Identification of electrochemical reaction products in lithium–oxygen cells with 7Li nutation spectroscopy

In the Li–O2 battery system, it is has been shown to be challenging to differentiate the discharge products or determine the electrolyte stability with direct 7Li NMR. Defined 7Li quadrupole lineshapes are not observed for cycled cathodes. Here, 7Li nutation NMR is demonstrated to be an effective method for the identification of Li2O2 in cycled cathodes. The 7Li quadrupole interaction of Li2O2 (35 kHz) and Li2CO3 (120 kHz) are of similar magnitude to typically radiofrequency fields (ranging from 40 to 60 kHz). The 7Li nutation frequency will therefore be influenced by both interactions. The discharge products of the cycled cathodes were determined by comparing the 7Li nutation frequencies of the cycled cathodes to the 7Li nutation frequency of the pristine materials when the applied radiofrequency field was 30 kHz. Li2CO3 was determined to be the main discharge product in the propylene carbonate/dimethyl carbonate and trimethyl phosphate electrolyte systems, since the 7Li nutation frequencies of the cathodes corresponded to the 7Li nutation frequency of pristine Li2CO3. The 7Li nutation frequency of the tetraethylene glycol dimethyl ether cathode was between the 7Li nutation frequencies of both pristine Li2O2 and pristine Li2CO3, indicating that both Li2O2 and Li2CO3 were discharge products influencing the observed nutation frequency. From 7Li nutation NMR the novel trimethyl phosphate electrolyte was determined to be an unsuitable Li–O2 electrolyte, as the fast 7Li nutation frequency indicated that Li2O2 was not a primary discharge species. With 17O NMR, Li2CO3 was confirmed to be a main discharge product formed with the trimethyl phosphate electrolyte.

Improvement and Realization of Miniature Flexible Gyro in the Photoelectric Platform

Generally ,it was precession of flexible gyroscopic not gyroscopic nutation which was just considered in engineering design. However, in photoelectric stabilized platform, this nutation characteristics of angular position flexible gyro has been restricting the stabilized accuracy of platform seriously. In this paper, firstly the output characteristics of a miniature flexible gyro was measured by characteristic of gyroscopic motion, four main kinds of frequency components in output characteristics was analysed. The methods were realized in the miniature flexible gyroscope in the laboratory by adopting the two measures of the secondary trap circuit and improvement of torque component.Test results showed that, the improvements made nutation frequency of gyro and envelope at 40Hz converged fastly , and the output noise of gyro angular position was decayed to more than15dB. In the end, the gyro was applied to chariot photoelectric stabilized platform ,the isolation of platform and carrier got improved from 1~2mil to 0.3mil.

Quadrupole Nutation NMR in Solids

The nutation frequency of a quadrupolar spin I depends on the quadrupole interaction. From nutation spectra, therefore, one obtains information about the direct surrounding of the atom. The theory of the straightforward and of more complicated nutation NMR experiments is outlined. Two applications of nutation NMR, to 23Na in zeolites and 27Al in alumina, are shown. In this way in CaO • 6 Al2O3 penta-coordinated aluminum has been detected