Enhanced lithium-ion storage of the SiOx@C anode enabled by carbon coating coupled with MXene as a conductive binder

Abstract

SiO_x is a promising anode material for lithium-ion batteries owing to its high theoretical capacity (2680 mA h g⁻¹), but it suffers from unsatisfactory cycling stability and rate capability caused by large volume changes during lithiation/delithiation and low electronic conductivity. Here, with low-density polyethylene as the carbon source, carbon-coated SiO_x (SiO_x@C) particles with Si–C bond at the interface are prepared, in which the carbon coating can significantly improve the conductivity and suppress the volume expansion of SiO_x. Furthermore, the SiO_x@C electrode is assembled with Ti₃C₂T_x MXene nanosheets as a multi-functional conductive binder via the conventional homogenizing-coating method. In the MXene-bonded SiO_x@C electrode, the SiO_x@C particles are embedded into the highly conductive MXene framework, which simultaneously facilitates fast electron transfer and ion diffusion, buffers the volume expansion of SiO_x@C, and provides additional porosity for fully exposing active sites. Benefiting from the combination of carbon coating and the MXene binder, the MXene-bonded SiO_x@C electrode displays excellent electrochemical performance for lithium-ion storage with a high reversible capacity (1363.3 mA h g⁻¹ at 0.1 A g⁻¹), outstanding cycling stability (962.7 mA h g⁻¹ after 300 cycles at 0.8 A g⁻¹) and superior rate performance (604.5 mA h g⁻¹ at 6.4 A g⁻¹). This work not only provides a promising anode material for high-energy-density lithium-ion batteries, but also proposes a strategy for constructing silicon-based electrodes with an MXene as a multi-functional binder.