Electrochemical Li Insertion Research Articles

Low-temperature mixed spinel oxides as lithium insertion compounds

Cation-deficient mixed oxides, Mn–Co, Mn–Fe and Co–Fe, with the spinel structure have been synthesized by a solution technique. Preliminary results on electrochemical Li insertion into these compounds are discussed in relation to their structural and chemical characteristics, and emphasize the strong effect of cation vacancies on their electrochemical properties. The best results were obtained with the Mn–Co system.

Low temperature molybdenum oxide as host lattice for lithium intercalation

The heat treatment of molybdenum oxide dihydrate resulting from the acidification of Na 2MoO 4 solution leads to various molybdenum trioxides MoO 3. Electrochemical Li insertion into these compounds varies depending on the temperature required for drying the MoO 3 · 2H 2O (250,400 and 500 °C). The lower the temperature of the heat treatment, the better is the electrochemical performance. The lowest temperature 250 °C induced the formation of a long-range disordered oxide characterized by a high surface area exhibiting the best performance both in terms of specific capacity (≈ 2F/MoO 3) and cycling efficiency, which were found to be significantly higher than that usually obtained for the conventional crystalline or amorphous MoO 3 or for the heat-treated form at 500 °C (≈ 1.5F/MoO 3). For example, when galvanostatic cycling experiments are performed at a C/10 discharge-charge rate within cycling limits 3.8/2 V, ∼ 300 Ah kg −1 oxide were still recovered after 10 cycles.

Mössbauer studies on high-temperature lithiated magnetite, Li xFe 3O 4

The influence of the insertion of lithium ions in magnetite by high-temperature techniques are studied by Mössbauer spectroscopy at room temperature. The results show: (i) the existence of two non-interacting phases, one corresponding to the pure magnetite and the other to a paramagnetic lithiated phase; (ii) that the mechanisms of electron hopping remain practically unaffected by the insertion of Li up to x ≈ 0.20. The results, when compared with those obtained by electrochemical Li insertion, show good agreement.

Birnessite manganese dioxide synthesized via a sol—gel process: a new rechargeable cathodic material for lithium batteries

In comparison with the classical birnessite compound synthesized by a conventional reaction, sol—gel lamellar birnessite having the formula MnO 1.84,0.6H 2O exhibits an important preferred orientation. Electrochemical Li insertion in this compound occurs in two reduction processes in both galvanostatic and voltammetric curves: the first (0 < x < 0.4) occurs between 4.25 and 2.85 V with a high kinetic transport and a strong decrease of the interlayer spacing, the second (0.4 < x < 0.9) occurs at 2.8 V with slower kinetics and no variation of the c parameter. Cycling capacity studies show that the sol—gel birnessite is the most promising rechargeable manganese dioxide with a high d.o.d. of 75% of the initial capacity (200 A h kg −1) reached after the fiftieth cycle.

Insertion electrochimique d'ions Li + dans les gels de pentoxyde de vanadium

EMF dependence versus Li composition is determined by electrochemical Li insertion in the V 2O 5 xerogel. The change in the lamellar structure of the xerogel which proceeds of Li insertion has been investigated by X-ray. The Li insertion is reversible. At the beginning of the reaction, the organic solvent (propylene carbonate) is intercalated between the layers; then the solvent is desintercalated owing Li insertion leading to a Li 0.4V 2O 5 formula. During the discharge, two compounds Li 1.1V 2O 5 and Li 1.6V 2O 5 have been evidenced.