A porous nitrogen and phosphorous dual doped graphene blocking layer for high performance Li-S batteries
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Conductive confinement of sulfur and polysulfide via carbonaceous blocking layers can simultaneously address the low conductivity, volume expansion of sulfur during charge/discharge process and polysulfides shuttling effect in lithium-sulfur (Li-S) batteries. Herein, conductive and porous nitrogen and phosphorus dual doped graphene (p-NP-G) blocking layer is prepared via a thermal annealing and subsequent hydrothermal reaction route. The doping levels of N and P in p-NP-G measured by the X-ray photoelectron spectroscopy are ca. 4.38% and ca. 1.93 %, respectively. The dual doped blocking layer exhibits higher conductivity than N or P single doped blocking layer. More importantly, the density function theory (DFT) calculation demonstrates that P atoms and -P-O groups in the p-NP-G layer offer stronger adsorption to polysulfides than the N species. The electrochemical evaluation results illustrate that the p-NP-G blocking layer could deliver superior initial capacity (1158.3 mA h/g at the current density of 1 C), excellent rate capability (633.7 mA h/g at 2 C), and satisfactory cycling stability (ca. 0.09% capacity decay per cycle), which are better than the N or P single doped graphene. This work suggests that this synergetic combination of conductive and adsorptive confinement strategies induced by the multi-heteroatoms doping scheme is a promising approach for developing high performance Li-S batteries.
Journal of Materials Chemistry A
© 2015 Royal Society of Chemistry. This is the author-manuscript version of this paper. Reproduced in accordance with the copyright policy of the publisher. Please refer to the journal website for access to the definitive, published version.
Energy Generation, Conversion and Storage Engineering