Selection And Application Of New Solvents And Additives For Lithium-ion Battery Electrolytes

Lithium ion battery electrolyte, a bridge connecting the positive and negative electrode, plays the role of ion transport in the battery. It mainly consists of lithium salts, organic solvents and additives. The choice of the electrolyte is closely related to the voltage, capacity, energy and power of lithium ion batteries. In this paper, the research content is based on the inorganic additives and fluorinated solvents TFPC for lithium-ion battery electrolyte. The research work mainly involves the influence of Ag PF6 and Cu TF as electrolyte additives on the electrochemical performance of graphite electrode and a binary cyclic carbonates-based electrolyte containing propylene carbonate(PC) and trifluoropropylene carbonate(TFPC) for 5 V lithium-ion batteries.Ag PF6 and Cu TF as the additives into the commercial electrolyte(1 M Li PF6/EC-DEC) can significantly improve the electrochemical behaviors of graphite anode, including the higher discharge capacity, smaller electrode polarization, better rate behavior performance ect. Ag and Cu nanoparticles derived from the electrochemical reduction of Ag+ and Cu2+ are homogenously distributed on the graphite surface. Those metal nanoparticles can decrease the resistance of solid-electrolyte interface and charge-transfer process, thus improving the electrochemical kinetics of the Li+ intercalation/deintercalation.An electrolyte based on PC and TFPC binary solvent was systematically investigated. The optimized electrolyte is 1 M Li PF6-TFPC/PC(1:2), which shows excellent compatibility with the graphite anode, Li Fe PO4 and Li Ni0.5Mn1.5O4 cathode in terms of improving the reversible capacity and rate capability of these materials compared to the traditional ECbased electrolyte. The detrimental effects of PC on graphite structure can be effectively suppressed by the addition of proper amount of TFPC solvent and the high interfacial impedance of the SEI formed on graphite surface by reduction reaction of TFPC can be substantially decreased by PC. The optimized electrolyte shows excellent anti-oxidation performance compared with various electrolyte systems adopted in this study, thus ensuring the well compatibility of 5 V Li Ni0.5Mn1.5O4 cathode with the electrolyte.