Pressurized physically activated carbon used as a high-performance, low cost cathode material in lithium–sulfur batteries

Lithium–sulfur (Li–S) batteries are promising candidates for next-generation energy storage given their high energy density and potential low cost. Chemically activated carbon (CAC) is often used for their cathodes, because it has a high specific surface area for sulfur loading. We have developed a pressurized physical activation (PPA) method that produced an activated carbon (PPAC) with a high specific surface area comparable to that of CAC. The pore structure of PPAC could be changed and its use as a cathode material for Li–S batteries was investigated. Battery tests at different capacity rates (C-rates) showed that it had a much improved high-rate performance with a discharge capacity of 900 mAh/(g of sulfur) at 1 C, in contrast to only 600 mAh/(g of sulfur) for CAC. Pore structure analyses showed that PPAC prepared at a high activation temperature (1000 °C) had unusual channel-like mesopores between the microdomains that are the basic structural units of artificial carbon materials. These are connected to micropores developed in each microdomain, and deliver ions from the surroundings to the internal pores and vice versa. The well-developed micropores and mesopores of PPAC respectively ensured the high adsorption of lithium polysulfides and a high rate of ion diffusion. Compared to CAC, PPAC is a high-performance, low-cost cathode material that is promising for use in future Li–S batteries.