Lithium–sulfur (Li–S) batteries are considered to be one of the most promising next‐generation energy storage devices due to their ultrahigh energy density. The development of energy storage devices has received increasing attentions as a vital transformative technology to realize low‐carbon economy and sustainable energy supply. Published on behalf of The Electrochemical Society by IOP Publishing Limited. In addition to the low solubility of polysulfides, the high t Li ⁺ is crucial for achieving high energy density Li-S batteries by reducing the electrolyte amount. Furthermore, -4.0HFE demonstrated an initial discharge capacity of 1130 mAh g⁻¹ at a low electrolyte volume to sulfur weight ratio of 4, whereas a typical organic electrolyte failed to achieve such a high capacity owing to limitations of the redox mechanism mediated by dissolved polysulfides. The higher transference number (t Li ⁺) of -4.0HFE may predominantly contribute to the rate performance, rather than polysulfide solubility and ionic conductivity. Cells with -4.0HFE exhibited better rate capability despite their lower ionic conductivity. The Li2S8 solubility is low (1 mM in atomic S concentration) in -4.3HFE and -4.0HFE.
To optimize the electrolytes for high energy density cells, effects of polysulfide solubility and Li ion transport properties on Li-S battery performance were investigated for tetraglyme (G4)-based solvate ionic liquids and a sulfolane (SL)-based concentrated electrolyte, which are both diluted with a hydrofluoroether (HFE). In this type of electrolytes, polysulfide dissolution and shuttling can be suppressed, resulting in high Coulombic efficiency and cycle life. Sparingly solvating electrolytes are an emerging class of electrolytes used in Li-S batteries. In conclusion, we offer our perspective for future development of Li-S batteries. The advantages and disadvantages of the three systems are compared in accordance with the multifaceted requirements.
Emphasis is placed on options to reduce the electrolyte solution/sulfur ratio and prolong battery cycle life. The stability of lithium metal anodes with these solutions is discussed with respect to side reactions, protective surface film formation, and dendritic Li deposition. Three fundamental types of electrolyte solution-moderately (conventional), sparingly, and highly solvating-are presented along with a multi-dimensional analysis of solution chemistry, polysulfide solubility, sulfur reaction pathway, Li2S deposition, and solution quantity. Factors that determine the solvation are discussed, including the solvent, salt, concentration, and interaction with Li-polysulfide species. This review evaluates the key role of solution properties and polysulfide solvation. Recently, it has become clear that the chemistry of electrolyte solutions and their ability to stabilize polysulfide Li2Sx species formed by sulfur reduction have a critical effect on energy density and cycling performance. Li-S batteries follow a conversion chemistry, which radically differs from intercalation-based lithium-ion batteries.
Lithium-sulfur (Li-S) batteries promise high energy density for next-generation energy storage systems, yet many challenges remain. The role of LiNO3 is the protection of lithium anode during cycling. Meanwhile, increasing the concentration of LiNO3 additive in the electrolyte is found effective in sustaining the cycling capacity and the Coulombic efficiency over a reasonable usage window (~200 cycles). Pre-passivation of the lithium anode with an ionic conductor Li3PO4 protection layer only improves the Coulombic efficiency retention at sulfur loading levels much lower than the practical threshold. Low E/S ratio and high sulfur loading both give rise to fast lithium anode corrosion, which induces fast capacity fade and Coulombic efficiency decay.
It is demonstrated that Li-S cells' power performance strongly depends on the E/S ratio, while both E/S ratio and sulfur loading significantly influence the cycle life of Li-S cells. In this work, a systematic investigation is performed to understand the impact of these two variables over key Li-S cell performance parameters. Practical lithium-sulfur batteries require high sulfur electrode loading and lean electrolyte designs, which entail more research efforts on the two cell-design parameters - sulfur loading and electrolyte/sulfur loading ratio (E/S).
0 kommentar(er)
