Unveiling the anchoring and catalytic effect of Co@C3N3 monolayer as a high-performance selenium host material in lithium-selenium batteries: a first-principles study

Suppressing the shuttle effect of high-order polyselenides is crucial for the development of high-performance host materials in lithium-selenium (Li-Se) batteries. Using first-principles calculations, the feasibility of Co@C3N3 monolayer as selenium cathode host material for Li-Se batteries is systematically evaluated from the aspects of binding energy, charge transfer mechanism, and catalytic effect of polyselenides in the present work. The Co@C3N3 monolayer can effectively prevent the solubilization of high-order polyselenides with large binding energy and charge transfer resulting from the synergistic effect of Li-N and Co-Se bonds. The polyselenides are inclined to adsorb on the surface of Co@C3N3 monolayer instead of interacting with the electrolytes, which effectively inhibits the shuttling of high-order polyselenides and improves cycling stability. The cobalt participation improves the conductivity of C3N3 monolayer, and the semi-metallic characteristics of the Co@C3N3 monolayer are maintained after the adsorption of Li2Sen (n = 1, 2, 4, 6, 8) or Se-8 clusters, which is advantageous for the utilization of active selenium material. The crucial catalytic role of the Co@C3N3 monolayer is evaluated by examining the reduction pathway of Se-8 and the decomposition barrier of Li2Se, and the results highlight the capability of Co@C3N3 monolayer to enhance the utilization of selenium and promote the transition of Li2Se. Our present work could not only provide valuable insights into the anchoring and catalytic effect of Co@C3N3 monolayer, but also shed light on the future investigation on the high performance C3N3-based host materials for Li-Se batteries.