Journal
ENERGY STORAGE MATERIALS
Volume 25, Issue -, Pages 416-425Publisher
ELSEVIER
DOI: 10.1016/j.ensm.2019.09.039
Keywords
Potassium ion battery; Dimensionality; Hierarchical structure; Diffusion barrier; Pseudocapacitance
Funding
- HIT Young Scientist Studio
- Harbin Institute of Technology
- National Top-notch Young Professionals, National Natural Science Foundation of China [51773049]
- Natural Science Funds of Heilongjiang Province [ZD2019B001]
- HIT Research Institute (Zhao Yuan) of New Materials and Intelligent Equipment Technology Co., Ltd. Scientific and Technological Cooperation and Development Fund [2017KJHZ002]
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Compared to the significant advances in its lithium and sodium analogue, the practical application of potassium ion batteries (KIBs) has been hindered by the sluggish K ion diffusion. Electrochemical storage via insertion/deinsertion reactions in lamellar electrode materials critically rests upon the host materials with wide interlayer spacing and the sizes of the guest ions. To uncover the underlying science behind the dimensionality in the KIBs regime, we investigated MoS2/K half-cell using uniform MoS2 rod, sheet, and sphere structures synthesized by a facile and controllable method for the first time. Impressively, whenMoS(2) is in the shape of a hierarchical rod, there is more intercalation pseudocapacitance (74.8% at the scan rate of 1.5 mV s(-1)) and the optimized electrode resulted in high-rate capacity (320 and 183 mAh g(-1) at 0.1 and 1 A g(-1), respectively). In contrast, MoS2 sheet and sphere contribute little pseudocapacitance (69.1% and 61.4%, respectively) and therefore exhibit low-rate capacity (232 and 110 mAh g(-1) for MoS2 sheet, 185 and 96 mAh g(-1) for MoS2 sphere at 0.1 and 1 A g(-1), respectively). Density functional theory (DFT) results uncover that the K atom is much more liable to occupy the octahedral (Oh) site. What's more, non-destructively 3D reconstruction of MoS2 rod electrode strongly demonstrated the integrity of the rod structure after K+ insertion. The work paves a new way for the design of two dimensional (2D) materials and offers profound insights into the charge storage mechanism of KIBs.
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