Design and modification for efficient Li-storage in advanced LiFePO4 cathodes
Lithium ion batteries(LIBs)have the advantages of high energy density,good cycling stability,and no memory effect,and have been widely used in various fields such as portable electronic products,electric vehicles,smart grids,and others.Among the numerous cathode materials for lithium-ion batteries,the polyanion cathode material has the advantages of easy production and low cost,as well as a theoretical voltage range of 2.0-4.8 V,making it an excellent cathode material.LiFePO4 has become the most widely used cathode material due to its high theoretical capacity,great cost-effectiveness,good safety,and environmental friendliness.However,due to the fact that in the orthorhombic crystal system of lithium iron phosphate with the Pnma space group,PO43-leads to the segregation of FeO6,which reduces the electronic conductivity and the rate of ionic diffusion along the b-axis,resulting in poor rate performance of pure LiFePO4.The utilization of crystallographic engineering to regulate the crystal size and morphology of LiFePO4 has greatly improved its electrical conductivity,enhanced its practical capacity,multiple performance and cycling stability,and realized the large-scale application of lithium iron phosphate in commerce.The common synthesis methods can be divided into liquid-phase and solid-phase methods.The solid-phase method has the advantage of a simple production process,making it easy to achieve large-scale production.Meanwhile,liquid-phase methods can prepare nanoparticles with a narrow range of particle size distributions and controllable morphology,along with lower energy consumption.Additionally,the electrochemical properties of the cathode materials can be effectively improved through the modification of LiFePO4 nanoparticles.The structural composite of LiFePO4 with conductive materials enables better contact between nanoparticles.The three-dimensional conductive network structure based on the composites also promotes the rapid transport of Li+and electrons,greatly enhancing the electrical conductivity of the cathode materials.Furthermore,ion doping can form a high electronic conductivity solid solution with vacancy defects in LiFePO4,broadening the Li+migration pathway and optimizing the properties of the material particles.In addition,interfacial modulation of LiFePO4 is also an effective way to enhance its performance.Carbon material possesses high electrical conductivity,excellent stability,and great economic efficiency.The carbon coating on the surface of LiFePO4 enhances the electrical conductivity between particles and provides electron tunneling for the crystal,inhibits the oxidation of Fe2+,and effectively prevents the coalescence phenomenon.Furthermore,the introduction of metal and metal compound coatings also improves the electrical conductivity of the cathode material,reduces the charge transfer resistance,and improves its thermal stability and cycling performance.The review covered various synthesis processes of LiFePO4,including a comparison of their strengths and weaknesses,and strengthened relevant modification strategies involved in improving the physical and chemical properties.By doing so,good electrochemical performance can be achieved.Finally,the possible future trends of advanced LiFePO4 cathode materials are outlined.
万方数据
维普
