Tuning the Linkers in Polymer-Based Cathodes to Realize High Sulfur Content and High-Performance Potassium–Sulfur Batteries

Abstract

The development of effective rechargeable potassium–sulfur (K–S) batteries has been retarded by a severe polysulfide shuttle effect and low sulfur content in the cathode (generally less than 40 wt %). Herein, a series of sulfur-linked polymers with different numbers of allyloxy linkers have been chosen to explore their effect on the performance of K–S batteries. By taking sulfur-linked tetra­(allyloxy)-1,4-benzoquinone polymer (poly­(S4-TABQ)) as the cathode of K–S batteries, its maximal sulfur content reaches ∼71 wt %, which displays a high capacity retention of 94.5% after 200 cycles (only 0.027% loss per cycle). Theoretical analyses and density functional theory calculations show that the abundant allyloxy linkers in poly­(S4-TABQ) cathodes play a vital role in inhibiting the polysulfide shuttle effect and realizing high capacity, owing to the strong interaction of the allyloxy moieties with potassium polysulfides and the accelerated charge transfer during charge/discharge process. Moreover, ex situ X-ray photoelectron spectroscopy and ultraviolet–visible spectroscopy analysis are conducted to explore the electrochemical mechanism in poly­(S4-TABQ) cathodes, indicating that −C-S n –·K+ (n = 2–6) and K2S n (n = 2–6) coexist in K–S batteries without the formation of K2S groups. This study provides a novel insight into the application of sulfur-linked polymers as cathode material in potassium–sulfur batteries.

Strong d−π Orbital Coupling of Co–C4 Atomic Sites on Graphdiyne Boosts Potassium–Sulfur Battery Electrocatalysis

“…The galvanostatic charge–discharge profiles of the S/Co-GDY cathode at different current densities could maintain a stable voltage plateau (Figure d), which is the best among the previously reported literature for K–S batteries (Figure e and Table S2). ,,,− The high redox kinetics is due to the structural advantages of the strong orbital coupling for the S/Co-GDY, resulting in a super performance at high current densities. Therefore, S/Co-GDY can deliver an even better capacity of 530 mAh g –1 at 1 A g –1 after 500 cycles with nearly 100% Coulombic efficiency and low average capacity degradation of 0.08% per cycle (Figure f).…”

Achieving Fast and Reversible Sulfur Redox by Proper Interaction of Electrolyte in Potassium Batteries

“…(D) Galvanostatic discharge–charge profiles of K–S batteries using a PAA binder at a current density of 1 C in different cycles. (E) Rate performance of K–S batteries using PAA binder at current densities of 0.2, 0.5, and 1 C. (F) Medium discharge voltage of the prepared S@KJB cathode material compared with literature values for K–S batteries. ,,,,,, …”

Metal–iodine batteries: achievements, challenges, and future

“…The redox potential of K/K + (−2.93 V vs. SHE), compared to that of Na/Na + (−2.70 V vs. SHE), is closer to that of Li/Li + (−3.04 V vs. SHE) in nonaqueous electrolytes. 153 Besides, potassium reserves in the Earth's crust show a high abundance of 2.09 wt%. These advantages suggest that potassium-based batteries might have high cost-efficiency and promising energy density, thus leading to the emergence of K–I 2 batteries.…”