Novel Sodium‐Rare‐Earth‐Silicate‐Based Solid Electrolytes for All‐Solid‐State Sodium Batteries: Structure, Synthesis, Conductivity, and Interface

Considering the limited reserve of lithium, the safety risks of liquid‐based electrolytes, and the increasing demand of energy density, all‐solid‐state sodium batteries (ASSSBs) are widely recognized as promising alternatives in the field of electrochemical energy storage. As one of the most crucial components in ASSSBs, solid electrolytes (SEs) feature acceptable ionic conduction, high safety, and wide electrochemical window. Particularly, sodium rare earth silicate (Na 5 RESi 4 O 12 ) is a new class of SEs with high ionic conductivity (10 −3 S cm −1 ) at room temperature, low synthesis temperature (900−1100 °C), and excellent chemical stability. In Na 5 RESi 4 O 12 , rare earth cations (e.g., Sm, Gd, Y, In) can occupy the position of RE, which enables huge potential on the regulation of physicochemical properties, facilitating the achievement of high‐performance SEs. Here, fundamental features, crystal structure, ionic transport mechanism, synthesis routes, and electrochemical performance of Na 5 RESi 4 O 12 SEs are systematically overviewed. To tackle the interfacial issues that hinder the stable operation of ASSSBs, several effective strategies are summarized and discussed. For future development, relevant outlook is made and constructive suggestions are proposed. This review is expected to provide a comprehensive introduction and understanding on the Na 5 RESi 4 O 12 SEs and advance further investigation toward high‐performance ASSSBs.