Fish‐scale‐like NiMn‐based layered double hydroxides for high‐energy aqueous supercapacitors
Adil Emin, Bingbing Gong, Hao Jiang
Abstract
Abstract Aqueous supercapacitors (SCs) exhibit exceptional electrochemical characteristics, including extended cycle stability and high‐power density, making them highly promising. Though their practical application and commercialization are hindered by low energy density, we developed a high‐performance, self‐supporting SC electrode to address this limitation using nickel manganese layered double hydroxide (NiMn‐LDH) directly synthesized on activated carbon cloth (ACC). This electrode achieved an extraordinary specific capacitance of 2838.8 F g −1 at a current density of 1 A g −1 , with 70.3% retention at 30 A g −1 and 86.1% retention after 6,000 cycles at 15 A g −1 , demonstrating its remarkable performance and durability. After being assembled into an asymmetric SCs (ASCs) device with the ACC negative electrode in 2M potassium hydroxide (KOH), a broad operating voltage window of 1.6 V with an energy density of up to 89.7 Wh kg −1 was achieved at a power density of 800.0 W kg −1 . Furthermore, the device retained 89.30% of its initial capacitance after 10,000 cycles at 10 A g −1 , with a near‐perfect Coulombic efficiency close to 100%. The fish‐scale‐like nanostructure effectively increases the active sites of the electrode to make sufficient full contact with the electrolyte, accelerating the transport of electrons/ions and enhancing its electrochemical performance. These findings emphasize the potential of NiMn‐LDH for application in wearable and microscale energy storage devices.