Interfacial study and modulation of high-voltage layered cathode based all-solid-state batteries.

Employing layered materials as the cathodes for solid-state batteries (SSBs) is vital in enhancing the batteries' energy density, whereas numerous issues are present regarding the compatibilities between cathode electrode and modified solid electrolyte (ME) in this battery configuration. By investigating the electrochemical performance and interfacial properties of SSBs using various cathodes, the fundamental reason for the poor compatibility between layered cathodes, especially LiCoO with ME is revealed. Because of the Li(solvent) intercalation environments formed in the ME, the resultant weak-interacted TFSI could be adsorbed and destabilized by Co ions on the surface. Besides, the high energy level offsets between LiCoO and ME lead to Li-ion transferring from the bulk electrode to the electrolyte, resulting in a pre-formed interface on the cathode particles before the electric current is applied, affects the formation of effective cathode-electrolyte interface (CEI) film during electrochemical process and deteriorated overall battery performance. From this view, an interlayer is pre-added on the LiCoO surface through an electrostatic adsorption method, to adjust the energy level offsets between the cathode and ME, as well as isolate the direct contact of surface Co ions to TFSI. The cycling properties of the SSB using modified LiCoO are greatly enhanced, and a capacity retention of 68.72 % after 100 cycles could be achieved, against 8.28 % previously, certifying the rationality of the understanding and the effectiveness of the proposed modification method. We believe this research could provide basic knowledge of the compatibility between layered cathodes and MEs, shedding light on designing more effective strategies for achieving SSBs with high energy density.