Layered MnO2 nanodots as high-rate and stable cathode materials for aqueous zinc-ion storage

MnO2 has recently received great concern as a cathode material for zinc-based energy storage owing to its many advantages. Unfortunately, the low rate capability and poor cyclability hinder its practical application. Herein, novel layered MnO2 nanodots (delta-MnO2 NDs) are synthesized by a facile redox reaction, and utilized as the cathode for aqueous zinc-ion batteries/hybrid capacitors (ZIBs/ZICs) for the first time. Benefiting from the layered structure and nanoscale size, the delta-MnO2 NDs//Zn ZIBs display a considerable specific capacity of 335 mAh g(-1) at 0.1 A g(-1) , an impressive rate capacity of 125 mAh g(-1) at 2.0 A g(-1) , a large specific energy (466.7 Wh kg(-1) at 139 W kg(-1)), and a superior durability with 86.2% capacity retention after 1000 cycles at 1.0 A g(-1) . Further, the H+/Zn2+ co-insertion energy storage mechanism of the delta-MnO2 NDs cathode is verified by electrochemical kinetics analyses and ex-situ characterizations. Simultaneously, the novel ZICs based on delta-MnO2 NDs cathode exhibit a high specific energy of 68.7 Wh kg(-1 )and a satisfactory cycle life with 86.9% capacity retention after 5000 cycles at 1.0 A g(-1) . The quantization design strategy opens a new gateway for the design and exploitation of advanced cathodes for aqueous ZIBs and ZICs.

Automated summary

In this study, novel layered MnO2 nanodots were synthesized and utilized as the cathode material for aqueous zinc-ion batteries/hybrid capacitors (ZIBs/ZICs) for the first time. The delta-MnO2 NDs displayed high specific capacity, impressive rate capacity, large specific energy, and superior durability. The H+/Zn2+ co-insertion energy storage mechanism of the cathode was also verified. The quantization design strategy provides a new approach for the design and development of advanced cathodes for aqueous ZIBs and ZICs.