The poor compatibility of carbonate-based electrolytes with lithium metal anodes results in unstable solid electrolyte interphase, leading to lithium dendrite formation, low Coulombic efficiency, and short cycle life. To address this issue, we propose a novel fluorinated electrolyte that leverages lithium bis(fluorosulfonyl)imide (LiFSI), along with fluorinated solvents. An extremely low concentration of lithium nitrate exerts a substantial impact on the Li ion solvation structure, inducing an anions-rich solvation structure, results in an inorganic-rich electrolyte interphase layer mainly composed of Li 3 N and LiF, which effectively inhibits lithium dendrite formation, enhances the interfacial stability between the electrode and electrolyte, and yields excellent cycling performance in lithium metal batteries. When coupled with a high nickel content cathode (LiNi 0.8 Co 0.1 Mn 0.1 O 2 ), the cells exhibit impressive cycling performance with 1000 cycles at 4 C, retaining 68.6 % capacity (with charge times under 15 min). Despite the relatively low oxidation stability of Dimethoxyethane in the electrolyte, the cell demonstrates exceptional high-voltage electrochemical performance, even up to 4.5 V, the cells do not show extensive electrolyte decomposition and structural changes, preserving 79.2 % capacity retention after 300 cycles. Using 50 µm lithium foil in the cells, remarkable capacity retention of 89.5 % is achieved after 400 cycles at 1 C. This remarkable compatibility between the anode and cathode represents a significant breakthrough in enhancing the reliability and performance of lithium metal batteries.
The development of practical lithium metal cells is plagued by their limited lifespan, primarily due to the poor interfacial stability of the electrolytes. Here we present a compact ion-pair aggregate (CIPA) electrolyte that enables high-performance Li metal pouch cells under lean electrolyte conditions. The electrolyte features a unique nanometre-scale solvation structure in which ion pairs are densely packed to form large CIPAs, in contrast to conventional electrolytes that comprise small aggregates. Notably, the CIPAs facilitate fast interfacial reduction kinetics on the Li metal anode via a collective electron-transfer process, leading to the formation of a stable interface. A 505.9 Wh kg −1 Li metal pouch cell with a high-nickel-content cathode (LiNi 0.905 Co 0.06 Mn 0.035 O 2 ) exhibited a 91% energy retention after 130 cycles. This work demonstrates nanostructured electrolyte design for realizing high-performance Li metal batteries. It also showcases the importance of understanding interfacial reaction mechanisms in the design and development of electrolytes.
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