Preparation method of modified lmo cathode material and use thereof

Abstract

The application provides a preparation method and application of a modified LMO positive electrode material, which comprises the following steps: preparing a MA binary precursor by a coprecipitation method; then mixing the MA binary precursor and a KMnO4 solution to prepare a MMA ternary precursor by a microwave reaction; uniformly mixing the MMA ternary precursor and a lithium salt, and placing the mixture in an oxygen or air atmosphere furnace for calcination, so that a modified LMO composite material is obtained after cooling. In the LMO material prepared by the application, the Al and Mg elements are introduced by a liquid phase method, so that the material has good uniformity, good structural stability, and the cycle performance is greatly improved compared with pure LMO.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of lithium ion batteries, in particular to a preparation method of modified LMO positive electrode material and its use. BACKGROUND

[0002] Lithium ion battery is a kind of high energy density, high efficiency energy storage device, which has been widely used in portable digital devices, electric vehicles and other fields. Lithium ion battery system is composed of four key materials, namely positive electrode material, negative electrode material, separator and electrolyte, so the properties of the materials are directly related to the performance of lithium ion battery.

[0003] Lithium manganate material has the advantages of low price, high potential, environmental friendliness, high safety performance, etc. and has attracted people's attention. However, pure lithium manganate has poor cycle performance in the cycle process due to the occurrence of Jahn-Teller effect, so people change its cycle performance by doping pure lithium manganate material. The conventional doping method is solid phase reaction, which has poor uniformity, and the liquid phase method can well solve this problem. SUMMARY

[0004] Based on the technical problems existing in the background technology, the present application proposes a preparation method of modified LMO positive electrode material and its use.

[0005] The preparation method of modified LMO positive electrode material proposed by the present application comprises the following steps:

[0006] S1, uniformly mix Mg salt solution and Al salt solution, adjust pH, and obtain MA precursor after aging;

[0007] S2, uniformly mix the MA precursor with KMnO4 solution, microwave process several times, and obtain MMA precursor after cooling and filtering;

[0008] S3, mix the MMA precursor with lithium salt, and obtain modified LMO positive electrode material after calcination and cooling and grinding.

[0009] Preferably, the modified LMO positive electrode material has the molecular formula LiMg x Al y Mn z O4, wherein x+y+z=2, x>0, y>0, and z:(x+y)=(99-80):(1-20).

[0010] Preferably, the pH in S1 ranges from 8 to 12, and the aging time is 0.1-12h.

[0011] Preferably, the Al salt in S1 is one or more of Al(NO)3 and AlCl3.

[0012] Preferably, the Mg salt in S1 is one or more of Mg(NO)2, MgCl2.

[0013] Preferably, the concentration of the KMnO4 solution in S2 is 1-10 M.

[0014] Preferably, the power of the microwave reaction in S2 is 100-2000 W, the single reaction time is 0.1-10 h, and the number of repetitions is 1-20.

[0015] Preferably, the lithium salt in S3 is one or more of LiCO3, LiOH, LiNO3; and the molar ratio of the MMA precursor to the lithium salt is 1:(1-1.5).

[0016] Preferably, the calcination in S3 is first pre-calcination at 450-650℃ for 4-12 h, and then sintering at 800-950℃ for 8-36 h.

[0017] Another object of the present application is to provide a modified LMO cathode material prepared by the above method.

[0018] Another object of the present application is to provide the use of the modified LMO cathode material as a cathode active material for lithium batteries.

[0019] The modified LMO cathode material prepared by the present application improves the crystal structure of pure-phase LMO by uniformly introducing Mg and Al, greatly improving the cycle performance of the material.

[0020] The lithium ion battery cathode comprises: a metal current collector, a cathode mixture coated on the current collector, and the cathode mixture comprising a cathode active material modified LMO cathode material, a binder, and a conductive agent. The current collector is metal Al or Al alloy, the conductive agent is acetylene black or SP, and the binder is PVDF.

[0021] The preparation method of the lithium ion battery cathode is as follows:

[0022] (a) mixing and grinding 80 parts by weight of the modified LMO cathode material and 10 parts by weight of the conductive agent to obtain a cathode active material powder; then adding 10 parts by weight of a binder and NMP solvent to obtain a cathode mixture slurry;

[0023] (b) coating the cathode mixture slurry on a metal current collector to form a layer with a thickness of 10-500 microns, and then vacuum drying in an oven at 80℃ for 12-24 h to remove the solvent, thereby obtaining a cathode.

[0024] Furthermore, the present application provides a lithium ion battery with good cycle performance assembled by using the positive electrode, which comprises a positive electrode, a negative electrode, a separator and an electrolyte, wherein the positive electrode is the positive electrode prepared above. The pair electrode comprises a pair electrode active material, the pair electrode active material comprises one of lithium intercalation material, lithium alloy material and lithium metal; and the electrolyte and the separator are placed between the negative electrode and the pair electrode.

[0025] The electrolyte comprises an electrolyte salt and an organic solvent and an additive. The electrolyte salt is one selected from lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), lithium perchlorate (LiClO4), lithium trifluoromethanesulfonate (CF3SO3Li), lithium bis(trifluoromethyl) sulfonylimide (LiN(SO2CF3)2) and combinations thereof; the organic solvent is one selected from benzene, toluene, ethanol, isopropanol, N,N-dimethylformamide, N,N-dimethylpyrrolidone, tetrahydrofuran, dimethylacetate, dimethylcarbonate, methyl ethyl carbonate, methyl propyl carbonate, methyl propionate, ethyl propionate, methyl acetate, ethyl acetate, propyl acetate, ethyl carbonate, propyl carbonate, γ-butyrolactone, diethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, ether compound, crown ether compound, dimethoxyethane compound, 1,3-dioxolane or combinations thereof. The electrolyte additive is one selected from SO2, NO x , CO2, vinylene carbonate, fluoroethylene carbonate, vinyl acetate, lithium carbonate, lithium nitrate or combinations thereof.

[0026] The separator is a polymer microporous membrane, such as polyethylene and polypropylene microporous membrane, multilayer microporous membrane of polyethylene and polypropylene membrane, and a film after surface modification of the above materials, such as a composite ceramic separator coated with ceramic powder (aluminum oxide, silicon oxide, etc.) on polyolefin.

[0027] The present application has the following advantages: the preparation method of the present application can control the particle size in the preparation process by using liquid phase method, and solves the problem of poor material uniformity; the present application improves the crystal structure of pure phase LMO by uniformly introducing Mg and Al, so that the structural performance of the material is stable and the cycle performance is greatly improved; the preparation method of the present application is simple to operate and is conducive to large-scale production. DETAILED DESCRIPTION

[0028] The technical solutions of the present application are described in detail through specific embodiments.

[0029] Example 1

[0030] 1) Mix 1M MgCl2 solution and 1M AlCl3 solution uniformly, add 1M NaOH / NaCO3 solution dropwise to the above mixed solution, adjust the pH to 9.5, and age for 0.1h to obtain MA precursor;

[0031] 2) The 0.01M MA precursor is mixed with 1M KMnO4 solution and stirred uniformly, and then reacted under 1000W microwave for 0.2h, and the microwave treatment is repeated for 5 times, and the MMA precursor is obtained after cooling and filtration;

[0032] 3) The MMA precursor and LiCO3 are mixed according to a molar ratio of 1:1.1, and then placed in an air atmosphere furnace and pre-fired at 500°C for 5h, and then heated to 900°C for calcination for 24h, and then cooled and ground to obtain the modified LMO positive electrode material LiMg 0.1 Al 0.1 Mn 1.8 O4.

[0033] Example 2

[0034] 1) The 2M MgCl2 solution and the 1M AlCl3 solution are mixed uniformly, and then the 2M NaOH / NaCO3 solution is added dropwise into the mixed solution, and the pH is adjusted to 9, and then the MA precursor is obtained after aging for 0.1h;

[0035] 2) The 0.01M MA precursor is mixed with 1M KMnO4 solution and stirred uniformly, and then reacted under 500W microwave for 0.5h, and the microwave treatment is repeated for 10 times, and the MMA precursor is obtained after cooling and filtration;

[0036] 3) The MMA precursor and LiCO3 are mixed according to a molar ratio of 1:1.1, and then placed in an air atmosphere furnace and pre-fired at 500°C for 6h, and then heated to 950°C for calcination for 24h, and then cooled and ground to obtain the modified LMO positive electrode material LiMg 0.075 Al 0.075 Mn 1.85 O4.

[0037] Example 3

[0038] 1) The 1M MgCl2 solution and the 1M AlCl3 solution are mixed uniformly, and then the 1M NaOH / NaCO3 solution is added dropwise into the mixed solution, and the pH is adjusted to 10, and then the MA precursor is obtained after aging for 0.1h;

[0039] 2) The 0.01M MA precursor is mixed with 1M KMnO4 solution and stirred uniformly, and then reacted under 1000W microwave for 0.1h, and the microwave treatment is repeated for 2 times, and the MMA precursor is obtained after cooling and filtration;

[0040] 3) The MMA precursor and LiCO3 are mixed according to a molar ratio of 1:1.1, and then placed in an air atmosphere furnace and pre-fired at 500°C for 5h, and then heated to 950°C for calcination for 24h, and then cooled and ground to obtain the modified LMO positive electrode material LiMg 0.125 Al 0.125 Mn 1.75 O4.

[0041] Comparative Example 1

[0042] 1) 1M KMnO4 solution was reacted under 1000W microwave for 0.2h, and the microwave treatment was repeated 5 times. After cooling and filtration, MnO2 was obtained;

[0043] 2) MnO2 and LiCO3 were mixed in a molar ratio of 1:1.1, and then pre-fired at 500°C for 5h in an air atmosphere furnace. The temperature was then increased to 900°C for calcination for 24h. After cooling and grinding, LiMn2O4 was obtained.

[0044] Comparative Example 2

[0045] MnO2 and LiCO3 were mixed in a molar ratio of 1:1.1, and then pre-fired at 500°C for 5h in an air atmosphere furnace. The temperature was then increased to 900°C for calcination for 24h. After cooling and grinding, LiMn2O4 was obtained.

[0046] Comparative Example 3

[0047] MnO2, MgO2, Al2O3 and LiCO3 were mixed in a molar ratio of 0.9:0.05:0.05:1.1, and then pre-fired at 500°C for 5h in an air atmosphere furnace. The temperature was then increased to 900°C for calcination for 24h. After cooling and grinding, LiMgAlMnO4 was obtained. 0.1 Al 0.1 Mn 1.8 O4.

[0048] The positive electrode materials prepared in the examples and comparative examples were assembled into batteries for performance testing. The batteries were cycled for discharge 500 times at a voltage of 3.0-4.3V and at a rate of 1C. The test data are shown in the following table.

[0049]

[0050]

[0051] In the examples 1-3 of the present application, the modified LMO positive electrode material is prepared by using the liquid phase method, and the cycle performance is obviously higher than that of the modified LMO positive electrode material prepared in the comparative example 3; compared with the comparative example 1, the example 1 is modified by adding Mg and Al elements, especially the co-precipitation method makes Mg and Al uniformly distributed, and the precursor particle size is controlled by the Mg and Al solution concentration and aging time, and then the microwave method is used to make Mn uniformly precipitated on MA, so that the material obtained has stable structure and good cycle performance; compared with the comparative example 2, the comparative example 1 uses the liquid phase method and the comparative example 2 uses the solid phase method, and in the case of basically consistent capacity, the cycle performance of the liquid phase method is better. Therefore, from the above examples and comparative examples, it can be seen that the uniformity of the modified LMO positive electrode material prepared by the liquid phase method in the present application is better than that of the solid phase method, the structure of the modified LMO positive electrode material is more stable, and therefore the cycle performance is better in the case of basically consistent capacity.

[0052] The above merely provides the preferred embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art, according to the technical solution and the inventive concept of the present application, can make equivalent replacements or changes within the technical range disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A method for preparing a modified LMO cathode material, characterized in that, The preparation method comprises the following steps: S1, uniformly mixing Mg salt solution and Al salt solution, adjusting pH to 8-12, and obtaining MA precursor after aging; S2, uniformly mixing and stirring the MA precursor with KMnO4 solution, microwave processing several times, and obtaining MMA precursor after cooling and filtering; S3, mixing the MMA precursor with lithium salt, and then calcining to obtain modified LMO positive electrode material after cooling and grinding; The modified LMO positive electrode material has a molecular formula of LiMg x Al y Mn z O4, wherein x+y+z=2, x>0, y>0, and z:(x+y)=(99-80):(1-20).

2. The method for preparing the modified LMO cathode material according to claim 1, characterized in that, In S1, the aging time is 0.1-12h.

3. The method for preparing the modified LMO cathode material according to claim 1, characterized in that, In S1, the Al salt is one or more of Al(NO)3 and AlCl3; in S1, the Mg salt is one or more of Mg(NO)2 and MgCl2.

4. The method for preparing the modified LMO cathode material according to claim 1, characterized in that, In S2, the concentration of the KMnO4 solution is 1-10M.

5. The method for preparing the modified LMO cathode material according to claim 1, characterized in that, In S2, the microwave processing power is 100-2000W, the single processing time is 0.1-10h, and the repetition number is 1-20.

6. The method for preparing the modified LMO cathode material according to claim 1, characterized in that, In S3, the lithium salt is at least one of LiCO3, LiOH and LiNO3; the molar ratio of MMA precursor to lithium salt is 1:(1-1.5).

7. The method for preparing the modified LMO cathode material according to claim 1, characterized in that, In S3, the calcining is first pre-burning at 450-650℃ for 4-12h, and then sintering at 800-950℃ for 8-36h.

8. A modified LMO cathode material, characterized in that, According to any one of claims 1-7.

9. Use of the modified LMO positive electrode material according to claim 8 as positive electrode active material for lithium batteries.

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