Optimizing yolk-shell structure and heteroatom doping strategy: enhaned lithium storage performance of Si-based composite material

초록

The development of lithium-ion batteries (LIBs) with high specific capacities and long lifespans has become a research hotspot in recent years because of the rapidly growing energy demands of many applications, such as electric vehicles, hybrid electric vehicles, and portable electronic devices.[1] Silicon-based anode materials, which have an extremely high theoretical capacity (4200 mAh g?1) and low working potential (<1.0 V vs. Li/Li+), have attracted great interest in energy storage applications.[2] However, drastic volume expansion of up to 400% during the alloying/dealloying of silicon with lithium seriously restricts its widespread application.[3] Herein, yolk-shell type SiO2@N, P co-doped carbon (SiO2@NPC Y.S.) with an optimized yolk size was fabricated by in-situ thermal phosphidation and carbonization of SiO2@PPy (polypyrrole), followed by the partial etching of SiO2 using HF. The successful etching of SiO2 with various yolk sizes and N, P co-doping into the carbon shell matrix were achieved by a three-step procedure. The SiO2@NPC Y.S. exhibits a superior initial capacity of 1261 mAh g?1 at a current density of 0.1 A g?1. Furthermore, the long-cycle reversible capacity of SiO2@NPC Y.S. is preserved at 705 mAh g?1 even after 300 cycles. The impact of the SiO2 yolk size and nitrogen and phosphorus co-dopants on the overall cell performance was investigated and discussed. Accordingly, this research will provide valuable insights into future research on the facile preparation of yolk-shell-structured anode materials with highly optimized yolk size and heteroatom-doped carbon shells for practical energy storage and conversion devices.