions, and with the increase of magnesium doping amount, the porous structure becomes more obvious. In addition, the structural stability of the material can be improved by doping magnesium ions, thereby improving the electrochemical performance of the material. performance.

According to an embodiment of the present invention, there is also provided a lithium-rich manganese-based cathode material prepared by the above preparation method. The lithium-rich manganese-based positive electrode material is modified by doping with magnesium ions, which not only improves the stability of the material structure, but also produces a porous structure, which shortens the migration path of lithium ions and provides more transportation for lithium ions. channels, thereby improving the electrochemical performance of the material.

The above-mentioned lithium-rich manganese-based positive electrode materials and their preparation methods will be described below with reference to specific examples. Those skilled in the art will understand that the following embodiments are only examples of the above-mentioned lithium-rich manganese-based positive electrode materials and their preparation methods of the present invention. Specific examples are not intended to limit them all.

Example 1: Preparation of Precursor Materials

The acetate of nickel, the acetate of cobalt and the acetate of manganese are dissolved in the ethylene glycol solvent according to the molar ratio of 0.13:0.13:0.54, and the first mixed solution is obtained after stirring to complete dissolution; adding into the first mixed solution and dissolving and mixing to obtain a second mixed solution; pouring the second mixed solution into a reaction kettle containing a polytetrafluoroethylene liner, and performing a solvothermal reaction at 160°C, The reaction time is 24h, and after the reaction is completed, cooling, washing and drying are performed to obtain the precursor material, wherein the molecular formula of the precursor material is Mn _0.54 Ni _0.13 Co _0.13 (CO ₃ ) _0.8 .

FIG. 2 is a scanning diagram of the precursor material prepared in Example 1 of the present invention. As shown in FIG. 2 , the precursor material prepared by the solvothermal method has a complete spherical structure and good dispersibility.

Examples 2-4: Preparation of Li-rich Manganese-Based Cathode Materials Modified by Doping with Magnesium Ions

The precursor material prepared in Example 1 was calcined at 500° C. for 6 h to obtain a calcined product;

Mixing the lithium salt compound and the magnesium salt compound with the calcined product uniformly according to a predetermined reaction ratio to obtain a mixed material; the predetermined reaction ratio is Li _1.2 [Mn _0.54 Ni according to the molecular formula of the lithium-rich manganese-based positive electrode material _0.13 Co _0.13 ] _1-x Mg _x O ₂ the requirement setting, wherein, the addition amount of the lithium carbonate should be 5% molar excess;

The mixed material was heated to 900° C. in an air atmosphere for calcination for 12 h, so as to obtain the lithium-rich manganese-based cathode material modified by magnesium ion doping.

In Examples 2 to 4, the difference is that the value of x in the lithium-rich manganese-based cathode material Li _1.2 [Mn _0.54 Ni _0.13 Co _0.13 ] _1-x Mg _x O ₂ is 0.01, 0.03 and 0.05, respectively, and the rest are the same.

Fig. 3 is the rich-rich doping modified prepared in Example 3 of the present invention (the lithium-rich manganese-based cathode material Li _1.2 [Mn _0.54 Ni _0.13 Co _0.13 ] _1-x Mg _x O ₂ in which the value of x is 0.03) The scanning cross-sectional view of the lithium-manganese-based cathode material, as shown in Figure 3, the lithium-rich manganese-based cathode material modified by magnesium ion doping has a porous structure, which is conducive to the diffusion of lithium ions and shortens the lithium ion. Diffusion path, which in turn is beneficial to improve the electrochemical performance of the material.

FIG. 4 is a graph showing the cycle performance of the lithium-rich manganese-based positive electrode materials obtained by adding different contents of magnesium acetate for doping modification in Examples 2 to 4 of the present invention. As shown in FIG. 4 , when the lithium-rich manganese-based positive electrode materials are When the value of x in Li _1.2 [Mn _0.54 Ni _0.13 Co _0.13 ] _{1- x} Mg _x O ₂ is 0.03, the cycle performance of the lithium-rich manganese-based cathode material is the best, and the capacity retention rate is 94.04% after 300 cycles .

Comparative Example 1: Preparation of Li-rich Manganese-Based Cathode Material without Doping Modification

The precursor material prepared in Example 1 was calcined at 500° C. for 6 h to obtain a calcined product;

Mixing the calcined product with an excess 5% molar lithium carbonate compound to obtain a mixed material;

The mixed material was heated to 900° C. in an air atmosphere for calcination for 12 hours, so as to obtain a lithium-rich manganese-based cathode material without doping modification.

Wherein, the difference between Comparative Example 1 and Examples 2 to 4 is only that no magnesium acetate is added in the preparation process.

FIG. 5 is a scanning cross-sectional view of the lithium-rich manganese-based positive electrode material without doping and modification prepared in Comparative Example 1 of the present invention. As shown in FIG. 5 , the lithium-rich manganese-based positive electrode material without doping and modification has no Porous structure, but uniform distribution of elements, which further shows that the solvothermal method is beneficial to the preparation of lithium-rich manganese-based cathode materials with good dispersibility, and the reason for the porous structure of lithium-rich manganese-based cathode materials is the addition of magnesium acetate for doping. Heterogeneous modification.

Figure 6(a) is a scanning diagram of the lithium-rich manganese-based positive electrode material without doping modification prepared in Comparative Example 1 of the present invention; Figure 6(b) is Example 3 of the present invention (lithium-rich manganese-based positive electrode material Li _1.2 [Mn _0.54 Ni _0.13 Co _0.13 ] _1-x Mg _x O ₂ in which the value of x is 0.03) The scanning diagram of the lithium-rich manganese-based cathode material after doping and modification. It can be seen from Fig. 6 that the spherical structure of the obtained lithium-rich manganese-based cathode material remains intact regardless of whether magnesium acetate is added for doping modification, and the spherical particle size is about 4 microns.

To sum up, the lithium-rich manganese-based positive electrode material and the preparation method thereof provided in the embodiments of the present invention use a solvent with dispersibility, and the precursor material of the lithium-rich manganese-based positive electrode material is synthesized by solvothermal method to obtain The precursor material has a complete spherical structure and good dispersibility, which is conducive to improving the agglomeration problem of the lithium-rich manganese-based cathode material during the synthesis process; and the preparation method also uses magnesium acetate as the magnesium source. Doping and modifying the lithium-rich manganese-based cathode material not only improves the structural stability of the material, but also produces a porous structure, which is conducive to the diffusion of lithium ions, shortens the migration path of lithium ions, and facilitates the transport of lithium ions. More channels are provided, and as the amount of magnesium doping increases, the porous structure becomes more obvious, thereby improving the electrochemical performance of the material; in addition, no harmful substances are generated during the preparation process, which avoids environmental pollution and harms the human body. healthy.

The foregoing describes specific embodiments of the invention. Other embodiments are within the scope of the appended claims.

The terms "exemplary", "example" and the like used throughout this specification mean "serving as an example, instance or illustration" and do not mean "preferred" or "advantage" over other embodiments. The detailed description includes specific details for the purpose of providing an understanding of the described technology. However, these techniques may be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form in order to avoid obscuring the concepts of the described embodiments.

The optional embodiments of the embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the embodiments of the present invention are not limited to the specific details of the above-mentioned embodiments. Within the scope of the technical concept of the embodiments of the present invention, the The technical solutions of the embodiments of the present invention undergo various simple modifications, and these simple modifications all belong to the protection scope of the embodiments of the present invention.

The above description of the present specification is provided to enable any person of ordinary skill in the art to make or use the present specification. Various modifications to this specification will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other variations without departing from the scope of this specification . Thus, this disclosure is not intended to be limited to the examples and designs described herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (10)

1. a preparation method of lithium-rich manganese-based positive electrode material, is characterized in that, described preparation method comprises: S110, adding nickel acetate, cobalt acetate and manganese acetate together with a predetermined amount of precipitant into a solvent to carry out a solvothermal reaction to prepare a precursor material; S120, calcining the precursor material, and obtaining a calcined product after cooling; S130 , mixing the lithium salt compound and the magnesium salt compound with the calcined product uniformly, and then calcining to obtain the lithium-rich manganese-based cathode material. 2. The preparation method according to claim 1, wherein the step S110 specifically comprises: Dissolving nickel acetate, cobalt acetate and manganese acetate in a solvent according to a predetermined molar ratio, and stirring until completely dissolved to obtain a first mixed solution; adding a predetermined amount of precipitant to the first mixed solution and dissolving and mixing to obtain a second mixed solution; The second mixed solution is placed in a reactor to perform a solvothermal reaction, and after the reaction is completed, cooling is performed to obtain the precursor material. 3 . The preparation method according to claim 2 , wherein the predetermined molar ratio is set according to the requirement that the molecular formula of the precursor material is Mn _0.54 Ni _0.13 Co _0.13 (CO ₃ ) _0.8 . 4 . 4. The preparation method according to claim 2, wherein the precipitating agent is urea. 5 . The preparation method according to claim 2 , wherein the reaction temperature of the solvothermal reaction is 160° C. to 180° C., and the reaction time is 10 h to 24 h. 6 . 6 . The preparation method according to claim 1 , wherein in the step S120 , the temperature of the calcination is 450° C.˜550° C., and the time of the calcination is 6 h˜10 h. 7 . 7. The preparation method according to any one of claims 1 to 6, wherein the step S130 specifically comprises: Mixing the lithium salt compound and the magnesium salt compound with the calcined product uniformly according to a predetermined reaction ratio to obtain a mixed material; The mixed material is heated to a predetermined temperature in an air atmosphere and then calcined to obtain the porous lithium-rich manganese-based cathode material; Wherein, the predetermined temperature is 850°C to 950°C, and the calcination time is 10h to 12h. 8 . The preparation method according to claim 7 , wherein the lithium salt compound is lithium carbonate, and the magnesium salt compound is magnesium acetate. 9 . The preparation method according to claim 8, wherein the molecular formula of the lithium-rich manganese-based cathode material is Li _1.2 [Mn _0.54 Ni _0.13 Co _0.13 ] _1-x Mg _x O ₂ , wherein x=0.01 ~0.05; the predetermined reaction ratio is set according to the requirement that the molecular formula of the lithium-rich manganese-based cathode material is Li _1.2 [Mn _0.54 Ni _0.13 Co _0.13 ] _1-x Mg _x O ₂ . 10. The lithium-rich manganese-based cathode material prepared according to the preparation method of any one of claims 1 to 9.

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