Dilution Strategy to Enhance Electrolyte Stability in Lithium Metal Batteries

Category Science

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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.

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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.

Lithiumy metal batteries are one of the most promising next-generation batteries

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.

Li metal anodes are complex due to its high reactivity, high cost and poor cycle life

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.

The electrolyte's main role in Li metal batteries is to transport lithium ions from one electrode to the other

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