Durable Li-S batteries with nano-sulfur/graphite nanoplatelets composites

• Sulfur composites with graphite nanoplatelets (GNPs) were prepared.
• The nano-S/GNPs (ex situ 20 wt% + in situ 20 wt%) is a homogenous composite.
• This composite delivered an initial capacity of 1201 mA h gsulfur−1.
• This composite retains 73% of its’ original capacity after 100 cycles.
• GNPs serve as barricades and prevent polysulfide migration and dissolution.

Sulfur composites were prepared with graphite nanoplatelets (GNPs) for the first time, wherein the GNPs served as a scaffold for tethering the nano-sulfur (nano-S) particles. Three protocols were employed: (i) an in situ route, wherein the GNPs (40 wt%) were introduced in the precursor solution of nano-S, (ii) by ex situ mixing of solid GNPs (40 wt%) with solid nano-S, and (iii) by using a combination of methods (i) and (ii). The sulfur particles are uniformly and contiguously attached to the ribbon like graphitic nanoplatelets in the nano-S/GNPs (ex situ 20 wt% + in situ 20 wt%) composite, whereas in the other two composites, the sulfur particles tend to agglomerate over different regions of the platelet fibers. A comparative study of the electrochemical performances of half-cells based on the three composites, nano-S and S revealed that the nano-S/GNPs (ex situ 20 wt% + in situ 20 wt%) composite retains 73% of its’ original capacity at the end of 100 cycles with a reversible capacity of 610 mA h gsulfur−1. The cell also showed an outstanding rate capability for the cell capacity reverted to nearly the same value, when the C-rate was ricocheted to 0.1 C after going through higher C-rates. The role of GNPs and the dependence of the method of embedding sulfur particles on GNPs demonstrate that GNPs have tremendous promise to unlock the potential of sulfur for producing cells with reproducible, stable and durable charge storage characteristics.

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