Free-Standing Sulfur Cathodes Enabled by a Cationic Polymer for Lean Electrolyte Lithium–Sulfur Batteries

Abstract

It is well-known that, under lean electrolyte and high sulfur loading conditions, it is challenging to achieve a high discharge platform, discharge capacity, and cycling stability for lithium–sulfur (Li–S) batteries. Here we report a free-standing sulfur cathode that can efficiently adsorb and electrochemically catalyze polysulfides. A cationic polymer, polyquaternium-10 (P10), is adopted as a new binder that produces viscoelastic fibers during casting, facilitates lithium-ion transportation, and electrostatically regulates polysulfides. The cationic polymer promotes the formation of the free-standing cathode with a desirable web-like microstructure. The Li–S battery constructed by the free-standing cathode with sulfur mass loading of 6 mg cm–2 achieves a high initial areal capacity of 7.09 mAh cm–2 (i.e., 344.5 Wh kg–1 and 471.6 Wh l–1) and stable areal capacity of 4.48 mAh cm–2 (i.e., 217.6 Wh kg–1 and 235.8 Wh l–1) during cycling at a low electrolyte/sulfur ratio of 4 μL mg–1.

Challenges and Solutions for Lithium–Sulfur Batteries with Lean Electrolyte

“…Zheng et al. [ 49 ] adopted a cationic polymer, polyquaternium‐10, as a new type of binder for lean‐electrolyte Li‐S batteries. The rich ether‐Li + coordination in polyquaternium‐10 polymer chains helped to promote the migration rate of Li + within the cathode.…”

“…Constructing an auxiliary ion migration path by introducing ion-conductive components is beneficial to improve the Li + accessibility of sulfur and achieve high sulfur utilization. Zheng et al [49] adopted a cationic polymer, polyquaternium-10, as a new type of binder for lean-electrolyte Li-S batteries. The rich ether-Li + coordination in polyquaternium-10 polymer chains helped to promote the migration rate of Li + within the cathode.…”

Aqueous Supramolecular Binder for High-Performance Lithium–Sulfur Batteries

“…Various strategies have been explored to alleviate the volume expansion and the dissolution of long-chain lithium polysulfides, such as the use porous materials [ 6 , 7 , 8 , 9 ], separator modification [ 10 , 11 , 12 , 13 ], solid-state electrolytes [ 14 , 15 ], and functional binders [ 16 , 17 , 18 , 19 , 20 , 21 ]. As a component of the electrode, the binder is one of the key factors required to improve the performance and prolong the service life of batteries [ 16 , 22 ].…”

Zwitterionic Covalent Organic Framework Based Electrostatic Field Electrocatalysts for Durable Lithium–Sulfur Batteries

“…Unlike point-to-point interactions between LiPSs and traditional polar catalysts, electrostatic interactions create more extensive local electric fields to affect the conversion behavior of LiPSs, which improves the catalytic efficiency and reduces the possibility of catalyst passivation. ,,− Electrostatic interactions can be divided into electrostatic repulsion and attraction. Generally, anionic substrates create a negative electric field for repulsing polysulfides, such as Nafion, , sulfonated acetylene black, styrene sulfonate and caffeic acid, while cationic substrates act as an adsorbent for trapping polysulfides, such as polyquaternium-10, layered double hydroxides, tetraethylammonium nitrate and Prussian blue analogues . However, the catalytic performance based on electrostatic interactions is still rarely studied, especially for bidirectional catalysis.…”