Alkaline batteries

Approach to the choice of charge termination criterion of nickel-cadmium accumulators forming cycles is described. The results of accumulators' physical models forming, using chosen criterion are represented. The research shows the effectiveness of prolonged – before voltage regulation – charges during nickel-cadmium accumulators capacity forming due to the considerable decrease in the number of charge-discharge forming cycles and improvement of their discharge characteristics.

It is shown by experiments that probability of thermal runway in nickel-cadmium batteries with sintered oxide-nickel electrodes is higher, than in the batteries with extruded and pasted electrodes. Besides, it is shown that the probability of thermal runaway decreases with decrease of battery capacitance.

Electrochemical activity of anodes on the basis of a nickel mesh grid for water electrolysis is investigated. Activation of anodes was made by three ways:
1) chemical covering sulfur-containing compounds of nickel and iron;
2) immersing in solution Na₂S₂O₃ + H₂SO₄ (till pH=3);
3) immersing in solution Na₂S + H₂SO₄ (till pH=3).
The water solution 6M KOH was used as the electrolyte while the electrodes testing. Current density varied in a range from 1 to 600 mAJ cm2 at temperature 20, 50 and 70°C. The greatest electrochemical activity have anodes activated by the third method. The anode potential at current density 600 mA/cm² and temperature 70°C is equal +0.57 V (concerning Hg/HgO – the comparison electrode).

Electrochemical activity of cathodes with Pt or Pt-Pd-electrocatalysts was studied by voltammetry method under galvanostatic conditions. The dependence of the overvoltage of hydrogen evolution reaction on the logarithm of current density and on the test time of the cathode with Pt-Pd-electrocatalysts are defined. It is shown that the electrochemical activity of cathode with Pt-Pd-electrocatalyst is two times higher than with Pt-electrocatalyst at the hydrogen evolution reaction in 30% KOH solution at 90°C. As the temperature increases from 15 to 90° C the current density at 40 mV overvoltage at the cathode with Pt-Pd-electrocatalyst increases by 8 times. The test results with this cathode electrocatalyst in the laboratory electrolyzer at a current density of 400 mA/cm² and 65° C temperature within 11 days of intermittent regime work confirm the overvoltage stability in time.

Comparative results of the tests of the sealed nickel-cadmium batteries for capacity safety during long-term storage after charging with direct and asymmetric currents are represented. Charging with asymmetric current was carried out in an accelerated manner at average value of the charging current equal to 0.8Crated. Charging with direct current was carried out at average value of the charging current equal to 0. lCrated in accordance with Technical Conditions. Tests prove that batteries acceleratedly charged with asymmetric current are compliant with technical conditions concerning capacity safety during long-time storage. Tests also prove discharge capacity advantage of batteries charged with asymmetric current after long storage, in comparison with batteries charged with direct current.

The research results of the sealed nickel-cadmium storage batteries reliability at the rapid charge with asymmetric current are represented. In accordance with the reliability theory postulates, the experimental data of the resource test in the mode of the storage batteries 10NKGZ-1,8-1, 10NKGZ-3,5-l, 10NKGZ-4 cycling. The predicted resource gain in comparison with the direct current charge, while using the device of automated storage batteries charge with asymmetric current is confirmed, as well as decrease in the mode of the heating-up charge, and the fall-off in gas emission intensity.

Comparison of asymmetric current parameters influence on nickel-cadmium accumulators forming time is performed. According to the results of capacity forming of NKM-22 accumulators with thin pressed cadmium and metal-ceramic electrodes, the perspective of application of asymmetric current with parameters chosen during experiments and used in this paper is established. Waveforms giving the biggest increase of capacity comply with the most economical parameters defined om models during experiments. In particular, application of asymmetric current with such parameters for NKM-22 accumulators forming gave 11% increase of discharge capacity compared with direct current forming.

Work of running double-chamber electrochemical reactor is investigational for an electrosynthesis Ni(OH)2. It is shown that the basic parameter of the mode is a relative current is attitude of current of I toward the theoretical equivalent current of I*, at that fully initial reagents are expended in a reactor. Mode of I/I* = 1 differentiates two areas (I < I* and I > I*) with salutatory and like changing physical and chemical and electrochemical properties Ni(OH)2.

The results of nickel-cadmium accumulators formation with asymmetric current, in the mode providing long life of the first cycle till the accumulator stress stops to grow, are represented. The possibility of using stress on the accumulator as criterion of charge completion is proved. Research shows efficiency of mode applying chosen criterion – consedirable decrease of charge-discharge cycles of formation while preserving given working characteristics.

Optimized methods of synthesis and modification of high efficient electrocatalysts for alkaline electrolysers have been described. The results of new electrocatalyst characterization by means of some physico-chemical methods are presented.