Garnet-type Li6.75La3Zr1.75Ta0.25O12 (LLZTO) is
a promising solid-state
electrolyte
(SSE) because of its fast ionic conduction and notable chemical/electrochemical
stability toward the lithium (Li) metal. However, poor interface wettability
and large interface resistance between LLZTO and Li anode greatly
restrict its practical applications. In this work, we develop an in
situ chemical conversion strategy to construct a highly conductive
Li2S@C layer on the surface of LLZTO, enabling improved
interfacial wettability between LLZTO and the Li anode. The Li/Li2S@C-LLZTO-Li2S@C/Li symmetric cell has a low interface
impedance of 78.5 Ω cm2, much lower than the 970
Ω cm2 of a Li/LLZTO/Li cell. Moreover, the Li/Li2S@C-LLZTO-Li2S@C/Li cell exhibits a high critical
current density of 1.4 mA cm–2 and an ultralong
stability of 3000 h at 0.1 mA cm–2. When used in
a LiFePO4 battery, the Li/Li2S@C-LLZTO/LiFePO4 battery exhibits a high initial discharge capacity of 150.8
mA h g–1 at 0.2 C without lithium storage capacity
attenuation during 200 cycles. This work provides a novel and feasible
strategy to address interface issues of SSEs and achieve lithium-dendrite-free
solid-state batteries.