Electrolyte design combining fluoro- with cyano- substitution solvents for anode- free Li metal batteries

• 成果类型: Article
• 署名作者: Mao, Minglei; Gong, Lei; Wang, Xiaobo; Wang, Qiyu; Zhang, Guoqun; Wang, Haoxiang; Xie, Wei; Suo, Liumin; Wang, Chengliang
• 署名单位: Huazhong University of Science & Technology; Chinese Academy of Sciences; Institute of Physics, CAS; Huazhong University of Science & Technology
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-9365
• DOI: 10.1073/pnas.2316212121
• 发表日期: 2024-01-30
• 关键词: lithium-ion batteries; fluoroethylene carbonate; reduction reactions; STABILITY; cathode; lipf6; instability; association; interphase; interfaces

摘要

Fluoro- substitution solvents have achieved great success in electrolyte engineering for high- energy lithium metal batteries, which, however, is beset by low solvating power, thermal and chemical instability, and possible battery swelling. Instead, we herein introduce cyanogen as the electron- withdrawing group to enhance the oxidative stability of ether solvents, in which cyanogen and ether oxygen form the chelating structure with Li+ not notably undermining the solvating power. Cyano-group strongly bonds with transition metals (TMs) of NCM811 cathode to attenuate the catalytic reactivity of TMs toward bulk electrolytes. Besides, a stable and uniform cathode-electrolyte interphase (CEI) inhibits the violent oxidation decomposition of electrolytes and guarantees the structural integrity of the NCM811 cathode. Also, a N- containing and LiF-rich solid-electrolyte interphase (SEI) in our electrolyte facilitates fast Li+ migration and dense Li deposition. Accordingly, our electrolyte enables a stable cycle of Li metal anode with Coulombic efficiency of 98.4% within 100 cycles. 81.8% capacity of 4.3 V NCM811 cathode remains after 200 cycles. Anode - free pouch cells with a capacity of 125 mAh maintain 76% capacity after 100 cycles, corresponding to an energy density of 397.5 Wh kg - 1. Significance A cyanosubstitution ether, ethylene glycol bis(propionitrile) ether (AN2- DME), was proposed, in which the strong electronwithdrawing cyano- group restrains the loss of lone - pair electrons of ether oxygen and enhances the oxidative stability. Paired with FEC and TTE, the 1 M LiPF6 in AN2- DME/FEC/TTE electrolyte facilitates the formation of N- containing and LiF- rich solid-electrolyte interphase as well as stable and uniform cathode-electrolyte interphase. A stable cycle of Li metal anode and 4.3 V NCM811 cathode is achieved. Anode - free pouch cells deliver a high energy of 397.5 Wh kg -1 with 76% capacity maintenance after 100 cycles. This work will inspire battery communities to introspect the very hot fluorosubstitution strategy and act as a primer to ignite the enormous enthusiasm on the cyanosubstitution solvents for highenergy Li metal batteries.