High Performance Sodium-Ion Hybrid Capacitor Based on Graphene-Tin Pyrophosphate Nanocomposite Anode

Abstract

The development of alternative energy storage technologies such as sodium-ion hybrid capacitors, which do not rely on critical raw materials such as cobalt or nickel, for the replacement of conventional lithium-ion batteries for some niche applications, is extremely important to successfully achieve a sustainable development in our planet. In this work, we introduce a novel sodium-ion hybrid capacitor system formed by the combination of an optimized nanostructured composite material containing reduced graphene oxide and tin pyrophosphate as negative electrode, and a high specific surface area graphene-carbon composite as positive electrode. The electrochemical performance of each material has been individually evaluated using NaPF₆ in EC/DMC as electrolyte, showing impressive specific capacity values above 100 mAh g⁻¹ at 2 A g⁻¹, for both faradaic and capacitive-type electrodes. The integration of the electrodes in an optimized full cell with anode-to-cathode mass balance of 1.5 : 1, enabled stable full cells that can provide energy densities of almost 60 Wh kg⁻¹ at 3,000 W kg⁻¹, showcasing the potential of these type of materials in the design of next generation energy storage systems.