Promising cathode material MnO₂/CoO₂ heterostructure for the Li and Na ion battery: A computational study

Although two-dimensional (2D) transition metal oxide monolayers have shown potential for applications in metal-ion batteries, the heterostructures of this family are yet to be studied in details for energy storage applications. In this work, we have made the heterostructure by taking half-metallic ferromagnetic 2D transition metal oxide $CoO 2$ and semiconducting $MnO 2$ monolayers and demonstrated its potential application as a cathode material in lithium and sodium-ion batteries by performing first-principles calculations using density functional theory approach. We have systematically studied the electronic structure and stability of the $MnO 2/ CoO 2$ heterostructure. We have carefully examined the adsorption and diffusion behavior of metal ions (lithium and sodium). Our structure has offered a maximum adsorption energy of $−3.84$ eV, which is greater than the adsorption energy of individual monolayers. We found that the lowest diffusion barrier is 0.4 eV for lithium ion and 0.32 eV for sodium ion. Also, our system has shown a maximum open circuit voltage of 2.18 V for lithium ion battery and 0.32 V for Na-ion battery. The specific capacity is found to be 584 mAh g $− 1$ for lithium ion and 529 mAh g $− 1$ for sodium ion battery. These findings can serve as a proof that the $MnO 2/ CoO 2$ heterostructure should be considered as a potential cathode for lithium- and sodium-ion batteries.