高比能锂离子电池层状富锂正极材料改性策略研究进展

Progress on Modification Strategies of Layered Lithium-Rich Cathode Materials for High Energy Lithium-Ion Batteries

层状富锂材料具有超过250 mAh·g-1的高可逆比容量,被认为是下一代高比能锂离子电池最具商业化前景的正极材料之一。然而,层状富锂材料在实际应用之前仍需解决诸多挑战,如高电压氧释放、层状到岩盐相的结构变化、过渡金属离子迁移等结构劣化,并由此带来了较低的初始库伦效率、电压/容量的衰减以及循环寿命的不足。针对以上问题,进行层状富锂材料改性无疑是一种行之有效的方法。本综述全面介绍了层状富锂材料的结构、组分以及电化学性能,在此基础上对材料改性策略进行了系统阐述,详细介绍了体相掺杂、表面包覆、缺陷设计、离子交换和微结构调控等一系列改性策略的现状以及发展趋势,最终提出了高容量和长循环层状富锂材料和高比能锂离子电池的设计思路。

High-performance rechargeable lithium-ion batteries have been widely used in portable electronic devices,electric vehicles and other fields of electrochemical energy storage.However,in order to achieve a wider range of commercial applications,the energy density of lithium-ion batteries needs to be further improved.Layered lithium-rich oxide materials with a high reversible specific capacity of over 250 mAh·g−1 are regarded as commercially promising cathodes for next-generation high-energy lithium-ion batteries.The high capacity of layered lithium-rich materials can be attributed to its unique oxygen redox chemistry,which can achieve additional charge storage thus increasing its capacity.However,many challenges must be addressed,including high-voltage oxygen release,structural changes from layered to rock-salt phase and structural degradation owing to the migration of transition metal ions,before it can be applied practically.These existing challenges result in low initial Coulombic efficiency,voltage/capacity decay,and insufficient cycle life.In view of the above issues,the modification of layered lithium-rich materials is an effective method.This review systematically introduces the composition and structure of lithium-rich materials,and then analyzes the electrochemical mechanism and internal causes which affect the electrochemical performance of lithium-rich materials.Furthermore,recent material modification strategies are discussed with regards to the current challenges.In addition,current methods and developmental trends of modification strategies such as bulk doping,surface coating,defect design,ion exchange and microstructure regulation are summarized in detail.According to the different charge properties,the doping modification can be divided into cationic doping,anion doping and anion-cation co-doping.Among them,cationic doping can be further categorized into transition metal layer doping substitution and lithium layer doping substitution,depending on the doping site.Two tables for the doping and ion exchange modifications were tabulated,and the representative scientific research was summarized.Recent research conducted on hotspot high-entropy materials were also mentioned.Finally,design ideas for high-capacity,long-cycle layered lithium-rich materials and high specific energy lithium-ion batteries were prospected.This comprehensive review is expected to promote further lithium-rich oxide materials research.