Commercially Applicable One-Step Method to Construct Homogeneous Anode/Electrolyte Interface and Cathode/Electrolyte Interface Layers in All-Solid-State Lithium–Sulfur Batteries

Using a solid electrolyte is considered to be the most effective strategy to solve the shuttle effect in lithium-sulfur batteries. However, the practical application of solid-state lithium-sulfur batteries (SLSBs) is still far from being realized. This is because SLSBs, like all other solid-state battery systems, also face the dilemma of interface degradation (including both the anode and cathode interfaces), in addition to terrible kinetics due to the nonliquid solid-state electrolytes infiltrating the nonconductive sulfur particles inside the cathode. It is necessary to consider the factors associated with the cathode, anode, electrolyte, and all the interfaces in an integrated manner to solve the problems existing in SLSBs. Similar to the anode/electrolyte interface formation in a liquid electrolyte, this work simultaneously synthesized the in situ anode/electrolyte and cathode/electrolyte interfaces by one-step electrochemically inducing the polymerization of thiophene monomers in the poly(ethylene oxide) electrolyte. By screening and adjustment of the thiophene polymerization process, a dual ion-electron conductive layer on both sides of the electrolyte as well as the inner surface of the sulfur cathode was synthesized. As a result of these improvements, an ionic conductivity of 1.1 × 10^-4 S cm^-1 was achieved by the composited electrolyte at 40 °C while maintaining a specific capacity of 1166.6 mAh g^-1 after 50 cycles by the SLSBs assembled. This study regulated the dual ion-electron conductive interface on both sides of the electrolyte in a one-step manner and emphasized the important role of the homogeneity inner cathode surface and cathode/electrolyte interface in SLSBs. It might be extended to production applications because of its competitiveness in both technology and economy.