磷酸铁锂的高性能化研究进展

Progress in High-Performance Lithium Iron Phosphate for Lithium Ion Batteries

工业革命以来,科技的迅速发展不断丰富着人类的物质生活,与此同时化石能源(石油、煤炭、天然气等)大量消耗,二氧化碳排放逐年增加,全球变暖趋势加剧。燃油汽车是石油消耗的主力军。为落实“双碳”战略目标,新能源汽车发展迅猛。作为新能源汽车的动力来源,动力电池备受关注。开发价格低廉、资源丰富、安全性优异的动力电池是发展新能源汽车的重中之重。目前磷酸铁锂(LiFePO_(4))和三元正极材料广泛用作混合动力汽车(Hybrid Electrical Vehicle,HEV)和电动汽车(Electrical Vehicle,EV)锂离子电池中。前几年,受国家补贴政策影响,由于能量密度比三元正极材料低,LiFePO_(4)正极材料的出货量几乎停止增长,而三元正极材料一路高歌猛进,占据了新能源汽车的主要市场。随着补贴政策的退出,具有橄榄石结构的LiFePO_(4)因其具有成本低、安全性高、环境友好等诸多优点又重新获得青睐。同时,由于刀片电池等结构设计上的技术进步,LiFePO_(4)电池的能量密度大幅提高。2021年LiFePO_(4)正极材料的出货量超过三元正极材料,达到47万吨。然而,LiFePO_(4)较低的电子电导率(<10^(-9)S cm^(-1))和Li+离子扩散系数(10^(-14)cm^(2)s^(-1)~10^(-16)cm^(2)s^(-1)),严重阻碍了其在动力电池领域的进一步扩展。基于市场对新能源汽车快速充放电的现实需要,提升LiFePO_(4)的电化学性能刻不容缓。目前的策略主要包括通过改善合成条件控制晶体的尺寸和取向、表面包覆、掺杂、缺陷控制等。本文从锂离子电池的组成及工作原理出发,结合LiFePO_(4)的晶体结构特征和充放电机制,深入探讨了LiFePO_(4)高性能化的研究进展,并提出了LiFePO_(4)未来的研究方向和发展趋势。

Since the industrial Revolution,the rapid development of science and technology has continuously enriched people's life.At the same time,fossil energy(oil,coal,natural gas,etc.)consumption and carbon dioxide emissions increase year by year,resulting in global warming and critical ecological environment issues.Fuel vehicles are the main source of oil consumption.In order to help the implementation of carbon peaking and carbon neutrality goals,new energy vehicles are developing rapidly and their sales are increasing year by year.As the power source of new energy vehicles,the power batteries have attracted much attention.It is very important to develop the power batteries with low price,abundant resources and excellent safety for new energy vehicles.At present,lithium iron phosphate(LiFePO_(4))and layered lithium nickel cobalt manganese oxides are widely used as cathode materials for lithium-ion batteries of hybrid electrical vehicle(HEV)and electric vehicle(EV).A few years ago,due to the impact of state subsidies,shipments of LiFePO_(4)almost ceased to increase because of its lower energy density than ternary cathode materials that have been surging ahead and dominating the market of new energy vehicles.With the withdrawal of subsidy policy,LiFePO_(4),as an olivine-structured compound,has regained favor because of its unprecedented combinations properties such as low cost,high safety and environmental friendliness.Meanwhile,the blade batteries,also known as LiFePO_(4),greatly improves the energy density significantly,benefiting to technological advances in structural design.In 2021,shipments of LiFePO_(4)cathode materials reversed the trend,reaching 470,000 tons.However,LiFePO_(4)is insufficient to meet today’s high-power demand due to its low electronic conductivity(<10^(-9)S cm^(-1))and low lithium-ion diffusion coefficient(10^(-14)cm^(2)s^(-1)~10^(-16)cm^(2)s^(-1)).Based on the market demand for fast charging-discharging of new energy vehicles,it is urgent to improve the electrochemical performance of LiFePO_(4).Current strategies mainly include control of crystal size and orientation by improving conditions,surface coating,doping,defect control,etc.In this review,based on the composition and working principle of lithium-ion battery and combined with the crystal structure characteristics and charge-discharge mechanism of LiFePO_(4),the progress in high-performance olivine-structured lithium iron phosphate is deeply discussed,and the future research direction and development trend of LiFePO_(4)are put forward.