Constructing hierarchical porous structure in microsized silicon/carbon nanotubes composite anode with LiF-rich solid-electrolyte interfaces for highly stable lithium-ion batteries

Abstract

Lithium-ion batteries (LIBs) with silicon microparticle anodes provide a high capacity, low cost, low environmental impact, and ease of production. However, the rapid capacity degradation and low Coulombic efficiency (CE) are impediments to their further development and commercialization, which are mainly caused by large volume variation and unstable solid–electrolyte interface (SEI) of silicon. To break this bottleneck, here, we demonstrate that designing silicon microparticles with nanoporous structure (PSi) and confining the PSi in the carbon nanotube (CNT) segregated network can effectively suppress the volume expansion of silicon, enabling the fabrication of high-performance electrodes. The rate capability and cycling performance of the electrode are further improved by creating a hierarchical open porous structure for the PSi-CNT composite anodes via freeze drying. In addition, the mixTHF electrolyte was employed to get a thin and uniform SEI, which can reduce the breakage of SEI during cycling and improve the CE and stability of the LIBs. As a result, the PSi-CNT composite anode delivers a high specific capacity of 3210.1 mAh g−1 at 1/15 °C rate and an initial Coulombic efficiency of 87.3%. After 100 cycles, the capacity could be maintained at over 2000 mAh g−1 with 99.5% CE. In addition, hierarchical porous structured PSi-CNT composites exhibit excellent rate performance, the specific capacity could reach 2264.5 mAh g−1 at 5 °C rate. The work suggests several effective solutions that could be used to facilitate the future commercialization of silicon anodes.