Improving Lithium–Sulfur Battery Performance under Lean Electrolyte through Nanoscale Confinement in Soft Swellable Gels

Abstract

Li-S batteries have been extensively studied using rigid carbon as the host for sulfur encapsulation, but improving the properties with a reduced electrolyte amount remains a significant challenge. This is critical for achieving high energy density. Here, we developed a soft PEOLiTFSI polymer swellable gel as a nanoscale reservoir to trap the polysulfides under lean electrolyte conditions. The PEOLiTFSI gel immobilizes the electrolyte and confines polysulfides within the ion conducting phase. The Li-S cell with a much lower electrolyte to sulfur ratio (E/S) of 4 g/g (3.3 mL/g) could deliver a capacity of 1200 mA h/g, 4.6 mA h/cm, and good cycle life. The accumulation of polysulfide reduction products, such as LiS, on the cathode, is identified as the potential mechanism for capacity fading under lean electrolyte conditions.

Rational Design of Statically and Dynamically Stable Lithium–Sulfur Batteries with High Sulfur Loading and Low Electrolyte/Sulfur Ratio

“…To solve these issues, a considerable amount of research has been devoted to the cathode material and its design. For example, the electrochemical characteristics of sulfur cathodes have been significantly improved with the application of (i) porous and/or functionalized substrates as sulfur hosts,[3d,6] (ii) new additives and/or solvents to optimize the electrolyte formulation,[4d,5,7] and (iii) porous current collectors and modified separators in specially designed cells . As a result of these innovations, researchers have reported cells that can perform satisfactorily with capacities (based on sulfur mass) approaching the maximum theoretical value and with stable cyclability for over 1000 cycles.…”

“…As a result of these innovations, researchers have reported cells that can perform satisfactorily with capacities (based on sulfur mass) approaching the maximum theoretical value and with stable cyclability for over 1000 cycles. [3d,4b,6–8]…”

“…[5b,7b,14a] In addition, although the high surface area created by micropores facilitates the reaction kinetics by offering a large reaction area among the confined active material, conductive substrate, and electrolyte,[5b,13] additional excess liquid electrolyte is often necessary to continuously wet the high reaction surface areas. [4d,e,7a] These factors are what make the electrolyte/sulfur ratio high, which is an attractive trick for keeping the cyclability of lithium–sulfur batteries stable, but it comes at the sacrifice of the practical electrochemical performances and energy density of the batteries. [4a,d,e,5b] As a result, there is a definitive downside for using nanoporous cathode substrates with high micro and/or mesoporosity in lithium–sulfur batteries.…”

Novel 2D Sb2S3 Nanosheet/CNT Coupling Layer for Exceptional Polysulfide Recycling Performance

“…[11][12][13] Despite their great promises, the commercialization of LSBs has been severely limited by several critical issues. [16] To address the aforementioned issues, extensive research efforts have been devoted to developing rationally designed cathode materials, [17] protection of lithium anodes, [18] and modification of electrolytes [19][20][21] in LSBs. [16] To address the aforementioned issues, extensive research efforts have been devoted to developing rationally designed cathode materials, [17] protection of lithium anodes, [18] and modification of electrolytes [19][20][21] in LSBs.…”

Fluorescence Probing of Active Lithium Distribution in Lithium Metal Anodes

“…When Li metal was applied in ap ouch cell with LiPF 6 -EC/DMC as the electrolyte and LiFePO 4 as the cathode,the battery suffered from quick capacity fading after 5cycles due to the lean electrolyte condition ( Figures S27 and S28). [51] Through DMA testing,asignificant coverage of dead Li was discovered at the wrapped area close to the current collector by the end of the fourth charge process,t hat is,b efore capacity fading (Figure 5g,h), while the planar area was still dominated by active lithium species with ar elative smooth surface (Figure 5i,j). These results suggest that an uneven distribution of Li tends to occur at the wrap area, leading to more electrolyte consumption and consequently to ap oor cycling performance.…”