Hierarchically porous carbon from waste coffee grounds for high-performance Li-Se batteries

Lithium-selenium (Li-Se) batteries represent a promising energy storage system due to the relatively high electronic conductivity and high volumetric energy density of Se as a cathode. The design of porous carbon with tunable structure and low cost is a key to enabling Se cathodes for high-performance Li-Se batteries. In this study, hierarchically microporous activated carbon (AC) was fabricated from waste coffee grounds through a carbonization and KOH-activation process. Despite the simple synthesis process, the optimized AC (AC-700) had a high surface area of 1355 m(2) g(-1) and a large microspore volume of 0.52 cm(3) g(-1). The Se/AC-700 cathode showed a reversible capacity of 655 mAh g(-1) after 100 cycles at 0.1C in Li-Se batteries based on a carbonate electrolyte. Moreover, the Se/AC-700 cathode demonstrated excellent cyclic performance over 400 cycles without appreciable capacity decay. The main reason for the good battery performance was attributed to fast electron transfer and Li-ion diffusion in Se confined in the microporous carbon of AC-700. It is expected that this work will shed light on the development of low-cost and stable Se cathodes for high-energy Li-Se batteries. (C) 2019 Elsevier Ltd. All rights reserved.