Construction of Hierarchical α-MnO₂ Nanowires@Ultrathin δ-MnO₂ Nanosheets Core–Shell Nanostructure with Excellent Cycling Stability for High-Power Asymmetric Supercapacitor Electrodes

Abstract

Poor electrical conductivity and mechanical instability are two major obstacles to realizing high performance of MnO2 as pseudocapacitor material. The construction of unique hierarchical core-shell nanostructures, therefore, plays an important role in the efficient enhancement of the rate capacity and the stability of this material. We herein report the fabrication of a hierarchical α-MnO2 nanowires@ultrathin δ-MnO2 nanosheets core-shell nanostructure by adopting a facile and practical solution-phase technique. The novel hierarchical nanostructures are composed of ultrathin δ-MnO2 nanosheets with a few atomic layers growing well on the surface of the ultralong α-MnO2 nanowires. The first specific capacitance of hierarchical core-shell nanostructure reached 153.8 F g(-1) at the discharge current density of as high as 20 A g(-1), and the cycling stability is retained at 98.1% after 10,000 charge-discharge cycles, higher than those in the literature. The excellent rate capacity and stability of the hierarchical core-shell nanostructures can be attributed to the structural features of the two MnO2 crystals, in which a 1D α-MnO2 nanowire core provides a stable structural backbone and the ultrathin 2D δ-MnO2 nanosheet shell creates more reactive active sites. The synergistic effects of different dimensions also contribute to the superior rate capability.

NiCo2S4@NiMoO4 Core-Shell Heterostructure Nanotube Arrays Grown on Ni Foam as a Binder-Free Electrode Displayed High Electrochemical Performance with High Capacity

“…Despite this progress, it is still a big challenge to fabricate the core-shell heterostructure with well-defined morphologies by effective and simple methods [33]. To further optimize the performance, the core-shell heterostructure can be directly grown on current collector which could offer good mechanical adhesion and electrical connection between the active materials and the substrates.…”

Hierarchically nanostructured transition metal oxides for supercapacitors

“…Electrochemical SCs based on manganese dioxide (MnO 2 ) have attracted considerable interest because of its rich polymorphisms (α-, β-, γ-, δ-, λ-, and ε-type), high theoretical specific capacitance, high natural abundance, and good environmental compatibility [68][69][70][71][72][73][74][75].…”

High‐Performance Yarn Supercapacitor Based on Metal–Inorganic–Organic Hybrid Electrode for Wearable Electronics

“…[26][27][28] Disappointingly, the experimental specific capacitance of MnO 2 is much lower than that of the theoretical value because the poor electrical conductivity of MnO 2 limits fast electron transport. [26][27][28] Disappointingly, the experimental specific capacitance of MnO 2 is much lower than that of the theoretical value because the poor electrical conductivity of MnO 2 limits fast electron transport.…”