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Ethylene diamine tetra-acetic acid (EDTA) was used to prepare spinel LiMn 2 O 4 at 650 °C. The prepared sample by EDTA (E-LiMn 2 O 4 ) is compared with another spinel sample (C-LiMn 2 O 4 ) prepared by citric acid as a common chelating agent at the higher temperature (800 C) adjusted to obtain the same size and shape of the particles as in (E-LiMn 2 O 4 ) sample, as probed by SEM and TEM images. Investigation of both samples by X-ray diffraction showed that both samples have the single phase cubic spinel LiMn 2 O 4 phase with space group Fd-3m. Vibration properties obtained from Raman scattering (RS) and Fourier Transform Infra-Red (FTIR) spectroscopy for both samples are identical with spinel LiMn 2 O 4 structure. 7 Li MAS NMR and XPS spectra show that the amount of Mn 4+ is larger in LiMn 2 O 4 sample prepared by citric acid. LiMn 2 O 4 sample prepared using EDTA as chelating agent has better structural properties, but the improvement of the electrochemical properties is much smaller than the results reported in the literature for lamellar compounds and silicate materials. This is attributed to the features specific to the spinel, which limit both the capacity and cycle ability: dissolution of manganese and Jahn-Teller distortions associated to Mn 3+ ions, that are not modified by the choice of chelating agent.

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For more than a century, manganese dioxides (MDOs) have been used as electrochemically active materials in energy storage and conversion applications. To reduce the cost and hazardous impact of synthesis, a redox method was used to prepare MnO2 using extracts of green (GT-MnO2) and black (BT-MnO2) tea as biological reducing agents. Polyphenols present in the extracts of tea not only reduce Mn 7+ ions but also act as "capping agents" to stabilize and prevent the produced MnO2 nanoparticles from degradation and aggregation. Elemental, structural properties and morphology of nanosized α-KxMnO2 were studied by thermogravimetric analysis, X-ray powder diffraction and Raman spectroscopy, which revealed the different crystallinity between GT-MnO2 and BT-MnO2 due to the strength of the antioxidant species. Electrochemical investigations highlight the beneficial presence of K + ions in (2×2) tunnels; with a higher concentration, α-K0.135MnO2 exhibits a discharge specific capacity of 155 mAh g-1 after 20 cycles at C/26 rate.

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