Constructing robust cathode/Li interfaces and intensifying ion transport kinetics for PEO-based solid-state lithium-sulfur batteries

Abstract

Solid-state lithium-sulfur batteries (SSLSBs) are attractive due to their potential to provide high energy densities. However, the battery chemistry of SSLSBs still faces significant challenges, such as sluggish ion transport and prominent interface failures. Here, a high-performance cell is demonstrated by designing a composite electrolyte (CPE) consisting of polyethylene glycol azobenzamide (PGA) and poly (ethylene oxide) (PEO). Meanwhile, 7Li solid-state NMR spectroscopy and density functional theory (DFT) results show that PGA promotes the dissociation of lithium salts and generate more free lithium ions, thereby improving the ion migration kinetics. Moreover, ex-situ XPS and DFT confirm that PGA has a significant confined effect on polysulfides and effectively suppresses the shuttle effect. Subsequently, the interfacial layer consisted of abundant LiF&Li3N, which could achieve rapid lithium-ion transport and uniform deposition. Therefore, a stable ultra-long cycle time of over 2800 h can be achieved for the Li/Li symmetric cells at 0.2 mA cm−2. The prepared CPE exhibits a high ionic conductivity of 4.9 × 10-4 S cm−1 and a lithium-ion transference number of 0.53 at 50 °C. The assembled SSLSBs show an excellent cycling performance, which accomplishes 100 cycles at 0.2C with the reversible discharge capacity of 541 mAh/g. The superior performance of the SSLSBs rationalizes the CPE construction concept and leads to considerations for the innovative design of PEO-based SSLSBs.