High-efficiency Lithium Metal Stabilization and Polysulfide Suppression in Li-S Battery Enabled by Weakly Solvating Solvent.

Lithium-sulfur batteries (LSBs) are considered a highly promising next-generation energy storage technology due to their exceptional energy density and cost-effectiveness. However, the practical use of current LSBs is hindered primarily by issues related to the "shuttle effect" of lithium polysulfide (LiPS) intermediates and the growth of lithium dendrites. In strongly solvating electrolytes, the solvent-derived solid electrolyte interphase (SEI) lacks mechanical strength due to organic components, leading to ineffective lithium dendrite suppression and severe LiPS dissolution and shuttling. In contrast, the weakly solvating electrolyte (WSE) can create an anion-derived SEI layer which can enhance compatibility with lithium metal anode, and restricting LiPS solubility. Herein, a WSE consisting of 0.4 Ð¼ LiTFSI in the mixture of 1,4-dioxane (DX):dimethoxymethane (DMM) is designed to overcome the issues associated with LSB. Surface analyses confirmed the formation of a beneficial SEI layer rich in LiF, enabling homogeneous lithium deposition with an average Coulombic efficiency CE exceeding 99% over 100 cycles. Implementing the low-concentration WSE in Li||SPAN cells yielded an impressive initial specific capacity of 671 mAh g-1. This research highlights the advantages of WSE and offers the pathway for cost-effective electrolyte development, enabling the realization of high-performance LSBs.

Practical High-Voltage Lithium Metal Batteries Enabled by Tuning the Solvation Structure in Weakly Solvating Electrolyte.

Li metal batteries (LMBs) are ideal candidates for future high-energy-density battery systems. To date, high-voltage LMBs suffer severe limitations because of electrolytes unstable against Li anodes and high-voltage cathodes. Although ether-based electrolytes exhibit good stability with Li metal, compared to carbonate-based electrolytes, they have been used only in ≤4.0 V LMBs because of their limited oxidation stability. Here, a high concentration electrolyte (HCE) comprising lithium bis(fluorosulfonyl)imide (LiFSI) and a weakly solvating solvent (1,2-diethoxyethane, DEE) is designed, which can regulate unique solvation structures with only associated complexes at relatively lower concentration compared to the reported HCEs. This effectively suppresses dendrites on the anode side, and preserves the structural integrity of the cathode side under high voltages by the formation of stable interfacial layers on a Li metal anode and LiNi0.8 Mn0.1 Co0.1 O2 (NMC811) cathode. Consequently, a 3.5 m LiFSI-DEE plays an important role in enhancing the stability of the Li||NMC811 cell with a capacity retention of ≈94% after 200 cycles under a high current density of 2.5 mA cm-2 . In addition, the 3.5 m LiFSI-DEE electrolyte exhibits good performance with anode-free batteries. This study offers a promising approach to enable ether-based electrolytes for high-voltage LMBs applications.