Noninterference Revealing of "Layered to Layered" Zinc Storage Mechanism of δ-MnO2 toward Neutral Zn-Mn Batteries with Superior Performance

Yuqi Jiang; Deliang Ba; Yuanyuan Li; Jinping Liu

doi:10.1002/advs.201902795

Noninterference Revealing of "Layered to Layered" Zinc Storage Mechanism of δ-MnO₂ toward Neutral Zn-Mn Batteries with Superior Performance

Adv Sci (Weinh). 2020 Jan 16;7(6):1902795. doi: 10.1002/advs.201902795. eCollection 2020 Mar.

Authors

Yuqi Jiang¹, Deliang Ba², Yuanyuan Li², Jinping Liu^{1

3}

Affiliations

¹ State Key Laboratory of Advanced Technology for Materials Synthesis and Processing and School of Chemistry Chemical Engineering and Life Science Wuhan University of Technology Wuhan Hubei 430070 P. R. China.
² School of Optical and Electronic Information Huazhong University of Science and Technology Wuhan Hubei 430074 P. R. China.
³ State Center for International Cooperation on Designer Low-carbon & Environmental Materials and School of Materials Science and Engineering Zhengzhou University Zhengzhou Henan 450001 P. R. China.

Abstract

MnO₂ is one of the most studied cathodes for aqueous neutral zinc-ion batteries. However, the diverse reported crystal structures of MnO₂ compared to δ-MnO₂ inevitably suffer a structural phase transition from tunneled to layered Zn-buserite during the initial cycles, which is not as kinetically direct as the conventional intercalation electrochemistry in layered materials and thus poses great challenges to the performance and multifunctionality of devices. Here, a binder-free δ-MnO₂ cathode is designed and a favorable "layered to layered" Zn²⁺ storage mechanism is revealed systematically using such a "noninterferencing" electrode platform in combination with ab initio calculation. A flexible quasi-solid-state Zn-Mn battery with an electrodeposited flexible Zn anode is further assembled, exhibiting high energy density (35.11 mWh cm^-3; 432.05 Wh kg^-1), high power density (676.92 mW cm^-3; 8.33 kW kg^-1), extremely low self-discharge rate, and ultralong stability up to 10 000 cycles. Even with a relatively high δ-MnO₂ mass loading of 5 mg cm^-2, significant energy and power densities are still achieved. The device also works well over a broad temperature range (0-40 °C) and can efficiently power different types of small electronics. This work provides an opportunity to develop high-performance multivalent-ion batteries via the design of a kinetically favorable host structure.

Keywords: Zn–Mn batteries; aqueous neutral Zn–MnO2 batteries; quasi‐solid‐state batteries; zinc storage mechanism; δ‐MnO2.