Porous carbon assembly optimised for Li-S batteries

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Pore size distribution substantially influences the performances of cathodes in Li-S batteries, says a team of researchers from Hefei University of Technology in China.

Li-S batteries are considered as promising alternatives for Li-ion batteries in new generations of energy storage devices, due to sulphur’s high specific capacity of 1675mAh/g and energy density of 2600mWh/g. But its poor conductivity and shuttle effect destroy the stability of the system.

A variety of porous carbon materials have been applied as sulphur host to improve the performance of Li-S batteries with regard to high conductivity, specific surface area and absorption effect.

Researchers found that an optimised assembly of micro/meso/macroporous carbon improves electrochemical performances. They also found that the micropore to volume ratio to the total pore volume influences cycling stability of batteries and that meso/macropore to volume ratio influences spaces for sulphur loading and channels to ion transfer.

Among the samples, the porous carbon possessed the largest micropore volume ratio of 47.54%. It also has a medium specific surface area of 1217m2/g and inferior total pore volume of 0.54cm3/g. This results in an initial discharge specific capacity of 1327mAh/g and a retention of 630mAh/g over 100 cycles at 0.2C.

According to the researchers, their conclusions can be applied to material fabrication for other energy storage devices and for further modification of Li-S batteries based on carbon material.