3D-crosslinked tannic acid/poly(ethylene oxide) complex as a three-in-one multifunctional binder for high-sulfur-loading and high-stability cathodes in lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries with traditional PVDF binders suffer from low active material utilization, poor cycling stability and low sulfur loading, which remarkably hinders their practical application. To address these issues once for all, we developed a three-in-one multifunctional binder based on three-dimensional (3D)-crosslinked tannic acid (TA)/poly(ethylene oxide) (PEO) complex, wherein TA can drastically enhance the stability of PEO in electrolyte solution. As-designed TA/PEO binder integrates multiple functions in one material: (1) greatly retard the shuttle effect, (2) effectively maintain cathodes integrity, (3) improve lithium ions transfer capacity, yet this point is often ignored in many existing binders. Benefiting from the above merits, even with a simple sulfur/carbon composite as cathode materials as a proof-of-concept, the assembled Li-S batteries using the TA/PEO binder present a discharge capacity of 476.7 mA h g−1 over 1000 cycles at 0.2 C, much higher than that with the PVDF binder (only 30 mA h g−1). The corresponding capacity fade is approximately 0.03%, superior to most reported binders. Even at a high sulfur loading of 5.0 mg cm−2, the cell delivers a capacity retention of 74.5% over 150 cycles. Additionally, the cathode preparation using our TA/PEO binder is an aqueous process, making it particularly promising for large-scale manufacturing.