An all-biomaterials-based aqueous binder based on adsorption redox-mediated synergism for advanced lithium–sulfur batteries

The complex multistep electrochemical reactions of lithium polysulfides and the solid–liquid–solid phase transformation involved in the S8 to Li2S reactions lead to slow redox kinetics in lithium–sulfur batteries(Li–S batteries).However,some targeted researches have proposed strategies requiring the introduction of significant additional inactive components,which can seriously affect the energy density.Whereas polymer binders,proven to be effective in suppressing shuttle effects and constraining electrode volume expansion,also have promising potential in enhancing Li–S batteries redox kinetics.Herein,a novel aqueous polymer binder is prepared by convenient amidation reaction of fully biomaterials,utilizing its inherent rich amide groups for chemisorption and redox mediating ability of thiol groups to achieve adsorption redox-mediated synergism for efficient conversion of polysulfides.Li–S batteries based on N-Acetyl-L-Cysteine-Chitosan(NACCTS)binder exhibit high initial discharge specific capacity(1260.1mAhg−1 at 0.2C)and excellent cycling performance over 400 cycles(capacity decay rate of 0.018%per cycle).In addition,the batteries exhibit great areal capacity and stable capacity retention of 83.6%over 80 cycles even under high sulfur loading of 8.4mgcm−2.This work offers a novel perspective on the redox-mediated functional design and provides an environmentally friendly biomaterials-based aqueous binder for practical Li–S battery.

A hydrophilic poly(methyl vinyl ether-alt-maleic acid) polymer as a green, universal, and dual-functional binder for high-performance silicon anode and sulfur cathode

Binders could play crucial or even decisive roles in the fabrication of low-cost, stable and high-capacity electrodes. This is especially the case for the silicon (Si) anodes and sulfur (S) cathodes that undergo large volume change and active material loss in lithium-ion batteries during prolonged cycles. Herein, a hydrophilic polymer poly(methyl vinyl ether-alt-maleic acid) (PMVEMA) was explored as a dual-functional aqueous binder for the preparation of high-performance silicon anode and sulfur cathode. Benefiting from the dual functions of PMVEMA, i.e., the excellent dispersion ability and strong binding forces, the as-prepared electrodes exhibit improved capacity, rate capability and long-term cycling performance. In particular, the as-prepared Si electrode delivers a high initial discharge capacity of 1346.5 mAh g^(−1) at a high rate of 8.4 A/g and maintains 834.5 mAh g^(−1) after 300 cycles at 4.2 A/g, while the as-prepared S cathode exhibits enhanced cycling performance with high remaining discharge capacities of 663.4 mAh g^(−1) after 100 cycles at 0.2 C and 487.07 mAh g^(−1) after 300 cycles at 1 C, respectively. These encouraging results suggest that PMVEMA could be a universal binder to facilitate the green manufacture of both anode and cathode for high-capacity energy storage systems.