RU2280298C2 - Method for producing sealed alkaline cell with nickel-oxide positive and cadmium negative plates - Google Patents

Abstract

FIELD: electrical engineering; manufacture of sealed nickel-cadmium tubular-plate cells.

SUBSTANCE: proposed method includes manufacture of sealed alkaline cell with positive nickel-oxide and negative cadmium plates, impregnation of porous nickel bases with solutions of active salts and alkali, formation of plates in alkaline electrolyte or heat treatment, formation of plate assembly incorporating positive plate, separator, and negative plate, installation of this assembly in case, and cell priming with electrolyte. Amount of electrolyte for cell priming is found from equation

that includes volume of separator pores found from measurement data on its volume V_sep and alkali resistance M_el taken for priming caustic-soda aqueous solution of specific gravity ρ_el and total volume of pores in positive and negative plates multiplied by priming factor K_pr, the latter being taken to equal 0.7 - 0.9. For calculating volume of plate pores, first of all plate volume (V₊ and V_-), porosity (P₊ and P_-), thickness (δ⁺ _in and δ⁺ _in), and mass (M⁺ ₀ and M^- ₀) are found prior to impregnation, plate mass (M⁺ ₁ and M^- ₁) and thickness (δ⁺ _fin and δ⁺ _fin), are determined after their finishing operation using reference data on active material density (ρ₊ and ρ_-) in plates ready for assembly.

EFFECT: enhanced capacity of cell and stability of its power characteristics.

2 cl, 2 tbl, 1 ex

Description

The invention relates to the electrical industry and can be used in the manufacture of nickel-cadmium sealed batteries with tubeless electrodes.

Known methods for the manufacture of an alkaline sealed battery (see [1] - V.V. Tenkovtsev, B.I. Center. Fundamentals of the theory and operation of sealed nickel-cadmium batteries. Leningrad, Energoatomizdat, 1985) with a nickel-oxide positive and cadmium negative electrodes by repeatedly sequentially impregnating porous nickel electrode bases in solutions of nickel and cadmium salts, respectively, in alkali, forming electrodes, assembling a block of a positive electrode, a separator and a negative electrode, and installation block into the body and fill with electrolyte, which is taken as an aqueous solution of potassium hydroxide with the addition of lithium hydroxide.

The disadvantage of this method is that the choice of composition and concentration of the electrolyte is made taking into account various factors, which are often contradictory; To determine the optimal amount of electrolyte, it is necessary to study the porometric curves of the electrodes and the separation in the coordinates "electrolyte content - pore radius" and the construction of flood curves, i.e. dependences "polarization - electrolyte content" for negative electrodes and separation, which is a complex and time-consuming work.

As a prototype, a method of manufacturing an alkaline sealed battery (see [2] - RF Patent No. 2176425, N 01 M 4/28, Project 12.10.1999) with a nickel oxide and cadmium negative electrodes, comprising filling a porous sintered nickel base, was selected. the necessary amount of the corresponding active mass by impregnating it in a solution of nickel nitrate or cadmium, drying, processing in an alkali solution, washing and drying, forming in an alkaline electrolyte in a charge-discharge mode or heat treatment, assembling a block from positive on the electrode, separator and negative electrode unit is mounted in the housing and pouring a predetermined amount of electrolyte with a given density.

The disadvantage of this method is that the sealed batteries made from it do not always have the required stability of electrical characteristics during cycling.

The inventive method allows to solve the problem of ensuring the highest capacity of the batteries with the electrodes used for their assembly, the stability of electrical characteristics during cycling and the preservation of charge during prolonged storage in a charged state.

The solution to this problem is achieved by the fact that in the known method of manufacturing an alkaline sealed battery with oxide-nickel positive and cadmium negative electrodes, including the impregnation of porous nickel bases in solutions of active salts and alkali, the formation of electrodes in an alkaline electrolyte or heat treatment, the assembly of the electrode block from a positive electrode , a separator and a negative electrode, the installation of the unit in the housing and filling the battery with electrolyte, according to the claimed technical solution NIJ, the amount of electrolyte for charging the battery is calculated from the expression

where V _zap - the amount of electrolyte for refueling the battery, cm ³ ;

V _sep is the volume of the separator, cm ³ ;

ρ _el - the density of the electrolyte, g / cm ³ ;

M _el - alkali retention of an aqueous solution of caustic potassium with a density ρ _el in terms of 1 cm ³ separation material, g;

V ₊ and V _- are the volume of the positive and negative electrodes, respectively, before impregnation, cm ³ ;

P ₊ and P _- - porosity of the positive and negative electrodes, respectively, before impregnation;

и

- толщина соответственно положительного и отрицательного электродов до пропитки, мкм;

and

- thickness, respectively, of the positive and negative electrodes before impregnation, microns;

и

- толщина соответственно положительного и отрицательного электродов после заключительной операции (формирования либо термообработки, подпрессовки или прокатки в валках) перед сборкой в электродный блок, мкм;

and

- the thickness of the positive and negative electrodes, respectively, after the final operation (forming either heat treatment, pre-pressing or rolling in the rolls) before assembly into the electrode block, microns;

и

- масса соответственно положительного и отрицательного электродов до пропитки, г;

and

- mass, respectively, of positive and negative electrodes before impregnation, g;

и

- масса соответственно положительного и отрицательного электродов после заключительной операции (формирования либо термообработки), г;

and

- mass, respectively, of positive and negative electrodes after the final operation (formation or heat treatment), g;

ρ ₊ and ρ _- - reference value of the density of the material of the active mass of the positive and negative electrodes, respectively, after the final operation (formation or heat treatment), g / cm ³ ;

To _zapr - refueling coefficient, which is taken equal to from 0.7 to 0.9.

The proposed method allows you to calculate the amount of electrolyte needed to charge the battery, based on the total pore volume of the porous elements that make up the electrode block, which is calculated according to the determination of alkali retention of the separation material and the results of weighing and measuring the geometric parameters of the electrodes at the beginning of the manufacturing process and after its completion, without the use of any complex and time-consuming research methods, and the derived expression for couple filling volume takes into account the changes that occur with the active mass and geometry of the electrodes during manufacture and end before the assembly operation. This makes it possible to determine the optimal refueling volume, which, in turn, ensures minimal loss of electric capacitance when electrodes are installed in a sealed battery and high stability of characteristics during cycling.

Table 1 shows the results of the experimental justification of the selected manufacturing modes of sealed batteries according to the proposed method.

The work was carried out with KR 15/51 batteries (type AA) with a nominal capacity of 0.6 Ah. The batteries were equipped with oxide-nickel and cadmium electrodes of size (82 × 41 × 0.525) mm and (102 × 41 × 0.540) mm, respectively. After impregnation, the nickel oxide electrodes were subjected to electrochemical formation in an alkaline electrolyte in the “charge-discharge” mode, cadmium electrodes were subjected to heat treatment in a hydrogen medium. When assembling the batteries, VARTA FS separation fabric was used (180 × 43 × 0.16) mm; its alkali retention when tested in an aqueous solution of caustic potassium with a density of 1.28 g / cm ³ amounted to 0.8 g of solution per 1 cm ^{3 of} material. The density of the electrolyte was selected taking into account moisture loss during heat treatment of the electrodes. When calculating the refueling volume, the reference value for nickel hydroxide (4.1 g / cm ³ ) was taken as the density of the positive active mass, and the negative active mass was the value obtained by averaging the reference values of the density of cadmium oxide of two modifications (7.55 g / cm ³ ) . The porosity of the electrodes before impregnation (P ₊ and P _- ) was determined based on the results of weighing and measuring the dimensions of the electrode substrates using the reference value of the density of nickel.

The batteries were tested by cycling in the mode “charge with a current of 60 mA for 16 hours - discharge with a current of 120 mA to a final voltage of 1 V”. For convenience, the table shows the values of the battery capacity only in the first, fifth cycles and then every five cycles.

As follows from table 1, refueling with an electrolyte with a selected range of K _ref values (from 0.7 to 0.9) ensures the manufacture of batteries with the required discharge characteristics with high stability during cycling (see table, op. 2 ÷ 4) . Refueling with a K _{value of} less than 0.7 (op. 1) and more than 0.9 (op. 5) leads to a decrease in battery capacity, since in the first case the batteries operate in conditions of shortage, in the second - in conditions of excess electrolyte; both of them reduce the utilization of the active surface of the electrodes. In addition, the electrolyte deficit in accumulators with a low charge coefficient increases from cycle to cycle due to corrosion processes that occur on the positive electrode and require water consumption, which leads to a decrease in capacity during battery cycling (see table, option 1). As for batteries with an excess of electrolyte (see table, op. 5), most of them at the very beginning of the citation showed traces of alkali, which was released in the places of sealing and on the safety valve due to the increased pressure that arose in the batteries due to worsening conditions for the implementation of recombination processes.

Example 1. For the assembly of KR 15/51 batteries (type AA), nickel oxide and cadmium electrodes of (82 × 41 × 0.54) mm and (102 × 41 × 0.44) mm in size and separation fabric FS in size were taken (180 × 43 × 0.16) mm with a pore volume (according to alkali retention measurements) of 0.76 cm ³ . Nickel oxide electrodes were made by impregnation of an electrode nickel base with a porosity of 69%, first in an aqueous solution of nickel nitrate followed by drying, exposure to potassium hydroxide solution, washing in water and drying (for a total of 4 impregnation cycles), then in a solution of cobalt nitrate also with drying, processing in a solution of alkali, washing and drying (1 cycle). The total weight gain of the active mass was 1.4 g / cm ³ . Cadmium electrodes were made by repeatedly impregnating (6 cycles) the electrode base with a porosity of 72% in a solution of cadmium nitrate, followed by drying, processing in an alkali solution, washing and drying. The weight gain of the active mass was 2 g / cm ³ . After completion of the impregnation operation, the nickel oxide electrodes were heat-treated in air at a temperature of 200 ° C, cadmium electrodes in a hydrogen atmosphere at a temperature of 270 ° C. The thickness of the electrodes after the heat treatment operation was brought to operating values by rolling in rolls.

The active mass content in the positive electrodes ready for assembly, calculated by the difference in the mass of the electrodes after heat treatment and before impregnation, averaged 2.25 g / pc., In negative electrodes - 4.35 g / pc. After installation of electrode blocks twisted into rolls into the case, they were charged with electrolyte and then sealed batteries were assembled. Refueling was carried out with an aqueous solution of potassium hydroxide with a density of 1.27 g / cm ³ in the amount of 1.8 cm ³ per battery. When calculating the volume of refueling, the coefficient K _ref was taken equal to 0.8.

Part of the electrodes was used to assemble the batteries according to the prototype method, for which the batteries were charged with an electrolyte with a density of 1.32 g / cm ³ in a volume of 1.6 cm ³ . The batteries were tested by cycling in the mode “charge with a current of 60 mA for 16 hours - discharge with a current of 120 mA to a final voltage of 1 V” and for the preservation of charge (only batteries made by the proposed method) in accordance with GOST 26367.1-93 (discharge with a current of 120 mA to a voltage of 1 V after storage in a charged state for 28 days with an open circuit and a temperature of 20 ° C). The test results are presented in table 2.

table 2
Battery Test Results №№ p.p A method of manufacturing batteries The number of cycles Capacity, Ah Capacity after storage of batteries for 28 days, Ah at the beginning of the cycle at the end of the loop one Proposed 25 0.620 0.614 0.523 2 Famous (prototype) fifteen 0.601 0.552 Requirements GOST 26367.1-93 ≥0.570 Ah ≥0.390 Ah

As can be seen from the table, the proposed manufacturing method provides high discharge characteristics of the batteries and their stability during cycling, as well as the preservation of charge during long-term storage of batteries in a charged state, which indicates a well-balanced ratio of the volume of electrolyte charged into the battery, obtained by calculation, on the one hand , and the total pore volume of the electrodes and the separator constituting the electrode block, on the other.

Information sources

1 V.V. Tenkovtsev, B.I. Center. Fundamentals of the theory and operation of sealed nickel-cadmium batteries. Leningrad, Energoatomizdat, 1985.

2 RF Patent No. 2176425, cl. IPC 7, H 01 M 4/28, Ave. 10/12/1999.

Claims (2)

1. A method of manufacturing an alkaline sealed battery with a nickel oxide and cadmium negative electrodes, comprising impregnating porous nickel substrates in solutions of active salts and alkali, forming electrodes in an alkaline electrolyte or heat treatment, assembling the electrode block from a positive electrode, separator and negative electrode, installation unit into the housing and filling the battery with electrolyte, characterized in that the amount of electrolyte for filling the battery is calculated from the expression

where v _zap - the amount of electrolyte for refueling the battery, cm ³ ; v _sep is the volume of the separator, cm ³ ; ρ _el - the density of the electrolyte, g / cm ³ ; M _el - alkali retention of an aqueous solution of caustic potassium with a density ρ _el in terms of 1 cm ³ separation material, g / cm ³ ; v ₊ and v _- is the volume of the positive and negative electrodes, respectively, before impregnation, cm ³ ; P ₊ and P _- - porosity of the positive and negative electrodes, respectively, before impregnation;

and

- thickness, respectively, of the positive and negative electrodes before impregnation, microns;

and

- the thickness of the positive and negative electrodes, respectively, after the final operation (forming either heat treatment, pre-pressing or rolling in the rolls) before assembly into the electrode block, microns;

and

- mass, respectively, of positive and negative electrodes before impregnation, g;

and

- mass, respectively, of positive and negative electrodes after the final operation (formation or heat treatment), g; ρ ₊ and ρ _- - reference value of the density of the material of the active mass of the positive and negative electrodes, respectively, after the final operation (formation or heat treatment), g / cm ³ ; To _zapr - refueling coefficient. 2. A method of manufacturing an alkaline sealed battery with a nickel oxide and cadmium negative electrodes according to claim 1, characterized in that K _is taken equal to from 0.7 to 0.9.