WO2015039318A1

WO2015039318A1 - Lithium-rich manganese-based solid solution/grapheme composite material and preparation method therefor

Info

Publication number: WO2015039318A1
Application number: PCT/CN2013/083842
Authority: WO
Inventors: 王要兵; 姚建年; 洪茂椿; 付芳
Original assignee: 中国科学院福建物质结构研究所
Priority date: 2013-09-18
Filing date: 2013-09-18
Publication date: 2015-03-26

Abstract

The present invention provides a lithium-rich manganese-based solid solution/graphene composite material and a preparation method therefor, and is applicable to the technical field of energy materials. The general structural formula of said lithium-rich manganese-based solid solution is xLi2MnO3·(1-x)LiMO2, wherein M is anyone of Ni, Co, Mn, Cr, Ni-Co, Ni-Mn, Ni-Co-Mn, Fe and Ru, and 0<x<1; it is characterized in that said lithium-rich manganese-based solid solution is dispersed between the layers of a layered graphene in the form of particles. The lithium-rich manganese-based solid solution/graphene composite material of the present invention can be used as an anode material for lithium ion batteries, and the electrical conductivity of the lithium-rich manganese-based solid solution can be effectively improved. The preparation method has the characteristics of simple technology, low cost and being suitable for large-scale production.

Description

Lithium-rich manganese-based solid solution/graphene composite material and preparation method thereof

The invention relates to a lithium-rich manganese-based solid solution/graphene composite material and a preparation method thereof, and belongs to the technical field of electrochemistry and material synthesis. Background technique

The theoretical specific capacity of the layered structure lithium-rich manganese-based solid solution cathode material xLi ₂ Mn0 ₃ '(lx)LiM0 ₂ (where M is a transition metal, 0<χ<1) exceeds SOOmAh.g- ¹ , and the actual usable capacity is greater than 250. mAh g ¹ is about twice the actual capacity of the cathode material currently used; in addition, since the material uses a large amount of Mn element, it is in phase with LiCo0 ₂ and LiM _1/3 Mn _1/3 Co _1/3 0 ₂ Compared with, it also has the advantages of low cost, good safety and environmental friendliness. Therefore, xLi ₂ Mn0 ₃ lx)LiM0 ₂ is considered to be an ideal choice for cathode materials for next-generation lithium-ion batteries. However, its poor rate performance limits its further development in commercialization.

To solve the problems of lithium-rich manganese-based solid solution materials, it is first necessary to analyze the underlying causes of these problems. The poor rate performance of the layered lithium-rich material is related to the poor conductivity and Li+ expansion of the material itself.

In response to the above problems, scientists have made unremitting efforts. At present, they mainly study from the following three aspects: 1 electrode material nano-particles; 2 bulk phase doping; 3 conductive materials such as carbon or carbon nanotubes Coating is performed to improve its apparent electronic conductivity. The first two are all improving the rate performance of the material from the microstructure, but improving the conductivity can fundamentally overcome the problem of poor rate performance. Although coating the material with a conductive material is a method for improving the electronic conductivity of the material, the effect of the improvement is relatively poor because the amount of coating is not excessive. Over-coating will increase the barrier of Li+ diffusion and migration, which is not conducive to the progress of the electrode reaction kinetics process, resulting in a decrease in the material discharge capacity. If the amount of coating is less, the electronic conductivity of the material will be changed. Good results are not obvious. Therefore, it is necessary to open a new path to improve the electronic conductivity of the material. Graphene is currently the material with the lowest resistivity. The valence band and the conduction band of graphene partially overlap at the Fermi level, and are two-dimensional semiconductors with zero energy gap, and carriers can move within a submicron distance without scattering. Graphene is widely used in the preparation of composite materials due to its good electrical conductivity. Therefore, the preparation of the lithium-rich manganese-based solid solution/graphene composite material can effectively solve the problem of poor rate performance of the layered lithium-rich material. Summary of the invention

The object of the present invention is to overcome the defects of the lithium-rich manganese-based solid solution as a positive electrode material of a lithium ion battery, and to prepare a lithium ion battery positive electrode material having a higher rate specific discharge capacity and an excellent high rate cycle performance. The invention provides a novel lithium-rich manganese-based solid solution/graphene composite material and a preparation method thereof, wherein the composite material is characterized in that lithium-rich manganese-based solid solution particles are dispersed in layers of layered graphene, thereby causing charging When discharged, graphene can provide more conductive points and conductive paths for the lithium-rich manganese-based solid solution, thereby improving the apparent conductivity of the composite. The lithium-rich manganese-based solid solution microparticles dispersed between the graphene layers are about

4-8 μm, the thickness of the layered graphene is about l-25 nm.

The lithium-rich manganese-based solid solution of the present invention has the following formula: xLi ₂ Mn0 ₃ *(lx)LiM0 ₂ ; wherein M is a transition metal, preferably M, Co, Mn, Cr, M-Co, M-Mn, Ni- Any of Co-Mn, Fe and Ru, more preferably M-Co, M-Mn, Ni-Co-Mn, most preferably Ni-Co-Mn; 0 < χ < 1, preferably 0.3-0.7, More preferably, it is 0.4-0.6.

The preparation of the lithium-rich manganese-based solid solution/graphene composite of the present invention can be prepared by the following method, which comprises the following steps:

(1) preparing a precursor of a lithium-rich manganese-based solid solution/graphene oxide doped material by a coprecipitation method or a solvothermal method;

(2) pre-calcining the precursor;

(3) subjecting the pre-calcined precursor to a solid phase reaction to obtain a lithium-rich manganese-based solid solution/graphene oxide doped material;

(4) The obtained doping material is mixed with graphene oxide, followed by reduction, thereby obtaining the lithium-rich manganese-based solid solution/graphene composite material. The steps will be described in detail below:

Preparation of a precursor of a lithium-rich manganese-based solid solution/graphene oxide doped material by a coprecipitation method, the coprecipitation method comprising a mixed solution of a salt containing M and Mn, a NaOH solution as a precipitating agent, and ammonia as a complexing agent The aqueous solution is simultaneously added to the graphene bottom liquid, thereby coprecipitating the salt of M and Mn, and then the resulting product is mixed with the lithium compound. Specifically, the coprecipitation method includes:

(1) preparing a mixed solution of salt of M and Mn salt according to a desired metering ratio;

(2) simultaneously reacting the mixture solution, the NaOH solution as a precipitating agent, and the ammonia aqueous solution as a complexing agent into a reactor containing a graphene oxide bottom liquid under an inert gas atmosphere;

(3) The reaction product of the step (2) is mixed with a lithium compound, and if necessary, ball-milled. The proportion of transition metal ions in the coprecipitation method step (1) is determined by the ratio of M and Mn in the desired lithium-rich manganese-based solid solution structural formula. Wherein the total concentration of the transition metal ion is not critical, generally 0.6-1.0mol L ^-1, more preferably 0.6-0.9mol L ^-1, and most preferably 0.6-0.8mol L ^-1. The salt of M and Mn in the step (1) may be an organic or inorganic salt of the corresponding metal, which is soluble in water at room temperature. For example, the salt may be one or more of an acetate, a nitrate or a sulfate. The lithium compound in the step (3) may be one or more of an acetate, a nitrate or a lithium hydroxide.

The amount of the NaOH and aqueous ammonia solution used in the coprecipitation method (2) varies depending on the amounts of the metal ions M and Mn, provided that the metal ions are precipitated and complexed. For example, the amount of NaOH in the reaction mixture may be from 1.0 to 4.0 mol-L ^-1 , preferably from 1.0 to 3.0 mol-L ^-1 , more preferably from 1.0 to 2.5 ηηο. ΐ based on the total reaction solution. The amount of ammonia solution (in terms ΝΗ ₃₎ may be 0.2-0.8mol L, preferably (-O mol I ^1, more preferably 0.2-0.5mol L, based on total reaction solution.

The reaction temperature in the step ( ² ) is ³ 0 to ⁸⁰ . C, preferably ⁴ ⁷ 0 0_. C is more preferably ⁵ 0_ ⁶⁰ . C; The reaction time is 2-36 h, preferably 6-28 h, more preferably 10-26 h, and most preferably 12-24 h.

The amount of graphene oxide used in the coprecipitation method step (2) can be varied as needed, for example, the total amount of the raw materials (the total weight of the M salt and the Mn salt) and the weight ratio of the graphene oxide are 10:0.1- 10: 0.8, preferably 10: 0.2-10: 0.7, preferably 10: 0.4-10: 0.6. After the completion of the coprecipitation reaction, the obtained product was suction filtered, washed, and vacuum dried to obtain the precursor.

The reactor used for coprecipitation was a CSTR reactor.

The amount of lithium salt used in step (3) is determined by the desired final lithium-rich manganese-based solid solution structure. The ball milling in the step (3) can be carried out in the presence of a dispersing agent. Suitable dispersing agents are well known to those skilled in the art, such as ethanol, acetone, petroleum ether and the like. The milling time is not critical and is usually from 2 to 12 hours, preferably from 3 to 8 hours, more preferably from 4 to 6 hours.

Preparation of Lithium Manganese-Based Solid Solution / Graphene Oxide Doped Material Precursor by Solvothermal Method

The solvothermal method includes adding oxalic acid to a salt containing Li, Mn, and M and a graphene oxide, whereby a solvothermal reaction occurs to obtain the lithium-rich manganese-based solid solution/graphene oxide doping. The precursor of the material. Specifically, the solvothermal method includes:

(1) Dissolving a salt of Li, Mn and M and graphene oxide (for a salt of Li, Mn and M) or a solvent (for graphene oxide) according to a desired doping material ratio Forming a mixture;

(2) preparing an oxalic acid solution, which is added to the mixed dispersion obtained in the step (1);

(3) The solution was completely transferred to a kettle to carry out a reaction to obtain a precursor of the lithium-rich manganese-based solid solution/graphene oxide-doped material.

The proportion of transition metal ions in the solvothermal step (1) is determined by the ratio of ruthenium and Mn in the desired lithium-rich manganese-based solid solution structure. Wherein the total concentration of the transition metal ion is not critical, generally 0.6-1.0mol L ^-1, more preferably 0.6-0.9mol L ^-1, and most preferably 0.6-0.8mol L ^-1. The salts of Li, Mn and M may be organic or inorganic salts of the corresponding metals. For example, the salt may be one or more of an acetate, a nitrate or a sulfate. The weight ratio of the total amount of the raw materials (the total weight of the salts of Li, Mn and M) to the graphene oxide is from 10:0.1 to 10:1, preferably from 10:0.1 to 10:0.8, more preferably from 10:0.2 to 10: 0.7, most preferably 10:0.4-10:0.6.

The solvent in the step (1) is ethanol or decyl alcohol, preferably ethanol.

In the solvothermal step (2), the concentration and amount of the oxalic acid solution are not particularly limited, and it is capable of undergoing a sufficient solvothermal reaction with the transition metal ion. For example, the concentration of the oxalic acid solution may be ( ^.Omol.I ¹ , preferably 0.5-1.5 mol.L ^-1 , more preferably Ο, δ-υιηοΙ.Ι ¹ » the amount of oxalic acid (as oxalic acid: 1\1 er Ratio can be 2.0:1-1.0:1, preferably 1.6: 1-1.0: 1, more preferably 1.5: 1-1.0: 1.

The reaction temperature in the solvothermal step (3) is usually from 100 to 300 ° C, preferably from 150 to 250 ° C, more preferably from 180 to 220 ° (: The reaction time is usually from 2 to 24 hours, preferably 4-20 hours, more preferably 10-18 hours.

Precalcination

The precursor of the obtained lithium-rich manganese-based solid solution/graphene oxide-doped material is pre-calcined. The pre-calcination temperature is usually from 300 to 700 ° C, preferably from 300 to 600 ° C, more preferably from 300 to 500 ° (: The pre-calcination time is usually from 1 to 8 hours, preferably from 2 to 6 hours, more preferably from 3 -5 hours. The pre-calcination is usually carried out under an inert atmosphere. The inert gas used is, for example, nitrogen, argon or the like.

Solid phase reaction

The pre-calcined material is sintered to cause a solid phase reaction. The solid phase reaction is carried out under an inert atmosphere. The sintering time in an inert atmosphere is 2 to 24 hours, preferably 4 to 20 hours, more preferably 8 to 18 hours. The temperature of the solid phase reaction is 800 to 1000 ° C, preferably 850 to 1000 ° C, more preferably 900 to 950 ° (:. After sintering, the obtained product is naturally cooled to room temperature, thereby obtaining the lithium-rich manganese Base solid solution / graphene oxide doped material.

Doping material and graphene oxide mixing and reduction

The resulting doping material is mixed with graphene oxide, subsequently reduced in a reducing atmosphere, and cooled to room temperature, thereby obtaining the lithium-rich manganese-based solid solution/graphene composite material. The mixing ratio of the doping material to graphene oxide is not particularly limited, and may be any ratio as needed, and is, for example, usually 10:0.1 to 10:1.0, preferably 10:0.3 to 10:0.8, more preferably 10:0.4-10:0.6, by weight.

The mixing method may be various conventional methods known in the art, such as dry blending, or dispersing the two in a dispersing agent such as ethanol, followed by drying, wherein the drying temperature may be, for example, 80 °C.

The reduction can be carried out in a tube furnace; the reduction time can be, for example, from 1 to 24 hours, preferably from 4 to 20 hours, more preferably from 6 to 18 hours, and most preferably from 8 to 16 hours. The reduction temperature may be from 600 to 1100 ° C, preferably from 700 to 1000 ° C, more preferably from 800 to 950 ° C, most preferably from 800 to 900 ° (: The reducing atmosphere may be hydrogen or hydrogen and an inert gas such as nitrogen. , a mixture of helium, neon, etc. (the volume ratio is, for example, 1: 0.1-1: 100). The novel composite material of the present invention can be used as a positive electrode material for a lithium ion battery.

Compared with the pure lithium-rich manganese-based solid solution, the novel composite material of the present invention and the preparation method thereof have the following advantages:

(1) The process of the preparation process is simple, the cycle is short, the efficiency is high, and the scale can be produced;

(2) The structure of the prepared lithium-rich manganese-based solid solution/graphene composite material is characterized in that the lithium-rich manganese-based solid solution is doped once by using graphene oxide, and then the surface is modified by graphene oxide. Finally, restore. The lithium-rich manganese-based solid solution particles are between the layered graphene, thereby causing graphene to provide more conductive points and conductive paths for the lithium-rich manganese-based solid solution during charge and discharge, thereby improving the apparent conductance of the composite material. Rate

(3) In the lithium-rich manganese-based solid solution/graphene composite material of the present invention, the lithium-rich manganese-based solid solution between the graphene layers is about 4-8 μm, and the thickness of the layered graphene is about 1 to 25 nm.

(4) The lithium-rich manganese-based solid solution/graphene composite material of the invention has remarkably improved rate performance, and the pure lithium-rich manganese-based solid solution has a discharge capacity of 100 mAh g ¹ when charged and discharged in O^100mAh-g- ¹ ). The composite material of the present invention has a discharge capacity of 258 mAh g ^-1 and an increase of 58 mAh g ^-1 at the same rate.

Therefore, the lithium-rich manganese-based solid solution/graphene composite material of the invention successfully overcomes the defects of the pure lithium-rich manganese-based solid solution, and is a promising lithium ion battery cathode material.

In particular, the invention relates to the following subject matter:

A lithium-rich manganese-based solid solution/graphene composite material, wherein the lithium-rich manganese-based solid solution has a general formula of xLi ₂ Mn0 ₃ (lx)LiM0 ₂ , wherein !V & M, Co, Mn, Cr, M- Any of Co, M-Mn, Ni-Co-Mn, Fe and Ru, 0<χ<1; characterized in that the lithium-rich manganese-based solid solution is dispersed in the form of particles in the layer of the layered graphene.

2. The lithium-rich manganese-based solid solution/graphene composite according to item 1, characterized in that the lithium-rich manganese-based solid solution between the graphene layers is about 4-8 μm, and the layered graphene has a thickness of about l- 25nm.

A method of producing a lithium-rich manganese-based solid solution/graphene composite according to Item 1 or 2, characterized in that the method comprises the steps of:

(1) preparing a precursor of a lithium-rich manganese-based solid solution/graphene oxide doped material by a coprecipitation method or a solvothermal method; (2) pre-calcining the precursor;

(3) subjecting the pre-calcined precursor to a solid phase reaction to obtain a lithium-rich manganese-based solid solution/graphene oxide doping material;

(4) The obtained doping material is mixed with graphene oxide, followed by reduction, thereby obtaining the lithium-rich manganese-based solid solution/graphene composite material.

4. The method according to item 3, characterized in that the coprecipitation method comprises: adding a mixed solution containing a salt of M and Mn, a NaOH solution as a precipitating agent, and an aqueous ammonia solution as a complexing agent to a graphene base liquid Thereby, a salt of M and Mn is coprecipitated, and then the obtained product is mixed with a lithium compound, thereby preparing a precursor of the lithium-rich manganese-based solid solution/graphene oxide doping material.

5. The method according to item 3 or 4, characterized in that the solvothermal method comprises adding oxalic acid to a body containing a salt of Li, Mn and M and graphene oxide, whereby a solvothermal reaction occurs, thereby obtaining a A precursor of a lithium-rich manganese-based solid solution/graphene oxide doped material.

The method according to any one of the items 3-5, characterized in that the pre-calcination is carried out at 300-700 under an inert atmosphere. C, preferably 300-600. C, more preferably 300-500. The temperature of C is carried out.

7. Process according to any one of the items 3-6, characterized in that the solid phase reaction is carried out at an inert atmosphere at 800-1000. C, preferably 850-1000. C, more preferably 900-950. The temperature of C is carried out.

The method according to any one of the items 3-7, characterized in that the reduction is in a reducing atmosphere at 600-1100. C, preferably 700-1100. C, more preferably 800-950. C, most preferably carried out at a temperature of from 800 to 900 °C.

9. The method according to item 8, wherein the reducing gas used is hydrogen or a mixture of hydrogen and nitrogen.

10. Use of a lithium-rich manganese-based solid solution/graphene composite material according to item 1 or 2 as a positive electrode material for a lithium ion battery. Drawing tube

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a TEM image of graphene oxide prepared according to Example 1.

2 is an XRD pattern of a lithium-rich manganese-based solid solution/graphene composite prepared according to Example 1. 3 is a graph showing the rate performance of a lithium-rich manganese-based solid solution/graphene composite prepared according to Example 1.

4 is an SEM image of a lithium-rich manganese-based solid solution prepared by a solvothermal method according to Example 4. Figure 5 is a graph showing the first week charge and discharge of a lithium-rich manganese-based solid solution/graphene composite material prepared by a solvothermal method according to Example 4 at 0.5C. detailed description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be further described in detail with reference to the accompanying drawings. Example 1 Preparation of lithium-rich manganese-based solid solution/graphene composite material by coprecipitation using nitrate as raw material

(1) Prepare a mixed solution of Μ(Ν0 ₃ ) ₂ ·6Η ₂ 0, Co(N0 ₃ ) ₂ -6H ₂ 0 and Mn(N0 ₃ ) ₂ in the desired molar ratio (0.58:0.11:0.11), transition The total concentration of metal ions is 0.8 mol.L ^-1 . A 1.5 mol.L ^-1 NaOH solution was used as a precipitant, and a 0.3 mol.L ^-1 aqueous ammonia solution was used as a complexing agent. A certain amount of graphene oxide was added to the bottom of the CSTR container, and the total amount of raw materials (M(N0 ₃ ) 2.6) H ₂ 0, Co(N0 ₃ ) ₂ .6H ₂ 0 and Mn(N0 ₃ ) ₂ ) and graphene oxide weight ratio is 10:0.5;

(2) Under the protection of inert gas, the three solutions are fed into the reactor containing the graphene bottom liquid by a peristaltic pump, and the pH is controlled at pH=ll, the stirring speed is 1000 rpm, and the reaction temperature is 60. C, reaction time 12h. After filtering, washing, vacuum drying, Mno.ssMo.nCoo. OH) graphene oxide precursor;

(3) The obtained precursor was ball-milled with lithium acetate at a certain molar ratio (1:1.06), during which 10 mL of ethanol was added as a dispersing agent. After ball milling, the material was dried, ground and refined, and pressed at 30 MPa, first at 450 under a nitrogen atmosphere. Pre-calcination was carried out for 8 hours at C, followed by 800. Under C, it is sintered at a high temperature for 12 hours in a nitrogen atmosphere, and naturally cooled to room temperature to obtain a lithium-rich manganese-based solid solution/graphene oxide doped material;

(4) The obtained doping material and the graphene oxide were mixed again in a certain ratio (10:0.5, weight ratio), in 100 mL of ethanol, at 80. Stir at a constant temperature in C, then in a tube furnace at 900. C, reduction in nitrogen atmosphere for 10h, natural cooling to room temperature, to obtain lithium-rich manganese-based solid solution Body/graphene composite.

An SEM image of the lithium-rich manganese-based solid solution/graphene composite prepared according to Example 1 is shown in Fig. 1.

The XRD pattern of the lithium-rich manganese-based solid solution/graphene composite prepared according to Example 1 is shown in Fig. 2.

The rate performance of the lithium-rich manganese-based solid solution/graphene composite prepared according to Example 1 is shown in Fig. 3. It can be seen from the figure that the discharge capacity of the composite material is 225 mAh.g at a discharge current of 0.5 C (100 mA/g). Example 2 Preparation of a lithium-rich manganese-based solid solution/graphite by coprecipitation using sulfate as a raw material Arene composite

(1) the desired molar ratio (0.58: 0.11: 0.11) prepared _{_{MS0 4 '6H 2 0, CoS0}} 4' 7H ₂ 0 and a mixed solution of MnS0 ₄ .H ₂ 0, and the total concentration of the transition metal ion is 1.0mol.L ^-1 . Using .Omol.L ¹ NaOH solution as precipitant and O.Smol.L ¹ ammonia solution as complexing agent, a certain amount of graphene oxide is added to the bottom of CSTR container, among which raw materials (MS0 ₄ .6H ₂ 0 , CoS0 ₄ .7H ₂ 0 and MnS0 ₄ .H ₂ 0) and graphene oxide weight ratio of 10:0.5;

(2) Under the protection of inert gas, the three solutions are fed into the reactor containing the graphene bottom solution by a peristaltic pump, and the pH is controlled to be ll, the stirring speed is 1000 rpm, and the reaction temperature is 50. C, reaction time 24h. After suction filtration, washing, and vacuum drying, Mno.ssMo.nCoo. OH) graphene oxide precursor is obtained;

(3) The obtained precursor was ball-milled with lithium hydroxide at a certain molar ratio (1:1.06), and 100 mL of ethanol was added as a dispersing agent. After ball milling, the material was dried, ground and refined, and pressed at 30 MPa, first at 450 under a nitrogen atmosphere. Pre-calcination was carried out for 3 hours at C, followed by 900. Under C, it is sintered at a high temperature for 16 hours in an inert atmosphere, and naturally cooled to room temperature to obtain a lithium-rich manganese-based solid solution/graphene oxide doped material;

(4) The obtained doping material and the graphene oxide were mixed again in a certain ratio (10:0.5, weight ratio), and dispersed in ethanol at 80. Stir at a constant temperature in C, then in a tube furnace at 700. C, reduction under nitrogen atmosphere for 12 h, and natural cooling to room temperature, to obtain a lithium-rich manganese-based solid solution/graphene composite material. The composite had a discharge capacity of 248 mAh'g ^{-1 at a} discharge current of 0.5 C (100 mA/g). Example 3 A lithium-rich manganese-based solid solution/graphene composite material was prepared by a solvothermal method using acetate as a raw material and decyl alcohol as an organic solvent.

(1) A molar ratio (0.58:0.11:0.11) of CH ₃ COOLi, (CH ₃ COO) ₂ Co, (CH ₃ COO) ₂ Mn, (CH ₃ COO) ₂ M, and graphene oxide (total amount of raw materials ( CH ₃ COOLi, (CH ₃ COO) ₂ Co, (CH ₃ COO) ₂ Mn and (CH ₃ COO) ₂ M) and graphene oxide in a weight ratio of 10:0.5) dissolved or dispersed (for graphene oxide In a sterol, stir well to form a mixture;

(2) preparing an oxalic acid solution of 1.0 mol.I / ¹ , slowly added to the mixed solution formed in the previous step according to a certain molar ratio (the molar ratio of the total amount of Co and M ions to oxalic acid is 1.3:1);

(3) magnetically stirring for ² h at room temperature to pre-react;

(4) Transfer the solution all the way to the reaction vessel at 200. Reaction at C for 10 h;

(5) ⁹ 0. C-cooled in a constant temperature water bath to obtain a precursor/graphene oxide material;

(6) The precursor/graphene oxide material was placed in a tube furnace, and pre-calcined at 550 ° C for 7 hours under a nitrogen atmosphere to obtain a precursor of a high-temperature synthesis reaction; Under C, sintering at a high temperature for 12 hours under a nitrogen atmosphere, a lithium-rich manganese-based solid solution/graphene oxide doped material is obtained;

(7) The obtained doping material and the graphene oxide are mixed again in a certain ratio (10:0.5, weight ratio), in ethanol, at 80. Stir under constant temperature at C, then in a tube furnace at 900. C, reduced in nitrogen for 12 h, and naturally cooled to room temperature to obtain a lithium-rich manganese-based solid solution/graphene composite.

At a discharge current of 0.5 C (100 mA/g), the composite has a discharge capacity of 250 mAh.g. Example 4 A lithium-rich manganese-based solid solution/graphene composite material was prepared by a solvothermal method using acetate as a raw material and ethanol as an organic solvent.

(1) Chemically molar ratio (0.58:0.11:0.11) of CH ₃ COOLi, (CH ₃ COO) ₂ Co, (CH ₃ COO) ₂ Mn, (CH ₃ COO) ₂ M and graphene oxide in ethanol , fully stirred to form a mixed solution; (2) preparing a oxalic acid solution of lO mol.L- ¹ , slowly adding the mixed solution formed in the previous step according to a ratio of Mn, Co and M ions to a molar ratio of oxalic acid of 1.3:1;

(3) magnetically stirring for ² h at room temperature to pre-react;

(4) Transfer the solution all the way to the reaction vessel at 180. Reaction under C for 18h;

(5) ⁸ 0. C-cooled in a constant temperature water bath to obtain a precursor/graphene oxide material;

(6) The precursor/graphene oxide material was placed in a tube furnace at 400 under a nitrogen atmosphere. Pre-calcination was carried out for 6 h at C to obtain a precursor for the high-temperature synthesis reaction; then at 850. Under C, sintering at high temperature for 18 h under nitrogen atmosphere, the lithium-rich manganese-based solid solution/graphene oxide doped material is obtained (Fig. 4);

(7) The obtained doping material and the graphene oxide are mixed again in a certain ratio (10:0.5, weight ratio), in ethanol, at 80. Stir under constant temperature at C, then in a tube furnace at 950. C, reduced in nitrogen for 12 h, and naturally cooled to room temperature to obtain a lithium-rich manganese-based solid solution/graphene composite.

At a discharge current of 0.5 C (100 mA/g), the discharge capacity of the composite is

258 mAh g ^-1 (Figure 5).

It is to be understood that the above description of the preferred embodiments of the invention is in no way intended to be construed as limiting the scope of the invention.

Claims

Rights request

A lithium-rich manganese-based solid solution/graphene composite material, wherein the lithium-rich manganese-based solid solution has a general formula of xLi ₂ Mn0 ₃ (lx)LiM0 ₂ , wherein 1\1 is, Co, Mn, Cr, M Any of -Co, M-Mn, Ni-Co-Mn, Fe and Ru, 0<χ<1; characterized in that the lithium-rich manganese-based solid solution is dispersed in the form of particles in the layer of the layered graphene .

The lithium-rich manganese-based solid solution/graphene composite according to claim 1, wherein the lithium-rich manganese-based solid solution between the graphene layers has a size of about 4 to 8 μm, and the layered graphene has a thickness of about 1 to 25 leg.

A method of preparing a lithium-rich manganese-based solid solution/graphene composite material according to claim 1 or 2, characterized in that the method comprises the following steps:

(2) pre-calcining the precursor;

The method according to claim 3, wherein said coprecipitation method comprises: adding a mixed solution of a salt containing cerium and Mn, a NaOH solution as a precipitating agent, and an aqueous ammonia solution as a complexing agent to the graphene base liquid. Thereby, a salt of M and Mn is coprecipitated, and then the obtained product is mixed with a lithium compound, thereby preparing a precursor of the lithium-rich manganese-based solid solution/graphene oxide doping material.

The method according to claim 3 or 4, characterized in that the solvothermal method comprises adding oxalic acid to a dispersion comprising a salt of Li, Mn and M and graphene oxide, whereby a solvothermal reaction occurs, thereby obtaining A precursor of the lithium-rich manganese-based solid solution/graphene oxide doped material.

6. Process according to any one of claims 3-5, characterized in that the pre-calcination is between 300 and 700 under an inert atmosphere. C, preferably 300-600. C, more preferably 300-500. The temperature of C is carried out.

The method according to any one of claims 3-6, characterized in that the solid phase reaction is at 800-1000 ° C, preferably 850-1000 ° C, more preferably 900-950 ° C under an inert atmosphere. The temperature is carried out.

Process according to any one of claims 3-7, characterized in that the reduction is in the reducing atmosphere at 600-1100 ° C, preferably 700-1100 ° C, more preferably 800-950 ° C Most preferably, it is carried out at a temperature of from 800 to 900 °C.

9. A method according to claim 8 wherein the reducing gas used is hydrogen or a mixture of hydrogen and nitrogen.

Use of a lithium-rich manganese-based solid solution/graphene composite material according to claim 1 or 2 as a positive electrode material for a lithium ion battery.