First-principle study of Ti2XS2 (X = C/N) MXenes as high capacity anodes for rechargeable potassium-ion batteries

Potassium-ion batteries (KIBs) are potential substitutions of lithium-ion batteries, considering the superiority of K in abundance and safety compared with lithium. Recently, the MXenes emerged as a significant class of two-dimensional materials in energy storage applications. Herein we investigated the performances of two S-functionalized MXenes (S-MXenes), Ti2CS2 and Ti2NS2, as anodes for KIBs through first-principle calculations. The results show that both S-MXenes possess metallic nature and structural integrity. Besides, the two functionalized structures exhibit strong adsorptions and low diffusion energy barriers, suggesting fast charge-discharge rates. By reaching the ultimate structural configurations, the theoretical capacities are as high as 312 mAh/g with low but positive open circuit voltage. All the performances reveal that the S-MXenes are promising anode materials for KIBs and expand their application as electrode materials.