Selection Of New Electrolyte Components And Compatibility With Graphite Anode For Lithium Ion Batteries

Electrolyte is one of the key materials of lithium ion batteries, and graphite anode is very sensitive to electrolyte composition, so it is very important of selecting and optimizing new electrolyte components to improve the compatibility of electrolyte with graphite anode for the development of high performance lithium ion batteries. In this paper, we focus on selection and optimization of new electrolyte components and improving the compatibility of electrolytes with graphite, which use N-Methylacetamide(NMA), N, N-Dimethylacetamide(DMAC) and butylene carbonate(BC) as solvents or additives, and investigate the influence of NMA and DMAC on the electrochemical performance of graphite electrode and the electrochemical properties comparison of propylene carbonate(PC) and BC at room temperature and low temperature.NMA and DMAC as the electrolyte co-solution, mixed with PC according to a certain proportion, electrolytes could effectively suppress PC co-intercalation into grapheme, which improved the compatibility of PC with graphite anode. Added into 1mol L-1 LiTFSI or LiPF6/EC: PC(1:1) as the electrolyte additives, the electrochemical performance of graphite electrode was significantly improved, including the first charge/discharge coulombic efficiency, reversible charge/discharge capacity and cyclic performance, even when the ratio of PC in electrolyte was increased to PC: EC(8:2), it still worked very well. Added into the commercial electrolyte 1mol L-1 LiPF6/EC: DEC(1:1), the first coulombic efficiency and specific capacity retention rate of natural graphite were still somewhat improved. Mainly because after the two kinds of solvents were added into electrolytes, a more efficient passive film was formed on the surface of graphite in the first cycle, which could suppress the destruction of graphite structure caused by PC molecules co intercalation into graphite layer and decrease the irreversible decomposition of electrolytes.The electrochemical performances of PC and BC under the conditions of room temperature and low temperature were compared. At room temperature, CV of graphite electrode in pure BC as solvent was different from which in PC. Mixed with EC, the first charge/discharge coulombic efficiency, reversible specific charge/discharge capacity and cyclic performance of the graphite electrode in EC: BC(1:1)-based electrolyte was superior to which in EC: PC(1:1)-based electrolyte. At room temperature, graphite electrode in EC: BC: EMC 2:2:5 based electrolyte showed similar reversible capacity and cycle performance with which in EC: PC: EMC 2:2:5 and EC: DMC: EMC(1:1:1) based electrolytes, but at minus 20 degrees celsius, the former was superior to the latter two, showing higher specific capacity retention rate, which indicates that BC has the advantage and prospect for low temperature lithium ion batteries.