A method for realizing the modification of lithium iron phosphate by graphene through solid-liquid separation

Abstract

The invention discloses a method for modifying lithium iron phosphate by graphene through solid-liquid separation. The method comprises the following characteristic steps: firstly, preparing a lithium iron phosphate saturated solution, adding graphene or oxidized graphene or graphite oxide into the lithium iron phosphate saturated solution to prepare graphene or oxidized graphene aqueous-phase suspension liquid, then adding lithium iron phosphate solids into the prepared graphene or oxidized graphene aqueous-phase suspension liquid for adsorbing, filtering, and carrying out drying and heat treatment on filtered lithium iron phosphate with adsorbed graphene or oxidized graphene to obtain graphene modified lithium iron phosphate. The method has the characteristics of low lithium iron phosphate modification cost, high electrical capacity after modification and high rate capability.

Description

technical field [0001] The invention relates to a method for modifying a cathode material of a lithium ion battery, in particular to a method for realizing the modification of lithium iron phosphate by graphene through solid-liquid separation. Background technique [0002] Lithium iron phosphate, as the cathode material of lithium-ion batteries, is popular because of its safe olivine structure, cheap raw materials and environmental protection. However, due to the poor conductivity of lithium iron phosphate, it needs to be modified to improve its conductivity. Only then can it be practically applied. [0003] At present, the modification methods for improving the performance of lithium iron phosphate batteries include: lattice doping method, surface carbon coating method, carbon nanotube doping method, graphene doping method, etc., especially the graphene doping method has the most effect on improving the performance of lithium iron phosphate battery Significantly, but at pr...

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Problems solved by technology

[0002] Lithium iron phosphate, as the cathode material of lithium-ion batteries, is popular because of its safe olivine structure, cheap raw materials and environmental protection. However, due to the poor conductivity of lithium iron phosphate, it needs to be modified to improve its conductivity. practical application only after

[0003] At present, the modification methods for improving the performance of lithium iron phosphate batteries include: lattice doping method, surface carbon coating method, carbon nanotube doping method, graphene doping method, etc., especially the graphene doping method has the most effect on improving the performance of lithium iron phosphate battery Significantly, but at present, most of the modification methods of graphene to lithium iron phosphate are realized by adding graphene or graphene oxide into the water phase and then spray drying. The dispersion of graphene or graphene oxide in water must be maintained well. The degree of dispersion must be very low, so that the amount of spray drying water is very large, resulting in high energy consumption for spray drying, resulting in high modification costs and no industrial practical value.

However, if a large amount of water is filtered and separated after adding lithium iron phosphate and then dried, because some constituent elements in lithium iron phosphate are dissolved in a large amount of water, especially lithium dissolves more, iron and phosphorus dissolve less, and each component It is not dissolved in water according to the theoretical ratio, which changes the component ratio of the solid lithium iron phosphate obtained after the water is separated, making the obtained lithium iron phosphate battery performance worse.