Gradient Defect Engineering Constructed Active Microregion to Assist Long‐Cycle‐Life Aqueous Soft‐Pack Device at High Current Density

Abstract To meet the requirements of fast charging/discharging scenarios, the cycle life of aqueous asymmetric supercapacitors at high current density needs to be elevated. Herein, at a high current density of 25 A g −1 , the capacitance retention rate of the Aqueous Soft‐Pack Device (SPD) is 91.66% after 20 000 cycles. Additionally, the SPD demonstrates both remarkable power density and exceptional energy density. Nickel‐Cobalt‐Layered‐Double‐Hydroxides (NiCo‐LDHs) are promising candidates as positive electrodes for supercapacitors with notable conductivity and capacitance. Nevertheless, enhancing the active microregion on nano‐sheets in situ while preserving the integrity of the LDHs structure remains a significant challenge. The active microregion of NiCo‐LDHs through gradient defect engineering is constructed, and NiCo‐LDHs‐Ov‐30 (process for “30” min) with specific oxygen defects (Ov) is successfully synthesized. Owing to the presence of Ov in NiCo‐LDHs‐Ov‐30, the layered structure of the original LDHs is preserved, while the active microregion is increased and the internal charge transfer resistance is reduced, thereby significantly enhancing the explicit electrochemical performance of NiCo‐LDHs‐Ov‐30. Meanwhile, this conclusion has been further substantiated by first‐principles calculation, particularly the positive shift in the d‐band center, which enhances the electrochemical reactivity of LDHs. The electrochemical reaction mechanism of NiCo‐LDHs‐Ov‐30 is confirmed using ex situ XRD and in situ Raman characterization.