Biomass Based Porous Carbons As Promising Composite Cathodes for Lithium Sulfur Battery

Abstract

The lithium sulfur battery is the one of the promising alternative rechargeable battery system to replace the conventional lithium ion battery system. It has a high capacity and energy density of 1,675 mA h g−1 and 2,500 Wh kg−1, respectively. The energy density is about five times higher compared to lithium ion batteries. Furthermore, sulfur is cheap, naturally abundant and safe . One of the main constraints is related to the poor electrical conductivity of sulfur which needs addition of high amount of conductive carbon, Another main problem is the high solubility of the intermediate polysulfides in the organic solvent electrolytes during discharge/charge process. Dissolved polysulfide components are moving back and forward between Li Anodes and Sulfur Cathodes, causing a rapid capacity loss and a low coulombic efficiency. The common approach to solve the problem was using the concept of sulfur encapsulation in the porous carbon structure. This strategy is the most popular study for cathodes in lithium sulfur battery in the last few years. It has been shown to solve the problems of low conductivity and dissolution of polysulfides simultaneously. As the results, the electrochemical performance of sulfur cathodes has been improved due the better electronic conductivity and the inhibation of polysulfide dissoltion. In this current works, biomass based porous carbons have been synthesized by using chemical activation of tropical salacca fruit peel with potassium carbonate and used as sulfur cathode component for lithium-sulfur batteries. The motivation was to obtain carbon with specific morphology and structures used for the application in composite sulfur cathodes for lithium sulfur battery. As shown by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and N2 adsorption isotherms, the porous carbon material has microporous-mesoporous structures with honeycomb morphology. Composite sulfur cathode has shown a large initial discharge capacity of 802 mAh g−1 at current density of 0.1 C , which remained stable during 50 charge-discharge cycles . This stable and reversible cycleability of this composite cathode has been contributed by a unique combination of micro and mesoporosity, as well assurface functional groups, which could allow the retention of the intermediate polysulfides within the carbon porous structures, without enormous dissolution in the electrolyte.