High Pseudocapacitance-Driven CoC₂O₄ Electrodes Exhibiting Superior Electrochemical Kinetics and Reversible Capacities for Lithium-Ion and Lithium-Sulfur Batteries

In this study, cuboid-like anhydrous CoC2O4 particles (CoC2O4-HK) are synthesized through a potassium citrate-assisted hydrothermal method, which possess well-crystallized structure for fast Li+ transportation and efficient Li+ intercalation pseudocapacitive behaviors. When being used in lithium-ion batteries, the as-prepared CoC2O4-HK delivers a high reversible capacity (approximate to 1360 mAh g(-1) at 0.1 A g(-1)), good rate capability (approximate to 650 mAh g(-1) at 5 A g(-1)) and outstanding cycling stability (835 mAh g(-1) after 1000 cycles at 1 A g(-1)). Characterizations illustrate that the Li+-intercalation pseudocapacitance dominates the charge storage of CoC2O4-HK electrode, together with the reversible reaction of CoC2O4+2Li(+)+2e(-)-> Co+Li2C2O4 on discharging and charging. In addition, CoC2O4-HK particles are also used together with carbon-sulfur composite materials as the electrocatalysts for lithium-sulfur (Li-S) battery, which displays a gratifying sulfur electrochemistry with a high reversibility of 1021.5 mAh g(-1) at 2 C and a low decay rate of 0.079% per cycle after 500 cycles. The density functional theory (DFT) calculations show that CoC2O4/C can regulate the adsorption-activation of reaction intermediates and therefore boost the catalytic conversion of polysulfides. Therefore, this work presents a new prospect of applying CoC2O4 as the high-performance electrode materials for rechargeable Li-ion and Li-S batteries.