Saponin-containing multifunctional binder toward superior long-term cycling stability in Li-S batteries

Saponin, comprising hydrophilic glycoside moieties with a hydrophobic aglycone structure, is introduced for the first time as a multi-functional additive for high-performance sulfur cathodes. The hydroxyl groups efficiently suppress the lithium polysulfide shuttle effect and prepare sites that can strengthen the mechanical properties of the cathode through crosslinking with a polymer binder. The amphiphilic structure of saponin also helps to disperse active electrode materials in the sulfur cathode. Through the synergistic effects from its unique structure, the addition of a small amount (1 wt%) of saponin into the sulfur cathode boosts a 300% increase in the specific capacity of the cathode with a capacity decay of 0.012% per cycle at 2C over 1000 cycles.