Lithium iron phosphate and ferrous phosphate, and preparation methods thereof

Abstract

The invention discloses lithium iron phosphate and ferrous phosphate, and preparation methods thereof. The preparation method of the ferrous phosphate comprises the following steps of: mixing bivalent iron salt aqueous solution and phosphate ion aqueous solution under the protection of inert gas; controlling the pH value in the reaction process to be between 6.0 and 7.0; drying after the reaction is finished to obtain a spherical ferrous phosphate hydrate precursor; and performing thermal processing to obtain the ferrous phosphate. The preparation method of the lithium iron phosphate comprises the following steps of: uniformly mixing the obtained ferrous phosphate, a phosphorus source compound, a lithium source compound and a carbon source compound; and performing thermal treatment in an inert gas atmosphere at a high temperature to obtain the lithium iron phosphate. The ferrous phosphate precursor with the particle diameter of between 0.5 and 10 mu m can be prepared by the method; reduction reaction is not required in the process of preparing the lithium iron phosphate from the precursor, so the thermal treatment temperature can be greatly reduced; and the prepared lithium iron phosphate material has higher stacking density and higher electrochemical performance and has a great application prospect in the field of lithium ion batteries.

Description

technical field [0001] The invention belongs to the technical field of energy materials, and relates to lithium ion battery positive electrode materials, in particular to lithium iron phosphate, a lithium ion battery positive electrode material, and its precursor, ferrous phosphate, and their preparation methods. Background technique [0002] LiFePO with orthorhombic olivine structure 4 Cathode materials have become ideal cathode materials for power lithium-ion batteries due to their excellent low cost, long cycle life and high safety performance. Its advantages are outstanding, but there are also some shortcomings. The low bulk density and poor high-current electrochemical performance are the main obstacles affecting the application of this material in the field of high-power and large-capacity lithium-ion batteries. Synthesizing powder particles with a spherical shape can greatly increase the packing density of the material; compounding with conductive carbon materials ca...

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Problems solved by technology

Currently commonly used iron source precursors mainly include: ferric phosphate, ammonium ferrous phosphate, ferrous oxalate, ferrous acetate, ferric oxide and ferric oxide; It must go through a high-temperature reduction reaction, and the high-temperature reduction reaction is difficult to control, so the ferric salt due to incomplete reaction or elemental iron due to excessive reduction is very likely to appear in the product; the precursor of ferrous ammonium phosphate It is difficult to control the morphology during the preparation process, and the crystals are easy to grow larger, which seriously affects the bulk density and high-current electrochemical performance of the final lithium iron phosphate product; if ferrous oxalate or ferrous acetate is used as the iron source precursor , then iron and phosphorus are in different compounds, and iron and phosphate radicals are difficult to diffuse in solid-state reactions, so as long as the raw materials are not mixed uniformly at the atomic level, the reaction may not be complete

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