A High Energy Density Lithium-Sulfur Pouch Cell Via Lignin-Based Ionic Conductive Binder With Oxygen-Rich Coordinating Sites.

Abstract

Bio-based binders exhibit outstanding advantages in maintaining electrode stability and suppressing the shuttle effect in lithium-sulfur (Li-S) battery. However, their inherent insulation and poor dispersion severely hinder Li⁺ transport within electrode, resulting in slow S reaction kinetics and low energy density. Here, a series of lignin-based ionic conductive binders (DAL-AA) were synthesized by mussel-mimicking demethylation and amino acids grafting modifications on alkali lignin (AL). It is found that acidic amino acids, e.g. phosphoserine, more easily restructure the spatial conformation via electrostatic repulsion and steric effect. It significantly eases the aggregation of lignin binder as well as bond active/conductive materials. Li⁺ diffusion coefficient in corresponding electrode improves 40% and lithium polysulfide conversion effectively accelerates. The Li-S battery delivers an initial discharge capacity of 971 mAh·g^- ¹ at a current density of 0.5 C and can stably run 500 cycles. Moreover, the high-loading pouch cell with a capacity of 1.125 Ah achieves gravimetric and volumetric energy densities of 328 Wh·kg^- ¹ and 517 Wh·L^- ¹ respectively. This work provides guidance on designing high-loading cathodes for advanced Li-S batteries.