A possible key to Li-sulfur batteries: highly crumpled nitrogen-doped graphene sheets

Sulfur (public domain)

Researchers at Pennsylvania State University have developed a promising new technique that may be able to overcome some of the challenges inherent to lithium-sulfur batteries.

In “Advanced Sulfur Cathode Enabled by Highly Crumpled Nitrogen-Doped Graphene Sheets for High-Energy-Density Lithium-Sulfur Batteries,” published in Nano Letters, Jiangxuan Song and colleagues explain how they synthesized highly crumpled nitrogen-doped graphene (NG) sheets with ultrahigh pore volume and large surface area, enabling strong polysulfide adsorption and high sulfur content for use as a cathode material in Li-sulfur batteries.

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“Practical applications of Li-S batteries are hindered by the low electrical conductivity of sulfur and the diffusion of soluble lithium polysulfides intermediates generated during cycling, which lead to lower utilization of sulfur, loss of active material from the cathode, and polysulfide shuttle phenomenon,” write the researchers. “As a result, Li-S cells experience fast capacity fading, low Coulombic efficiency, and poor rate capability. To address these issues, various types of cathode materials, including porous carbon-sulfur, low-dimensional conducting material (such as carbon nanotube and graphene-sulfur), and conducting polymer-sulfur composites, have been exploited to improve the overall electrochemical performance of the Li-S cells.”

Lithium-sulfur battery cells using these wrinkled graphene sheets as both sulfur host and interlayer achieved high capacity (1227 mAh/g) and long cycle life (75% capacity retention after 300 cycles) even at high sulfur content (≥80 wt %) and sulfur loading (5 mg sulfur/cm2).

 

Source: Nano Letters via Green Car Congress