A Fluoride-Ion-Conducting Solid Electrolyte with Both High Conductivity and Excellent Electrochemical Stability.

Solid-state fluoride-ion batteries (FIBs) circumvent multiple formidable bottlenecks of lithium-ion batteries, but their overall performance remains inferior due to the absence of appropriate solid electrolytes. Presently the conductivity of most solid electrolytes for FIBs is too low to enable room-temperature cycling, while the few sufficiently conductive ones only allow for very low discharge voltages because of the narrow electrochemical stability window (ESW). Here, high room-temperature conductivity and a decent ESW are simultaneously achieved by designing a solid electrolyte CsPb0.9 K0.1 F2.9 . Its room-temperature conductivity is 1.23 × 10-3  S cm-1 , comparable to the most conductive system reported so far (PbSnF4 , 5.44 × 10-4 -1.6 × 10-3  S cm-1 ), but the ESW is several times broader. With these appealing characteristics simultaneously achieved in the solid electrolyte, a cell with much higher voltages than other room-temperature-operable solid-state FIBs in literature is successfully constructed, and stably cycled at 25 °C for 4581 h without considerable capacity fade.

A cost-effective and humidity-tolerant chloride solid electrolyte for lithium batteries.

Li-ion-conducting chloride solid electrolytes receive considerable attention due to their physicochemical characteristics such as high ionic conductivity, deformability and oxidative stability. However, the raw materials are expensive, and large-scale use of this class of inorganic superionic conductors seems unlikely. Here, a cost-effective chloride solid electrolyte, Li2ZrCl6, is reported. Its raw materials are several orders of magnitude cheaper than those for the state-of-the-art chloride solid electrolytes, but high ionic conductivity (0.81 mS cm-1 at room temperature), deformability, and compatibility with 4V-class cathodes are still simultaneously achieved in Li2ZrCl6. Moreover, Li2ZrCl6 demonstrates a humidity tolerance with no sign of moisture uptake or conductivity degradation after exposure to an atmosphere with 5% relative humidity. By combining Li2ZrCl6 with the Li-In anode and the single-crystal LiNi0.8Mn0.1Co0.1O2 cathode, we report a room-temperature all-solid-state cell with a stable specific capacity of about 150 mAh g-1 for 200 cycles at 200 mA g-1.