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Given the increased use of room temperature ionic liquid electrolytes in Li-ion batteries, due to their non-flammability and negligible volatility, this study evaluates the lithiation kinetics to understand and improve the rate performance of Li-ion batteries. Lithium titanate spinel is used as a model electrode and the electrolyte is composed of LiTFSI and TFSI-coordinated alkoxy-modified phosphonium ionic liquid. Based on the analysis of activation energies for each process, we report that the charge-transfer reaction at the electrode/electrolyte interface is the rate-limiting step for cell operation. This finding is further supported by the observation that a 50-fold decrease in charge-transfer resistance at higher temperatures leads to a significant performance improvement over that of a traditional organic electrolyte at room temperature. Charge-transfer resistance and electrolyte wetting on the electrode surface are critical processes for optimal battery performance, and such processes need to be included when designing new ionic liquids in order to exceed the power density obtained with the use of current carbonate-based electrolytes. [ABSTRACT FROM AUTHOR]

A nanoporous all-solid-state MOF-laden polymer electrolyte that is simply mediated by an electronic effect shows remarkably high lithium electrodeposition stability of hundreds of charge–discharge cycles and over 1500 operating hours, while maintaining a very small voltage polarization. This result is a significant improvement relative to conventional PEO and, when used in an all-solid-state battery (ASSB), this electrolyte enabled enhanced cycle life. This new all-solid-state electrolyte shows a promising rational design for the emerging microporous polymeric materials as novel SPEs in ASSBs. [ABSTRACT FROM AUTHOR]