Gallium regulated MnO2 toward high performance Zn ion batteries

Abstract

α-MnO2 with open tunnel structure has received ever-increasing attention because of its superior specific capacity, yet generally undergoes unstable phase transition from the tunnel architecture to layered structure upon Zn2+ insertion as well as the disadvantages of low electrical conductivity and slow Zn2+ diffusion kinetics, thereafter triggering inactive reaction dynamics. In this regard, a gallium (Ga) doped α-MnO2 nanowires (denoted as MnO2-Ga) is firstly built in this work to address the abovementioned issue and the MnO2-Ga2 displays enhanced performance with reversible capacity of 205.1 ± 5 mAh g−1 undergoing 200 cycles at 0.2 A g−1. After repeated 2000 cycles at 1 A g−1, a capacity of 123.7 ± 5 mAh g−1 can be still obtained. Validated by the theoretical calculation, it is noted that the Ga could effectively regulate the electronic distribution of α-MnO2 and narrows the bandgap, prompting the electronic cloud polarization of O and therafter accelerating ion diffusion efficiency. Fundamentally, the Ga intercalation results in the formation of Ga–O bonds. This special building not only guarantees the reversible phase transition and alleviates the Mn dissolution of Ga-MnO2, but also weakens the Zn2+-O2- interactions, leading to elevated cyclic durability and capacity.