Evaluation of Co-doping on the electrochemical properties of the sol-gel birnessite and the new lithiated manganese oxide
Li0.45MnO2+δ is reported. For both compounds the synthesis of Co-doped materials via a solution technique is described. We demonstrate
the interest of Co-doped structures with the selected content of 0.15 Co per mole of oxide as the optimum composition. In
the case of Li0.45Mn1−yCoyO2+δ. prepared at 300 °C, a mixture of a lamellar phase and a cubic one is identified while the Co-doped birnessite appears as
a single phase. A probable substitution of Mn by Co ions explains the better specific capacity of 185 mAh/g found and the
excellent stability observed over 40 cycles in the voltage range 4.2−2.0 V.
Paper presented at the 7th Euroconference on Ionics, Calcatoggio, Corsica, France, Oct. 1–7, 2000. 相似文献
We report here several synthesis routes and their respective drawbacks/advantages for the preparation of pure LiFePO4. We demonstrate the possibility of using LiFePO4 for electrochemical applications, with respect that an effective carbon coating was realized onto the smallest particles. Actually, to bypass the weak ionic conductivity of lithium iron phosphate, the thinnest would be the particles; the highest would be the performance under severe electrochemical conditions. 相似文献
Getting to the root of Hg: Experiments with amalgams as a source for laser-ablated Hg atoms as reaction partners with OF(2) gave strong HgF(2) IR absorptions and new bands in the Hg?F stretching region for OHgF and FOHgF molecules trapped in solid neon and argon. Assignment of these new bands to the first oxyfluoride of mercury, OHgF, and to the FOHgF insertion product is supported by quantum-chemical methods. 相似文献
α-LiFeO2 prepared as nanoparticles exhibits substantially increased electrochemical activity in lithium cells. Thus, in the first half-cycle, the nanoferrite provides a capacity close to 70 mAh g−1 (i.e. approximately 0.25 mol lithium ions is deinserted from the lithium ferrite network), which is several times higher than the values for other ferrites. Even higher capacities have been observed for solid solutions of α-LiFeO2 and rock-salt lithium titanate. In this work, we prepared nanocomposites with improved electroactivity in the first half-cycle. Also, we compared their electrochemical properties with those of nanosized lithium ferrite and lithium titanate. Based on them, explanation for their disparate behaviour involving a protective role of the titanate coating from unwanted reactions with the electrolyte is provided.
Mesoporous iron phosphate containing CTAB as templating agent was synthesized and characterized by means of X-ray diffraction, Fourier transform infrared spectroscopy and TGA techniques. The mesoporous material shows a highly ordered structure, that collapses when submitted to extraction with acetate ions. The treatment of the exchanged samples at 573 K under nitrogen atmosphere leads to amorphous phases with an electrochemical behaviour typical of carbon-coated iron phosphate electrodes. The existence of this coating, proceeding from incomplete pyrolysis of the organic exchange agent, enhances the electronic properties of the system, as evidenced by galvanostatic experiments and impedance spectroscopy measurements. 相似文献
Low temperature synthesis and electrochemical properties of partially substituted lithium manganese oxides are reported. We
demonstrate various metallic cations (Cu2+, Ni2+, Fe3+, Co3+) can be incorporated in the 3 V layered cathodic material Li0.45MnO2.1. New compounds Li0.45Mn0.88Fe0.12O2.1, Li0.45Mn0.84Ni0.16O2.05, Li0.45Mn0.79Cu0.21O2.3, Li0.45Mn0.85Co0.15O2.3 are prepared. These 3 V cathode materials are characterized by the same shape of discharge-charge profiles but different
values of the specific capacity, between 90 mAh g−1 and 180 mAh g−1. The best results in terms of capacity and cycle life are obtained with the selected content of 0.15 Co per mole of oxide,
as the optimum composition. The high kinetics of Li+ transport in Li0.45Mn0.85Co0.15O2.3 compared to that in the Co-free material is consistent with a substitution of Mn(III) by Co(III) in MnO2 sheets. 相似文献
Exploring soft-chemistry synthesis of Fe-based battery cathode materials, we have optimized combustion synthesis as an ultra-rapid approach to produce Na2FePO4F fluorophosphate cathode. It yields nanoscale, carbon-coated target product by annealing (at 600 °C) for just 1 min. The purity of the material crystallizing in the orthorhombic structure was confirmed by powder X-ray diffraction pattern and XPS analysis, while the morphology was studied by scanning electron microscopy. The as-synthesized material exhibits good electrochemical performance delivering a first discharge capacity of more than 70 mAh/g at C/10 rate versus both Li+/Li and Na+/Na, hence acting as an efficient host for both Li-ion and Na-ion insertion. Combustion synthesis can be employed as an economic route for synthesis and rapid screening of various phosphate-based insertion materials. 相似文献