Li2S-Ag interlayer via electrochemical conversion of Ag2S for enhanced cycling performance of anode-less solid-state batteries

초록

Reversible Li plating and stripping in anode-less all-solid-state batteries continues to present challenges, primarily due to the aggressive localized accumulation of Li at the current collector/solid electrolyte (Li6PS5Cl) interface, which drives Li dendrite propagation and causes premature short-circuiting. Here, we report the chemically engineered formation of a Ag2S interlayer on the current collector to promote spatially uniform lithium deposition. The Ag2S layer is generated through a spontaneous room-temperature sulfidation reaction of Ag-coated stainless steel (SUS) foil in aqueous Na2S. During the initial charge, Ag2S undergoes electrochemical conversion into Ag and Li2S: the metallic Ag provides well-distributed nucleation sites for Li, whereas Li2S mitigates Li dendrite formation by preventing direct contact between the Li metal and solid electrolyte. In half-cells with this interlayer, the Ag2S-coated current collector delivers an average Coulombic efficiency of 99.6% over 100 cycles at 1.0 mA cm-2 and 3.0 mAh cm-2. Full cells paired with high-loading NCM cathodes (7.8 mAh cm-2) retain 77% of their initial capacity after 50 cycles. These results demonstrate that the electrochemical formation of Li2S from the Ag2S interlayer is crucial for achieving stable reversible cycling and high Coulombic efficiency in anode-less all-solid-state batteries.

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