Nafion membranes as electrolyte and separator for sodium-ion battery

Nafion 115 commercial membranes in the Na+-form (Nafion-Na) swollen with non-aqueous solvent used as both electrolyte and separator for sodium-ion battery were investigated. After swollen with ethylene carbonate (EC) – propylene carbonate (PC) mixed solvent, the Nafion-Na membranes showed ionic conductivity of 3.52 × 10−4 S cm−1 at room temperature and 1.52 × 10−3 S cm−1 at 70 °C, respectively. Compared with the conventional sodium-ion battery using the liquid electrolyte, the battery using the Nafion-Na membranes as electrolyte showed good cycling stability. For Na0.44MnO2 cathode in the sodium-ion battery, the capacity retention using the conventional liquid electrolyte (1 mol L−1 NaClO4 in EC:PC = 1:1, v:v) was about 67.6% after 50 cycles, however, the capacity retention using the Nafion-Na membrane electrolyte was about 92.5% after 50 cycles.