Hierarchical and Nanocrystallite-Assembled Ultraporous NiO/MnCo<sub>2</sub>O<sub>4</sub> for All Solid-State Hybrid Supercapacitors with Robust Energy Efficiency and Extended Operational Durability
Nemi Chand Mawari, Siddhant Srivastav, Sumanta Kumar Meher
Abstract
To address the growing demand of highly Ragone efficient electrochemical energy storage devices, we have innovated a synthetic design strategy and employed a tartrate-mediated kinetic precipitation process to fabricate an ultraporous ribbon-like hierarchical microstructure of Ni-, Mn-, and Co-based ternary oxide, i.e., NiO/MnCo 2 O 4, and employed it as a battery-type positive electrode material to assemble an ASSHSC (all-solid-state hybrid supercapacitor) device with nitrogen-doped reduced graphene oxide (N-rGO) as the positive electrode material. NiO/MnCo 2 O 4 exhibits distinct crystallographic phase, near-perfect elemental stoichiometry, evident bulk porosity, and rich nanocrystallite assembly in the randomly arranged microstructure of near-uniform size and shape. Thorough electrochemical studies corroborate that the battery-type NiO/MnCo 2 O 4 exhibits remarkable electrochemical reversibility during charge transfer, high efficiency in supercapacitive charge storage, low charge transfer, series and diffusion resistance. The NiO/MnCo 2 O 4 ||N-rGO ASSHSC device assembled with the PVA-KOH film as the separator electrolyte offers rich charge storage physiognomies, which accentuates excellent electromicrostructural compatibility between the electrode materials in the device. The NiO/MnCo 2 O 4 ||N-rGO ASSHSC device shows low charge transfer and diffusion resistance, and it also delivers high mass and areal specific capacitance/capacity, energy and power density, Ragone efficiency (∼131 Wh kg – 1 at ∼2134 W kg – 1 and ∼31 Wh kg – 1 at ∼5005 W kg – 1 ), and extended operational durability (98.2% specific capacitance retention after 12,000 successive GCD cycles) under high-rate working conditions. The present optimized approach to design highly efficient multiple transition-metal-based oxides as battery-type electrode materials and fabricate rich Ragone-efficient ASSHSC devices can be widely adopted in the future development of high-performance hybrid supercapacitors, which may be largely integrated in various pioneering technologies.