期刊
JOURNAL OF POWER SOURCES
卷 378, 期 -, 页码 40-47出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/j.jpowsour.2017.12.027
关键词
Li-S battery; Luffa sponge; Carbon matrixes; Dihydrogen phosphate groups; DFT calculation
资金
- Shenzhen Fundamental Research Program of Subject Distribution [JCYJ20170413102735544, JCYJ20160226201232552]
- project of Innovative group for high-performance lithium-ion power batteries R&D and industrialization of Guangdong Province [2013N079]
Carbon matrix (CM) derived from biomass is low cost and easily mass produced, showing great potential as sulfur host for lithium sulfur batteries. In this paper we report on a dihydrogen phosphate modified CM (PCM-650) prepared from luffa sponge (luffa acutangula) by phosphoric acid treatment. The phosphoric acid not only increases the surface area of the PCM-650, but also introduces dihydrogen phosphate onto PCM-650 (2.28 at% P). Sulfur impregnated (63.6 wt%) PCM-650/S, in comparison with samples with less dihydrogen phosphate LPCM-650/S, shows a significant performance improvement. XPS analysis is conducted for sulfur at different stages, including sulfur (undischarged), polysulfides (discharge to 2.1 V) and short chain sulfides (discharge to 1.7 V). The results consistently show chemical shifts for S-2p in PCM-650, suggesting an enhanced adsorption effect. Furthermore, density functional theory (DFT) calculations is used to clarify the molecular binding: carbon/sulfur (0.86 eV), carbon/Li2S (0.3 eV), CH3-O-PO3H2/sulfur (1.24 eV), and CH3-O-PO3H2/Li2S (1.81 eV). It shows that dihydrogen phosphate group can significantly enhance the binding with sulfur and sulfide, consistent with XPS results. Consequently a CM functionalised with dihydrogen phosphate shows great potential as the sulfur host in a Li-S battery.
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