Photopolymerized Gel Electrolyte with Unprecedented Room-Temperature Ionic Conductivity for High-Energy-Density Solid-State Sodium Metal Batteries

Solid-state sodium metal batteries (SMBs) are highly promising rechargeable batteries owing to the abundance and cost effectiveness of sodium. However, the low room-temperature ionic conductivity and narrow voltage window of solid-state electrolytes seriously inhibit the development of SMBs. Herein, an ethoxylated trimethylolpropane triacrylate based quasisolid-state electrolyte (ETPTA-NaClO4-QSSE) is developed by photopolymerization for high-energy-density solid-state SMBs. The ETPTA-NaClO4-QSSE exhibits remarkable room-temperature ionic conductivity of 1.2 mS cm(-1), a wide electrochemical window of >4.7 V versus Na+/Na, and excellent flexibility. Owing to outstanding interfacial compatibility between this electrolyte and the electrode, Na metal symmetrical batteries show ultralong cyclability with 1000 h at 0.1 mA cm(-2), and ultralow overpotential of 355 mV at 1 mA cm(-2), indicative of significant suppression of the Na dendrite growth. Notably, Na3V2(PO4)(3) (NVP) full batteries (NVP||ETPTA-NaClO4-QSSE||Na) display unprecedented rate capability, with a recorded capacity of 55 mAh g(-1) at 15 C, higher than any achieved so far in solid-state SMBs, and long-term cycling stability at 5 C, offering a capacity retention of 97% after 1000 cycles. Furthermore, NVP||ETPTA-NaClO4-QSSE||Na pouch cells represent excellent flexibility and exceptional safety, demonstrative of wide applicability. Therefore, this work will open new opportunities to develop room-temperature high-energy-density solid-state SMBs.

Automated summary

The newly developed ETPTA-NaClO4-QSSE quasi-solid-state electrolyte shows excellent performance in solid-state sodium metal batteries, with high ionic conductivity and wide electrochemical window. Its outstanding properties contribute to high cycling stability and low overpotential, effectively suppressing sodium dendrite growth.