三种二次电池正极材料的第一性原理研究凝聚态物理专业论文.docxVIP

三种二次电池正极材料的第一性原理研究因此可以通过调控C／O来调控电极的能量密度和功率密度，从而为实验上制备高性能的 三种二次电池正极材料的第一性原理研究 因此可以通过调控C／O来调控电极的能量密度和功率密度，从而为实验上制备高性能的 碳基正极提供参考。 关键词：二次电池；正极材料；第一性原理 万方数据 大连理工大学博士学位论文AB 大连理工大学博士学位论文 AB STRACT Battery is one of the most important energy storage technologies，and is widely used in portable electronic devices．Battery is also promising for large—scale applications，such as electric vehicles and energy grid，and the key issue relies on improving its energy density．An effective approach is to use cathode materials with high specific capacity．This thesis work is to understand the fundamental properties of various cathode materials for rechargeable batteries，and to improve the electrochemical performance of these materials，based on density functional theory(DFT)calculations．In details，this thesis focuses on the following three aspects： First is to improve the physical and chemical properties of conventional cathode material ——LiC002 for lithium ion battery．LiC002 possesses high capacity，and has been widely used in Li．ion batteries．However．the lattice of LiC002 contracts／expands severely along the axes during the charging／discharging processes．This non—uniform lattice variation Can lead to mechanical fracture and is detrimental to the battery capacities and cycling life．To overcome this problem，we exploited halogen substitution of the oxygen sites in LiC002 systems to suppress the lattice variation．Our results show that halogen doping enhances the structural stability of LiC002 during the intercalation／deintercalation of lithium ions．The doping does not affect the electrode voltage of LiC002，and can improve its electronic properties． Moreover，the presence of halogen species facilitates the migration of Li ions in LiC002，and is helpful for improving the rate capacity of the system． Second is to explore cathode materials for sodium ion batteries．The limited lithium source is a potential problem for large-scale applications of Li-ion batteries in the long run． Sodium，which is abun