Polypyrrole Modification of High Sulfur-Loaded Three-Dimensional Aluminum Foam Cathode in Lithium–Sulfur Batteries for High-Rate Capability

Abstract

A low-resistance polypyrrole (PPy) film that can achieve high rates (rates of >1C) while suppressing polysulfide dissolution is developed in this study. To achieve high-rate characteristic in a sulfur cathode with high sulfur loading, a three-dimensional (3D) aluminum foam current collector is used and the Li+ concentration of the PPy film is enhanced by a glyme–Li equimolar complex as the polymerization electrolyte. A PPy–sulfur/ketjenblack (S/KB) 3D aluminum foam laminated cell with a sulfur loading of 5 mg cm−2 is prepared. Consequently, a high discharge capacity of 794 mAh g−1-sulfur at 3.0C is achieved using 1 M lithium bis-(trifluoromethylsulfonyl)imide (LiTFSI) with dimethoxyethane (DME) and 1,3-dioxolane (DOL), (DME/DOL = 1/1 vol.) as the electrolyte and Li foil as the anode. In the cycling test, PPy-S/KB 3D Al foam cathode achieved a significant improvement in discharge capacity retention compared to bare S/KB 3D Al foam cathode without PPy coating. Moreover, almost no polysulfide dissolution is confirmed from the ultraviolet–visible spectrum of the electrolyte after the cycle evaluation. Here, we prepare a 3D structure S/KB cathode that can support high rates while suppressing sulfur dissolution by PPy coating, and reveal its potential for lithium–sulfur battery application.

Communication—Cross-Linked Anionic Polymer Coating Prepared by UV and Thermal Curing for Long-Life Lithium-Sulfur Battery

“…18,19 The strategy of coating the sulfur cathode with PPy inhibits the polysulfide dissolution and allows the flexibility of choosing electrolytes. 20,21 However, the electropolymerization method requires a counter electrode and potentiostat, which requires more cost than a conventional LIB production line. Therefore, we should consider and develop a more suitable system for the production line without a normal potentiostat system.…”

“…The surface of the electrode is coated with a negatively-charged polymer, so that the polysulfide anion is retained in the electrode owing to the repulsion between the negative charges. Few anionic polymer coatings were applied to the sulfur/ketjenblack composite cathode using a three-dimensional foam current collector (S/KB 3D Al cathode, S loading = 10 mg cm −2 ), 20,21 and characteristics of a battery with few anionic polymer coatings were compared. Linear and cross-linked anionic polymers were prepared by ultraviolet (UV) curing and thermosetting.…”

Synthesis of Li Conductive Polymer Layer on 3D Structured S Cathode by Photo-Polymerization for Li–S Batteries

“…[27][28][29][30][31] We have previously reported the key role played by a polypyrrole layer coated on sulfur cathode and poly(3,4-ethylenedioxythiophene)-poly (styrenesulfonate) (PEDOT:PSS) in improving the electrochemical performance of Li-S batteries. [32][33][34][35] We showed that the polymeric materials selectively conduct Li-ions and can effectively prevent LiPS dissolution during the charge/discharge process, which enhances cyclability and CE. To increase the S loading capacity and electric conductivity of the S cathode, we tested a three-dimensional (3D) aluminum (Al) foam with high porosity (∼98%) as a current collector for the S cathode.…”

Facile one-pot synthesis of biomass-derived activated carbon as an interlayer material for a BAC/PE/Al2O3 dual coated separator in Li–S batteries

“…[23][24][25][26][27][28] Despite the materials and electrochemical advantages of a sulfur cathode, commercialization of LSB is limited owing to several critical issues like (1) the low utilization of active material in sulfur cathodes due to low electrical conductivity of elemental S, (2) dissolution of lithium polysulde (LiPS) from cathode to a liquid electrolyte leading to the shuttle effect, (3) volume exchange of elemental S (∼80%), and (4) safety issues in Li dendrite growth during the charge and discharge process. To address these limitations, several studies have focused on various solutions, including immobilization of LiPS using porous cathode additives, [29][30][31] lithium penetrated polymer layer on the cathode, [32][33][34] multi-functional separators, [35][36][37] and electrolyte additives [38][39][40] for better formation of surface electrolyte interface on the surface of Li anodes. Among these, multifunctional separators, which function by suppressing the LiPS and Li dendrite growth during charge and discharge cycling, are the most simple way to enhance the electrochemical performance of LSB.…”