Mitigating the capacity fading of silicon nanoparticles through double carbon coatings and cobalt doping

Abstract

Silicon (Si) is considered a highly promising anode material for lithium-ion batteries (LIBs), attributing to its suitable working potential and high specific capacity. Nevertheless, the enormous volume expansion during the lithiation, poor electron conductivity, and low lithium-ion (Li+) diffusion rate limit the application of Si anodes. Here, we design a novel single carbon layer and carbon nanotubes (CNT) coated Si nanoparticle (Si NP@C@CNT composites), in which the single carbon layer derived from citric acid separates between Si nanoparticle (Si NP), effectively avoiding the aggregation of Si NP, while the external carbon framework (CF) composed of CNT boosts the electrical contact between Si NP. Such micro-morphology structure can reduce the stresses during lithiation and promote the formation of stable solid electrolyte interface. Besides, the metallic cobalt (Co) and CNT can effectively enhance electrode conductivity and promote rapid electron transfer. The electrochemical testing results indicate that Si NP@C@CNT anode presents faster electrochemical reaction kinetics with excellent cycle stability (1055.1 mAh g−1 after 300 cycles at 0.5 A g−1) and rate performance (809.9 mAh g−1 at 5 A g-1). The special capacities and capacity retention of Si NP@C@CNT composites are 885.3 mAh g−1 and 85.9 % after 1000 cycles at 1 A g−1. In addition, the constructed full-cell NCM811// Si NP@C@CNT shows well reversible capacity. This research provides a novel idea for Si -based anode with excellent cycling stability, high electron transfer and fast Li+ diffusion ability for LIBs.