Clear Representation of Surface Pathway Reactions at Ag Nanowire Cathodes in All-Solid Li-O2 Batteries

Hao Wang; Ning Zhao; Zhijie Bi; Shenghan Gao; Qiushi Dai; Tingting Yang; Jiawei Wang; Zhiqing Jia; Zhangquan Peng; Jianyu Huang; Yong Wan; Xiangxin Guo

doi:10.1021/acsami.1c02923

Clear Representation of Surface Pathway Reactions at Ag Nanowire Cathodes in All-Solid Li-O₂ Batteries

ACS Appl Mater Interfaces. 2021 Aug 25;13(33):39157-39164. doi: 10.1021/acsami.1c02923. Epub 2021 Aug 11.

Authors

Affiliations

¹ College of Physics, Qingdao University, Qingdao 266071, China.
² Clean Nano Energy Center, State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004, China.
³ Laboratory of Advanced Spectro-electrochemistry and Lithium-ion Batteries, Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China.
⁴ School of Civil Engineering, Qingdao University of Technology, Qingdao 266033, China.

PMID: 34378380
DOI: 10.1021/acsami.1c02923

Abstract

All-solid Li-O₂ batteries have been constructed with Ag nanowire (AgNW) cathodes coated on Au-buffered garnet ceramic electrolytes and Li anodes on the other sides. Benefiting from the clean contacts of Li⁺, e^-, and O₂ on the AgNWs, the surface pathway reactions are demonstrated. Upon discharge, two types of Li₂O₂ morphologies appear. The film-like Li₂O₂ forms around the smooth surfaces of AgNWs, and hollow disk-like Li₂O₂ forms at the joints in between the AgNWs as well as at the garnet/AgNW interfaces. The formation of films and hollow disks is in accordance with the process of O₂ + Li⁺ + e^- → LiO₂ and 2LiO₂ → Li₂O₂ + O₂, indicating that the disproportionation of LiO₂ occurs at the solid interfaces. During the initial charge, decomposition occurs below the potential of 3.5 V, indicating the process of Li₂O₂ → LiO₂ + Li⁺ + e^- and LiO₂ → Li⁺ + e^- + O₂ rather than Li₂O₂ → 2Li⁺ + 2e^- + O₂. The Li₂O₂ decomposition starts at the AgNWs/Li₂O₂ interfaces, causing the film-like Li₂O₂ to shrink and the gas to release, followed by the collapse of hollow disk-like Li₂O₂. The results here clearly disclose the Li-O₂ reaction mechanism at the all-solid interfaces, facilitating a deep understanding of key factors influencing the electrochemical performance of the solid-state Li-O₂ batteries.

Keywords: Li2O2 growth and decomposition; all-solid interfaces; carbon-free cathodes; environmental TEM characterization; solid-state Li−O2 batteries.