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

Abstract In this study, cuboid‐like anhydrous CoC 2 O 4 particles (CoC 2 O 4 ‐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 CoC 2 O 4 ‐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 CoC 2 O 4 ‐HK electrode, together with the reversible reaction of CoC 2 O 4 +2Li + +2e − →Co+Li 2 C 2 O 4 on discharging and charging. In addition, CoC 2 O 4 ‐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 CoC 2 O 4 /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 CoC 2 O 4 as the high‐performance electrode materials for rechargeable Li‐ion and Li–S batteries.