钴酸锂正极材料充电结构失效机理研究  

Study on failure mechanism of charging structure of lithium cobalt oxide cathode material

作　　者：黄志濠 袁静怡 谢雨飞 唐静怡 覃吴[1,2] HUANG Zhihao;YUAN Jingyi;XIE Yufei;TANG Jingyi;QIN Wu(School of New Energy,North China Electric Power University,Beijing 102206,China;School of Engineering,China University of Petroleum-Beijing at Karamay,Karamay Xinjiang 834000,China)

机构地区：[1]华北电力大学新能源学院,北京102206 [2]中国石油大学(北京)克拉玛依校区工学院,新疆克拉玛依834000

出　　处：《电源技术》2024年第12期2374-2379,共6页Chinese Journal of Power Sources

基　　金：国家科工技术基础科研项目(JSZL2022204B003)。

摘　　要：层状相结构钴酸锂正极材料体积能量密度高,广泛应用于商业锂离子电池。但在反复充放电过程中层状钴酸锂易发生微观结构形变致电性能下降和引发安全隐患。通过密度泛函理论计算探究不同充电电压下钴酸锂正极结构变化、晶格原子溶出和界面反应机理。发现充电电压超过4 V后,钴酸锂层状结构滑移,晶格原子重排和电子轨道变化引发体相结构明显弛豫。分析钴酸锂与电解液分子(EC、DMC和LiPF_(6))相互作用发现4 V及更大电压下,电解液分子分解,EC、DMC与钴酸锂正极表面发生反应导致钴酸锂晶体氧溶出;LiPF_(6)分解,氟化钴酸锂表界面,破坏表界面嵌锂的本体结构。研究揭示了钴酸锂正极材料的失效机制,为过渡金属氧化物正极材料的研究提供了基础数据和参考。Lithium cobalt oxide cathode material with layered phase structure has high volume energy density,which is widely used in lithium-ion batteries.However,layered lithium cobalt oxide is prone to microstructure deformation in the repeated charging and discharging,which leads to battery degradation and safety risks.Density functional theory was employed to investigate the structure change,lattice atom dissolution,and interfacial reaction mechanism of lithium cobalt oxide cathode under different charging voltages.When the charging voltage exceeds 4 V,the lithium cobalt oxide layer slips,the lattice atoms are rearranged,and the electron orbitals are changed,resulting in a significant relaxation of the bulk structure.The interfacial interaction between lithium cobalt oxide and electrolyte molecules(EC,DMC and LiPF6)under different charging voltages were investigated.Under 4 V and higher voltages,the electrolyte molecules decompose,and EC and DMC react with the positive surface of lithium cobalt oxide,leading to oxygen dissolution of lithium cobalt oxide crystal.The decomposition of LiPF6 and the surface and interface of lithium cobalt fluoride can damage the bulk structure of lithium intercalation at the surface and interface.The research results indicate the failure mechanism of lithium cobalt oxide cathode materials,providing basic data and references for the research on transition metal oxide cathode materials.

关 键 词：锂离子电池 钴酸锂 失效机理 密度泛函理论 

分 类 号：TM912[电气工程—电力电子与电力传动]