A core-shell structure lithium-rich manganese-based positive electrode material and a preparation method and application thereof

Abstract

This invention discloses a core-shell structured lithium-rich manganese-based cathode material with the general formula Li. 1+a Mn x Co y Ni z O 2‑b‑d (XO c ) b X d It has a core-shell structure, with the core being a disordered polyanion-doped lithium-rich manganese-based material, Li. 1+a Mn x Co y Ni z O 2‑b (XO c ) b The outer shell is made of lithium-rich manganese-based material Li, which is doped with gradient non-metallic ions. 1+ a Mn x Co y Ni z O 2‑d X d This application also provides a method for preparing a core-shell structured lithium-rich manganese-based cathode material. The method employs a combination of rapid Joule heating and surface plasma cleaning to prepare the aforementioned core-shell structured lithium-rich manganese-based cathode material, achieving a bulk disordered structure design with polyanion doping and a core-shell structure with surface gradient non-metallic ion doping. Specifically, the bulk polyanions can immobilize transition metal elements to suppress their migration to the lithium layer, reducing harmful consumption of active sites and stabilizing the crystal structure. Furthermore, the strong bond energy between the surface non-metallic elements and the transition metal elements can suppress transition metal dissolution during cycling, reducing irreversible oxygen oxidation and inhibiting harmful phase transitions.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of battery material preparation, and particularly relates to a core-shell structure lithium-rich manganese-based positive electrode material and a preparation method and application thereof. BACKGROUND

[0002] With the rapid growth of the energy storage market, some traditional positive electrode materials have been unable to meet the demand of the power market. Lithium-rich manganese-based layered oxides (LLOs, general formula: xLi2MnO3-(1-x)LiTMO2(TM=Ni, Co, Mn, etc., 0≤x≤1) have attracted extensive attention of researchers due to their high specific capacity (≥250 mAh g -1 ), high energy density (≥1000 Wh kg -1 ), low cost and environmental friendliness. However, LLOs still face great challenges, including low initial coulombic efficiency, severe voltage decay and poor cycling and rate performance. The anionic redox reaction in LLOs is part of the high capacity source, but this reaction is accompanied by a reversible oxygen redox reaction and an irreversible surface oxygen release. In this process, the high oxidation energy generated by the oxygen redox reaction will slow down the diffusion speed of lithium ions. However, too low oxidation energy will accelerate the combination of O-O dimers with oxygen, easily leading to irreversible phase transition and severe voltage decay. In addition, the O-O dimers between oxygen atoms will make more transition metal ions migrate to the lithium layer, deteriorating the diffusion dynamics of lithium ions, leading to poor rate performance. More importantly, the irreversible oxygen release also hinders the charge transport within the cathode-electrolyte interface (CEI), accelerating the surface reconstruction, thereby reducing the cycling performance.

[0003] At present, in view of the above problems, the commonly used modification methods include surface doping modification, surface coating modification, morphology design modification, etc. In fact, the initial discharge capacity stability of lithium-rich layered oxides is greatly improved by surface doping and coating modification, which benefits from the fact that surface modification can slow down the formation of spinel phase from the surface of the particles at the initial stage of the cycle. However, due to the gradual transformation of the local structure in the bulk phase from a layered structure to a cubic spinel in the bulk phase, the lithium-rich layered oxides with such surface modification still cannot satisfy the requirement for the stability of the discharge potential plateau during the cycle. It is worth mentioning that the discharge potential plateau of the cathode is greatly related to the stability of the bulk phase crystal structure, and the main reaction at high potential is the oxidation and reduction of the bulk phase oxygen anions, as mentioned above, which brings a series of hazards to the irreversible anion redox. In addition, morphology design modification often brings about low tap density, causing severe capacity decay, which is not conducive to the construction of high energy density lithium ion batteries. SUMMARY

[0004] Based on this, the object of the present invention is to provide a core-shell structured lithium-rich manganese-based cathode material and its preparation method. The core-shell structured lithium-rich manganese-based cathode material has the characteristics of significantly suppressed voltage decay and oxygen release, as well as higher initial discharge specific capacity and long cycle stability.

[0005] Part I:

[0006] For the core-shell structured lithium-rich manganese-based cathode material of the present invention, the chemical general formula of the material is Li 1+ a Mn x Co y Ni z O 2-b-d (XO c ) b X d , where 0 < a ≤ 0.4, 0 < b ≤ 0.1, 2 ≤ c ≤ 4, 0 < d ≤ 0.1, 0.3 ≤ x ≤ 0.6, 0 < y ≤ 0.25, 0 < z ≤ 0.25; in the formula, X is selected from one or more of Si, Te, S, As, Se, P, and B;

[0007] The core of the core-shell structured lithium-rich manganese-based cathode material is a disordered polyanion-doped lithium-rich manganese-based material Li 1+a Mn x Co y Ni z O 2-b (XO c ) b ; the shell of the core-shell structured lithium-rich manganese-based cathode material is a gradient non-metal ion-doped lithium-rich manganese-based material Li 1+a Mn x Co y Ni z O 2-d X d .

[0008] For the core-shell structured lithium-rich manganese-based cathode material of the present invention, through bulk doping combined with the design of a gradient disordered core-shell structure, the binding of transition metal cations in the shell with polyanions in the core is strengthened to improve the electrochemical performance. Further, in the core, large tetrahedral (XO4) 2- (X = Si, Te, S, As, Se, P, and B, 2 ≤ n ≤ 5) polyanions with high electronegativity relative to spherical O n- anions are incorporated, and they form an open and stable layered framework structure with transition metal-oxygen polyhedra MO x (M = Ni, Co, Mn, 1.9 ≤ x ≤ 2) in the shell, thereby stabilizing the local oxygen structure, avoiding oxygen release caused by irreversible anion oxidation, and realizing the stable energy density of the cathode.

[0009] Second Part:

[0010] A preparation method of a core-shell structure lithium-rich manganese-based positive electrode material as described in the first part, comprising the following steps:

[0011] mixing a lithium-rich manganese-based positive electrode carbonate precursor Ni 1 / 6 Co 1 / 6 Mn 4 / 6 CO3 powder a and a polyanion salt b containing (XO4) n- in a dispersant, and drying to obtain a precursor powder containing a polyanion salt c;

[0012] mixing the precursor powder c with a lithium source to obtain powder d;

[0013] subjecting the powder d to joule heat discharge treatment to obtain powder e;

[0014] subjecting the powder e to plasma treatment in a reducing atmosphere to obtain powder f with a surface structure containing oxygen vacancies;

[0015] calcining the powder f to obtain the core-shell structure lithium-rich manganese-based positive electrode material.

[0016] The present application first synthesizes a lithium-rich manganese-based positive electrode material Li 1+a Mn x Co y Ni z O 2-b (XO c ) b (i.e. powder e) through instantaneous heating by joule heat treatment. On the one hand, the construction of the bulk phase disordered crystal structure reduces the conflict between the activated lattice oxygen and the ordered crystal, adjusts the intrinsic redox properties of the material, and effectively inhibits the irreversible loss of lattice oxygen; on the other hand, the bulk phase polyanion can fix the transition metal elements to inhibit their migration to the lithium layer, reduce the harmful consumption of active sites, and stabilize the lattice structure. Secondly, through surface plasma cleaning treatment and calcination, a gradient non-metallic ion doped surface structure Li 1+a Mn x Co y Ni z O 2-b (XO c ) b is constructed near the surface of the lithium-rich manganese-based positive electrode material Li 1+a Mn x Co y Ni z O 2-d X d(i.e. the powder f with core-shell structure is formed). The strong bond energy between surface non-metallic ions and transition metal elements can inhibit the dissolution of transition metal in the cycle process, reduce the irreversible oxidation of anion oxygen, and inhibit the occurrence of harmful phase transition.

[0017] Wherein, the introduction of oxygen vacancies on the surface of the powder f firstly reduces the covalence of transition metal-oxygen polyhedron and O2p band state density, thereby alleviating the irreversible oxygen release in the oxygen ion redox process. Secondly, the spinel phase induced by oxygen vacancies, due to its three-dimensional Li + The channel and the enlarged Li layer interlayer spacing not only improve the conductivity and migration ability of Li ions, but also improve the stability of the structure; the oxygen vacancies can also improve the lithium electronic conductivity and promote the rate performance.

[0018] The core-shell structure lithium-rich manganese-based positive electrode material prepared by the method has an inner core base material of a highly disordered polyanion-doped lithium-rich manganese-based material Li 1+a Mn x Co y Ni z O 2-b (XO c ) b , and an outer shell of a gradient non-metallic ion-doped lithium-rich manganese-based material Li 1+a Mn x Co y Ni z O 2-d X d The core-shell structure makes the positive electrode material have the characteristics of significantly inhibited voltage decay, higher initial discharge specific capacity and long cycle stability. In addition, the preparation method provided by the present application is simple and mature, which will strongly promote the commercial use of the lithium-rich manganese-based positive electrode material.

[0019] As a preferred solution, the carbonate precursor Ni 1 / 6 Co 1 / 6 Mn 4 / 6The molar ratio of the powder a to the polyanion salt b is 4-99:1, the polyanion salt b is at least one of (NH4)2HPO4, NH4HB4O7, (NH4)2HAsO4, NH4HSO4, (NH4)2SiO4, (NH4)2SeO4 or NH4TeO4, the dispersant comprises at least one of anhydrous ethanol, deionized water or tetrahydrofuran, the mixing temperature of the powder a and the polyanion salt b is 60-120℃, the mixing time is 1-12h, the mixing of the powder a and the polyanion salt b comprises stirring, and the stirring speed is 500-1000r / min. The polyanion salt b can easily form a polyanion (XO4) n- , and the amount is less.

[0020] As a preferred solution, the lithium source comprises at least one of lithium carbonate, lithium oxalate, lithium oxide, lithium peroxide, lithium chloride, lithium hydroxide and lithium sulfate, the molar ratio of the precursor powder c to the lithium source is 1:1-2, the mixing of the precursor powder c and the lithium source comprises ball milling, the rotation speed of the ball milling is 500-1000r / min, the ball milling time is 2-5h, and the ball-to-material ratio of the ball milling is 10-30:1. The lithium source has good performance and is easy to obtain, and the more preferred lithium source is lithium carbonate.

[0021] As a preferred solution, the joule heat discharge treatment further comprises cooling after the joule heat discharge treatment, and the powder e is obtained after the cooling; the temperature rising rate of the joule heat discharge treatment is 100-1000℃ / s, the temperature of the joule heat discharge treatment is 600-1000℃, and the cooling rate is 100-1000℃ / s; the powder d is placed in a tungsten boat for the joule heat discharge treatment, the current in the tungsten boat during the joule heat discharge treatment is 50-100A, the discharge voltage is 100-200V, and the current passing time is 1-10s.

[0022] As a preferred solution, the powder e is placed in a plasma instrument cavity with a pressure of 10-100Pa for plasma treatment, the plasma comprises at least one of H2, CO and CH4, the plasma flow rate is 20-100mL / min, and the plasma treatment time is 5-60min.

[0023] As a preferred solution, the powder f is heated to 400-800℃ at a rate of 2-4℃ / min, the calcination time is 3-8h, and the core-shell structure lithium-rich manganese-based positive electrode material is obtained after cooling.

[0024] The third part:

[0025] Use of the core-shell structure lithium-rich manganese-based positive electrode material of the first aspect or the core-shell structure lithium-rich manganese-based positive electrode material prepared by the preparation method of the second aspect in preparation of a lithium ion battery.

[0026] Fourth part:

[0027] A lithium ion battery positive electrode is prepared from the core-shell structure lithium-rich manganese-based positive electrode material of the first aspect or the core-shell structure lithium-rich manganese-based positive electrode material prepared by the preparation method of the second aspect.

[0028] Fifth part:

[0029] A lithium ion battery comprises the lithium ion battery positive electrode of the fourth aspect. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 X-ray diffraction patterns of the core-shell structure lithium-rich manganese-based positive electrode material prepared for Example 1 and the lithium-rich manganese-based positive electrode material prepared for Comparative Example 1;

[0031] Figure 2 SEM and EDS-Mapping images of the core-shell structure lithium-rich manganese-based positive electrode material prepared for Example 1;

[0032] Figure 3 First cycle charge-discharge curves of the core-shell structure lithium-rich manganese-based positive electrode material prepared for Example 1 and the lithium-rich manganese-based positive electrode material prepared for Comparative Example 1 at 0.1C;

[0033] Figure 4 Long cycle performance comparison graphs of the core-shell structure lithium-rich manganese-based positive electrode material prepared for Example 1 and the lithium-rich manganese-based positive electrode material prepared for Comparative Example 1 at 4.6V and 1C rate;

[0034] Figure 5 Voltage attenuation comparison graphs of the core-shell structure lithium-rich manganese-based positive electrode material prepared for Example 1 and the lithium-rich manganese-based positive electrode material prepared for Comparative Example 1 at 4.6V and 1C rate;

[0035] Figure 6 Rate performance graphs of the core-shell structure lithium-rich manganese-based positive electrode material prepared for Examples 1, 4 and the lithium-rich manganese-based positive electrode material prepared for Comparative Example 1. DETAILED DESCRIPTION

[0036] A core-shell structure lithium-rich manganese-based positive electrode material has a chemical general formula of Li 1+a Mn x Co y Ni z O 2-b-d (XO c ) b X d, where \(0 < a\leq0.4\), \(0 < b\leq0.1\), \(2\leq c\leq4\), \(0 < d\leq0.1\), \(0.3\leq x\leq0.6\), \(0 < y\leq0.25\), \(0 < z\leq0.25\); in the formula, X is selected from one or more of Si, Te, S, As, Se, P, and B;

[0037] The inner core substrate of the core-shell structured lithium-rich manganese-based cathode material is a lithium-rich manganese-based material doped with highly disordered polyanions, Li 1+a Mn x Co y Ni z O 2-b (XO c ) b ; the outer shell of the core-shell structured lithium-rich manganese-based cathode material is a lithium-rich manganese-based material doped with gradient non-metal ions, Li 1+a Mn x Co y Ni z O 2-d X d .

[0038] A preparation method of a core-shell structured lithium-rich manganese-based cathode material includes the following steps:

[0039] S1, dissolving the carbonate precursor Ni 1 / 6 Co 1 / 6 Mn 4 / 6 CO3 powder a and the polyanionic salt b of (XO4) n- in absolute ethanol, stirring and reacting at 60 - 120 °C for 1 - 12 h, with a stirring speed of 500 - 1000 r / min. After the reaction, the mixed solution is washed and dried to obtain a precursor powder c containing the polyanionic salt.

[0040] The carbonate precursor Ni 1 / 6 Co 1 / 6 Mn 4 / 6 CO3 powder a is calculated by O, the polyanionic salt b is calculated by X, and the molar ratio of the powder a to the polyanionic salt b is 4 - 99:1; the polyanionic salt b includes at least one of (NH4)2HPO4, NH4HB4O7, (NH4)2HAsO4, NH4HSO4, (NH4)2SiO4, (NH4)2SiF6, (NH4)2SeO4, or NH4TeO4.

[0041] S2, adding the precursor powder c containing the polyanionic salt obtained in S1 and a lithium source into an agate jar for ball milling to obtain a uniformly mixed powder d, where the ball milling speed is 500 - 1000 r / min, the ball milling time is 2 - 5 h, and the ball-to-material ratio is 10 - 30:1.

[0042] The lithium source includes at least one of lithium carbonate, lithium oxalate, lithium oxide, lithium peroxide, lithium chloride, lithium hydroxide, and lithium sulfate. The lithium source is calculated based on Li, and the molar ratio of the precursor powder c to the lithium source is 1:1 to 2.

[0043] S3, the powder d obtained in S2 is placed in a tungsten boat and spread evenly, then subjected to rapid Joule thermal discharge treatment, followed by rapid cooling to obtain powder e. The heating rate of the rapid Joule thermal treatment is 100-1000℃ / s, and the cooling rate of the rapid cooling is 100-1000℃ / s. The temperature of the heat treatment is 600-1000℃, the current passing through the tungsten boat in the rapid Joule thermal treatment is 50-100A, the discharge voltage is 100-200V, and the energizing time is 1-10s.

[0044] S4, the powder e obtained in S3 is placed on a glass container and placed in the cavity of a plasma instrument for plasma treatment to obtain powder f. The pressure in the cavity of the plasma instrument is 10-100 Pa, the plasma atmosphere is at least one of H2, CO and CH4, the gas flow rate is 20-100 mL / min, the plasma treatment power is 100-300 W, and the plasma treatment time is 5-60 min.

[0045] S5, the powder f obtained in S4 is placed in a muffle furnace for calcination and annealing, and then cooled to obtain the core-shell structured lithium-rich manganese-based cathode material. The calcination temperature is 400-800℃, the holding time is 3-8h, the heating rate is 2-4℃ / min, and the core-shell structured lithium-rich manganese-based cathode material is obtained by natural cooling with the furnace after calcination.

[0046] Example 1

[0047] The method for preparing a core-shell structured lithium-rich manganese-based cathode material according to the present invention includes the following steps:

[0048] S1, Weigh 42g of lithium-rich manganese-based cathode carbonate precursor Ni 1 / 6 Co 1 / 6 Mn 4 / 6 CO3 powder a and 6.94 g of (NH4)2HPO4 were dissolved in 100 ml of anhydrous ethanol and stirred at 80 °C for 5 h at a stirring speed of 800 r / min. After the reaction was completed, the mixed solution was washed and dried to obtain precursor powder c containing polyanionic salt.

[0049] S2, 15g of the precursor powder c containing polyanionic salt obtained in S1 and 6.67g of Li2CO3 were added to an agate jar and ball-milled to obtain powder d, wherein the ball milling speed was 500rpm, the ball milling time was 5h, and the ball-to-material ratio was 20:1.

[0050] S3, 2g of powder d obtained from S2 is placed in a tungsten boat and spread evenly. It is then subjected to rapid Joule thermal discharge treatment and then rapidly cooled to obtain powder e. The heating rate of the rapid Joule thermal treatment is 200℃ / s, the cooling rate of the rapid cooling is 200℃ / s, the heat treatment temperature is 850℃, the current through the tungsten boat reaches 80A, the discharge voltage is 150V, and the energizing time is 5s.

[0051] S4. Place the powder e obtained in S3 on a glass container and place it in the cavity of a plasma analyzer for plasma treatment to obtain powder f. The pressure in the cavity of the plasma analyzer is 50 Pa, the plasma treatment atmosphere is H2, the gas flow rate is 50 mL / min, the plasma treatment power is 200 W, and the plasma treatment time is 30 min.

[0052] S5, the powder f obtained in S4 is placed in a muffle furnace for calcination and annealing, followed by cooling to obtain the core-shell structured lithium-rich manganese-based cathode material. The calcination temperature is 500℃, held for 5 hours, and the heating rate is 3℃ / min. After calcination, the material is naturally cooled in the furnace to obtain the core-shell structured lithium-rich manganese-based cathode material Li. 1.14 Mn 0.54 Co 0.13 Ni 0.13 O 1.95 (PO4) 0.04 P 0.01 .

[0053] Example 2

[0054] The method for preparing a core-shell structured lithium-rich manganese-based cathode material according to the present invention includes the following steps:

[0055] S1, Weigh 42g of lithium-rich manganese-based cathode carbonate precursor Ni 1 / 6 Co 1 / 6 Mn 4 / 6 CO3 powder a and 12.01g NH4HBO7 were dissolved in 100ml anhydrous ethanol and stirred at 80℃ for 5h at a stirring speed of 1000r / min. After the reaction was completed, the mixed solution was washed and dried to obtain precursor powder c containing polyanionic salt.

[0056] S2, 15g of the precursor powder c containing polyanionic salt obtained in S1 and 6.67g of Li2CO3 were added to an agate jar and ball-milled to obtain powder d, wherein the ball milling speed was 500r / min, the ball milling time was 5h, and the ball-to-material ratio was 20:1.

[0057] S3, 2g of powder d obtained from S2 is placed in a tungsten boat and spread evenly. It is then subjected to rapid Joule thermal discharge treatment and then rapidly cooled to obtain powder e. The heating rate of the rapid Joule thermal treatment is 200℃ / s, the cooling rate of the rapid cooling is 200℃ / s, the heat treatment temperature is 850℃, the current through the tungsten boat reaches 80A, the discharge voltage is 150V, and the energizing time is 5s.

[0058] S4. Place the powder e obtained in S3 on a glass container and place it in the cavity of a plasma analyzer for plasma treatment to obtain powder f. The pressure in the cavity of the plasma analyzer is 50 Pa, the plasma treatment atmosphere is H2, the gas flow rate is 50 mL / min, the plasma treatment power is 200 W, and the plasma treatment time is 30 min.

[0059] S5, the powder f obtained in S4 is placed in a muffle furnace for calcination and annealing, followed by cooling to obtain the core-shell structured lithium-rich manganese-based cathode material. The calcination temperature is 500℃, held for 5 hours, and the heating rate is 3℃ / min. After calcination, the material is naturally cooled in the furnace to obtain the core-shell structured lithium-rich manganese-based cathode material Li. 1.14 Mn 0.54 Co 0.13 Ni 0.13 O 1.95 (BO4) 0.04 B 0.01 .

[0060] Example 3

[0061] The method for preparing a core-shell structured lithium-rich manganese-based cathode material according to the present invention includes the following steps:

[0062] S1, Weigh 42g of lithium-rich manganese-based cathode carbonate precursor Ni 1 / 6 Co 1 / 6 Mn 4 / 6 CO3 powder a and 6.05 g (NH4)2HSO4 were dissolved in 100 ml of anhydrous ethanol and stirred at 80 °C for 5 h at a stirring speed of 800 r / min. After the reaction was completed, the mixed solution was washed and dried to obtain precursor powder c containing polyanionic salt.

[0063] S2, 15g of the precursor powder c containing polyanionic salt obtained in S1 and 6.67g of Li2CO3 were added to an agate jar and ball-milled to obtain powder d, wherein the ball milling speed was 500r / min, the ball milling time was 5h, and the ball-to-material ratio was 20:1.

[0064] S3, 2g of powder d obtained from S2 is placed in a tungsten boat and spread evenly. It is then subjected to rapid Joule thermal discharge treatment and then rapidly cooled to obtain powder e. The heating rate of the rapid Joule thermal treatment is 200℃ / s, the cooling rate of the rapid cooling is 200℃ / s, the heat treatment temperature is 850℃, the current through the tungsten boat reaches 80A, the discharge voltage is 150V, and the energizing time is 5s.

[0065] S4. Place the powder e obtained in S3 on a glass container and place it in the cavity of a plasma analyzer for plasma treatment to obtain powder f. The pressure in the cavity of the plasma analyzer is 50 Pa, the plasma treatment atmosphere is H2, the gas flow rate is 50 mL / min, the plasma treatment power is 200 W, and the plasma treatment time is 30 min.

[0066] S5, the powder f obtained in S4 is placed in a muffle furnace for calcination and annealing, followed by cooling to obtain the core-shell structured lithium-rich manganese-based cathode material. The calcination temperature is 500℃, held for 5 hours, and the heating rate is 3℃ / min. After calcination, the material is naturally cooled in the furnace to obtain the core-shell structured lithium-rich manganese-based cathode material Li. 1.14 Mn 0.54 Co 0.13 Ni 0.13 O 1.95 (SO4) 0.04 S 0.01 .

[0067] Example 4

[0068] The method for preparing a core-shell structured lithium-rich manganese-based cathode material according to the present invention includes the following steps:

[0069] S1, Weigh 42g of lithium-rich manganese-based cathode carbonate precursor Ni 1 / 6 Co 1 / 6 Mn 4 / 6 CO3 powder a and 9.374 g of (NH4)2SiF6 were dissolved in 100 ml of anhydrous ethanol and stirred at 80 °C for 5 h at a stirring speed of 800 r / min. After the reaction was completed, the mixed solution was washed and dried to obtain precursor powder c containing polyanionic salt.

[0070] S2, 15g of the precursor powder c containing polyanionic salt obtained in S1 and 6.67g of Li2CO3 were added to an agate jar and ball-milled to obtain powder d, wherein the ball milling speed was 500r / min, the ball milling time was 5h, and the ball-to-material ratio was 20:1.

[0071] S3, 2g of powder d obtained from S2 is placed in a tungsten boat and spread evenly. It is then subjected to rapid Joule thermal discharge treatment and then rapidly cooled to obtain powder e. The heating rate of the rapid Joule thermal treatment is 200℃ / s, the cooling rate of the rapid cooling is 200℃ / s, the heat treatment temperature is 850℃, the current through the tungsten boat reaches 80A, the discharge voltage is 150V, and the energizing time is 5s.

[0072] S4. Place the powder e obtained in S3 on a glass container and place it in the cavity of a plasma analyzer for plasma treatment to obtain powder f. The pressure in the cavity of the plasma analyzer is 50 Pa, the plasma treatment atmosphere is H2, the gas flow rate is 50 mL / min, the plasma treatment power is 200 W, and the plasma treatment time is 30 min.

[0073] S5, the powder f obtained in S4 is placed in a muffle furnace for calcination and annealing, followed by cooling to obtain the core-shell structured lithium-rich manganese-based cathode material. The calcination temperature is 500℃, held for 5 hours, and the heating rate is 3℃ / min. After calcination, the material is naturally cooled in the furnace to obtain the core-shell structured lithium-rich manganese-based cathode material Li. 1.14 Mn 0.54 Co 0.13 Ni 0.13 O 1.95 (SiO4) 0.04 Si 0.01 .

[0074] Example 5

[0075] The method for preparing a core-shell structured lithium-rich manganese-based cathode material according to the present invention includes the following steps:

[0076] S1, Weigh 42g of lithium-rich manganese-based cathode carbonate precursor Ni 1 / 6 Co 1 / 6 Mn 4 / 6 CO3 powder a and 9.42 g (NH4)2SeO4 were dissolved in 100 ml of anhydrous ethanol and stirred at 80 °C for 5 h at a stirring speed of 800 r / min. After the reaction was completed, the mixed solution was washed and dried to obtain precursor powder c containing polyanionic salt.

[0077] S2, 15g of the precursor powder c containing polyanionic salt obtained in S1 and 6.67g of Li2CO3 were added to an agate jar and ball-milled to obtain powder d, wherein the ball milling speed was 500r / min, the ball milling time was 5h, and the ball-to-material ratio was 20:1.

[0078] S3, 2g of powder d obtained from S2 is placed in a tungsten boat and spread evenly. It is then subjected to rapid Joule thermal discharge treatment and then rapidly cooled to obtain powder e. The heating rate of the rapid Joule thermal treatment is 200℃ / s, the cooling rate of the rapid cooling is 200℃ / s, the heat treatment temperature is 850℃, the current through the tungsten boat reaches 80A, the discharge voltage is 150V, and the energizing time is 5s.

[0079] S4. Place the powder e obtained in S3 on a glass container and place it in the cavity of a plasma analyzer for plasma treatment to obtain powder f. The pressure in the cavity of the plasma analyzer is 50 Pa, the plasma treatment atmosphere is H2, the gas flow rate is 50 mL / min, the plasma treatment power is 200 W, and the plasma treatment time is 30 min.

[0080] S5, the powder f obtained in S4 is placed in a muffle furnace for calcination and annealing, followed by cooling to obtain the core-shell structured lithium-rich manganese-based cathode material. The calcination temperature is 500℃, held for 5 hours, and the heating rate is 3℃ / min. After calcination, the material is naturally cooled in the furnace to obtain the core-shell structured lithium-rich manganese-based cathode material Li. 1.14 Mn 0.54 Co 0.13 Ni 0.13 O 1.95 (SeO4) 0.04 Se 0.01 .

[0081] Example 6

[0082] The method for preparing a core-shell structured lithium-rich manganese-based cathode material according to the present invention includes the following steps:

[0083] S1, Weigh 42g of lithium-rich manganese-based cathode carbonate precursor Ni 1 / 6 Co 1 / 6 Mn 4 / 6 CO3 powder a and 33.01g (NH4)2HPO4 were dissolved in 100ml anhydrous ethanol and stirred at 80℃ for 5h at a stirring speed of 800r / min. After the reaction was completed, the mixed solution was washed and dried to obtain precursor powder c containing polyanionic salt.

[0084] S2, 15g of the precursor powder c containing polyanionic salt obtained in S1 and 6.67g of Li2CO3 were added to an agate jar and ball-milled to obtain powder d, wherein the ball milling speed was 500r / min, the ball milling time was 5h, and the ball-to-material ratio was 20:1.

[0085] S3, 2g of powder d obtained from S2 is placed in a tungsten boat and spread evenly. It is then subjected to rapid Joule thermal discharge treatment and then rapidly cooled to obtain powder e. The heating rate of the rapid Joule thermal treatment is 200℃ / s, the cooling rate of the rapid cooling is 200℃ / s, the heat treatment temperature is 850℃, the current through the tungsten boat reaches 80A, the discharge voltage is 150V, and the energizing time is 5s.

[0086] S4. Place the powder e obtained in S3 on a glass container and place it in the cavity of a plasma analyzer for plasma treatment to obtain powder f. The pressure in the cavity of the plasma analyzer is 50 Pa, the plasma treatment atmosphere is H2, the gas flow rate is 50 mL / min, the plasma treatment power is 200 W, and the plasma treatment time is 30 min.

[0087] S5, the powder f obtained in S4 is placed in a muffle furnace for calcination and annealing, followed by cooling to obtain the core-shell structured lithium-rich manganese-based cathode material. The calcination temperature is 500℃, held for 5 hours, and the heating rate is 3℃ / min. After calcination, the material is naturally cooled in the furnace to obtain the core-shell structured lithium-rich manganese-based cathode material Li. 1.14 Mn 0.54 Co 0.13 Ni 0.13 O 1.8 (PO4) 0.1 P 0.1 .

[0088] Example 7

[0089] The method for preparing a core-shell structured lithium-rich manganese-based cathode material according to the present invention includes the following steps:

[0090] S1, Weigh 42g of lithium-rich manganese-based cathode carbonate precursor Ni 1 / 6 Co 1 / 6 Mn 4 / 6 CO3 powder a and 6.94 g of (NH4)2HPO4 were dissolved in 100 ml of anhydrous ethanol and stirred at 120 °C for 1 h at a stirring speed of 500 r / min. After the reaction was completed, the mixed solution was washed and dried to obtain precursor powder c containing polyanionic salt.

[0091] S2, 30g of the precursor powder c containing polyanionic salt obtained in S1 and 6.67g of Li2CO3 were added to an agate jar and ball-milled to obtain powder d, wherein the ball milling speed was 500r / min, the ball milling time was 5h, and the ball-to-material ratio was 20:1.

[0092] S3, 2g of powder d obtained from S2 is placed in a tungsten boat and spread evenly. It is then subjected to rapid Joule thermal discharge treatment and then rapidly cooled to obtain powder e. The heating rate of the rapid Joule thermal treatment is 200℃ / s, the cooling rate of the rapid cooling is 200℃ / s, the heat treatment temperature is 850℃, the current through the tungsten boat reaches 80A, the discharge voltage is 150V, and the energizing time is 5s.

[0093] S4. Place the powder e obtained in S3 on a glass container and place it in the cavity of a plasma analyzer for plasma treatment to obtain powder f. The pressure in the cavity of the plasma analyzer is 50 Pa, the plasma treatment atmosphere is H2, the gas flow rate is 100 mL / min, the plasma treatment power is 300 W, and the plasma treatment time is 5 min.

[0094] S5, the powder f obtained in S4 is placed in a muffle furnace for calcination and annealing, followed by cooling to obtain the core-shell structured lithium-rich manganese-based cathode material. The calcination temperature is 500℃, held for 5 hours, and the heating rate is 3℃ / min. After calcination, the material is naturally cooled in the furnace to obtain the core-shell structured lithium-rich manganese-based cathode material Li. 1.14 Mn 0.54 Co 0.13 Ni 0.13 O 1.95 (PO4) 0.04 P 0.01 .

[0095] Example 8

[0096] The method for preparing a core-shell structured lithium-rich manganese-based cathode material according to the present invention includes the following steps:

[0097] S1, Weigh 42g of lithium-rich manganese-based cathode carbonate precursor Ni 1 / 6 Co 1 / 6 Mn 4 / 6 CO3 powder a and 6.94 g of (NH4)2HPO4 were dissolved in 100 ml of anhydrous ethanol and stirred at 80 °C for 5 h at a stirring speed of 800 r / min. After the reaction was completed, the mixed solution was washed and dried to obtain precursor powder c containing polyanionic salt.

[0098] S2, 15g of the precursor powder c containing polyanionic salt obtained in S1 and 6.67g of Li2CO3 were added to an agate jar and ball-milled to obtain powder d, wherein the ball milling speed was 1000r / min, the ball milling time was 2h, and the ball-to-material ratio was 30:1.

[0099] S3, 2g of powder d obtained from S2 is placed in a tungsten boat and spread evenly. It is then subjected to rapid Joule thermal discharge treatment and then rapidly cooled to obtain powder e. The heating rate of the rapid Joule thermal treatment is 500℃ / s, the cooling rate of the rapid cooling is 500℃ / s, the heat treatment temperature is 1000℃, the current through the tungsten boat in the rapid Joule thermal treatment reaches 100A, the discharge voltage is 200V, and the energizing time is 1s.

[0100] S4. Place the powder e obtained in S3 on a glass container and place it in the cavity of a plasma instrument for plasma treatment to obtain powder f. The pressure in the cavity of the plasma instrument is 100 Pa, the plasma treatment atmosphere is H2, the gas flow rate is 100 mL / min, the plasma treatment power is 100 W, and the plasma treatment time is 15 min.

[0101] S5, the powder f obtained in S4 is placed in a muffle furnace for calcination and annealing, followed by cooling to obtain the core-shell structured lithium-rich manganese-based cathode material. The calcination temperature is 800℃, held for 3 hours, and the heating rate is 4℃ / min. After calcination, the material is naturally cooled in the furnace to obtain the core-shell structured lithium-rich manganese-based cathode material Li. 1.14 Mn 0.54 Co 0.13 Ni 0.13 O 1.95 (PO4) 0.04 P 0.01 .

[0102] Example 9

[0103] The method for preparing a core-shell structured lithium-rich manganese-based cathode material according to the present invention includes the following steps:

[0104] S1, Weigh 42g of lithium-rich manganese-based cathode carbonate precursor Ni 1 / 6 Co 1 / 6 Mn 4 / 6 CO3 powder a and 6.94 g of (NH4)2HPO4 were dissolved in 100 ml of anhydrous ethanol and stirred at 80 °C for 5 h at a stirring speed of 800 r / min. After the reaction was completed, the mixed solution was washed and dried to obtain precursor powder c containing polyanionic salt.

[0105] S2, 30g of the precursor powder c containing polyanionic salt obtained in S1 and 6.67g of Li2CO3 were added to an agate jar and ball-milled to obtain powder d, wherein the ball milling speed was 500r / min, the ball milling time was 5h, and the ball-to-material ratio was 20:1.

[0106] S3, 2g of powder d obtained from S2 is placed in a tungsten boat and spread evenly. It is then subjected to rapid Joule thermal discharge treatment and then rapidly cooled to obtain powder e. The heating rate of the rapid Joule thermal treatment is 400℃ / s, the cooling rate of the rapid cooling is 400℃ / s, the temperature of the heat treatment is 1000℃, the current of the rapid Joule thermal discharge through the tungsten boat reaches 100A, the discharge voltage is 200V, and the energizing time is 1s.

[0107] S4. Place the powder e obtained in S3 on a glass container and place it in the cavity of a plasma analyzer for plasma treatment to obtain powder f. The pressure in the cavity of the plasma analyzer is 100 Pa, the plasma treatment atmosphere is CO, the gas flow rate is 80 mL / min, the plasma treatment power is 100 W, and the plasma treatment time is 40 min.

[0108] S5, the powder f obtained in S4 is placed in a muffle furnace for calcination and annealing, followed by cooling to obtain the core-shell structured lithium-rich manganese-based cathode material. The calcination temperature is 600℃, held for 8 hours, and the heating rate is 2℃ / min. After calcination, the material is naturally cooled in the furnace to obtain the core-shell structured lithium-rich manganese-based cathode material Li. 1.14 Mn 0.54 Co 0.13 Ni 0.13 O 1.95 (PO4) 0.04 P 0.01 .

[0109] Example 10

[0110] The method for preparing a core-shell structured lithium-rich manganese-based cathode material according to the present invention includes the following steps:

[0111] S1, Weigh 42g of lithium-rich manganese-based cathode carbonate precursor Ni 1 / 6 Co 1 / 6 Mn 4 / 6 CO3 powder a and 6.94 g of (NH4)2HPO4 were dissolved in 100 ml of anhydrous ethanol and stirred at 60 °C for 12 h at a stirring speed of 1000 r / min. After the reaction was completed, the mixed solution was washed and dried to obtain precursor powder c containing polyanionic salt.

[0112] S2, 30g of the precursor powder c containing polyanionic salt obtained in S1 and 6.67g of Li2CO3 were added to an agate jar and ball-milled to obtain powder d, wherein the ball milling speed was 800r / min, the ball milling time was 3h, and the ball-to-material ratio was 30:1.

[0113] S3, 2g of powder d obtained from S2 is placed in a tungsten boat and spread evenly. It is then subjected to rapid Joule thermal discharge treatment and then rapidly cooled to obtain powder e. The heating rate of the rapid Joule thermal treatment is 100℃ / s, the cooling rate of the rapid cooling is 100℃ / s, the temperature of the heat treatment is 600℃, the current of the rapid Joule thermal discharge through the tungsten boat reaches 50A, the discharge voltage is 100V, and the energizing time is 10s.

[0114] S4. Place the powder e obtained in S3 on a glass container and place it in the cavity of a plasma analyzer for plasma treatment to obtain powder f. The pressure in the cavity of the plasma analyzer is 10 Pa, the plasma treatment atmosphere is CH4, the gas flow rate is 20 mL / min, the plasma treatment power is 250 W, and the plasma treatment time is 60 min.

[0115] S5, the powder f obtained in S4 is placed in a muffle furnace for calcination and annealing, followed by cooling to obtain the core-shell structured lithium-rich manganese-based cathode material. The calcination temperature is 400℃, held for 8 hours, and the heating rate is 4℃ / min. After calcination, the material is naturally cooled in the furnace to obtain the core-shell structured lithium-rich manganese-based cathode material Li. 1.14 Mn 0.54 Co 0.13 Ni 0.13 O 1.95 (PO4) 0.04 P 0.01 .

[0116] Comparative Example 1

[0117] A method for preparing a layered lithium-rich manganese-based cathode material includes the following steps:

[0118] 15g of lithium-rich manganese-based cathode carbonate precursor Ni 1 / 6 Co 1 / 6 Mn 4 / 6 CO3 powder a and 6.67g Li2CO3 were added to an agate jar and ball-milled to obtain a homogeneous mixture. The ball milling speed was 500 r / min, the milling time was 5 h, and the ball-to-powder ratio was 20:1. The homogeneous mixture obtained from the agate jar was then placed in a muffle furnace and pre-sintered at 500℃ under air atmosphere at a heating rate of 3℃ / min for 5 h. Then, the temperature was increased to 850℃ at the same heating rate and held for 12 h. After the furnace temperature was allowed to cool naturally to room temperature, the original layered lithium-rich manganese-based cathode material Li2CO3 was obtained. 1.14 Mn 0.54 Co 0.13 Ni 0.13 O2.

[0119] Figure 1The images show the X-ray diffraction patterns of the core-shell structured lithium-rich manganese-based cathode material prepared in Example 1 and the lithium-rich manganese-based cathode material prepared in Comparative Example 1. Figure 1 As can be seen, the XRD characteristic peak positions of the unmodified lithium-rich cathode material (Comparative Example 1) and the modified lithium-rich manganese-based cathode material (the core-shell structure lithium-rich manganese-based cathode material described in Example 1) are completely consistent, and no impurity peaks appear. This indicates that both Example 1 and Comparative Example 1 successfully prepared lithium-rich manganese-based cathode materials, and the core-shell structured lithium-rich manganese-based cathode material maintained the good layered crystal structure before modification.

[0120] Figure 2 The images show the SEM and mapping results of a core-shell structured lithium-rich manganese-based cathode material prepared in Example 1. The top left image is the SEM image, and the remaining five images are EDS-Mapping images of the corresponding elements. The SEM images show that the core-shell structured lithium-rich manganese-based cathode material prepared in Example 1 consists of secondary spherical particles with a rough surface, composed of primary particles approximately 200 nm in size, and a diameter of approximately 15 μm. The EDS-Mapping results show that phosphorus (P) is uniformly distributed on the surface of the core-shell structured lithium-rich manganese-based cathode material, indicating the successful preparation of the P-gradient doped core-shell structured lithium-rich manganese-based cathode material.

[0121] To further verify whether the electrochemical performance of the core-shell structure lithium-rich manganese-based cathode material described in this invention is improved, the lithium-rich manganese-based cathode materials described in Examples 1-5 and Comparative Example 1 were prepared as cathodes and assembled into lithium-ion batteries, and their performance was tested.

[0122] The preparation method of the positive electrode is as follows: The lithium-rich manganese-based positive electrode material described in Examples 1-5 and Comparative Example 1, the conductive agent SP and the binder PVDF are mixed at a mass ratio of 8:1:1, and an appropriate amount of NMP solvent is added. The mixture is then mixed using a defoamer to form a uniform slurry. The defoamer is operated at a speed of 8000 r / min for 10 min. The mixed slurry is then coated onto aluminum foil and dried in an oven at 80°C for 12 h. After that, it is placed in a vacuum oven at 120°C for vacuum drying for 4 h. Finally, the electrode sheet is punched into a circular positive electrode sheet with a diameter of 16 mm for later use.

[0123] Lithium-ion battery preparation method: The circular positive electrode sheet is used as the positive electrode, the negative electrode is a metallic lithium sheet, the separator is a microporous polypropylene (PP) film, and the electrolyte of the lithium-ion battery is a solution formed by dissolving 1 mol / L LiPF6 in DEC+EC (volume ratio of 7:3). The CR2032 type coin cell is assembled in a glove box.

[0124] The charge-discharge performance of coin cells was tested using a Newway battery tester. The charge-discharge performance test conditions were as follows: constant current charge-discharge voltage window of 2.0–4.6V; in the cycle performance test, the operating temperature was 25℃; charge-discharge and coulombic efficiency tests were performed on the batteries prepared with the cathode materials of Examples 1-5 and Comparative Example 1 at a rate of 0.1C; long-cycle stability tests were performed on the batteries prepared with the cathode materials of Examples 1 and Comparative Example 1 at a rate of 1C; and rate tests were performed on the batteries prepared with the cathode materials of Examples 1, 4, and Comparative Example 1 at rates ranging from 0.1C to 4C.

[0125] Table 1 shows the 0.1C first-cycle charge-discharge specific capacity and initial coulombic efficiency of the core-shell structure lithium-rich manganese-based cathode material prepared in Examples 1-5 and the lithium-rich manganese-based cathode material prepared in Comparative Example 1. As can be seen from the table, the core-shell structure lithium-rich manganese-based cathode material in Examples 1-5 has a higher charge-discharge capacity and coulombic efficiency at 0.1C than the lithium-rich manganese-based cathode material in Comparative Example 1.

[0126]

[0127] like Figure 3 As shown, the Li prepared in Example 1 1.14 Mn 0.54 Co 0.13 Ni 0.13 O 1.95 (PO4) 0.04 P 0.01 It exhibits a higher charge / discharge specific capacity, reaching 296.83 mAh·g. -1 and 283.05mAh·g -1 The initial efficiency is as high as 95.4%, which is far higher than the 287.44 mAh·g of the lithium-rich manganese-based cathode material in Comparative Example 1. -1 / 259.56mAh·g -1 / 90.3%.

[0128] In addition, the Li prepared in Example 1 1.14 Mn 0.54 Co 0.13 Ni 0.13 O 1.95 (PO4) 0.04 P 0.01 It exhibits higher long-cycle stability and lower voltage decay. For example... Figures 4-5 As shown, after 200 cycles at 1C, the Li prepared in Example 1... 1.14 Mn 0.54 Co 0.13 Ni 0.13 O 1.95 (PO4) 0.04 P 0.01With a capacity of up to 92.7% and a voltage decay of only 1.01 mV / cycle, compared to the lithium-rich manganese-based cathode material described in Comparative Example 1, which has a capacity retention of only 80.8% after 200 cycles and exhibits a higher voltage decay of 1.66 mV / cycle.

[0129] like Figure 6 As shown, Example 1 is a preferred embodiment of the present invention, exhibiting the best rate capability.

[0130] In summary, compared with the unmodified lithium-rich manganese-based cathode materials described in the comparative examples, the core-shell structured lithium-rich manganese-based cathode materials prepared in Examples 1-5 exhibit significantly suppressed voltage decay, as well as higher initial discharge specific capacity and long-cycle stability. The superior electrochemical performance is mainly attributed to the following characteristics: First, thanks to the instantaneous heating and cooling process of Joule heat treatment, a highly disordered bulk polyanion-doped lithium-rich manganese-based cathode material, Li, was synthesized. 1+ a Mn x Co y Ni z O 2-b (XO c ) b On the one hand, the construction of a bulk disordered crystal structure reduces the conflict between activated lattice oxygen and ordered crystals, modulates the material's intrinsic redox properties, and effectively suppresses irreversible lattice oxygen loss. On the other hand, bulk polyanions can fix transition metal elements to inhibit their migration to the lithium layer, reduce harmful consumption of active sites, and stabilize the lattice structure. Secondly, through surface plasma cleaning and high-temperature calcination annealing, in Li... 1+ a Mn x Co y Ni z O 2-b (XO c ) b Gradient nonmetallic ion-doped surface structures were constructed near the surface of Li. 1+a Mn x Co y Ni z O 2-d X d The strong bond energy between surface nonmetallic ions and transition metal elements can inhibit the dissolution of transition metals during cycling, reduce irreversible oxidation by oxygen, and suppress harmful phase transitions.

[0131] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. Those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the protection scope of the present invention.

Claims

1. A core-shell structured lithium-rich manganese-based cathode material, characterized in that, The chemical general formula of the material is Li 1+ a Mn x Co y Ni z O 2-b-d (XO c ) b X d , where 0 < a ≤ 0.4, 0 < b ≤ 0.1, 2 ≤ c ≤ 4, 0 < d ≤ 0.1, 0.3 ≤ x ≤ 0.6, 0 < y ≤ 0.25, 0 < z ≤ 0.25; in the formula, X is selected from one or more of Si, Te, S, As, Se, P, and B; The core of the core-shell structured lithium-rich manganese-based cathode material is a disordered polyanion-doped lithium-rich manganese-based material, Li. 1+a Mn x Co y Ni z O 2-b (XO c ) b The outer shell of the core-shell structured lithium-rich manganese-based cathode material is a graded non-metallic ion-doped lithium-rich manganese-based material, Li. 1+a Mn x Co y Ni z O 2-d X d ; The preparation method of the core-shell structured lithium-rich manganese-based cathode material includes the following steps: Ni, a lithium-rich manganese-based cathode carbonate precursor 1 / 6 Co 1 / 6 Mn 4 / 6 CO3 powder a and containing (XO4) n- The polyanionic salt b is dissolved in a dispersant and mixed, and then dried to obtain a precursor powder c containing the polyanionic salt; The precursor powder c is mixed with a lithium source to obtain powder d; The powder d is subjected to Joule thermal discharge treatment to obtain powder e; The powder e is placed in a reducing atmosphere for plasma treatment to obtain powder f with oxygen vacancies in its surface structure; The powder f is calcined to obtain the core-shell structured lithium-rich manganese-based cathode material.

2. A method for preparing the core-shell structured lithium-rich manganese-based cathode material according to claim 1, characterized in that, Includes the following steps: Ni, a lithium-rich manganese-based cathode carbonate precursor 1 / 6 Co 1 / 6 Mn 4 / 6 CO3 powder a and containing (XO4) n- The polyanionic salt b is dissolved in a dispersant and mixed, and then dried to obtain a precursor powder c containing the polyanionic salt; The precursor powder c is mixed with a lithium source to obtain powder d; The powder d is subjected to Joule thermal discharge treatment to obtain powder e; The powder e is placed in a reducing atmosphere for plasma treatment to obtain powder f with oxygen vacancies in its surface structure; The powder f is calcined to obtain the core-shell structured lithium-rich manganese-based cathode material.

3. The method for preparing the core-shell structured lithium-rich manganese-based cathode material according to claim 2, characterized in that, The carbonate precursor Ni 1 / 6 Co 1 / 6 Mn 4 / 6 CO3 powder a is calculated as O, and the polyanionic salt b is calculated as X. The molar ratio of powder a to polyanionic salt b is 4~99:

1. The polyanionic salt b includes at least one of (NH4)2HPO4, NH4HB4O7, (NH4)2HAsO4, NH4HSO4, (NH4)2SiO4, (NH4)2SeO4, or NH4TeO4. The dispersant includes at least one of anhydrous ethanol, deionized water, or tetrahydrofuran. The mixing temperature of powder a and polyanionic salt b is 60~120℃, and the mixing time is 1~12h. The mixing of powder a and polyanionic salt b includes stirring at a stirring speed of 500~1000r / min.

4. The method for preparing the core-shell structured lithium-rich manganese-based cathode material according to claim 2, characterized in that, The lithium source includes at least one of lithium carbonate, lithium oxalate, lithium oxide, lithium peroxide, lithium chloride, lithium hydroxide, and lithium sulfate. The lithium source is calculated as Li. The molar ratio of the precursor powder c to the lithium source is 1:1~2. The mixing of the precursor powder c and the lithium source includes ball milling. The ball milling speed is 500~1000 r / min, the ball milling time is 2~5 h, and the ball-to-material ratio of the ball milling is 10~30:

1.

5. The method for preparing the core-shell structured lithium-rich manganese-based cathode material according to claim 2, characterized in that, The Joule thermal discharge treatment further includes cooling, after which the powder e is obtained; the heating rate of the Joule thermal discharge treatment is 100~1000℃ / s, the temperature of the Joule thermal discharge treatment is 600~1000℃, and the cooling rate is 100~1000℃ / s; the powder d is placed in a tungsten boat for Joule thermal discharge treatment, and the current passing through the tungsten boat during the Joule thermal discharge treatment is 50~100 A, the discharge voltage is 100~200V, and the energizing time is 1~10 s.

6. The method for preparing the core-shell structured lithium-rich manganese-based cathode material according to claim 2, characterized in that, The powder e is placed in a plasma chamber at 10~100 Pa for plasma treatment. The plasma includes at least one of H2, CO and CH4. The plasma flow rate is 20~100 mL / min, and the plasma treatment time is 5~60 min.

7. The method for preparing the core-shell structured lithium-rich manganese-based cathode material according to claim 2, characterized in that, The powder f is heated to 400-800℃ at a rate of 2-4℃ / min, and calcined for 3-8h. After cooling, the core-shell structured lithium-rich manganese-based cathode material is obtained.

8. The application of a core-shell structured lithium-rich manganese-based cathode material as described in claim 1 or a core-shell structured lithium-rich manganese-based cathode material prepared by any one of claims 2 to 7 in the preparation of lithium-ion batteries.

9. A lithium-ion battery cathode, prepared from a core-shell structure lithium-rich manganese-based cathode material as described in claim 1, or prepared from a core-shell structure lithium-rich manganese-based cathode material prepared by any one of claims 2 to 7.

10. A lithium-ion battery, comprising the lithium-ion battery positive electrode as described in claim 9.

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