Secondary Lithium Cells Research Articles

Optimization of the efficiency and cycling performance of Na 0.1CrS 2 electrodes in nonaqueous secondary lithium cells

The effect of the macrostructure (grain size) and the microstructure (crystal lattice parameters) factors on the coulombic efficiency of Na 0.1CrS 2 cathodes in secondary Li cells is studied. An attempt is made to employ Atlung's model in assessing the chemical diffusion coefficient of Li + in the host structure leading to more realistic values with respect to effective interface area. The possibility of enhancing the mobility rate of Li + by intercalation of water in the host structure is revealed. Using Atlung's model as a guideline it was possible to improve considerably the performance of the Na 0.1CrS 2 cathodes, while retaining their good cycling stability.

V 2 O 5 ‐ P 2 O 5 Glasses as Cathode for Lithium Secondary Battery

not Available.

Capacity—cycle life behavior in secondary lithium cells

The practical utilization of high energy density rechargeable lithium cells is dependent upon maintaining high capacity for the duration of the required cycle life. However, a critical, yet generic problem with room temperature lithium systems is that the capacity often declines considerably during the early stages of cycling. We report the results of our studies on electrolyte degradation which we observe after cells have undergone 300 and 700 deep cycles with 3-methylsulfolane- and 2-methyltetrahydrofuran—LiAsF 6 electrolytes, respectively.

Conductivity of the LiBF4 / Mixed Ether Electrolytes for Secondary Lithium Cells

Electrolytic conductivity of has been studied in the mixed system of 1,3‐dioxolane with 1,2‐dimethoxyethane or with tetrahydrofuran. Relative permittivity (dielectric constant) of the solvents suggested the formation of associated ion pairs in the systems, but the conductivity measured was higher than that expected from the viewpoint of ionic association. Conductivity maxima were observed in the solutions containing about 1:1 (by volume) mixed solvents. Viscosities of the solvent and the solution were also measured, and their contribution to the conductivity change with the solvent composition was discussed. Solute concentration dependence of the molar conductivity was specific for the ether solutions. Apparent activation energy for conduction, which was determined by the temperature dependence of the conductivity, varied with concentration. Structural specificity of the mixed ether solutions was discussed with these parameters and 1H NMR spectra of the solutions.

Lithium Insertion in Wadsley‐Roth Phases Based on Niobium Oxide

We have found the Wadsley‐Roth class of crystallographic shear structures in chemical systems based on to undergo lithium insertion reactions at ambient temperature to stoichiometries of 0.4 to 1.4 Li per host metal on reaction with n‐BuLi. For the general case of structures with intersecting shear planes, minimal structural distortion occurs on lithiation even for compounds with the largest block sizes. We report crystal‐chemical data for 14 lithium insertion compounds of this type, and the behavior of selected host compounds mixed with carbon as the positive electrodes in small lithium secondary test cells.

Thin film solid electrolyte and its application to secondary lithium cell

A thin film solid-state lithium secondary cell, Li/Li3.6Si0.6P0.4O4/TiS2, has been studied and cell performance evaluated. The electrolyte thin film developed was amorphous, ionic conductivity was 5×10−6 (ohm cm)−1 and its Li+ transference number was 1.0. The cathode film was composed of small and narrow plate-like TiS2 crystals intersecting each other, and had a preferred orientation of the crystallographic c-axis parallel to the substrate plane. The apparent chemical diffusion coefficient of Li+ in TiS2 film was 1.1×10−11 cm2/s. The open circuit voltage of the cell was about 2.5 V, and the short circuit current was 1.3 mA/cm2. It was also demonstrated that the cell was discharged about 2000 times.

Charge-Discharge Characteristics of Graphite as a Positive Electrode of Lithium Secondary Cells

Charge-Discharge Characteristics of Graphite as a Positive Electrode of Lithium Secondary Cells

Elastomeric Binders for Electrodes

not Available.

Galvanostatic cycling of vanadium oxide (V 6O 13) in a nonaqueous secondary lithium cell

The galvanostatic cycling of Li(Al)-V 6O 13 cells in 1M LiAsF 6/propylene carbonate (PC)-acetonitrile (AN) and 1M LiAsF 6/PC electrolytes is reported. The discharge capacity and voltage of the Li(Al)-V 6O 13 cell were shown to be consistently higher than those of the corresponding Li(Al)-TiS 2 cell. Discharge rates of 1.2, 2.5, 5.0 and 10.0 mA cm −2 with active material utilisations of 20 – 60% were obtained from the Li(Al)-V 6O 13 cell. The addition of fresh PC-AN electrolyte resulted in an improvement in cell capacity, but did not stop capacity decline on cycling. Cycle life of Li(Al)-V 6O 13 cells was normally less than 50 cycles. It was also found that exposure of the V 6O 13 electrode to moist air reduced the OCV and the discharge capacity of the cell. Short circuiting and complete discharge of the cell resulted in lower capacity and this may have been due to some degree of irreversible reduction of the V 6O 13.

Optimization of the vanadium oxide (V 6O 13) electrode in a nonaqueous secondary lithium cell

The V 6O 13 electrode was tested in a nonaqueous lithium cell using 1M LiAsF 6 in propylene carbonate- acetonitrile mixture as the electrolyte. It was shown that incorporation of acetylene black in the V 6O 13 electrodes improved cell performance in terms of active material utilisation. Also, cells using hydrophilic microporous polypropylene separators, e.g., Celgard 5511 and 3501, displayed less resistive losses enabling larger charge/discharge rates to be used. Voltage changes in the cell were shown to be controlled almost entirely by the V 6O 13 electrode. Analysis of the exhausted V 6O 13 electrodes showed that they contained at least 4 moles of lithium per mole of V 6O 13.

Nb<sub>2</sub>O<sub>5</sub> as an Active Material of Positive Electrode for Nonaqueous Lithium Secondary Cells

Nb<sub>2</sub>O<sub>5</sub> as an Active Material of Positive Electrode for Nonaqueous Lithium Secondary Cells

Phthalocyanine Cathode Materials for Secondary Lithium Cells

Discharge and charge characteristics of various phthalocyanine cathodes coupled with lithium metal are studied. The best capacity based only on cathode active material weight is 1440 A‐hr/kg in the lithium/iron phthalocyanine system, and the cycle life of the lithium/Cu phthalocyanine system is more than 100 times at the discharge depth of 157 A‐hr/kg. The cathode reaction mechanism is supposed to be lithium intercalation between phthalocyanine molecules. The results indicate that these phthalocyanines are promising cathode active materials for lithium secondary batteries.

Non aqueous lithium cells

Recent developments of lithium organic and inorganic electrolyte batteries are reviewed and discussed. Particular attention is dedicated to the role of anode passivation phenomena in the performance of both primary and secondary lithium cells.

Lithium Incorporation by V 6 O 13 and Related Vanadium (+4, +5) Oxide Cathode Materials

The known vanadium oxides have been examined as cathode materials in ambient temperature nonaqueous secondary lithium cells. The discharge products have also been chemically prepared and characterized by x‐ray diffraction, thermal analysis, and magnetic susceptibility. The best cathode materials are and a slightly oxygen‐rich . Electrochemical and chemical preparations afford . The is described as an insertion compound of .

ChemInform Abstract: MOLYBDENUM OXIDE CATHODES IN SECONDARY LITHIUM CELLS

AbstractVon den Oxiden M04O11aM017O47 , (M00 .92 v0.08 )s 014a MO8O23 und M09O26 besitzt MOI7O47 nach einigen Lade‐Entlage‐Cyclen in Zellen mit LiClO4/Propylencarbonat‐Elektroly‐ ten die größte reversible Kapazität für den Li‐Einbau ( 1 Li/Mo).

Molybdenum Oxide Cathodes in Secondary Lithium Cells

The electrochemical behavior of molybdenum oxide cathode materials with stoichiometries between and in nonaqueous lithium secondary cells are examined. Of the oxides , , , , and the greatest reversible capacity (>1 Li/Mo) after several deep discharge/charge cycles was exhibited by in cells with a electrolyte. Excepting , which gives a reversible capacity of >0.75 Li/Mo after 20 deep discharge/charge cycles, the reversible capacities of the other molybdenum oxides are considerably less than that of . The limiting reversible lithium capacity of 1.5 Li/Mo for was determined by treating with an n‐butyllithium solution and the lithium bronze formed with an solution. For an average cell voltage of 1.85V and a capacity of 1.5 Li/Mo, the theoretical energy density of (∼490 W‐hr/ kg) is comparable to that reported for and stoichiometric . The magnetic properties of both and the lithium bronze were also investigated and are discussed.

Non-stoichiometric molybdenum oxides as cathodes for lithium cells Part II. Secondary batteries

Mo 4 O 11 , Mo 8 O 23 and Mo 9 O 26 have been examined as cathodes for secondary lithium cells. These oxides can form ternary phases from which Li + can be almost quantitatively recovered on charge, for limited e /Mo values (e.g. 0.8 for Mo 8 O 23 ). Higher values of e /Mo make the reduction process irreversible due to the destruction of the original lattices. Cyclic voltammetry experiments have shown that these oxides can maintain their reversible behaviour for many cycles, provided the cathodic scanning is limited. Cycling of prismatic Li/Mo 8 O 23 cells has confirmed that this oxide can behave reversibly with good voltage retention even at discharge depths near the limiting value.

Non-stoichiometric molybdenum oxides as cathodes for lithium cells: Part II. Secondary batteries

Mo 4O 11, Mo 8O 23 and Mo 9O 26 have been examined as cathodes for secondary lithium cells. These oxides can form ternary phases from which Li + can be almost quantitatively recovered on charge, for limited e/Mo values (e.g. 0.8 for Mo 8O 23). Higher values of e/Mo make the reduction process irreversible due to the destruction of the original lattices. Cyclic voltammetry experiments have shown that these oxides can maintain their reversible behaviour for many cycles, provided the cathodic scanning is limited. Cycling of prismatic Li/Mo 8O 23 cells has confirmed that this oxide can behave reversibly with good voltage retention even at discharge depths near the limiting value.

Vanadium Oxide Cathode Materials for Secondary Lithium Cells

not Available.