It is still challenging to develop sulfur electrodes for Li−S batteries with high electrical conductivity and fast kinetics, as well as efficient suppression of the shuttling effect of lithium polysulfides. To address such issues, herein, polar MoTe 2 with different phases (2H, 1T, and 1T′) were deeply investigated by density functional theory calculations, suggesting that the 1T′-MoTe 2 displays concentrated density of states (DOS) near the Fermi level with high conductivity. By optimization of the synthesis, 1T′-MoTe 2 quantum dots decorated threedimensional graphene (MTQ@3DG) was prepared to overcome these issues, and it accomplished exceptional performance in Li−S batteries. Owing to the chemisorption and high catalytic effect of 1T′-MoTe 2 quantum dots, MTQ@3DG/S exhibits highly reversible discharge capacity of 1310.1 mAh g −1 at 0.2 C with 0.026% capacity fade rate per cycle over 600 cycles. The adsorption calculation demonstrates that the conversion of Li 2 S 2 to Li 2 S is the rate-limiting step where the Gibbs free energies are 1.07 eV for graphene and 0.97 eV for 1T′-MoTe 2 , revealing the importance of 1T′-MoTe 2 . Furthermore, in situ Raman spectroscopy investigation proved the suppression of the shuttle effect of LiPSs in MTQ@3DG/S cells during the cycle.
A physics model for the electromagnetic scattering from large-scale rough surface of layered medium is established. Stratton-Chu integral equation and Kirchhoff approximation are adopted to calculate the electromagnetic scattering field. The Gaussian random rough surface is selected to simulate the actual rough surface of layered medium. The scattering echo is detected with a single-station nadir-looking radar sounder. A comparison of radar echoes from Martian mare areas with different roughness is demonstrated. A radar sounder echo simulator is developed, which could be used to validate the radar echoes processing and to support the interpretation of Martian exploration data. By using the simulator, the B-scan images of Martian highland areas with different crater density are studied. Besides, special attentions are paid to the effect of radar waveforms on the B-scan imaging of highland areas. Simulation-based results show that the method presented is feasible in the detection of Martian subsurface structure.
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