Lithium-conducting phosphates as artificial solid-electrolyte interphase on silicon anode for supreme lithium storage

Abstract

Silicon (Si) anode is an ideal material for next-generation lithium-ion batteries due to its high specific capacity. Unfortunately, the fragmentation and reconstruction of solid electrolyte interface (SEI) film caused by volume expansion during the (de)lithiation is still a problem to be overcome. Constructing a stable SEI film on Si surface through interface engineering is a very effective strategy to improve the electrochemical performance. In this work, we construct lithium-conducting phosphates (Li₃PO₄, denoted as LPO) as SEI film and SiO_x buffer layer on Si surface. The obtained Si@SiO_x@LPO anode retains 2015 mAh g⁻¹ after 100 cycles at 0.2 A g⁻¹ with a capacity retention of 73.6%, and 1636 mAh g⁻¹ after 500 cycles at 1 A g⁻¹ with a capacity retention of 81.7%, which is significantly higher than the Si anode under the same conditions, respectively. In addition, in/ex-situ tests demonstrate that Si@SiO_x@LPO anode has faster lithium-ion diffusion and structural reversibility. The analysis shows that LPO has higher mechanical strength and provides better ionic conductivity. On the other hand, SiO_x buffer layer can not only reduce the volume expansion of Si, but also reduce the energy barrier between Si and LPO interface and increase the electrical conductivity. Therefore, this work provides a novel strategy for boosting electrochemical performance by artificial SEI and surface modification.