Bifunctional macromolecular design for dual interface-passivating regulation towards practical stable lithium-sulfur batteries

Abstract

Lithium-sulfur (Li-S) battery is recognized for the high theoretical energy density and cost-effective raw materials. However, the instability of Li metal anodes limits the cycle life of Li-S batteries under practical conditions. In this study, we propose a dual interface-passivating regulation strategy using nitrocellulose (NC), a macromolecular nitrate, to stabilize the interface/interphase between the electrolyte and Li metal anode. Specifically, the macromolecular crowding effect and the reduction in lithium polysulfides (LiPSs) activity through nitrate coordination endow NC desirable bifunctionality to simultaneously suppress the depletion of Li salts and LiPSs corrosion, leading to better interface passivation than mono-functional additives such as LiNO₃ and carboxymethyl cellulose. Consequently, the cycle life of Li-S batteries under practically demanding conditions (50 μm Li anodes; 4.0 mg cm⁻² S athodes) is extended to 180 cycles, outperforming those of additive-free or LiNO₃-containing commercial electrolytes. This study highlights the potential of bifunctional macromolecular additive design for effectively dual-passivating the anode/electrolyte interface towards highly stable practical Li-S batteries.