O- or/and S-functionalized Cr2C as electrode material for metal-ion (Li, Na, K, and Mg) batteries: A first principles study

MXenes are ideal electrode materials for metal-ion batteries due to their remarkable mechanical properties, high electronic conductivity, and hydrophilic. In this work, the electrochemical performance of O- or/and S-functionalized Cr2C as electrode material are studied by density functional theory. The Cr2CO2 and Cr2CS2 monolayers have the characteristics of favorable structural stability and high electrical conductivity. At the same time, they have low diffusion barriers for metal-ions (Li, Na, K, and Mg). Most notably, the maximum capacity of Cr2CO2 to Mg-ion and Cr2CS2 to Li-ion are up to 878.721 and 724.351 mA h g−1, corresponding to open circuit voltages of 0.164 and 0.117 V. Furthermore, bi-functionalized Cr2C monolayers are designed and investigated, the results indicate that the preparation of functionalized surfaces is more conducive to improving the capacity performance of specific metal-ions compared with bi-functionalized surfaces. This work provides new choices for the experimental research of MXene based electrode materials in the future.