Theoretical Screening of Metal Borocarbide Sheets for High-Capacity and High-Rate Li - and Na -Ion Batteries (original) (raw)

2021, Physical Review Applied

Two-dimensional (2D) materials with intrinsic metal properties are promising for battery applications. Herein, we theoretically design a series of X 2 BC (X = Mg, Ca, Sr, Ti, V, Mo) sheets as anode materials for Li-ion and Na-ion batteries (LIBs and NIBs) using first-principles calculations based on density functional theory. The X 2 BC sheets are found to be intrinsically metallic with good stability. Besides, X 2 BC (X = Mg, Ca, Sr) sheets are auxetic 2D materials. More interestingly, the highest predicted specific capacities are calculated to be 1502, 1042, and 905 mAh g −1 for Mg 2 BC, Ca 2 BC, and Ti 2 BC, respectively. The activation energy barrier of Na on Ti 2 BC (0.105 eV) is the lowest among all the considered Li and Na X 2 BC structures. The calculated open-circuit voltage values of 0.040 V (0.153 V) and 0.353 V (0.200 V) for Li (Na) of Ca 2 BC and Ti 2 BC, respectively, fall within the acceptable range of 0.1-1.0 V for anode materials. They are found to be smaller than or comparable with those of commercial graphite anode. The results show that X 2 BC sheets are promising candidates for both LIBs and NIBs.