The solid/liquid Li-S battery shows promise in solving both the polysulfide “shuttle effect” in liquid batteries and the interfacial contact in all-solid-state batteries. However, increasing the interfacial stability of the electrolyte and the solid electrolyte remains a challenge in the solid/liquid batteries. In this work, a high ionic conductivity Li 3 PS 4 solution is synthesized using a nano-Li 2 S precursor, which is then utilized to form a solid electrolyte Li 3 PS 4 @Li 7 P 3 S 11 via dip-coating. The Li 3 PS 4 @Li 7 P 3 S 11 can form a dense protective interface Li 3 PS 4 -DME with the DOL/DME and DME electrolyte. This interface can prevent direct contact between the solid electrolyte and the electrolytes, efficiently inhibiting further solid electrolyte decomposition. The lithium symmetric battery with the solid electrolyte Li 3 PS 4 @Li 7 P 3 S 11 is cycled stably for 1000 h, at a current density of 0.38 mA cm −2 and a capacity of 1.51 mA h cm −2 . The Li-S battery with the solid electrolyte Li 3 PS 4 @Li 7 P 3 S 11 can cycle stably for 300 cycles at 0.2C with a capacity of 600 mA h g −1 remaining.
Sulfide electrolytes show great potential as solid electrolytes for all-solid-state batteries due to their high ionic conductivity and low interfacial resistance toward electrode materials. The structure of the P–S framework in the composition of sulfides plays a crucial role in the conductivity. Introducing LiI in the Li3PS4 structure can tailor the P–S frameworks and thus achieve high ionic conductivities. Herein, the dopant of LiI is optimized by high-rotation milling, followed by a sintering route to achieve the highest Li-ion conductivity of 2.3 mS cm–1 for the Li3PS4-50% LiI electrolyte (also denoted as Li7P2S8I) among different compositions. The phase variations and structure evolution of the P–S frameworks in the LiI-doped Li3PS4 electrolytes are carefully investigated in a combination of X-ray diffraction and Raman spectra. All-solid-state Li–S batteries using the prepared Li7P2S8I electrolyte combined with a nano Li2S cathode and a Li–In anode deliver a high initial discharge capacity of 739.7 mA h g–1 and sustain a discharge capacity of 517.7 mA h g–1 after 60 cycles with a capacity retention of 70.0% at 0.13 mA cm–2 at room temperature. When the operating temperature rises to 60 °C, it shows a higher discharge capacity of 862.8 mA h g–1 with fast capacity decay. However, it exhibits stable capacities and superior cycling performance under 0 °C over 70 cycles. Electrochemical impedance spectroscopy and in situ stack-pressure results find that the electrochemical performance differences of the assembled battery at different operating temperatures are associated with the interfacial resistance caused by volume changes. This work provides the strategy to obtain highly conductive sulfide electrolytes for SSBs and unravels the temperature effects on the electrochemical performance of all-solid-state Li–S batteries.
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