Fluorine-Like BH4-Doped Li6PS5Cl with Improved Ionic Conductivity and Electrochemical Stability.

Sulfide-based solid electrolytes with high ionic conductivity have attracted a lot of attention. However, the incompatibility and interfacial instability of sulfides with the lithium metal anode have emerged as pivotal constraints on their development. To address this challenge, we proposed and successfully synthesized the BH4- doped argyrodite-type electrolyte Li6PS5Cl0.9(BH4)0.1 by mechanical ball milling and annealing. This electrolyte not only exhibits an exceptionally high ionic conductivity of 2.83 × 10-3 S cm-1 at 25 °C but also demonstrates outstanding electrochemical stability. The Li/Li6PS5Cl0.9(BH4)0.1/Li symmetric cell can stably run for more than 400 h at a current density of 0.2 mA cm-2. In sharp contrast, although the F- doped sample, Li6PS5Cl0.3F0.7, can highly improve Li6PS5Cl's electrochemical stability, the ionic conductivity will reduce dramatically to 6.63 × 10-4 S cm-1. The stepwise current method reveals a critical current density of 3.5 mA cm-2 for Li6PS5Cl0.9(BH4)0.1, which makes it a competitive sulfide-based solid electrolyte. This research offers valuable insights for designing new borohydride-containing solid electrolytes.

A Novel Time-Saving Synthesis Approach for Li-Argyrodite Superionic Conductor.

The wet-chemical synthetic approach for Li-argyrodite superionic conductors for all-solid-state batteries (ASSBs) is promising as it saves time, energy, and cost, while achieving scalable production. However, it faces certain commercialization issues such as byproduct generation, nucleophilic attack of the solvent, and long processing times. In this study, a facile and time-saving microwave-assisted wet synthesis (MW-process) approach is proposed for Li6 PS5 Cl (LPSC), which is completed in 3 h at the precursor-synthesis stage. The LPSC crystal obtained from the MW-process presents various advantages such as fast-PS4 3- generation, high solubility of LiCl, and low adverse effects from solvent molecules. These features help in achieving a high Li-ion conductivity (2.79 mS cm-1 ) and low electric conductivity (1.85×10-6 mS cm-1 ). Furthermore, the LPSC crystal is stable when reacting with Li metal (2000 h at 0.1 mA cm-2 ) and exhibits superior cyclability with LiNi0.6 Co0.2 Mn0.2 (NCM622) (145.5 mA h g-1 at 0.5 C, 200 cycles with 0.12% of capacity loss per cycle). The proposed synthetic approach presents new insights into wet-chemical engineering for sulfide-based solid-electrolytes (SEs), which is crucial for developing ASSBs from a commercial-scale perspective.