Preparation method and application of network structure nano NaVPO4F/C composite material and application thereof

Abstract

The invention discloses a network structure nano NaVPO4F / C composite material, and a preparation method thereof. The preparation method comprises the steps of adding a proper amount of alcohol to a mixed aqueous solution of a sodium source, a vanadium source, a fluorine source, a phosphorus source, a reducing agent and a carbon source; carrying out a solvothermal reaction at a temperature of 120-210 DEG C to obtain a carbon coated NaVPO4F precursor; and then calcining at a temperature of 750-900 DEG C under an inert atmosphere. In a high temperature environment, amorphous carbon is partially burned; a degree of graphitization is increased; NaVPO4F particles are fused and crystallized; grains grow; the carbon layer coating the NaVPO4F precursor can inhibit NaVPO4F particles from fusing together to some degree; and finally the network structure nano NaVPO4F / C composite material is formed. The material has a unique network structure and good porosity, and is beneficial to rapid migration of an electrolyte. Electrical conductivity of the whole material is improved due to effective compounding with carbon, and further electrochemical performance of NaVPO4F is increased. The network structure nano NaVPO4F / C composite is an excellent positive electrode material of the sodium ion battery.

Description

technical field [0001] The invention belongs to the field of materials, and relates to a sodium vanadium fluorophosphate (NaVPO 4 F) material, its preparation method and application in battery field. Background technique [0002] With the popularity of consumer electronics and the rise of electric vehicles, the market demand for lithium-ion batteries is increasing. Sodium-ion batteries and lithium-ion batteries have many similarities, and compared with lithium-ion batteries, they also have some obvious advantages, such as lower raw material costs, the ability to use electrolytes with lower decomposition voltages, and better safety. Therefore, sodium-ion batteries will be a promising new battery. [0003] NaVPO 4 F is a polyanionic material with a stable crystal structure and can provide a two-dimensional channel for ion conduction, which is conducive to the improvement of discharge stability and capacity. In 2002, Barker synthesized NaVPO for the first time 4 F and use ...

AI Technical Summary

Problems solved by technology

In 2002, Barker synthesized NaVPO for the first time 4 F and use it as the positive electrode material of sodium ion battery, when metal lithium is used as the negative electrode material, the positive electrode material NaVPO 4 The first charge and discharge specific capacities of F are 101mAh / g and 95mAh / g respectively; when activated carbon is used as the negative electrode material, the positive electrode material NaVPO 4 The first charge and discharge specific capacities of F are 82mAh / g and 79mAh / g respectively, and the discharge platform is 3.7V; however, NaVPO 4 The discharge capacity of F after 30 charge-discharge cycles is only 50% of the first time, and its structural stability and comprehensive electrochemical performance still need to be improved by appropriate methods

[0006] However, the carbon-doped NaVPO prepared by the above method 4 The morphology of F all presents an inhomogeneous structure and is bonded to each other, the particles are too large, and the carbon coating is uneven, which leads to the disadvantages of low battery capacity and poor rate performance.

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