Bifunctional binder enables controllable deposition of polysulfides for high-loading Li-S battery

Illustration of LiPSs conversion and concentration in PVDF a) and LSBP c) binder. The role of PVDF b) and LSBP d) binder on LiPSs suppression and Li 2 S regulation in Li-S battery. Poor ion transport results in slow conversion rates and high concentrations of LiPSs in case of the cell using conventional PVDF binder. Besides, the cell suffers from severe shuttle effects due to the poor interactions between PVDF and LiPSs ( Fig. (a) and (b) ). The introduction of polar groups into the binder segment can significantly enhance the binder-LiPSs interaction, which can produce a “charge-coordination mechanism” on the adjacent medium. “Charge-coordination mechanism” can not only induce the orderly deposition of LiPSs, but also regulate the mass transfer behavior of Li + and increase the conversion rate of LiPSs. Herein, a hydrophilic bifunctional polymer (LSBP) obtained by in situ dynamic cross-linked was proposed, which demonstrates excellent capability in high loading Li-S battery ( Fig. (c) and (d) ). Firstly, we synthesized poly(Acrylic acid- co -Acrylamide- co -2-Acrylamido-2-methyl-1-propanesulfonic acid) (poly(AA- co -AM- co -AMPS, donated as PAMS)) with abundant polar groups by radical polymerization. Secondly, polyethyleneimine (PEI) was introduced to form a cross-linked network with PAMS through in situ dynamic cross-linking. Low-field nuclear magnetic resonance (LF-NMR) proved the superiority of in situ dynamic cross-linking during the preparation of electrode. The adsorption and rapid conversion of LiPSs by LSBP binder were proved by in situ time-resolved ultraviolet–visible (UV–vis) measurement. The experimental results and molecular simulation illustrate that the precise control of LiPSs conversion and Li + diffusion is achieved. The specific capacity of the surful cathode using LSBP binder is 730 mAhg −1 after 500 cycles at 0.5C with a high-loading of 3.5 mg cm −2 . • A lithiophilic and sulfiphilic polymer binder was synthesized by dynamic crosslinking. • In-situ ultraviolet–visible was performed to observe the conversion of polysulfides. • Balance of LiPSs nucleation-growth transition and lithium-ion diffusion was archived. Lithium-sulfur (Li-S) battery are regarded as a strong candidate for the next generation of high-performance battery due to its ultra-high capacity and low cost. However, severe shuttle effect of polysulfides (LiPSs) and the random deposition of lithium sulfide (Li 2 S) are vital challenges that impede the popularization of Li-S chemistry. Herein, inspired by charge-coordination interaction, a novel lithiophilic and sulfiphilic bifunctional polymer (LSBP) synthesized by in situ dynamic cross-linked is proposed to anchor LiPSs and enable controllable deposition of Li 2 S. The LSBP binder significantly improves the conversion reaction activity of LiPSs while the co-existence of lithiophilic (–COO - , -SO 3 - ) and sulfiphilic (–NH 2 ) sites effectively suppresses the shuttle of LiPSs, which is confirmed by in-situ time-resolved ultraviolet–visible (UV–vis) measurement. As a result, a high-loading (3.5 mgcm −2 ) and crack-free sulfur-based cathode with LSBP binder is achieved. Besides its stable cycling performance, the cathode exhibits an outstanding rate capacity under a high rate of 2.5C. This work proposes a scalable strategy to obtain practicable Li-S battery through the improvement in binder, which is inherently low-cost and environmentally friendly.