Integrating dual-ion storage and D-A effect into a nitrogen-rich polymer for symmetric all-organic sodium batteries

Abstract

Organic sodium-ion battery has emerged as an appealing theme due to its low-cost and environmentally benign features. However, the limited active sites, relatively low voltage, and poor conductivity of organic molecules hinder the simultaneous achievement of high energy and high power densities. Herein, a bipolar polymer with D-A character consisting of both n-type Hexaazatrinaphthalene (HATN) for Na⁺ storage, and p-type 5,10-dihydrophenazine(PZ) for anion storage is designed and synthesized. The elevated working potential from p-type PZ and enhanced electron transfer due to the D-A effect are crucial for achieving high power density. Specifically, the PZ-HATN cathode delivers a high discharge capacity of 235 mAh g^-1 at 0.2 A g ^-1 and 157 mAh g^-1 at 10 A g^-1, leading to an ultrahigh power density of 20.4 kW kg ^-1 and a competitive energy density of 409.0 Wh kg^-1(at 10 A g^-1, corresponding to 42C). Furthermore, the bipolar nature of PZ-HATN ensures a substantial potential disparity of 2.1 V, facilitating the symmetric all-organic battery (SAOB) construction. The SAOBs exhibit high-rate capability and outstanding cycling stability (with a sustained discharge capacity of 96.8 mAh g^-1 after 10,000 cycles at 1 A g^-1). This study offers insights into the structure-property relationships of organic electrode material, and will be inspiring to the development of high-performance all-organic sodium-ion batteries.