A preparation method of interface strongly coupled graphene-lithium iron phosphate nanocomposite positive electrode material

Abstract

The invention discloses a preparation method of an interface strong coupling graphene-lithium iron phosphate nano-composite positive electrode material. The preparation method comprises the following steps: regulating and controlling the morphology sizes of lithium iron phosphate nano particles by taking a polymer as a carbon source precursor via adopting a collaborative self-organization technology; further, depositing the polymer modified lithium iron phosphate nano particles on the surface of graphene by utilizing a solution phase separation technique; and carbonizing at a high temperature so as to obtain the graphene-lithium iron phosphate nano-composite material with extremely high positive electrode active material specific surface area. Different from the traditional principle that conductive particles and lithium iron phosphate are directly mixed physically so as to establish a conductive channel, the strong coupling connection among interfaces via polymer carbonization of the prepared graphene-lithium iron phosphate nano-composite positive electrode material can be used for obviously improving the charge transfer efficiency in the electrode, and further obviously improving the performances of the lithium battery positive electrode material.

Description

technical field [0001] The invention belongs to the field of lithium-ion battery electrode materials, in particular to a method for preparing a strongly interface-coupled graphene-lithium iron phosphate nanocomposite cathode material. Background technique [0002] Lithium-ion batteries are widely used in portable electronics, computing communications, transportation and many other fields. The performance of lithium-ion batteries critically depends on the physicochemical properties of the electrodes, among which the impact of the positive electrode on the overall battery performance is decisive. Many materials have been used as cathodes for lithium batteries, including lithium cobalt oxide (LiCoO 2 ), lithium manganate (LiMn 2 o 4 )Wait. However, since 1999, J.B.Goodenough et al. (US Patent 591382de) of the University of Texas in the United States proposed lithium iron phosphate (LiFePO 4 ) can be used as a cathode material for lithium batteries, its unique structure and...

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Problems solved by technology

First, when LiFePO 4 When the particle size is reduced to the nanometer scale, with the sharp increase in the surface area, the tendency of particle aggregation is significantly enhanced. The agglomerated nanoparticles will seriously hinder the diffusion and intercalation of lithium ions, prolong the diffusion path of lithium ions, and thus inhibit the rate performance of positive electrode materials. improvement; secondly, when using nano-carbon materials on LiFePO 4 When carrying out conductive modification, the charge transport efficiency between interfaces is crucial, and the existing technologies mostly use physical blending or in-situ growth to prepare LiFePO 4 Based nanocomposite electrode material, LiFePO 4 The interface connection between nanoparticles and conductive carbon materials is relatively weak, which is not conducive to improving the charge transfer efficiency inside the positive electrode material; third, the existing conductive modifiers mostly use more expensive carbon nanomaterials, such as conductive carbon black , acetylene black and carbon nanotubes, the cost is high, and the development of low-cost, high-efficiency conductive additives, especially those that can be combined with LiFePO 4 A low-cost, scalable technical route combining nanoparticle morphology control and interface optimization processes is still an unsolved problem