Construction and Interfacial Modification of a ß-PbSnF4 Electrolyte with High Intrinsic Ionic Conductivity for a Room-Temperature Fluoride-Ion Battery.

Solid-state fluoride-ion batteries (FIBs) attract significant attention worldwide because of their high theoretical volume, energy density, and high safety. However, the large interfacial resistance caused by the point-point contact between the electrolyte and the electrode seriously impedes their further development. Using liquid-phase therapy to construct a conformal interface is a good choice to eliminate the influence of inadequate contact between the electrode and the electrolyte. In this study, a ß-PbSnF4 solid-state electrolyte with high room-temperature ionic conductivity is prepared, and a trace amount of the liquid electrolyte (LE) between the electrode and the electrolyte is introduced in order to minimize the interfacial resistance and enhance the cycle life. The Allen-Hickling simulations show that the introduction of an interfacial wetting agent (LE) can significantly reduce the energy barrier of charge transfer and mass transfer processes at the interface and reciprocate FIBs an enhanced interfacial reaction kinetics. As a result, the initial discharge capacity of the fabricated FIBs is 210.5 mAh g-1 and the capacity retention rate is 82.6% after 50 cycles at room temperature, while the initial discharge capacity of the unmodified battery is only 170.9 mAh g-1 and the capacity retention rate is 22.1% after 50 cycles. Therefore, interfacial modification with a trace amount of LE provides a significant exploration for the improvement of FIB performances.

Efficient Mutual-Compensating Li-Loss Strategy toward Highly Conductive Garnet Ceramics for Li-Metal Solid-State Batteries.

Garnet-type Li7La3Zr2O12 (LLZO) is a promising solid-state electrolyte (SSE) due to its high Li+ conductivity and stability against lithium metal. However, wide research and application of LLZO are hampered by the difficulty in sintering highly conductive LLZO ceramics, which is mainly attributed to its poor sinterability and the hardship of controlling the Li2O atmosphere at a high sintering temperature (∼1200 °C). Herein, an efficient mutual-compensating Li-loss (MCLL) method is proposed to effectively control the Li2O atmosphere during the sintering process for highly conductive LLZO ceramics. The Li6.5La3Zr1.5Ta0.5O12 (LLZTO) ceramic SSEs sintered by the MCLL method own high relative density (96%), high Li content (5.54%), high conductivity (7.19 × 10-4 S cm-1), and large critical current density (0.85 mA cm-2), equating those sintered by a hot-pressing technique. The assembled Li-Li symmetric battery and a Li-metal solid-state battery (LMSSB) show that the as-prepared LLZTO can achieve a small interfacial resistance (17 Ω cm2) with Li metal, exhibits high electrochemical stability against Li metal, and has broad potential in the application of LMSSBs. In addition, this method can also improve the sintering efficiency, avoid the use of mother powder, and reduce raw-material cost, and thus it may promote the large-scale preparation and wide application of LLZO ceramic SSE.