A 3.5 V Supercapacitor with Ultrahigh Energy and Power Capabilities using Thermally Deoxygenated Graphite Oxide Electrodes and Water-in-Salt Electrolyte
M.S. Arsha, V Biju
Abstract
This study addresses a key challenge in supercapacitors, namely, simultaneously achieving high energy and high power densities. By synergistically harnessing the potential of two thermally reduced graphite oxide (TDGO) electrode materials, each exhibiting distinctly different charge-storage mechanisms, we optimized the energy-storage capabilities of an asymmetric supercapacitor (ASC) using a 17 m sodium perchlorate (NaClO 4 ) water-in-salt (WIS) electrolyte. This approach extended the electrochemical stability window to 3.5 V. We used a TDGO active material with diffusion-controlled charge-storage mechanism as the anode and another TDGO sample with a different level of deoxygenation exhibiting a surface-controlled charge-storage mechanism as the cathode. The ASC system exhibited a specific capacitance of 143 F/g (1 A/g). It achieved a record-breaking energy density of 244.8 Wh/kg at a power density of 3500 W/kg (1 A/g) and maintained significant energy and power density values of 183.7 Wh/kg and 17500 W/kg at 5 A/g, respectively. Additionally, the ASC system exhibited exceptional performance stability, retaining 99.6% of its capacitive performance at 20 A/g even after 10,000 continuous charge and discharge cycles. Performance of this ASC surpasses the performance benchmarks set by its symmetric counterparts and any aqueous supercapacitor previously reported in the literature.