Lithium iron phosphate nanorod/graphene composite material as well as preparation method and application thereof

Abstract

The invention discloses a lithium iron phosphate nanorod / graphene composite material as well as a preparation method and an application thereof; the preparation method comprises the following steps offirstly, providing ferrous oxalate / graphene oxide composite material and then carrying out mixing on the ferrous oxalate / graphene oxide composite material and ammonium dihydrogen phosphate and lithium acetate dihydrate according to a certain molar ratio, and carrying out grinding and drying, and next, carrying out high-temperature reaction under the protection of inert gas to obtain the compositematerial. The lithium iron phosphate nanorod / graphene composite material prepared by adopting a two-step solid phase reaction method is small in particle size and uniform in particle size distribution, and has a one-dimensional nanorod-shaped structure, so that the transmission rate of ions can be effectively increased, and the capacity in large-current discharge is not attenuated; graphene is added, so that the surface conductivity of the material is further improved, and meanwhile, the rate performance and the cycling performance of the material are remarkably improved; and in the preparation process of the lithium iron phosphate nanorod / graphene composite material, the reaction conditions are easy to control, the operation is simple, the production cost is low, and industrial production is easy to realize.

Description

technical field [0001] The invention belongs to the technical field of positive electrode materials for lithium ion batteries. Specifically, it relates to a lithium iron phosphate nanorod / graphene composite material and its preparation method and application. Background technique [0002] Lithium iron phosphate with olivine structure is regarded as one of the most promising cathode materials for power batteries. It has many advantages such as abundant raw material sources, safety and environmental protection, and stable cycle performance. However, due to its structural limitations, the electronic and ionic conductivity is low. , resulting in a lower actual capacity. The composite of graphene and lithium iron phosphate can significantly improve its electrochemical performance. [0003] At present, the method for preparing lithium iron phosphate / graphene oxide composite cathode material is mainly the liquid phase method, because the liquid phase method can control the partic...

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Problems solved by technology

In the preparation process, the molar ratio of raw materials in the solvothermal reaction and the reaction temperature need to be strictly controlled, and a large amount of ethylene glycol is required as a solvent in the reaction process, which not only increases the cost of raw materials, but also causes a lot of waste of raw materials, making it difficult to realize industrial production

[0004] The powder particles prepared by the traditional solid phase method have no agglomeration, good filling, low cost, large output, and simple preparation process, such as Li Qiru et al. (Li Qiru. Preparation and electrochemical performance of graphene-coated lithium iron phosphate cathode material[ D]. Soochow University, 2016.) In the preparation and electrochemical performance of graphene-coated lithium iron phosphate cathode materials, a simple solid-phase method was used, using ferrous oxalate, ammonium dihydrogen phosphate, and lithium carbonate as raw materials. The organic carbon source glucose and graphene oxide were used as composite carbon sources, and LiFePO was successfully synthesized 4 / graphene / C composite material, and proved that the double-coated lithium iron phosphate material has a higher discharge specific capacity than the sample only coated with graphene, but the obtained LiFePO 4 / Graphene composite materials are all granular, which will affect the transmission rate of ions, and the capacity will easily decay during high-current discharge; at the same time, there are problems such as uneven dispersion and easy agglomeration of graphene, which leads to the conductivity and rate performance of the composite material. and cycle performance may be affected. At the same time, the preparation process has the disadvantages of high energy consumption, low efficiency, powder is not fine enough, and impurities are easily mixed

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