Microfluidic‐Enabled Solid‐State Electrolytes With Enhanced Electrochemical Performance

ABSTRACT Conventional batch style sol–gel synthesis of ceramic solid‐state electrolyte (SSE) tends to suffer from irreproducibility in particle shape, size, and overall quality from batch to batch. The physical and electrochemical properties of ceramic SSE is highly dependent on its microstructure, which is correlated to the synthesis conditions. Previous synthesis methods primarily relied on extrinsic modifications, such as additive or surface coating, rather than intrinsically improving the electrochemical properties of ceramic SSEs. This inspired us to develop a synthesis method based on microfluidic (MF) engineering to enable a superior ceramic SSE with fundamentally improved solid‐state battery performance by directly optimizing the microstructure of ceramic SSEs. Using MF‐enabled sodium‐ion superionic conductor (NASICON) as an example, the ionic conductivity increased from 0.5 to 1.1 mS/cm, while the interfacial impedance decreased from 1350 to 285 Ω⋅cm 2 compared to that of conventional NASICON. Solid‐state sodium battery with MF‐enabled NASICON exhibited a specific capacity of 110 mAh/g over 1000 cycles with 80% capacity retention. Moreover, as a proof of concept, lithium lanthanum zirconium oxide (LLZO) is also fabricated by the MF method for a lithium solid‐state battery, which exhibited similarly superior electrochemical performances. Overall, this study provides new insights on ceramic SSE synthesis to intrinsically improve the electrochemical performances via tuning the microstructure of the sol–gel precursors.