A High-Energy Density Li-Ion Hybrid Capacitor Fabricated from Bio-Waste Derived Carbon Nanosheets Cathode and Graphite Anode.

The Li-ion hybrid capacitor (LIHC) system explores the possibility of achieving both high energy and power density in a single energy storage system with an intercalation anode and capacitive cathode. However, to achieve a high power and energy-based system, the properties of the cathode electrode material are vital. Here, bio-waste plant stem-derived activated porous carbon is explored as a cathode for LIHC application. A specific surface area of 1826 m2 g-1, enhanced degree of crystallinity, and graphitization results for porous carbon from activation by potassium hydroxide. When employed as supercapacitor material, the device exhibits good rate capability, energy, and power attributes with a specific capacitance of 116 F g-1 (1 A g-1). Simultaneously when tested for LIHC application the formulated device shows good capacity retention for 2500 cycles with a high energy density of 125 Wh kg-1 at a power density of 69 W kg-1. The work demonstrates unique, cost-effective strategy to develop a crystalline high surface area carbon from any such bio-waste sources to be employed as potential electrodes for energy storage applications.

Natural biomass derived hard carbon and activated carbons as electrochemical supercapacitor electrodes.

With every moving day, the aspect that is going to be the most important for modern science and technology is the means to supply sufficient energy for all the scientific applications. As the resource of fossil fuel is draining out fast, an alternative is always required to satisfy the needs of the future world. Limited resources also force to innovate something that can utilise the resource more efficiently. This work is based on a simple synthesis route of biomass derived hard carbon and to exploring the possibility of using it as electrochemical supercapacitors. A cheap, eco-friendly and easily synthesized carbon material is utilized as electrode for electrochemical energy-storage. Four different hard carbons were synthesized from KOH activated banana stem (KHC), phosphoric acid treated banana stem derived carbons (PHC), corn-cob derived hard carbon (CHC) and potato starch derived hard carbons (SHC) and tested as supercapacitor electrodes. KOH-activated hard carbon has provided 479.23 F/g specific capacitance as calculated from its cycle voltammograms. A detailed analysis is done to correlate the results obtained with the material property. Overall, this work provides an in depth analysis of the science behind the components of an electrochemical energy-storage system as well as why the different characterization techniques are required to assess the quality and reliability of the material for electrochemical supercapacitor applications.