Dilution Strategy to Enhance Electrolyte Stability in Lithium Metal Batteries

Monday - May 1 2023, 08:58 UTC - 1 year ago

This study demonstrates a dilution strategy to adjust the decomposition order of solvated species in ether-based electrolyte solutions, to enhance the electrolyte stability of LiMBs. When tested with a Li metal negative electrode (50 μm thick) and a LiNi0.8Co0.1Mn0.1O2-based positive electrode (3.3 mAh/cm2), the proposed dilution strategy yielded a specific discharge capacity retention of 74% after 150 cycles.

From the perspective of fundamental research on new LMB technologies, it is critical to meticulously develop suitable liquid electrolyte chemistry that works with promising anodes and cathodes.

In ether-based electrolyte solutions, the potential instability of solvated Li+/solvent species hinders the practical application of Li metal battery technology, as they usually require higher voltages and a thinner Li metal anode when compared to conventional Li-ion battery systems. This is concerning given that Li+/solvent molecules usually predominate at high voltages, resulting in the solvent self-decomposition.

To circumvent this issue, a dilution strategy to lose the Li+/solvent interaction was proposed here. The aim was to adjust the decomposition order of solvated species using a non-polar DPE-based electrolyte solution with lithium bis(fluorosulfonyl) imide salt, to favor the decomposition of Li+/salt-derived anion clusters over the free ether solvent molecules. This selective mechanism favors the formation of a robust cathode electrolyte interphase (CEI) as well as a solvent-deficient electric double-layer structure at the positive electrode interface.

The DPE-based electrolyte with Li+/salt-derived anion clusters was successfully tested in combination with a Li metal negative electrode and a LiNi0.8Co0.1Mn0.1O2-based positive electrode in a pouch cell configuration at 25°C. Results showed a promising specific discharge capacity retention of 74% after 150 cycles (0.33 and 1 mA/cm2) charge and discharge.

This study provides a system-level understanding of the dilution strategy as a tool to enhance the electrochemical stability of ether-based electrolyte solutions in high-voltage LiMBs. Additionally, the methodology described can serve as a platform for developing novel high-voltage LiMBs, thus inducing a new generation in energy storage about LiMBs.