Engineering Oxygen Vacancies on Mixed-Valent Mesoporous α-MnO₂ for High-Performance Asymmetric Supercapacitors

Abstract

Intrinsically poor conductivity and sluggish ion-transfer kinetics limit the further development of electrochemical storage of mesoporous manganese dioxide. In order to overcome the challenge, defect engineering is an effective way to improve electrochemical capability by regulating electronic configuration at the atomic level of manganese dioxide. Herein, we demonstrate effective construction of defects on mesoporous α-MnO2 through simply controlling the degree of redox reaction process, which could obtain a balance between Mn3+/Mn4+ ratio and oxygen vacancy concentration for efficient supercapacitors. The different structures of α-MnO2 including the morphology, specific surface area, and composition are successfully constructed by tuning the mole ratio of KMnO4 to Na2SO3. The electrode materials of α-MnO2-0.25 with an appropriate Mn3+/Mn4+ ratio and abundant oxygen vacancy showed an outstanding specific capacitance of 324 F g–1 at 0.5 A g–1, beyond most reported MnO2-based materials. The asymmetric supercapacitors formed from α-MnO2-0.25 and activated carbon can present an energy density as high as of 36.33 W h kg–1 at 200 W kg–1 and also exhibited good cycle stability over a wide voltage range from 0 to 2.0 voltage (kept at approximately 98% after 10 000 cycles in galvanostatic cycling tests) and nearly 100% Coulombic efficiency. Our strategy lays a foundation for fine regulation of defects to improve charge-transfer kinetics.

Hierarchical and Nanocrystallite-Assembled Ultraporous NiO/MnCo2O4 for All Solid-State Hybrid Supercapacitors with Robust Energy Efficiency and Extended Operational Durability

“…7 These oxides possess redox-active multiple transition-metal ions, tunable surface functionality, and bulk microstructural architecture, which offer multiple electrochemical advantages. 4,5 These factors of the electrode materials collectively minimize polarization and improve the redox reversibility of the electrochemical reactions during the working of the supercapacitors. 8 In this regard, various oxides, i.e., NiO, Co 3 O 4 , MnO 2 , Mn 3 O 4 , etc.…”

“…In the past few years, significant research has been targeted towards the development of compact and robust electrochemical energy storage devices with extended operational durability, which can meet the growing energy consumption need of modern society. − Among various such devices, hybrid electrochemical capacitors/pseudocapacitors/supercapacitors have gained significant attention, as they are known for their long shelf life, ease of handling, mechanical durability, remarkable power density, and extreme portability. , However, the limited practical applicability of supercapacitors is ascribed to their low energy deliverability as compared to the broadly used rechargeable batteries . Various strategies are adopted in order to enhance the energy efficiency of supercapacitors; one such strategy involves the design of electrode materials with facilitated electroactive ions throughout the materials’ matrices, which increases the number of electrochemical reactions.…”

“…Among various electrode materials for pseudocapacitors, first-row transition-metal oxides, particularly those based on Ni, Mn, and Co, are preferred due to their superior conductivity and pseudocapacitive physiognomics during charge storage . These oxides possess redox-active multiple transition-metal ions, tunable surface functionality, and bulk microstructural architecture, which offer multiple electrochemical advantages. , These factors of the electrode materials collectively minimize polarization and improve the redox reversibility of the electrochemical reactions during the working of the supercapacitors . In this regard, various oxides, i.e., NiO, Co 3 O 4 , MnO 2 , Mn 3 O 4 , etc.…”

Direct-Writing Flexible Metal Circuit with Polymer/Metal Precursor Ink and Interfacial Reaction

“…Therefore, the printing method is considered to be an ideal choice due to its low cost and simple process. It has been widely used in the manufacture of flexible electronic devices, such as electronic skin, , sensors, , thin film transistors, solar cells, and supercapacitors. , …”

“…It has been widely used in the manufacture of flexible electronic devices, such as electronic skin, 11,25 sensors, 26,27 thin film transistors, 28 solar cells, 29 and supercapacitors. 30,31 As a nonplate printing technique, direct writing could print various patterned conductive structures without complex nozzles, which has attracted a lot of attention to printing electronics. 32−36 In this process, conductive nanoparticle inks, such as silver nanoparticles, require high-temperature sintering to remove the nonconductive capping protectant attached to the nanoparticle surface after printing, thereby further improving the electrical conductivity of the circuit.…”