Progress in sodium silicates for all-solid-state sodium batteries—a review

All solid-state sodium batteries (ASSSBs) are considered a promising alternative to lithium-ion batteries due to increased safety in employing solid-state components and the widespread availability and low cost of sodium. As one of the indispensable components in the battery system, organic liquid electrolytes are the currently used electrolytes due to their high-ionic conductivity (10−2 S cm−1) and good wettability; however, their low-thermal stability, flammability, and leakage tendency pose safety concerns. The growing sodium-ion battery technology with solid electrolytes is a viable solution due to their improved safety. However, solid electrolytes suffer from insufficient ionic conductivity at room temperature (10−4–10−3 S cm−1), poor interface stability, high charge-transfer resistance, and low wettability, yielding inferior battery performance. Sodium rare-earth silicates are a new class of materials with a 3D structure framework similar to sodium-superionic conductors (NASICONs). These silicates can be used as a solid electrolyte for solid-state sodium batteries due to their high-ionic conduction (10−3 S cm−1) at 25 °C. Herein, the sodium rare-earth silicate synthesis, crystal structure, ion-conduction mechanism, doping, and electrochemical properties are discussed. This emerging type of inorganic solid electrolyte can pave the way to building next-generation ASSSBs.</p

Characterization of lithium-rich garnet-type Li_6.5La_2.5Ba_0.5ZrTaO₁₂ for beyond intercalation chemistry-based lithium-ion batteries

Li-rich garnet-type Li6.5La2.5Ba0.5ZrTaO12 (LLBZT) electrolyte is characterized as a Li protecting layer for potential application in aqueous Li-O2 battery. AC impedance spectroscopy and DC electrical measurements, high temperature powder X-ray diffraction (HT-PXRD), scanning electron microscopy (SEM) and thermogravimetic analysis (TGA) were used to investigate the electrochemical and chemical properties of Li/LLBZT and LLBZT/aqueous interfaces. Stable open circuit voltage (OCV) of ~ 3 V was observed for Li/LLBZT/0.1 M LiOH, Li/LLBZT/1 M LiOH and Li/LLBZT/1 M LiCl at 25 °C. DC galvanostatic Li plating/stripping cycle at varying current density was performed and the area specific polarization resistance (ASR) for Li+ ion charge transfer was found to be 473 Ω cm2 at 25 °C. The impedance of LLBZT was found to be improved after treating the samples with 1 M LiOH, and 1 M LiCl, and retains its crystal structure and electrochemical stability with Li; thus, Li-rich LLBZT garnet can be successfully employed in next generation beyond Li-ion batteries.</p