Regulating Lithium Bond to Reduce Polysulfide Parasitic Reactivity for High-Stability Lithium Metal Anode

Lithium-sulfur (Li-S) batteries hold great potential as high-energy-density energy storage devices, yet their practical application is hindered by rapid cycling failure caused by parasitic reactions between lithium polysulfides (LiPSs) and lithium metal anodes. Inspired by lithium bond chemistry, we herein propose a weak cation interaction strategy as a new molecular design principle to intrinsically mitigate the parasitic reactivity of LiPSs and endow long-cycling Li-S batteries operating at 500 Wh kg^-1 level. Specifically, molecular-level interaction regulation is introduced by employing ammonium cation (NH₄ ⁺) with weaker polarizing power than Li⁺ to interact with LiPSs, thereby attenuating their electrophilicity, elevating their lowest unoccupied molecular orbital energy levels, and suppressing the detrimental parasitic reactions with lithium metal anodes. This regulation strategy markedly prolongs the lifespan of Li-S coin cells from 53 to 149 cycles under harsh conditions of using 4.2 mg cm^-2-loading sulfur cathodes and 50 µm-thick lithium anodes. More importantly, an 8 Ah-level Li-S pouch cell achieves a high initial energy density of 502 Wh kg^-1 and stable 16 cycles. This work establishes a new weak cation interaction regulation strategy following lithium bond chemistry, offering a generalizable route toward long-cycling and high-energy-density Li-S batteries.