A kind of preparation method of battery cathode material lithium iron phosphate

Abstract

The present invention discloses a method for preparing a battery cathode material lithium iron phosphate. The method comprises the following steps: performing wet ball milling mixing on a lithium source compound, an iron source compound and oxides of doping metal cations until a particle size is less than 1 [mu]m, and then transferring slurry to an reaction kettle to perform high temperature reaction, so that the raw material is subjected atomic-level mixing; adding a carbon source to perform primary carbon coating; performing primary drying; performing primary calcinating; performing secondary carbon coating; performing secondary drying; performing secondary calcinating; and performing grinding. According to the method provided by the present invention, after being subjected to the wet ball milling and then being transferred to the reaction kettle to be subjected to high temperature reaction, the raw material is subjected to the atomic-level mixing, then carbon coating is performed twice and calcinating is performed twice, so as to uniformly coat the surface of lithium iron phosphate particles with the carbon source, so that the possibility that gaps are formed in lithium iron phosphate during the production process is reduced or formed gaps are smaller, thereby improving a product capacity and tap density.

Description

technical field [0001] The invention relates to the technical field of battery materials, in particular to a method for preparing battery material lithium iron phosphate. Background technique [0002] Lithium-ion power battery is currently recognized as the most potential vehicle battery at home and abroad. It is mainly composed of positive electrode materials, negative electrode materials, separators, electrolytes, etc. Among them, positive electrode materials are an important part of lithium-ion batteries and also determine the quality of lithium-ion batteries. Therefore, in terms of resources, environmental protection and safety performance, finding the ideal electrode active material for lithium-ion batteries is still the primary problem to be solved by international energy materials workers. [0003] Lithium cobalt oxide (LiCoO 2 ), lithium manganate (LiMn 2 o 4 ) and lithium iron phosphate (LiFePO 4 ); Lithium cobaltate is currently widely used as a positive electr...

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Problems solved by technology

[0003] Lithium cobalt oxide (LiCoO 2 ), lithium manganate (LiMn 2 o 4 ) and lithium iron phosphate (LiFePO 4 ); Lithium cobaltate is currently widely used as a positive electrode material for small lithium-ion batteries, but because cobalt is toxic, resource reserves are limited and expensive, and batteries assembled with lithium cobaltate materials as positive electrode materials have poor safety and thermal stability. Oxygen will be generated at high temperature, which cannot meet the technical requirements of power batteries; although lithium manganate is cheap, environmentally friendly, safe, and has good rate performance and safety performance, its theoretical capacity is not high, and its cycle performance, thermal stability and high temperature performance are relatively low. Poor, the biggest problem in application is poor cycle performance, especially at high temperature, the trivalent manganese ions in the material and the divalent manganese ions formed on the particle surface during high-rate discharge make the material dissolve significantly in the electrolyte , eventually destroying the structure of lithium manganate and reducing the cycle performance of the material; the lithium manganate materials that can be used in the market are all obtained through modification measures. On the one hand, such modification measures require high-standard Synthetic equipment, on the other hand, also needs to be at the cost of reducing the reversible capacity of the material, so these materials have been difficult to replace lithium cobalt oxide; lithium iron phosphate is a new lithium-ion battery cathode material that has attracted widespread attention in recent years. It has superior safety performance and good cycle performance, and has a good application prospect, but one of the difficulties in the application of lithium iron phosphate is that the conductivity of lithium iron phosphate is low (10-10S / cm), especially for large current discharge , the actual capacity decreases; on the other hand, in the synthesis process and preparation of lithium iron phosphate, it is difficult to control the valence state of iron, which usually needs to be carried out in reducing gas or inert gas.

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