Flame retardant high-power Li-S flexible batteries enabled by bio-macromolecular binder integrating conformal fractions

Chenrayan Senthil,Sun-Sik Kim,Hyun Young Jung

doi:10.1038/s41467-021-27777-5

Chenrayan Senthil, Sun-Sik Kim + Show 1 more

Open Access

https://doi.org/10.1038/s41467-021-27777-5

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Journal: Nature Communications	Publication Date: Jan 10, 2022
Citations: 48	License type: open-access

Affiliation: Gyeongsang National University

Abstract

Polymer binders for sulfur cathodes play a very critical role as they prerequisites for an in-situ immobilization against polysulfide shuttle and volume change, while ensuring good adhesion within active materials for ion conduction along with robust mechanical and chemical stability. Here, we demonstrate anionic surface charge facilitated bio-polymer binder for sulfur cathodes enabling excellent performance and fire safety improvement. The aqueous-processable tragacanth gum-based binder is adjusted to house high sulfur loading over 12 mg cm−2 without compromising the sulfur utility and reversibility, imparting high accessibility for Li-ions to sulfur particles about 80%. The intrinsic rod and sphere-like saccharidic conformal fraction’s multifunctional polar units act as active channels to reach the sulfur particles. As a result, the binder entraps polysulfides with 46% improvement and restrains the volume changes within 16 % even at 4 C. Moreover, the flexible Li-S battery delivers a stack gravimetric energy density of 243 Wh kg–1, demonstrating high reactivity of sulfur along with good shape conformality, which would open an avenue for the potential development of the compact and flexible high-power device.

Highlights

Polymer binders for sulfur cathodes play a very critical role as they prerequisites for an in-situ immobilization against polysulfide shuttle and volume change, while ensuring good adhesion within active materials for ion conduction along with robust mechanical and chemical stability
The complex and macromolecular biopolymer reported as a binder for the first time in Li-S battery, Astragalus gummifer gum (Tragacanth gum, TG), inherits heterogenous polysaccharide fractions which mitigate three critical prerequisites for a better operation of highperformance Li-S battery; (1) enables high access for Li-ions to sulfur-active particles through the anionic polymeric backbone moieties triggering efficient sulfur reactivity, (2) exposed polar functional groups of saccharidic units expedite trapping of soluble polysulfides (Li2Sn, n = 4–8) into the electrolyte to maintain its concentration, and (3) actively regulate large volume changes through stretchable rod-like tragacanthin and sphere-like bassorin molecular conformations ensuring robust mechanical strength (Fig. 1a and Supplementary Figs. 1, 2)
The TG-driven enhanced electrochemical kinetics of sulfur cathodes, i.e., reversible interconversion of S8/Li2S was confirmed through cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) measurements performed using the Li-S cells that employ either polyvinylidene difluoride (PVDF), poly(ethylene oxide) (PEO), or TG as the binder for sulfur cathode (Fig. 1c–e)

Summary

Introduction

Polymer binders for sulfur cathodes play a very critical role as they prerequisites for an in-situ immobilization against polysulfide shuttle and volume change, while ensuring good adhesion within active materials for ion conduction along with robust mechanical and chemical stability. The complex and macromolecular biopolymer reported as a binder for the first time in Li-S battery, Astragalus gummifer gum (Tragacanth gum, TG), inherits heterogenous polysaccharide fractions which mitigate three critical prerequisites for a better operation of highperformance Li-S battery; (1) enables high access for Li-ions to sulfur-active particles (up to 80.3% of S) through the anionic polymeric backbone moieties triggering efficient sulfur reactivity, (2) exposed polar functional groups of saccharidic units expedite trapping of soluble polysulfides (Li2Sn, n = 4–8) into the electrolyte to maintain its concentration, and (3) actively regulate large volume changes through stretchable rod-like tragacanthin and sphere-like bassorin molecular conformations ensuring robust mechanical strength These definite improvements in the sulfur battery chemistries would pave the way to realize highperformance electrochemical energy devices for e-transportation, portable power electronics, and so on, considering the prevalence, cost-effective and sustainable characteristics of sulfur[7,8,9,10,11,17,18,19,20,21,22]

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