Hailong Chen

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Lithium metal has the highest volumetric and gravimetric energy density of all negative-electrode materials when used as an electrode material in a lithium rechargeable battery. However, the formation of lithium dendrites and/or 'moss' on the metal electrode surface can lead to short circuits following several electrochemical charge-discharge cycles,(More)
The cooperative Jahn-Teller effect (CJTE) refers to the correlation of distortions arising from individual Jahn-Teller centres in complex compounds. The effect usually induces strong coupling between the static or dynamic charge, orbital and magnetic ordering, which has been related to many important phenomena such as colossal magnetoresistance and(More)
The tremendous growth of Li-ion batteries into a wide variety of applications is setting new requirements in terms of cost, energy density, safety, and power density. One route toward meeting these objectives consists in finding alternative chemistries to current cathode materials. In this Article, we describe a new class of materials discovered through a(More)
Van der Waals heterostructures composed of two-dimensional transition-metal dichalcogenides layers have recently emerged as a new family of materials, with great potential for atomically thin opto-electronic and photovoltaic applications. It is puzzling, however, that the photocurrent is yielded so efficiently in these structures, despite the apparent(More)
Water rotational dynamics in NaSCN and KSCN solutions at a series of concentrations are investigated using femtosecond infrared spectroscopy and theory. Femtosecond infrared measurements, consistent with previous NMR observations, detect that sodium slows down while potassium accelerates the water O-H bond rotation. Results of reported neutron scattering(More)
Morphology control of functional materials is generally performed by controlling the growth rates on selected orientations or faces. Here, we control particle morphology by "crystal templating": by choosing appropriate precursor crystals and reaction conditions, we demonstrate that a material with rhombohedral symmetry-namely the layered, positive electrode(More)
Dr. L. Liu, Prof. X. Li, Dr. S.-H. Bo, Dr. Y. Wang, Dr. N. Twu, Prof. G. Ceder Department of Materials Science and Engineering Massachusetts Institute of Technology Cambridge , MA 02139 , USA E-mail: gceder@mit.edu Prof. X. Li John A. Paulson School of Engineering and Applied Sciences Harvard University Cambridge , MA 02138 , USA Prof. H. Chen The Woodruff(More)
A perylenetetracarboxylic diimide (PDI) trimer (3) linked by a triazine ring has been prepared. The UV-vis absorption spectra together with the (1)H NMR spectra revealed that two of the three PDI subunits in the trimer presents a face-to-face stacked configuration while the third one appended acts as a monomer. There is no strong interaction between the(More)
In this work, through investigating a series of liquid, glassy, and crystalline samples with ultrafast multiple-mode 2D IR and IR transient absorption methods, we demonstrated that the signal anisotropy of vibrational relaxation-induced heat effects is determined by both relative molecular orientations and molecular rotations. If the relative molecular(More)
An ultrafast two-dimensional visible/far-IR spectroscopy based on the IR/THz air biased coherent detection method and scanning the excitation frequencies is developed. The method allows the responses in the far-IR region caused by various electronic excitations in molecular or material systems to be observed in real time. Using the technique, the relaxation(More)