Solid‐state Li batteries using Na+ superionic conductor type solid electrolyte attracts wide interest because of its safety and high theoretical energy density. The NASCION type solid electrolyte LAGP (Li1.5Al0.5Ge0.5P3O12) shows favorable conductivity as well as good mechanical strength to prevent Li dendrite penetration. However, the instability of LAGP with Li metal remains a great challenge. In this work, an amorphous Ge thin film is sputtered on an LAGP surface, which can not only suppress the reduction reaction of Ge4+ and Li, but also produces intimate contact between the Li metal and the LAGP solid electrolyte. The symmetric cell with the Ge‐coated LAGP solid electrolyte shows superior stability and cycle performance for 100 cycles at 0.1 mA cm−2. A quasi‐solid‐state Li–air battery has also been assembled to further demonstrate this advantage. A stable cycling performance of 30 cycles in ambient air can be obtained. This work helps to achieve a stable and ionic conducting interface in solid‐state Li batteries.
Strong photoluminescence from silicon-ion-implanted thermal SiO 2 film was investigated under various conditions. The photoluminescence spectrum of as-implanted samples or samples annealed in N 2 at a temperature below 1000°C consists of three bands centered at about 470, 550, and 630 nm. Annealing at a temperature above 1000°C for a long enough time brings about one photoluminescence band peaking at about 730 nm. The peak wavelengths of these four bands are all independent of annealing or excitation conditions. As the annealing temperature is increased, 470-, 550-, and 630-nm bands are initially intensified and then weakened with the intensity maxima at 600, 300, and 200°C, respectively; as the annealing time increases from 1 min, they are monotonously weakened. The 730-nm band is always strengthened whether with increasing annealing time or temperature within our experimental range. In addition, these four bands show different excitation behaviors. The discussion section argues that the 470-, 550-, and 630-nm bands result from different point defects in the bulk of silicon implanted SiO 2 , while the 730-nm one results from luminescence centers at the interface between the nanocrystal silicon and SiO 2 matrix. ͓S0163-1829͑97͒03011-7͔
Lithium metal for rechargeable aprotic Li–O2 batteries is considered one of the most fascinating anode materials that can deliver high theoretical specific capacity, low density, and low negative electrochemical potential. Although lithium‐metal anodes have been studied extensively for decades, the cycling performance of rechargeable aprotic Li–O2 batteries based on lithium‐metal anodes is rather poor because of the unresolved security issues related to lithium dendrites and contaminant (O2, H2O) crossover from cathode to anode. Here, the critical issues and challenges facing lithium‐containing anodes associated with the security, stability, and efficiency are analyzed. Moreover, the latest research progress and strategies used to improve the performance of aprotic Li–O2 batteries based on lithium‐containing anode are reviewed. Perspectives toward the development of highly stable lithium‐containing anodes are also presented.
Intense ultraviolet photoluminescence centered at 370 nm was observed from magnetron-sputtered silicon oxide films after they were annealed at about 1000 °C in N2 atmosphere. This photoluminescence is found to be associated with the formation of nanocrystal silicon particles in the specially structured SiO2, which highly resembles the oxide layer of porous silicon. The luminescence centers at the interface between the nanocrystal silicon particles and the SiO2 matrix are responsible for the strong ultraviolet luminescence.
We report the optical spectroscopic results of a single self-assembled In0.75Al0.25As/Al0.3Ga0.7As quantum dot. The polarization-dependent shift of the Zeeman splitting in a single InAlAs QD has been observed. The induced Overhauser field is estimated to be ∼0.16 T in this InAlAs QD and the magnitude is shown to be controllable by the degree of circular polarization of excitation light.
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