Electrochemical Insights, Developing Strategies, and Perspectives toward Advanced Potassium–Sulfur Batteries

Abstract

The boosting demand for high-capacity energy storage systems requires innovative battery technologies with low-cost and sustainability. The advancement of potassium-sulfur (K-S) batteries have been triggered recently due to abundant resource and cost effectiveness. However, the functional performance of K-S batteries is fundamentally restricted by the vague understanding of K-S electrochemistry and the imperfect cell components or architectures, facing the issues of low cathode conductivity, intermediate shuttle loss, poor anode stability, electrode volume fluctuation, etc. Inspired by considerable research efforts on rechargeable metal-sulfur batteries, the holistic K-S system can be stabilized and promoted through various strategies on rational physical regulation and chemical engineering. In this review, first an attempt is made to address the electrochemical kinetic concept of K-S system on the basis of the emerging studies. Then, the classification of performance-improving strategies is thoroughly discussed in terms of specific battery component and prospective outlooks in materials optimization, structure innovations, as well as relevant electrochemistry are provided. Finally, the critical perspectives and challenges are discussed to demonstrate the forward-looking developmental directions of K-S batteries. This review not only endeavors to provide a deep understanding of the electrochemistry mechanism and rational designs for high-energy K-S batteries, but also encourages more efforts in their large-scale practical realization.

Liquid electrolyte design for metal‐sulfur batteries: Mechanistic understanding and perspective

“…In addition, cation also affects the relative stability of various solid polysulfides and sulfides. For instance, the thermodynamic stability of K 2 S 3 (ΔG f 0 = −528 kJ mol −1 at 25°C) is higher than K 2 S (ΔG f 0 = −410 kJ mol −1 at 25°C), which leads to sluggish reduction kinetic from K 2 S 3 to K 2 S. This explains the low capacity and the formation of K 2 S 3 (instead of K 2 S) at the end of discharge 36 . Similarly, Na 2 S 2 was reported as the preferred product in Na–S batteries instead of Na 2 S, 86 which supports the strong influence of the cation on the relative stability of solid polysulfide and sulfide.…”

“…And DOL as a co‐solvent is selected due to its ability to form a protective SEI film on the surface of lithium metal 35 . Instead of DME/DOL, in sodium–sulfur (Na–S) and potassium–sulfur (K–S) batteries, TEGDME, and diglyme are more feasible due to their greater stability and higher boiling point 36,37 …”

Room‐temperature metal–sulfur batteries: What can we learn from lithium–sulfur?

“…In the Li-S system, Li 2 S is commonly believed to be the most stabilized discharge product in spite of some controversy on the existence of Li 2 S 2 as it was reported as a metastable phase that could spontaneously decompose into Li 2 S and sulfur. 56 By contrast, the thermodynamic stability of K 2 S 3 (ΔG f 0 = 528 kJ mol À1 ) is theoretically higher than K 2 S (ΔG f 0 = 410 kJ mol À1 ), indicating a sluggish reduction kinetic from K 2 S 3 to K 2 S. 57,58 This accounts for why K 2 S 3 was frequently observed as the only end discharge product of K-S batteries. 34,59,60 Similar results were also observed in Na-S batteries where Na 2 S 2 was detected as the only discharge product rather than Na 2 S. 61 By comparison, CaS and Al 2 S 3 were observed as the only discharge product in Ca-S and Mg-S batteries, respectively.…”

Recent Advances and Perspectives on the Polymer Electrolytes for Sodium/Potassium‐Ion Batteries

“…[ 56,178 ] Moreover, potassium has good flexibility, enabling better contact between materials and can expand the application field of technology. [ 68,179,180 ] Therefore, KIBs also have good research value and application potentials. Growing attention has been being paid to K + ‐conductive PEs (KCPEs) for KIBs (inset in Figure 1b,d).…”