Li-ion complex enhances interfacial lowest unoccupied molecular orbital for stable solid electrolyte interface of natural graphite anode

Abstract

To increase cycle life and reduce costs for natural graphite anode, graphite tailings grafted with polyether amine (PEA) is prepared for artificial solid electrolyte interphase (SEI). The complex of PEA and Li+ has a well-tuned lowest unoccupied molecular orbital (LUMO) energy (0.216 eV∼-0.239 eV) to improve the chemical stability of SEI components, effectively hinders electron transfer from anode to electrolyte, and inhibits electrolyte decomposition. Meanwhile, the strong adsorption between Li+ and PEA enhances the de-solvation ability of SEI, thus improving the rate performance of the anode. After 1000 cycles, the capacity retention of the anode material with grafted PEA molecular weight of 2000 is increased from 22% to 98%. The method can also improve rate performance for graphite anode, with the capacity retention rate at a current density of 1 A g−1 (vs. 0.1 A g−1) increasing from 42% to 72%. As expected, the full cell life with LiFePO4 as the cathode material is significantly extended, the capacity retention improved from 44% to 77% after 200 cycles.