A safe, low-cost and high-efficiency presodiation strategy for pouch-type sodium-ion capacitors with high energy density

Sodium-ion capacitors (SICs) have attracted appreciable attention in virtue of the higher energy and power densities compared with their rivals, supercapacitors and sodium-ion batteries. Due to the lack of sodium resources in cathode, presodiation is critical for SICs to further augment performances. However, current presodiation strategy utilizes metallic sodium as the presodiation material. In this strategy, assembling/disassembling of half-cells is required, which is dangerous and increases the time and cost of SIC leading to the restriction of their industrialization and commercialization. Herein we present a safe, low-cost and high-efficiency presodiation strategy by first employing Na2C2O4 as the sacrificial salt applied in SICs. Na2C2O4 is environmentally friendly and possesses considerably low expenditure. No additional residues remain after sodium extraction ascribed to its “zero dead mass” property. When paired with commercial activated carbon as the cathode and commercial hard carbon as the anode, the constructed pouch-type SICs exhibit high energy and power densities of 91.7 Wh/kg and 13.1 kW/kg, respectively. This work shows a prospect of realizing the safe and low-cost manufacturing for high-performance SICs commercially.