Synthesis And Electrochemical Characterization Of SnO₂,Based Anode Material And Li-rich Cathode Material For Lithium-ion Battery

In recent years, Li-ion batteries (LIBs) are becoming one of the most important power sources in consumer electronic devices such as cell phones and laptops for their advantages in energy density and cyclic life. However, with the development of smart grid and electric vehicles, there is urgent demand on LIBs with higher density energy, higher power density and longer cycle life. To explore novel electrode materials is the key for the advance of LIBs. The thesis focuses on the synthesis, modification and electrochemical characterization of SnO2based anode material and Li-rich layered oxide cathode material, which are emerging as the promising electrode materials for LIBs.Chapter1includes a general introduction about the structure, working principle and development status of LIBs. After making a generalized summarization for the cathode and anode materials, two novel electrode materials (SnO2and Li-rich layered oxide) are reviewed including the structure, reaction mechanism, synthesis and modification methods.In Chapter2, the experimental reagents, equipments and processes used in the this thesis are briefly introduced. Followed by a detailed description on assembling a2025coin cell, the material characterization methods and electrochemical measurement technology are presented.In Chapter3, tin oxide/graphene nanocomposites with variety in oxide phase structure and composition were prepared by a tailored synthesis through the control of oxidation-reduction hydrothermal reaction between graphite oxide and Sn2+. The amount ratio of graphite oxide and SnCl2is critical to achieve either SnO/SnO2-graphene or pure SnO2/graphene composites, which are electrochemically evaluated as the anode materials in lithium ion batteries. It is found that the phase-structure and composition play a key role in the lithium ion storage ability. A superior cycling performance is obtained when the nanocomposites exist in pure SnO2-graphene (mass percentage of SnO2:68%) after90cycles, with a reversible capacity of525mAh/g and an ultra-low capacity loss of～0.3%per cycle.In Chapter4, a fast combustion method was applied for the synthesis of solid solution cathode material Li[Li0.2Mn0.54Ni0.i3Co0.13]O2. Urea and citric acid were selected as fuels, seperately. The effects of the two different fuels on the structure, morphology and electrochemical performance of Li[Li0.2Mno.54Ni0.13Co0.13]O2cathode were investigated systematically. The sample systhesized with urea shows better electrochemical performance:the highest discharge capacity is264.6mAh/g at0.1C and167.5mAh/g at1C. The capacity retention is90%after100cycles at1C.