Lithium ion battery anode material with LiCoO2 coated on surface and preparation method for lithium ion battery anode material

Abstract

The invention provides a lithium ion battery anode material with LiCoO2 coated on the surface and a preparation method for the lithium ion battery anode material. The preparation method comprises the following steps of: uniformly mixing an anode material, a low-melting-point salt, a lithium compound and a cobalt compound; raising the temperature to be between the melting point and the boiling point of the low-melting-point salt to form a molten salt medium; reacting for a certain period of time, and then cooling to the room temperature; and washing and drying to obtain the lithium ion battery anode material with the LiCoO2 coated on the surface. By the preparation method, the molten salt is used as a reaction medium, the process is simple, the synthesis temperature is low, the holding time is short, a layer of electrochemical active substance is formed on the surface of base material particles, the performance and the structure of the base material of the anode material are not changed, and advantages of a modified layer is obtained.

Description

Technical field: [0001] The invention relates to the field of lithium ion batteries, in particular to a lithium ion battery cathode material with lithium cobalt oxide coated on the surface and a preparation method thereof. Background technique: [0002] With the miniaturization and thinning of portable electronic devices such as mobile phones, digital cameras, and notebook computers, the market's requirements for the energy density, electrochemical performance, and safety performance of lithium-ion batteries continue to increase. The technical bottleneck of lithium-ion batteries mainly lies in the cathode material. At present, the commonly used cathode materials for lithium-ion batteries are LiCoO 2 、LiNi 0.8 co 0.2 o 2 、LiNi 0.8 co 0.15 al 0.05 o 2 、LiNi 1 / 3 co 1 / 3 mn 1 / 3 o 2 , LiMn 2 o 4 、LiFePO 4 wait. These cathode materials have their own disadvantages: LiCoO 2 The price is high, the structure is unstable after the charging voltage exceeds 4.2V, and the...

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Problems solved by technology

These cathode materials have their own disadvantages: LiCoO 2 The price is high, the structure is unstable after the charging voltage exceeds 4.2V, and the safety becomes poor; LiNi 0.8 co 0.2 o 2 The cycle performance of LiNi is not good, the water absorption is strong, and the storage performance is poor; LiNi 0.8 co 0.15 Al 0.05 o 2 Easy to absorb water, poor storage performance; LiNi 1 / 3 co 1 / 3 mn 1 / 3 o 2 The structure of LiMn is unstable, and the high temperature storage performance is not good; LiMn 2 o 4 The capacity is low and the high temperature performance is poor; LiFePO 4 Low electrical conductivity, poor low temperature performance

[0004] Of particular note is the recent adoption of LiMO 2 (M=Co, Al, Sn, Zn), LiMPO 4 Active substances such as (M=Fe, Co) modify the surface of positive electrode materials (such as: [1] Cao Hui, Xia Baojia, Han Xuewu. Surface coating materials and techniques for lithium ion battery positive electrode materials: China, CN1242501[ P].2006-02-15.[2]H.Wang, W.D.Zhang, L.Y.Zhu, M.C.Chen.Effect of LiFePO 4 coating on electrochemical performance of LiCoO 2 at high temperature[J].Solid State Ionics, 2007,178:131-136.[3]H.Lee, M.G.Kim, J.Cho.Olivine LiCoPO 4 phase grown LiCoO 2 cathode material for high density Li batteries [J] Electrochemistry Communications, 2007, 9: 149-154. [4] J.T.Son, E.J.Cairns.Characterization of LiCoO 2 coated Li 1.05 Ni 0.35 co 0.25 mn 0.4 o 2 cathode material for lithium secondary cells[J].Journal of Power Sources, 2007,166:343-347), however, the method used in the coating modification process is still the conventional sol-gel method, solution adsorption method or precipitation These methods are acceptable for the coating modification of inactive substances, but when used for the modification of active substances, there are problems such as that the firing temperature between the substrate and the modified layer cannot be unified, the firing time is too long, and the resulting product Disadvantages such as inability to guarantee consistency

In addition, because the coating modification process must first go through a liquid phase process, the precursor substances in the liquid phase are generally strong acid and weak alkali salts, and the acidity of the solution is relatively high. The active substance will be dissolved to varying degrees, so that the structure of the active substance change, resulting in a reduction in its capacity or deterioration in cycle performance

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