Hybrid Electrolyte with Dual‐Anion‐Aggregated Solvation Sheath for Stabilizing High‐Voltage Lithium‐Metal Batteries

• Published in: Advanced materials (Weinheim) 2021-12, Vol.33 (52), p.e2007945-n/a
• Main Authors: Wang, Xianshu, Wang, Shuwei, Wang, Huirong, Tu, Wenqiang, Zhao, Yun, Li, Song, Liu, Qi, Wu, Junru, Fu, Yongzhu, Han, Cuiping, Kang, Feiyu, Li, Baohua
• Format: Article
• Language: English
• Subjects: Anions; Anodes; Cathodes; dual‐anion aggregation; Electric potential; electrode/electrolyte interfaces; Electrolytes; Energy storage; Heterostructures; high voltage applications; Li + solvation; Lithium batteries; lithium‐metal batteries; Materials science; Modulus of elasticity; Sheaths; Solid electrolytes; Solvation; Voltage
• ISSN: 0935-9648; 1521-4095
• DOI: 10.1002/adma.202007945

Lithium (Li)‐metal batteries (LMBs) with high‐voltage cathodes and limited Li‐metal anodes are crucial to realizing high‐energy storage. However, functional electrolytes that are compatible with both high‐voltage cathodes and Li anodes are required for their developments. In this study, the use of a moderate‐concentration LiPF6 and LiNO3 dual‐salt electrolyte composed of ester and ether co‐solvents (fluoroethylene carbonate/dimethoxyethane, FEC/DME), which forms a unique Li+ solvation with aggregated dual anions, that is, PF6− and NO3−, is proposed to stabilize high‐voltage LMBs. Mechanistic studies reveal that such a solvation sheath improves the Li plating/stripping kinetics and induces the generation of a solid electrolyte interphase (SEI) layer with gradient heterostructure and high Young's modulus on the anode, and a thin and robust cathode electrolyte interface (CEI) film. Therefore, this novel electrolyte enables colossal Li deposits with a high Coulombic efficiency (≈98.9%) for 450 cycles at 0.5 mA cm−2. The as‐assembled LiǁLiNi0.85Co0.10Al0.05O2 full batteries deliver an excellent lifespan and capacity retention at 4.3 V with a rigid negative‐to‐positive capacity ratio. This electrolyte system with a dual‐anion‐aggregated solvation structure provides insights into the interfacial chemistries through solvation regulation for high‐voltage LMBs. A moderate‐concentration electrolyte with an inner dual‐anion‐aggregated Li+ solvation sheath is developed, which guarantees the reversibility of Li plating/stripping and meets the requirements of a high‐voltage cathode. This peculiar solvated structure plays an important role in tailoring the electrode/electrolyte interphases, so as to realize the long‐term cyclability of lithium‐metal batteries with limited Li anodes and LiNi0.85Co0.10Al0.05O2 cathodes.