High‐Capacity and Stable Sodium‐Sulfur Battery Enabled by Confined Electrocatalytic Polysulfides Full Conversion

Abstract

The efficient polysulfide capture and reversible sulfur recovery during reverse charging process are critical to exploiting the full potential of room temperature NaS batteries. Here, based on a core‐shell design strategy, the structural and chemical synergistic manipulation of sodium polysulfides quasi‐solid‐state reversible conversion is proposed. The sulfur is encapsulated in the multi‐pores of 3D interconnected carbon fiber as the core structure. The Fe(CN)64−‐doped polypyrrole film serves as a redox‐active polar shell to lock up polysulfides and promote complete polysulfide conversion. Importantly, the short‐chain Na2S4 polysulfides are reduced to Na2S directly leaving with a small fraction of soluble intermediates as the cation‐transfer medium at the core/shell interface, and freeing up formation of solid Na2S2 incomplete product. Further, the redox mediator with open Fe species electrocatalytically lowers the Na2S oxidation energy barrier and renders the high reversibility of electrodeposited Na2S. The tunable quasi‐solid‐state reversible sulfur conversion under versatile polymer sheath greatly enhances sulfur utilization, affording a remarkable capacity of 1071 mAh g−1 and a stable high capacity of 700 mAh g−1 at 200 mA g−1 after 200 cycles. The confined electrocatalytic effect provides a strategy for tuning electrochemical pathway of sulfur species and guarantees high‐efficiency sulfur electrochemistry.

Exploration of the Unique Structural Chemistry of Sulfur Cathode for High‐Energy Rechargeable Beyond‐Li Batteries

“…Reproduced with permission. [ 147 ] Copyright 2021, Wiley‐VCH GmbH. d) Schematic of the possible surface redox reaction between Na 2 S 6 and Mn x O y .…”

“…In pursuit of improving S-loading, Hwang and co-workers proposed a 3D interconnected network with carbon fiber (CFC) with a high S-loading of 6.4 mg cm À2 . [147] A "redox-active polar shell" constituting of a bifunctional sheath of Fe(CN) 6…”

“…-doped polypyrrole film [147] Thermal alkali activation and interfacial polarization strategy 1 M NaFSI in TEGDME with NaNO 3 additive…”

Generating Short‐Chain Sulfur Suitable for Efficient Sodium–Sulfur Batteries via Atomic Copper Sites on a N,O‐Codoped Carbon Composite

“…[9][10][11][12][13] Thus, room temperature Na-S batteries relying on liquid electrolytes have attracted a lot of attention as low-cost energy storage alternative. [14][15][16][17] There are still a number of challenges for those Na-S batteries, such as i) insulating nature of S, which results in a low reactivity of S with Na, and ii) ease of formation of polysulfides (Na 2 S n , 4 ≤ n ≤ 8) which could dissolve into and shuttle through liquid electrolyte ("shuttle effect"), resulting in fast capacity Sodium-sulfur batteries have attracted attention due to their high energy capacities and low costs, but the dissolution of sodium polysulfides still severely affects their cycle life, limiting their real-world applications. Herein, a stable sulfur host is reported, based on a N,O-codoped carbon composite derived from a bimetallic Cu-Zn metal-organic framework, which ensures high sulfur loading (67 wt%).…”

“…[ 9–13 ] Thus, room temperature Na–S batteries relying on liquid electrolytes have attracted a lot of attention as low‐cost energy storage alternative. [ 14–17 ] There are still a number of challenges for those Na–S batteries, such as i) insulating nature of S, which results in a low reactivity of S with Na, and ii) ease of formation of polysulfides (Na 2 S n , 4 ≤ n ≤ 8) which could dissolve into and shuttle through liquid electrolyte (“shuttle effect”), resulting in fast capacity fading and low Coulombic efficiency of the batteries. [ 18–20 ] Different methods have been reported to overcome these issues, such as the confinement of sulfur physically by carbon hosts or chemically by covalent CS bonds.…”