Barium Titanate-Based Porous Ceramic Flexible Membrane as a Separator for Room-Temperature Sodium-Ion Battery

Sodium-ion batteries (NIBs) are an alternative low-cost battery technology for large-scale energy storage application, and the development of high-performance polymer-based electrolytes is crucial for further advancement of low-cost NIBs. Though electrode materials provide significant contribution to the energy density of the battery, the separator plays a vital role in deciding the safety, duration, and performance of batteries. The glass fiber membrane is considered as the most compatible separator for NIBs because of its high ionic conductivity and reasonable performance. However, the leakage and flammability of the liquid electrolytes while using the glass fiber separator can lead to safety issues. Therefore, herein, we present an alternative approach for the first time to replace the glass fiber separator in NIBs using the porous ceramic membrane (PCM). The polymer blend-based PCM is prepared by a simple solution-casting technique and used as the separator in NIBs. The good thermal stability of the PCM up to 400 °C, high ionic conductivity of about 10^-3 S cm^-1, high electrolyte uptake, and porous nature make it a better choice over the glass fiber membrane. To demonstrate the applicability of PCM in NIBs, the sodium-ion storage property of hard carbon is evaluated using the PCM as the separator at room temperature. The specific capacity of hard carbon using the PCM-based separator is about 270 mA h g^-1 at a current density of 30 mA g^-1 which is ∼23% higher than the glass fiber separator (208 mA h g^-1) at the same current density. The enhancement in specific capacity is due to the compatibility of the PCM with sodium electrodes, low interfacial resistance, high sodium-ion transference number (0.8), and good electrochemical stability (4.9 V) than the glass fiber separator. This study demonstrates a promising alternative separator to the glass fiber membrane, which can lead to the development of a practical and safe NIB.