Liquid‐Phase Synthesis of Highly Deformable and Air‐Stable Sn‐Substituted Li₃PS₄ for All‐Solid‐State Batteries Fabricated and Operated under Low Pressures

Abstract

The liquid‐phase synthesis (LS) of sulfide solid electrolytes (SEs) has promising potential for mass production of practical all‐solid‐state Li batteries (ASLBs). However, their accessible SE compositions are mostly metal‐free. Moreover, liquid‐phase‐synthesized‐SEs (LS‐SEs) suffer from high electronic conductivity due to carbon impurities, resulting in below‐par electrochemical performance of ASLBs. Here, the LS of highly deformable and air‐stable Li3+xP1‐xSnxS4 (0.19 mS cm−1) using 1,2‐ethylene diamine‐1,2‐ethanedithiol with tetrahydrofuran is reported. A low heat‐treatment temperature (260 °C) prevents the carbonization of organic residues. Importantly, a remarkable enhancement in the deformability of LS‐SEs compared to that of conventional solid‐state‐synthesized SEs (SS‐SEs) is identified for the first time. LiNi0.7Co0.15Mn0.15O2 electrodes employing LS‐SEs in ASLBs significantly outperform those using SS‐SEs, notably when assembled under a low fabricating pressure (148 vs 370 MPa, e.g., capacity loss: 2 vs 41 mA h g−1) or tested under a low operating pressure (12 or 3 MPa), which is attributed to reduced electrochemo‐mechanical effects. Finally, when employing SEs that are exposed to air (dew point of −20 °C), LiNi0.7Co0.15Mn0.15O2 electrodes employing SEs with Sn‐substituted composition or prepared by LS exhibit significantly better capacity retention than conventional SEs with Sn‐free composition or prepared by SS (e.g., 92.2% for LS‐Li3.2P0.8Sn0.2S4 vs 32.5% for SS‐Li3PS4).

Enhancing Ionic Conductivity and Electrochemical Stability of Li3PS4 via Zn, F Co-Doping for All-Solid-State Li–S Batteries

“…The Li 3 PS 4 all-solid-state cell can deliver discharge capacities of only 902.6, 804.3, 750, 670.9, 550.3, 454.2, 371.4, and 292 mAh g –1 at 0.02, 0.05, 0.1, 0.2, 0.4, 0.6, 0.8, and 1 C, respectively, displaying poor rate performance. The high ionic conductivity of the electrolyte contributes to the higher capacity of the cell during cycling . This suggests that the superionic conductivity of the Zn, F co-doping electrolyte provides higher power to the cells.…”

“…The high ionic conductivity of the electrolyte contributes to the higher capacity of the cell during cycling. 60 This suggests that the superionic conductivity of the Zn, F codoping electrolyte provides higher power to the cells. Figure 6d,e shows the discharge curves of Li 3 PS 4 and Li 3.04 P 0.96 Zn 0.04 -S 3.92 F 0.08 all-solid-state cells at different rates.…”

Research progress of all-solid-state lithium–sulfur batteries with sulfide solid electrolytes: materials, interfaces, challenges, and prospects

“…THF can provide high solubility and help disperse the precursor to promote liquid-phase reaction. 92 In general, the prerequisite for preparing sulfide SEs using the liquid-phase method is to find a solvent that is compatible with sulfide electrolytes. Reproduced with permission.…”

“…THF can provide high solubility and help disperse the precursor to promote liquid-phase reaction. 92…”