Journal
ENERGY STORAGE MATERIALS
Volume 12, Issue -, Pages 216-222Publisher
ELSEVIER
DOI: 10.1016/j.ensm.2017.12.018
Keywords
Transition metal dichalcogenides; Potassium ion battery; Stage structure; Ether-based electrolyte; Layer structure
Funding
- National Natural Science Foundation of China [51502032, 11327902, 51725206, 51502007, 51672007, 21673033, 11234013, 21473022]
- Fundamental Research Funds for the Central Universities, China [ZYGX2016J044]
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Potassium ion batteries are potential energy storage devices owing to their low cost and good K+ diffusion kinetics due to the small Stoke's radius. Here, we report a layered TiS2 cathode material, demonstrating outstanding potassium storage cycling and rate performances in ether-based electrolyte, with a capacity of 80 mAh g(-1) at 20 C and 63 mAh g(-1) after 600 cycles (1.5-3.0 V, corresponding to 4.8 A g(-1)). The phase transitions during K ion intercalation at the atomic level are explored via High Resolution Transmission Electron Microscopy (HRTEM) and ex-situ X-ray diffraction (XRD) combined with Rietveld refinements. It undergoes a second-stage structure to be K0.11TiS2 and then first-stage K0.56TiS2. The K cations intercalate into trigonal prismatic sites with a sliding of Ti-S plane by 120 degree-rotation, rendering a root 3 x root 3 commensurate superstructure along the [001] zone. The K stage intercalation is in favor of a Daumas-Herold model rather than Rudorff model. This study demonstrates that the layer structure materials are promising candidates for high performances K-ion batteries and highlights the importance of improving electrochemical performances with electrolyte modification.
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