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Formation of stable phases of the Li–Mn–Co oxide system at 800 °C under ambient oxygen pressure

“…These conditions correspond to charge-discharge rates about 20 mA/g (approximately 0.2 C). 7 Li NMR spectra have been acquired on a Bruker Avance III 300 spectrometer (Larmor frequency 117 MHz) equipped with a 1.3-mm probehead. Spectra have been acquired at magic angle spinning (MAS) frequencies of 40 to 65 kHz.…”

“…According to the XRD, 7 Li NMR, and electrochemical data, the following phases (co)exist in the area restricted to the quadrangle LiCoO 2 -LiCo 0.85 Mn 0.15 O 2 -LiMn 2 O 4 -LiMnCoO 4 at 800°C and ambient oxygen pressure: (1) mixed spinels with octahedral sites being partly inhabited by Li atoms together with Mn and Co atoms; (2) layered mixed phases with lack of cations in the Li sublattice, and (3) lithium manganate (IV). Normally, the oxidation states of Mn atoms are higher and thus their electrochemical properties are poorer in comparison with the pure spinel or lithium cobaltate materials.…”

“…The most promising way was considered to be the replacement of a part of Co atoms in the layered structure or a part of Mn atoms in the LiMn 2 O 4 spinel with atoms of other transition metals [5][6][7][8]. However, most of these works were directed onto the preparation of single-phase homogeneous substances.…”

“…1. To check this assumption and to understand the structure and properties of these compounds, we have synthesized some compositions inside the above-mentioned quadrangle and studied them by means of XRD, 7 Li NMR, and electrochemical methods.…”

Oxide materials as positive electrodes of lithium-ion batteries

“…Spinels synthesised at low temper-atures contain higher concentrations of oxygen and lower concentrations of trivalent manganese, which reduces the specific capacity of a sample to a certain extent but enhances its cyclability due to the weaker distortions associated with the Jahn ± Teller effect. 107,108 Moreover, both anionic and cationic kinds of nonstoichiometry were shown to depend not only on the temperature of synthesis but also on the nature of the starting compounds. 109,110 The anionic nonstoichiometry has the greater effect on the properties of LiMn 2 O 4 , as compared with cationic nonstoichiometry (the Li/Mn ratio).…”