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Cui Group improves Li-S battery performance with new separator design

A new study coming out of Dr. Yi Cui’s group at Stanford highlights the role of the separator in the capacity decay of a Li-Sulfur battery—i.e., the separator can accommodate a large amount of polysulfides inside which then precipitates as thick layer of inactive S-related species.

Lithium-Sulfur (Li-S) batteries are highly attractive for future generations of portable electronics and electric vehicles due to their high energy density and potentially low cost. In the past decades, various novel electrodes and electrolytes have been tested to improve Li-S battery performance. However, these designs on electrodes and electrolytes have not fully addressed the problem of low cycling stability of the Li-S battery.

—Yao et al.

The researchers applied a thin conductive coating on the separator to prevent the formation of the inactive sulfur-related species layer; the result was a significant improvement in both the specific capacity and the cycling stability compared to the battery with a pristine separator.

Combining the new separator design with a monodisperse sulfur nanoparticle cathode, Li-S batteries showed a life of more than 500 cycles with initial specific capacity of 1,350 mAh/g at C/2 and a cycle decay as low as 0.09%/cycle.


  • Hong bin Yao, Kai Yan, Weiyang Li, Guangyuan Zheng, Desheng Kong, Zhi Wei Seh, Vijay Kris Narasimhan, Zheng Liang and Yi Cui (2014) “Improved lithium-sulfur batteries with a conductive coating on the separator to prevent the accumulation of inactive S-related species at the cathode-separator interface” Energy Environ. Sci. doi: 10.1039/C4EE01377H



"500 cycles with initial specific capacity of 1,350 mAh/g at C/2 and a cycle decay as low as 0.09%/cycle."

500 x 0.09% = 45% or 65% capacity retention; that's still a long way to go to reach acceptable results.


If polysulfides were not created in the first place, battery designers would not have to protect against the damage they do. There is a lot of emphasis on energy density, but less on cost, longevity, charge speed, safety and other factors.

If the dual carbon design works, science can take the time required to develop lithium sulfur and magnesium. We will have a battery that can charge in 5 minutes, give us 150 mile range at a lower cost, while science is working on energy density in parallel.

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