Abstract
Spinel LiAl 0.05Mn 1.95O 4 has been successfully synthesized by a new ultrasonic-assisted sol–gel (UASG) method. The structure and physicochemical properties of this as-prepared powder compared with the pristine LiMn 2O 4 and LiAl 0.05Mn 1.95O 4 synthesized by the traditional sol–gel method were investigated by differential thermal analysis (DTA) and thermogravimetery (TG), powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), cyclic voltammetry (CV), and galvanostatic charge–discharge testing in detail. The results show that all samples have high phase purity, and ultrasonic process plays an important role in controlling morphology; LiAl 0.05Mn 1.95O 4 has higher Mn oxidation state, and the absorption peak of Mn(III) O and Mn(IV) O bonds has blue shift because of the doped Al. CV confirms that the LiAl 0.05Mn 1.95O 4 sample (UASG) has a good reversibility and its structure is very advantageous for the transportation of lithium ions. The charge–discharge tests indicate that LiAl 0.05Mn 1.95O 4 (UASG) has nearly equal initial capacity with LiMn 2O 4 (sol–gel) at 1 C discharge rate, but LiAl 0.05Mn 1.95O 4 (UASG) has higher discharge potential than that of LiMn 2O 4 (sol–gel). In addition, LiAl 0.05Mn 1.95O 4 (UASG) has higher discharge potential and capacity than that of LiAl 0.05Mn 1.95O 4 (sol–gel) at 1 C discharge rate, and LiAl 0.05Mn 1.95O 4 (UASG) has high capacity retention at C/3 and 1 C discharge rate among three samples after 50 cycles, which reveals that the sample obtained via UASG method, has the best electrochemical performance among three samples.
Published Version
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