Method for preparing lithium iron phosphate-lithium vanadium phosphate by quenching method

Abstract

A method for preparing lithium iron phosphate-lithium vanadium phosphate by a quenching method. The method comprises the following steps: well mixing a vanadium source compound, an iron source compound, a lithium source compound and a phosphor source compound according to a stoichiometric ratio of the composite material, adding a carbon source, stirring and mixing, uniformly distributing the mixture in a solvent, performing spray drying to prepare a spherical precursor mixture, calcining the precursor mixture at 500-900 DEG C in nonoxidative atmosphere for 2-48 hours, finally transferring the high-temperature powder to a low-temperature medium with a temperature of -209 DEG C-35 DEG C, quenching for 1 min-2 h so as to prepare the lithium iron phosphate-lithium vanadium phosphate composite material. The invention can prepare a composite cathode material with a high tap density and high magnification performance, and greatly improves the energy density and magnification performance of the material.

Description

technical field [0001] The invention relates to a preparation method of lithium iron phosphate-lithium vanadium phosphate, a composite positive electrode material for a lithium ion battery, in particular to the preparation of a composite positive electrode material by a spray drying-quenching method x LiFePO 4 · y Li 3 V 2 (PO 4 ) 3 Methods. Background technique [0002] LiFePO 4 and Li 3 V 2 (PO 4 ) 3 are two representative phosphate system cathode materials, but LiFePO 4 The conductivity of Li 3 V 2 (PO 4 ) 3 It has a high theoretical specific capacity (197 mAh·g -1 ), high working potential (3.6-4.5V vs. Li / Li + ), stable structure, good electrochemical performance, etc., but the metal ions in the crystal structure are far apart, which reduces the mobility of electrons in the material, resulting in low electronic conductivity of the material, and the charging and discharging effect under high current is not good. Ideally, the two traditional phosphate ca...

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Problems solved by technology

[0002] LiFePO 4 and Li 3 V 2 (PO 4 ) 3 are two representative phosphate system cathode materials, but LiFePO 4 The conductivity of Li 3 V 2 (PO 4 ) 3 It has a high theoretical specific capacity (197 mAh·g -1 ), high working potential (3.6-4.5V vs. Li / Li + ), stable structure, good electrochemical performance, etc., but the metal ions in the crystal structure are far apart, which reduces the mobility of electrons in the material, resulting in low electronic conductivity of the material, and the charging and discharging effect under high current is not good. Ideally, the two traditional phosphate cathode materials LiFePO 4 and Li 3 V 2 (PO 4 ) 3 Copy it together and prepare it, use Li 3 V 2 (PO 4 ) 3 LiFePO has the advantages of high ionic conductivity, high theoretical specific capacity, high discharge voltage platform, and good low-temperature discharge performance. 4 It is an effective method to modify the base material

At present, Jun-chao Zheng, Mu Rong Yang, Lina Wang and others have synthesized a series of composite positive electrode materials by wet chemical reduction method, solid phase sintering method, rheological phase method, etc. Although the electrochemical performance of the material is good, the material The tap density is low, and the high rate charge and discharge performance is not ideal

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