Atomic Sn4+ Decorated into Vanadium Carbide MXene Interlayers for Superior Lithium Storage

Ion intercalation is an important way to improve the energy storage performance of 2D materials. The dynamic energy storage process in such layered intercalations is important but still a challenge mainly due to the lack of effective operando methods. Herein, a unique atomic Sn4+-decorated vanadium carbide (V2C) MXene not only exhibiting highly enhanced lithium-ion battery (LIB) performance, but also possessing outstanding rate and cyclic stability because of the expanded interlayer space and the formation of V-O-Sn bonding is demonstrated. In combination with ex situ tests, an operando X-ray absorption fine structure measurement is developed to explore the dynamic mechanism of V2C@Sn MXene electrodes in LIBs. The results clearly reveal the valence changes of vanadium (V), tin (Sn), and positive contribution of oxygen (O) atoms during the charging/discharging process, confirming their contribution for lithium storage capacity. The stability of intercalated MXene electrode is further in situ studied to prove the key role of V-O-Sn bonding.