Dielectric and electrical characterization of (PEO–PMMA)–LiBF4–EC plasticized solid polymer electrolyte films

Insight into the Key Factors in High Li+ Transference Number Composite Electrolytes for Solid Lithium Batteries

Solid lithium batteries (SLBs) have received much attention due to their potential to achieve secondary batteries with high energy density and high safety. The solid electrolyte (SE) is believed to be the essential material for SLBs. Among the recent SEs, composite electrolytes have good interfacial compatibility and customizability, which have been broadly investigated as promising contenders for commercial SLBs. The high Li⁺ transference number (t Li + ${{_{{\rm Li}{^{+}}}}}$ ) of composite electrolytes is critically important concerning the power/energy density and cycling life of SLBs, however, which is often overlooked. This Review presents a current opinion on the key factors in high t Li + ${{_{{\rm Li}{^{+}}}}}$ composite electrolytes, including polymers, Li-salts, inorganic fillers, and additives. Various strategies concerning providing a continuous pathway for Li-ions and immobilizing anions via component interaction are discussed. This Review highlights the major obstacles hindering the development of high t Li + ${{_{{\rm Li}{^{+}}}}}$ composite electrolytes and proposes future research directions for developing composite electrolytes with high t Li + ${{_{{\rm Li}{^{+}}}}}$ .

Recent Advances and Strategies toward Polysulfides Shuttle Inhibition for High-Performance Li-S Batteries

Lithium-sulfur (Li-S) batteries are regarded as the most promising next-generation energy storage systems due to their high energy density and cost-effectiveness. However, their practical applications are seriously hindered by several inevitable drawbacks, especially the shuttle effects of soluble lithium polysulfides (LiPSs) which lead to rapid capacity decay and short cycling lifespan. This review specifically concentrates on the shuttle path of LiPSs and their interaction with the corresponding cell components along the moving way, systematically retrospect the recent advances and strategies toward polysulfides diffusion suppression. Overall, the strategies for the shuttle effect inhibition can be classified into four parts, including capturing the LiPSs in the sulfur cathode, reducing the dissolution in electrolytes, blocking the shuttle channels by functional separators, and preventing the chemical reaction between LiPSs and Li metal anode. Herein, the fundamental aspect of Li-S batteries is introduced first to give an in-deep understanding of the generation and shuttle effect of LiPSs. Then, the corresponding strategies toward LiPSs shuttle inhibition along the diffusion path are discussed step by step. Finally, general conclusions and perspectives for future research on shuttle issues and practical application of Li-S batteries are proposed.

Molecular Design of a Highly Stable Single-Ion Conducting Polymer Gel Electrolyte

Single-ion conducting (SIC) polymer electrolytes with a high Li transference number (t_Li⁺) have shown the capability to enable enhanced battery performance and safety by avoiding liquid-electrolyte leakage and suppressing Li dendrite formation. However, issues of insufficient ionic conductivity, low electrochemical stability, and poor polymer/electrode interfacial contact have greatly hindered their commercial use. Here, a Li-containing boron-centered fluorinated SIC polymer gel electrolyte (LiBFSIE) was rationally designed to achieve a high t_Li⁺ and high electrochemical stability. Owing to the low dissociation energy of the boron-centered anion and Li⁺, the as-prepared LiBFSIE exhibited an ionic conductivity of 2 × 10^-4 S/cm at 35 °C, which is exclusively contributed by Li ions owing to a high t_Li⁺ of 0.93. Both simulation and experimental approaches were applied to investigate the ion diffusion and concentration gradient in the LiBFSIE and non-cross-linked dual-ion systems. Typical rectangular Li stripping/plating voltage profiles demonstrated the uniform Li deposition assisted by LiBFSIE. The interfacial contact and electrolyte infiltration were further optimized with an in situ UV-vis-initiated polymerization method together with the electrode materials. By virtue of the high electrochemical stability of LiBFSIE, the cells achieved a promising average Coulombic efficiency of 99.95% over 200 cycles, which is higher than that of liquid-electrolyte-based cells. No obvious capacity fading was observed, indicating the long-term stability of LiBFSIE for lithium metal batteries.