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 (≈1360 mAh g‐1 at 0.1 A g‐1), good rate capability (≈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. Well‐crystallized CoC2O4 particles are synthesized by the chelating agent‐assisted hydrothermal method, which display fast Li+ transportations and efficient Li+ intercalation pseudocapacitive behaviors to achieve outstanding Li‐ion performance. CoC2O4 particles are also used together with carbon–sulfur composite materials as the electrocatalysts for lithium–sulfur battery, which delivers a gratifying sulfur electrochemistry with a high reversibility and long cycling lifespan.