New Insight into the Working Mechanism of Lithium-Sulfur Batteries under a Wide Temperature Range.
Sweet potato-derived carbon with a unique solid core/porous layer core/shell structure is used as a conductive substrate for gradually immobilizing sulfur to construct a cathode for Li-S batteries. The first discharge specific capacity of the Li-S batteries with the C-10K@2S composite cathode at 0.1C is around 1645 mAh g-1, which is very close to the theoretical specific capacity of active sulfur. Especially, after 175 cycles at 0.5C, the maintained specific discharge capacities of the C-10K@2S cathode at -20, 0, 25, and 40 °C are about 184.9, 687.2, 795.5, and 758.3 mAh g-1, respectively, and the cathode is superior to most of the classical carbon form matrices. Working mechanisms of the cathodes under different temperatures are confirmed based on X-ray photoelectron spectroscopy (XPS) and in situ X-ray diffraction (XRD) characterizations. Distinctively, during the discharge stage, the widely proposed two-step cathodic reactions occur simultaneously rather than sequentially. In addition, the largely accelerated phase conversion efficiency of the cathode at a higher temperature (from room temperature to 40 °C) contributes to its enhanced charge/discharge specific capacity, while the byproduct Li2S2O7 or Li3N irreversibly formed during the cycles limits its application performance at 0 °C. These conclusions would be very significant and useful for designing cathodes for Li-S batteries with excellent wide working temperature performance.
['Peng|Guiping|G|', 'Hai|Chunxi|C|https://orcid.org/0000-0002-0430-2757', 'Sun|Chao|C|', 'Zhou|Yuan|Y|https://orcid.org/0000-0003-0540-5560', 'Sun|Yanxia|Y|', 'Shen|Yue|Y|https://orcid.org/0000-0001-9163-5148', 'Li|Xiang|X|https://orcid.org/0000-0002-2682-7853', 'Zhang|Guotai|G|', 'Zeng|Jinbo|J|', 'Dong|Shengde|S|']
XPS spectroscopy graphitic structure in situ XRD sweet potato starch-derived carbon wide-temperature working mechanisms