Ca2C MXene monolayer as a superior anode for metal-ion batteries

Rechargeable batteries can effectively mitigate the increasing crisis associated with clean energy storage technologies. The alkali metal-ion based rechargeable batteries require a low diffusion barrier, a low average open-circuit voltage (OCV), and a high storage capacity for their superior performance. Using comprehensive first-principle calculations, we demonstrate that calcium carbide monolayer (Ca2C-ML) MXene meets all the aforementioned criteria and is a superior anode material for lithium (Li), sodium (Na), and potassium (K) metal-ion batteries. By first-principles calculations, the structural and electronic properties of Ca2C-ML and its extensive ion battery applications are studied. The adsorption properties of Li, Na, and K alkali ions on the Ca2C-ML sheet confirm excellent charge transfer and electrical conductivity. The ultra-low diffusion barriers of 0.027, 0.059, and 0.028 eV for Li, Na, and K alkali ions, respectively, indicate the superior mobility and fast cycling caliber (metal adsorption and desorption) of the Ca2C-ML. The OCV of the Ca2C-ML is 0.10, 0.24, and 0.28 V for Li, Na, and K-ions, respectively, ensuring a better battery performance. The specific capacity of 582 mAh g(-1) is achieved for all three cases, which is much higher than that of a traditional graphite anode with Li, Na, and K ions. The volume expansion during the intercalation is negligible for all three cases, indicating long term structural integrity of the anode using Ca2C-ML. Our investigations suggest that the newly designed 2D Ca2C-ML is a suitable anode candidate for use in the next-generation of high-performance Li, Na, and K-ion batteries.