Enhancement of the Cycling Performance of Sodium-Metal Cells By Use of a Conductive Polymer Additive

Among a variety of energy storage devices, sodium-ion batteries have received considerable attention as a promising alternative to lithium-ion batteries due to the natural abundance, distribution and cost of sodium resources. In order to achieve higher energy density, the cell voltage should be high enough. There have been a lot of studies on high-voltage cathodes for sodium-ion batteries, and Na3V2(PO4)2F3(NVPF) is one of the promising cathode materials. However, the cells assembled with NVPF exhibit poor cycling performance at high voltage due to electrolyte oxidation and low electronic conductivity of cathode material. In our work, we added amino-anthraquinone (AAQ) into the electrolyte solution as an additive, which can be electrochemically oxidized to poly(amino-anthraquinone) (PAAQ) on the surface of the cathode material. The conductive PAAQ layer formed on the cathode improved the electronic conductivity of NVPF and enhanced its electrochemical performance. The cycling performance of Na/NVPF cells assembled with electrolyte containing AAQ additive was evaluated and the detailed mechanism for improvement of cycling performance was investigated.