Carbon Additive-Free Crumpled Ti3C2TX MXene-Encapsulated Silicon Nanoparticle Anodes for Lithium-Ion Batteries

Silicon anodes are promising for future lithium-ion battery applications, but the large volume expansion of silicon particles causes electrode disintegration and excessive solid electrolyte interphase buildup during charge–discharge. This results in diminished cycling capacities and Coulombic efficiencies. "Yolk-shell" structures, wherein silicon particles are encapsulated within a conductive coating, have been explored in the recent past to address this issue, but most use amorphous carbon shells that have poor interactions with silicon. Here, conductive Ti3C2TX MXene nanosheets are crumpled around silicon particles via a one-step spray-drying process to create carbon-free anodes. The hydroxyl (−OH) terminal groups on the MXene surface contribute to the formation of a robust electrode via hydrogen bonding interactions with neighboring MXenes and encapsulated silicon particles. The relative silicon and MXene contents are varied to obtain crumpled MX/Si capsules of varying compositions, leading to different particle morphologies and energy storage performance metrics. The best-performing anode contains crumpled MX/Si = 32/68 wt % without any carbon additives required, demonstrating the cycling capacities of ∼550 mAh/gtotal at a current density of ∼1.7 A/gtotal (0.5 C-rate). Compared to equivalent electrodes containing uncrumpled MX/Si or crumpled reduced graphene oxide/Si, the crumpled MX/Si was far superior.