MXPA97008369A - Active material for a catellite of nickel cell, method of production thereof, and method of production of a category of an niq cell - Google Patents

Abstract

The invention describes an active material for a cathode of a nickel cell, a nickel-metal hydroxycarbonate having the formula Ni1-2xM2x (OH) 2 (CO3) x (0

Description

ACTIVE MATERIAL FOR A CELL OF NICKEL CELL METHOD OF PRODUCTION THEREOF, AND METHOD OF PRODUCTION OF A CELL OF A NICKEL CELL DESCRIPTION OF THE INVENTION The present invention relates to an active material for a cathode of a nickel cell, a method of producing it, and a method of producing a cathode of a nickel cell, and in particular providing an active material for a cathode of a nickel cell, a method of producing it, and a method of producing a cathode of a nickel cell to enable the production of a cell that has a high capacity. Recently, the reduction in size and lightening of new portable electronic machines such as integrated VTR camera systems, audio systems, personal laptops, portable telephones and the like, have made it necessary to improve the efficiency and capacity of a cell. In particular, trying to reduce the production cost of the cell is now continuing in economic aspects. In general, the cells are classified as primary or secondary depending on their ability to be electrically recharged. A primary cell, such as a manganese battery, an alkaline battery, a mercury battery and a silver oxide battery are not easily recharged electrically and, therefore, discharged once and removed. A secondary cell, such as a lead storage battery, a metal-nickel hydride battery that uses metal hydride as an active material for a cathode, a closed nickel-cadmium battery, a lithium-metal battery, a battery of lithium-ion, a lithium-polymer battery can be recharged electrically, after being discharged, to its original condition. In addition to the batteries, a fuel cell and a solar battery were developed. The disadvantages of a primary cell are low capacity, short life and contribute to environmental contamination by the disposal of non-reusable cells. On the other hand, the advantages of a secondary cell are a higher efficiency, a longer duration, a relatively higher voltage than that of a primary cell, and a reuse thus contributing to less waste for the environment. Among the secondary cells described above, a nickel cell is desired in environmental aspects due to the more developed recirculation technology and which increases the capacity of an electrode plate by increasing the amount of packing per volume, packing the material paste active in a multiporous alkali resistant plate to provide a cell that has a high capacity and is widely used today. Currently, nickel hydroxide is used as an active material for a cathode in the nickel cell and the reaction is as follows. ß-Ni (OH) 2? ß-NiOOH The oxidation number of nickel changes by one while the reversible reaction and therefore the theoretical capacity of nickel hydroxide is 289 mAh / g. But the oxidation number of the nickel changes from +2.3 to + 3.0- + 3.7 in the real reaction, and it is possible that the capacity varies from 200-280 mAh / g, that is, 70-140% of the theoretical value. Despite the possibility described in the above, a high nickel oxidation number results in the reduction of cell and electrode life, severe self-discharge, and low reaction reversibility, and therefore, the known available capacity is 250-280 mAh / g. In a cathode of a nickel cell, the main reason for the inferiority of the electrode is the swelling of the electrode, that is, the expansion of the volume of the electrode that occurs during the transition to form J which has a larger structure size for the electrode. hydrogen ion transfer, ie, ß-NiOOH changes to X-NiOOH which has a low density of over-discharge ß having a greater density than form a. The swelling of the electrode causes the loss of an active material, the reduction of conductivity and a severe reduction of the electrode duration cycle and its efficiency. The reason why low density y-NiOOH is formed is because a compact crystalline structure of a high-density nickel hydroxide, that is, hydrogen ions can not move efficiently in the reaction due to the small number of internal micropores . Therefore, it is desirable to avoid the formation of low density X-NiOOH to improve the properties of an electrode. To suppress the transition of form ß-? Y a new material, nickel-metal hydroxycarbonate is used whose atoms such as cobalt, cadmium, zinc, etc., are added to the nickel hydroxide and these atoms replace a part of the nickel and therefore they keep the stable form in the strong alkaline solution. The method causes deformation of the base structure by atomic substitution and can therefore suppress the formation of X-NiOOH as the hydrogen ions move efficiently and the overvoltage is reduced in the charge-discharge cycle. In addition to the method, a method for improving the conductivity of an active material is widely used, which raises the availability of an active material using the cobalt oxide that forms the effective conductive matrix in the strong alkaline solution. But both methods present limits when increasing the capacity due to the fixation of an active material and a load-discharge reaction device and therefore, it is essential to change the same active material to increase the capacity, efficiently. Recently, an active material that has a new active material structure has a high density and a globular shape that were developed by controlling the content of trivalent metal atoms, such as cobalt and iron. That is, the materials use a reversible reaction, a-Ni (OH) 2? Y-NiOOH, which has relatively small density differences for the charge-discharge cycle and more electron transfer, due to a large change in the states of nickel oxidation during the reaction and therefore, the method has a high theoretical capacity, and prevents the swelling of an electrode and in this way prolongs the life cycle of the electrode. But the taper density of the powder used now is 1.4 g / cm3 or less, it is its tubular, non-globular shape, which makes it difficult to control the particle size distribution. As for the degree of crystallization, the average bandwidth (001) of the plane is 0.5 or more, so that it has an amorphous phase property. Therefore, it is difficult for the material to be made to have a high density and a globular shape and for the electrode to be made to have a high density and consequently, the capacity of the cell is unsatisfactorily increased. It is difficult to obtain the best properties of the powder produced and the theoretical value, -375 mAh / g or 130% of the theoretical capacity of nickel hydroxide can not be obtained. The results are due to the non-establishment of the load-discharge characteristics and therefore an increase in the capacity of the cell has limits without the establishment of the load-discharge characteristics. In order to solve the problems described above, an object of this invention is to provide an active material for a cathode of a nickel cell, a method of producing it and a method of producing a cathode of a nickel cell, in where the properties such as the shape, particle size, density and specific surface area of the nickel-metal hydroxycarbonate powder as the active material, are controlled and thus in the overload of a cathode, the swelling of the electrode is prevented and the efficiency of a charge-discharge cycle is improved and in this way a high-capacity cell can be produced. One embodiment of the present invention provides an active material for a cathode of a nickel cell, a nickel-metal hydroxycarbonate powder having the formula Nil-2xM2? ° H 2 03 ^ x (0 <; x = 0.05), where M is trivalent metal, the average diameter of the active material is 8-20 μm, its taper density is greater than 1.6 g / cm3, the network structure constant of its C axis is 4-6 Á, the structure constant of axis A of the same is 2.5-2.7 Á, the shape of the same is globular. The active material has a ß form before a charge or discharge reaction, a transition from ß-? To form occurs during the charge or discharge reaction, in this way the shape transition ?? (ie, a shape transition -? and during the charge reaction and transition form Y -? ot during the discharge reaction) occurs, and therefore, the cells' discharge capacity increases. In the active material described above, M is selected from the group consisting of Al, Co, Fe, Ga, Mn, In, and mixtures thereof. One embodiment of the present invention also provides a method for producing the active material, which comprises the steps of making a mixture, mixing a solution of nickel sulfate and an ammonia solution, adding a precipitating agent to the mixture, and stirring and filtering the mixture under a decompressor condition. In the method described above, the precipitating agent is a NaOH solution containing metal oxide and the same ratio of nickel sulfate to ammonia is from 1 to 0.5-1.0% per mole. One embodiment of the present invention also provides the method for producing a cathode of a nickel cell, which comprises the steps of producing a paste by mixing the active material described above, a viscosity-increasing agent, and a conductive agent, laminating the paste on a metallic support and drying and compressing the metallic support. In the method described above, the conductive agent is selected from the group consisting of Co, CoO and Co (0H) 2 and the content thereof is 5-18% by weight of the total weight of the active material. As described above, in the active material with the method presented in this invention, the availability of the active material increases to a maximum of 20%, so that the capacity of the cells is increased from 289 mAh / g to 350 mAh / g . Also, in the charge-discharge characteristics, a high-speed charge is possible as the capacity is relatively unchanged in a charge reaction of IC compared to a charge reaction of 0.2C. And the cycle of duration, when the electrode plate experiment is carried out, the capacity is effective even after 100 cycles of charge-discharge reactions compared with more or less 50 cycles of charge-discharge reactions in the case of using the nickel hydroxide above and, therefore, the duration cycle is improved by more than 2 times. In addition, if the cell is produced using the active material presented in this invention, the swelling of the electrode is prevented and in this way the charge-discharge characteristics are improved and the capacity of the cell is increased. BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a graph showing a pattern XRD with the Al + 3 content substituted for an active material for a cathode of the nickel cell produced by the method of the present invention. FIGURE 2 is a graph showing an XRD pattern indicating the transition so that it occurs for a charge-discharge reaction in the nickel cell produced by the method of the present invention. FIGURE 3 is a graph showing the charge-discharge characteristics of the powder of the active material for the cathode of the nickel cell produced by the method of this invention, in particular, substituted by Al + 3. FIGURE 4 is a graph showing the change in discharge capacity with the number of charge-discharge cycles and with the Al + 3 content substituted for the cell produced using the active material for a cathode of the nickel cell presented in this invention. FIGURE 5 is a graph showing the change in discharge capacity with the number of a charge-discharge cycle of the cell produced using the active material for a cathode of the nickel cell presented in this invention. The present invention is explained in more detail with reference to the following examples, which do not limit this invention. EXAMPLE 1 ~ 3 2.5% per mole of a solution of nickel sulfate and 15.3% per mole of an ammonia solution in a mixing container with the molar ratio of nickel to ammonia from 1 to 0.5-1.0 and then the Mixed solution was provided directly and continuously in a reaction vessel. The solution containing 0.01-1% per mole of Al + 3 and 6% ions per mole of an NaOH solution with the molar ratio of nickel provided in the reaction vessel to the NaOH solution of 1 to 1.5-2.5 and a H2C03 solution with the molar ratio of Al + 3 provided to H2C03 from 1 to more than 0.5, were continuously provided. The solutions are provided using constant speed circulation pumps and one of them was connected to a pH controller.

The reaction vessel is a 5 1 beaker, which continuously segregates and is stirred at 900 rpm through a CD motor. For sufficient agitation of the solution and efficient excretion of the precipitates, two impellers and a tubular type baffle were fitted in a disc-type baffle which was fitted in the upper zone. The reaction vessel is maintained at a constant temperature using a thermostat and equipped with the pH electrode in the middle zone to control the pH and the speed of the precipitation agent is automatically adjusted and thus a constant pH was maintained. The excreted solution is filtered on a suction filter and sufficiently washed with distilled water to avoid precipitation in the upper zone. The solutions are provided with an FMI piston pump and a constant speed motor of 3-180 rpm and the speed of these is controlled within the range of 3.0 m / aberration or less per hour. The nickel-metal hydroxycarbonate powder produced is differentiated by the size of sieved particle in meshes 200, 325, 400 (75, 46, 32 μm) and sample A, in example 1, is 46 ~ 75 μm, sample B, in example 2, is 32 ~ 46 μm, and sample C in example 3 is smaller than 32 μm in size. Then, the properties were analyzed by means of analysis of shape, size, distribution, taper density, thermal analysis and shape analysis of the particles and the results are presented in Table 1 below. Table 1 Properties and characteristics of charge-discharge with a particle size after 10 cycles Example 1 Example 2 Example 3 particle size [μm] 46-75 32-46 < 32 average particle size [μm] 54 38 12 specific surface area [m2 / g] 15 23 36 taper density [g / m2] 1.84 1.98 2.13 average width [001] 2.3 2.3 2.3 CoO content [%] 12 12 12 packing density [g / m3] 1.65 1.73 1.96 availability [%] 108 112 123 capacity [mAh / g] 312 324 355 EXAMPLE 4-6 An active material, sample A produced by the method presented in example 1-3 described above, 0. 1-1.0% by weight of the active material weight of hydroxypropylmethylcellulose and polytetrafluoroethylene as a viscosity-increasing agent and CoO as a conductive agent, the content of which was varied, as shown in Table 2 below and added to produce a paste and A cathode plate was made by laminating the paste and packing in a nickel-foam plate and made a hydrogenated alloy of type ABc of the metal Mm (manufactured by Ovonic Battery Company) was used as a conjugate electrode or an anode. Subsequently, the respective electrode was completely separated through the separator. An electrolytic solution was injected and the separator was soaked in an electrolytic solution, but the electrode was prevented from soaking directly in the electrolytic solution and thus a cell was produced. EXAMPLE 7-9 Example 4-6 was repeated except that the active material, sample B was used. EXAMPLE 10-12 Example 4-6 was repeated except that the active material, sample C was used. The efficiency of the conductive agent with the content thereof was measured and the results are presented in Table 2 below.

Table 2 The availability of the active material in the charge-discharge cycles with the content of conductive agent (CoO) CoO content 10 cycles 30 cycles 50 cycles shows TJ? MplO [% by weight] [% of availability] [% of availability ] [% availability] example 4 6 101 100 102 A example 5 12 108 107 108 example 6 18 103 103 102 example 7 6 102 102 103 B example 6 12 112 112 112 example 9 18 104 105 104 example 10 6 114 113 115 C example 11 12 123 121 122 example 12 18 112 110 111 In the experiments using Al + 3 as the metal atom, a powder was obtained in a form when the content of Al + 3 was more than 10% per mole of the total moles of the active material, and the nickel hydroxide of ß form was obtained when the content of Al + 3 was 10% per mole or less than the total moles of the active material.

Figure 1 is the XRD result with the content of Al + 3 and as shown there, it is known that the hidró-form nickel hydroxide is obtained when the content of Al + 3 is 10% per mole or less. Like this, the measurement network structure constant resulting from the XRD shows that the larger the content of Al + 3, the greater the constant of the C axis and the smaller the constant of the axis A. It is assumed that the constant of the C axis increases because the larger the substituted Al + 3 content, the greater the number of C032 ions interspersed EXAMPLE 13 To measure the shape transition of the active material on the electrode plate, cycles of load-discharge, the cell produced with the method presented in Example 4-6 was experienced in the charge-discharge cycles and then the intensities were measured after 1 cycle, 10 cycles, 30 cycles and the results are respectively shown in the drawings 2 (a), 2 (b), 2 (c) As shown in Figure 2, the shape transition occurs after 10 charge-discharge cycles In this case, the electrode swelling was not observed, the loss of active material and the reduction of capacity due to the shape transition. The reason for the results is assumed to be the substitution of the abrupt deformation of trivalent Al + 3 regulators of the base structure due to the shape transition since the interval of the base structure has been previously arranged. The charge-discharge curve during the shape transition is shown in Figure 3. It is known from the result that a? Y participates in the charge-discharge reaction. The load curve consisting of only the ß-ß pairs simply shows a single plate, but a charge-discharge reaction in pairs a- and causes the load curve to have 2 plates. Also, the discharge capacity increases as the a-Y pairs also participate in the charge-discharge reaction. Starting from this, it is assumed that the availability of an increase of active material with the reaction occurring within the same dust of active material of the shape transition. The discharge capacity with the number of charge-discharge cycles is shown in Figure 4. The discharge capacity is increased within the scale of 40 charge-discharge reaction cycles with the shape transition. The availability of the cell made of nickel hydroxide powder (manufactured by Tanaka Co. in Japan) ordinarily used as the cell materials and the availability of the cell made of the powder presented in this invention are measured.

The result is that the availability of the former is 280 mAh / g, 90% of the maximum value and abrupt reduction of capacity is observed by the loss of an active material in a load of high load speed of IC. But the availability of the latter is invariable in an IC load compared to a 0.2C load and an abrupt reduction in capacity does not occur even after 100 cycles. The unloading capacity of measuring the results of the cell using the active material presented in this invention is shown in Figure 5.

Claims (8)

1. CLAIMS 1. An active material for a cathode of a nickel cell, characterized in that it has the formula, N ^ i- 2xM2x (OH) 2 (CO3) x (0 <Xs0-05): where M is a trivalent metal, the average diameter of the active material is 8-20 μm, its taper density is 1.6 g / cm3 or greater, the network structure constant of its C axis is 4-6 Á, the structure constant of its axis A is 2.5-2.7 Á, and its shape is globular.
2. 2. The active material according to claim 1, characterized in that the active material has a β-form prior to a charge or discharge reaction, a transition of form β-? Cx occurs during the charge or discharge reaction, thus the transition of form to? Y occurs and therefore the capacity of discharge of the cells is increased.
3. 3. The active material according to claim 1, characterized in that M is selected from the group consisting of Al, Co, Fe, Ga, Mn, In, and mixtures thereof.
4. 4. A method for producing the material according to claim 1, the method is characterized in that it comprises the steps of: (a) producing a mixture, by mixing a solution of nickel sulfate and an ammonia solution; (b) adding a precipitating agent to the mixture; and (c) stirring and filtering the mixture under an uncompressed condition.
5. 5. The method of compliance with the claim 4, characterized in that the precipitating agent is a NaOH solution containing a metal oxide.
6. 6. The method of compliance with the claim 5, characterized in that the content of the ammonia is 0.5-1.0% per mole of the moles of nickel sulfate.
7. 7. A method for producing a cathode of a nickel cell, the method is characterized in that it comprises the steps of: (a) producing a paste by mixing the active material described in claim 1, an agent that increases the viscosity and a conductive agent; (b) rolling the pulp on a metal support; and (c) drying and compressing the metal carrier. The method according to claim 7, characterized in that the conductive agent is selected from the group consisting of Co, CoO and Co (0H) 2 and the content of the conductive agent is 5-18% by weight of the total weight of the product. active material