A facile and low-cost AlO coating as an artificial solid electrolyte interphase layer on graphite/silicon composites for lithium-ion batteries.

Graphite/silicon (G/Si) composites are considered as possible alternative anode materials to commercial graphite anodes. However, the unstable solid electrolyte interphase (SEI) on G/Si particles results in rapid capacity decay, impeding practical applications. Herein, a facile and low-cost AlO coating was developed to fabricate stable artificial SEI layers on G/Si composites. The amorphous AlO coating with a thickness of 10-15 nm was synthesized by a simple sol-gel method followed by high-temperature annealing. The AlO coated G/Si anode delivers an initial discharge capacity of 540 mAh g at 25 °C and has improved Coulombic efficiency and cycling stability. After 100 cycles, the capacity retention is 76.4%, much higher than the 56.4% of the uncoated anode. Furthermore, the AlO coating was found to be more effective at improving the stability of G/Si at a higher temperature (55 °C). This was explained by the AlO coating suppressing the growth of SEI on Si/G and thus reducing the charge transfer resistance at the G/Si-electrolyte interface. It is expected that the AlO coating prepared by the sol-gel process can be applied to other Si-based anodes in the manufacture of practical high-performance lithium-ion batteries.