Spinel cycling performance

Cells based on this process (Eq. (47)) show lower cycling performance with respect to those based on the 4 V process because charge-discharge reactions are accompanied by an asymmetric lattice contraction-expansion of the Lii+.vMn204 electrode. This lattice distortion mainly results from the Jahn-Teller effect of the Mn + ion which transforms the crystal symmetry of the spinel oxide [118],... 

Fig. 2.9 Cycling performance of Mg-doped spinels at 60°C. Mg010-C800 oxygen-deficient Lij 3jMg ,3Mnj3 03 Mg075-N600 oxygen stokhiometric Li,...

Conventional active materials in positive electrodes of lithium-ion batteries are metal oxides that accommodate lithium via the intercalation mechanism. Intercalation involves the insertion of lithium into unoccupied sites in the crystal lattice, thus resulting in a small change in the imit cell volume and reversibility on the order of hundreds or thousands of cycles. The most common intercalation materials for positive electrodes are LiCo02, which has a two-dimensional layered structure, and LiMn204, which has a three-dimensional spinel structure. Nanoparticulate or nanocrystalline versions of these materials have been examined with the hope of achieving enhanced capacity, rate capability, or cycling performance. 

In addition, besides these three factors, the decrease in initial capacity and the deterioration of the cycling performance of the LiMn204 spinel at... 

When LiPFg is substituted by the mixture of LiF and tri-(pentafluorobenzyl) borane, the stability of the electrolyte is increased, and no HF is produced. As a result, the electrochemical performance of the spinel LiMn204 at elevated temperature will also be markedly improved. U2CO3 can also react with acid. When it is added to the electrolyte, the reaction between acid and spinel LiMn204 can be prevented, also leading to an improved cycling performance. 

When copper is introduced into spinel LiMn204, it exists in divalent and trivalent forms, with the chemical formula written as LiCu Cuy Mn2 yy04. At around 4.9 V, there is a new voltage plateau, corresponding to the oxidation/ reduction of the Cu +/Cu + couple. This material can be used as a positive electrode material for 5 V lithium-ion batteries. Similar to other heteroatoms, after doping, the reversible capacity decreases, and better cycling performance is observed. 

Liu D, Bai Y, Zhao S, Zhang W (2012) Improved cycling performance of 5 V spinel LiMni 5Nio.504 by amorphous FeP04 coating. J Power Sourc 219 333-338... 

The lithium-titanium oxides are prepared by heating a mixture of anatase (Ti02) and LiOH at a high temperature. The product heated at 800-900 °C has a spinel structure of Li4/3Ti5y304. When the charge and discharge cycles are performed... 

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