Succinimide-modified graphite as anode materials for lithium-ion batteries

Abstract

Surface modification of graphite and the use of electrolyte additives are two effective ways to stabilize the performance of graphite anodes and to extend the life of lithium-ion batteries (LIBs). In this study, these two methods are combined by chemically bonding succinimide and N-phenylsuccinimide fragments (-SI and -PSI) to the graphite (G) surfaces, respectively, via the Diels-Alder (D-A) reactions. Two modified graphite materials (G-SI and G-PSI) are prepared and their electrochemical properties are compared with those of the pristine graphite. The cell performance degrades due to the partial destruction of the graphite structure caused by the introduction of electrochemically inert -PSI group. In contrast, -SI modification basically does not affect the initial charge-discharge coulombic efficiency and reversible capacities of the graphite, but significantly improves the cycling stability of the corresponding lithium-ion cells, nearly doubles the cycle life of the graphite-lithium iron phosphate full-cell. This is because -SI can suppress the destruction of graphite by the solvent, promote the charge transfer of Li+ ions at the electrode surface, and reduce the impedance of the SEI layer and the consumption of active lithium.