MXPA97006613A - An active material for a cathod of a denikel cell and production method of a cat of my - Google Patents

Abstract

Described in this invention is an active material for a cathode of a nickel cell having the formula Ni1-2xM2x (OH) 2 (CO3) x (0

Description

AN ACTIVE MATERIAL FOR A CÁTODO OF A NICKEL CELL AND PRODUCTION METHOD OF A CÁTODO OF THE SAME DESCRIPTION OF THE INVENTION The present invention relates to an active material for a cathode of a nickel cell and to a method of producing a cathode thereof, and particularly, provides ur. active material for a cathode of a nickel cell and a method of producing a cathode thereof to make the production of a cell having a high capacity feasible. Recently, the smaller size and lightening of new portable electronic machines such as integrated VTR camera systems, audio systems, personal laptops, portable telephones, and the like, has made it necessary to improve the efficiency and capacity of a cell. In particular, trying to reduce the cost of production continues now 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, once discharged are discarded. A secondary cell, such as a lead storage battery, a nickel metal hydride battery, using metal hydride as an active material for an anode, a nickel-cadmium, closed battery, a lithium-metal battery, a Lithium-ion battery, a lithium-polymer battery, can be recharged electrically, after being discharged, to its original condition. In addition to the batteries, fuel cells and solar batteries have been 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 with efficiency, longer life, a relatively long voltage Higher than a primary cell, and re-ization, contributing to lower temperature in the environment Among the secondary cells described above, a nickel cell is desirable with respect to environmental aspects, due to the recirculation technology that is more developed since it increases the capacity of an electrode plate through increasing the amount of packing per volume, packing the paste of active material in a multiporoea plate that respects the alkali to provide a cell that has a high capacity, and is widely used at present.

Currently, nickel hydroxide is used as an active material for a cathode in a nickel cell and the reaction is as follows. . ß-Ni (OH) 2 ** ß-NiOOH The oxidation number c: < Nickel changes by one, while the reversible reaction is emitted, and therefore the theoretical capacity of nickel hydroxide is 269 mAh / g. But the nickel oxidation number changes from -2.3 to +? .0 ~ -r3.7 in a real reaction and it is possible that the capacity varies from 200 ~ 280mAh / g, ie, 70 ~ 140%, of the theoretical value. In spite of the above-mentioned possibility, a high number of nickel oxidation results in a reduction of one cell and the life of the electrode, severe self-discharge, and a low capacity for reversal of the reaction and therefore, the available capacity is known as 250 ~ 280mAh / g. In a nickel cell cathode, the main reason for the inferiority of the electrode is the swelling of the electrode, that is, the expansion in volume of the electrode that occurs during the transition to the gamma shape having a larger structure size for the transfer of the electrode. ions "of hydrogen, ie, ß-NiOOH changes to gamma-NiOOH having a low deneity by over-discharging the ß form having a higher deneity of form a.The swelling of the electrode causes the loss of an active material, the reduction of conductivity, and a severe reduction of a life cycle of the electrode and its efficiency The reason why it is formed ga-NiOOH of low deneityBecause a compact crystalline structure of a high density nickel oxide, that is, the hydrogene ion, 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 gamma -Ni00H of an electrode. To suppress traneition of the ß? Gamma form, a new material, nickel-metal hydroxycarbonate used, which atomizes as cobalt, cadmium, zinc, etc., is added to the nickel hydroxide and atoms are a part of the nickel. and therefore they have the stable form a in a strongly alkaline solution. The method causes the deformation of the base structure through atomic substitution and therefore can suppress the formation of gamma-NiOOH as the hydrogen ions move efficiently and the overvoltage in the charge-discharge cycle is reduced . In addition to the method, a method to improve the conductivity of an active material is widely used, which raises the capacity of the active material, using cobalt oxide that forms an efficient conductive matrix in a strongly alkaline solution or additives.

But the methods present limits when increasing the capacity due to the fixation of an active material and a load-discharge action device, and, therefore, it is essential to change the same active material to efficiently increase the capacity. It was recently controlled, uh active material that has a new structure - active material has a high density and a globular form that was developed through the content of trivalent, co or cobalt and ferrous metal atoms. That is, the materials use a reversible reaction, a-Ki (OK) 2 ** gamma-NiOOH, which has relatively small deficiency differences for the charge-discharge cycle and more electron transfer, due to a large change in loe The nickel oxidation during the reaction and, therefore, the method has a high theoretical capacity, and also prevents the swelling of an electrode and therefore prolongs the life of the electrode cycle. But the density of the powder used now is 1.4 g / cm3 or less, it is tubular in shape, not globular, the control of particle size distribution is difficult, the degree of crietalization is 0.6 of the average width of the flat (001) or smaller and has an amorphous property. Therefore, it is difficult that the material is made to have a high deneity and a globular shape and that the electrode is made to have a high density and consequently, the capacity of the cell is not satisfactorily increased. It is difficult to obtain the best properties of the produced powder and the theoretical value ~ 375mAg / g or 130% of the theoretical capacity of the 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 a cell has limits in establishing the load-discharge characteristics. In order to overcome the above-described problems, it is an object of this invention to provide an active material of a cathode of a nickel cell and a method of producing a cathode thereof, wherein the properties, such as shape, size of particle, deneity, specific surface area of the nickel-metal hydroxycarbonate powder used as the active material are controlled and thus in the overload of a cathode, the swelling of an electrode and the efficiency of a charge cycle are avoided- discharge 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 having the formula, Ni1_2? M2? (OH) 2 (C03)? (O <x <0.1), where M a trivalent metal, the average diameter of such active material is 2 ~ 30 μm, the average width of the XRD peak in the plane, (001) of the m ee m ee m ee 1.0 ° / 2T, the density of the same ee of more than 1.6g / cm3, its specific surface area ee of 5 ~ 50m2 / g, and its ee globular shape. In the invention described above, M ee selects from the group consisting of Al, Co, Fe, In, Mn and mixtures, and the content of M is 10 ~ 25% per molar of the molar The method of the present invention also provides a method for producing a cathode of a nickel cell, the method comprising the step of producing a plate, by mixing the active material, a viscosity-increasing agent, and a conducting agent, spread the paste over ur. metallic support; and dry and compress the metal support. In the method described above, the conductive agent is selected from the group consisting of Co, CoO, and Co (OH) 2 and the content of the conductive agent ee of 6 ~ 18% by weight of the total weight of the active materials. BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a graph that shows a pattern XRD of the Al + 3 powder substituted as an active material for a cathode of the nickel cell produced by the method presented in this invention. FIGURE 2 shows a graph showing the results of the TG-DSC analysis of the Al + 3 powder substituted in 20 mole% of the molar of an active material as the active material by a cathode of a nickel cell produced by the method presented in this invention. FIGURE 3 shows a SEM image of the Al + 3 powder substituted 20 mole% of an active material as the active material for the cathode of a nickel cell produced by the method disclosed in this invention. The present invention is explained in more detail with reference to the following examples that do not limit this invention. EXAMPLES 1"3 2.5 mole% of a nickel sulfate solution and 15.3 mole% of an ammonia solution in a mixed vessel with a molar ratio of nickel to ammonia from 1 to 0.6 were previously mixed and then the mixed solution was provided directly and continuously in a reaction vessel A solution of A12 (S04) 3 containing Al + 3 ions and an NaOH solution was provided as a precipitating agent in the reaction vessel.The solutions were provided using constant velocity circulatory pumps and a of them was connected to a pH controller.The reaction vessel was a 5 1 beaker excreting, continuously and stirred at 900 RPM through a CD motor. For sufficient agitation of the solution and efficient excretion of precipitates, two impellers and a tubular baffle and a disk type baffle were equipped in the upper zone. The reaction vessel was kept at a constant temperature using a thermostat and was equipped with a pK electrode in the middle zone to control the pH and velocity? The precipitation agent was adjusted automatically and this way it kept a constant pH. The excreted solution was filtered on an eduction filter and there it was washed efficiently with deethylated water to avoid precipitation. The ee eolution was provided with an FMI piston pump and on a constant speed motor of 3 ~ 180 RPK and providing speed to it was found within the range of 3.0 ml / aberration per hour. The produced nickel-metal hydroxycarbonate powder was differentiated by particle size through sieving in 200, 325, 400 mesh (75, 46, 32 μm) and sample A, in example 1, was 46 ~ 75 μm, sample B in example 2, was 32 ~ 46 μm and sample C in example 3 was less than 32 μm in size. The properties were then analyzed through shape analysis, size distribution, service deficiency, thermal analysis, and a particle analysis was formed, and the results are shown in Table 1 below.

Table 1 Properties and characteristics of charge-discharge with 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 service density [g / m2] 1.64 1.98 2.13 average width [001] 2.3 2.3 2.3 content of CoO [%] 12 12 12 packaging deficiency [g / m3] 1.65 1.73 1.96 availability [%] 108 112 123 capacity [mAh / g] 312 324 355 EXAMPLE 4 ~ 6 Materialee activee, sample A produced by the method presented in the example described above, was added. carboxymethylcellulose and polytetrafluoroethylene as a viscosity-increasing agent, and CoO, as a conductive agent, to produce a paste and therein the respective amount was varied as shown in Table 2. The pulp was packed into a foam plate. nickel, the cathode was dried and the nickel foam plate was fixed by compressing both sides with acrylic plates using doe metal hydride anodes as conjugate electrodes. Successively, the respective electrode was completely separated through a separator. The electrolytic solution was injected and the separator was soaked in an electrolytic solution, but it prevented the electrode from being soaked directly in an electrolytic solution and from this it produced a cell. EXAMPLES 7 ~ S Axis ploe 4 ~ 6 were repeated, except that the active material, sample B was used. EXAMPLES 10 ~ 12 Example 4 ~ ß was repeated except that the active material used was the C-parameter. Efficiency and conductive agent as well as the content of the membrane were measured and the results are shown in Table 2 below. Table 2 shows example Contents 10 cycles 30 cycles 50 cycles of CoO [% (% available- (% available- (% available by weight] nibility) nibility) example 4 6 101 100 102 Example 5 12 108 107 108 example 6 18 103 103 102 example 7 6 102 102 103 B example 8 12 112 112 112 example 9 18 104 10? 1-4 C example 10 6 114 113 115 example 11 12 123 121 122 example 12 16 112 12 '. 111 The analysis of prop iad -princit ee rea in the substituted Al + 3 powder and the powder substituted with Ce, Fe, Ga, Ir. And Mn, etc., showed a glular form with an amount of 10% or more. molar of the nickel molar and the ß form of the nickel hydroxide was measured with the amount of less than 10 mol% of the total molar of the active materials. The result of the XRL2 analysis of the powder 20% molar Al + 3 ee shown in Figure 1 and its TG-DSC results are shown in Figure 2. The shape of the substituted Al + 3 powder is shown in Figure 3 as representative and the shape of the dust is similar without considering the substituted trivalent metal atoms. In the substituted Al + 3 powder, the density attained and the availability of an active material vary with a particle size and even in the same particle size vary with the content of the conductive agent. The density and availability of an active material with particle size has been shown in table 1 above, and the availability of active materials with the content of the conductive agent are shown in table 2 above. The results show that the smaller the particle, the greater the availability of an active material and that an active material swells less than in the previous nickel hydroxide. The availability of an active material increases the content of the conductive agent to 12% by weight of the total weight of the active materials and then reduces again. As described above, the active material produced by the method presented by this invention has the availability which is increased by a maximum of 23% and the capacity of the cell is increased from 289 mAh / g to 355mAh / g as compared to the nickel hydroxide, as an active material. Also, in the load-discharge characteristics, a capacity does not change in a charge-discharge cycle of high-speed charging 1C, compared to a 0.2C load and, therefore, a load at high speed is feasible. Also, in the life of the cycle, since the active materialee is not lost in the electrode plate experiment, the electrode plate has an effective capacity even after more than 100 cycles and therefore, it is compared with either men or women. 50 cycloe in the previous electrode plate using nickel hydroxide, the life of the electrode cycle is improved by more than doe times.

Claims (5)

1. CLAIMS 1. An active material for a cathode of a nickel cell having the formula, ^? - 2xM2x (OH) 2 (CO3)? (0 <x <0.1): characterized by K ee? N trivalent metal , the average diameter of the active material is 2 ~ 30 μm, the average width of the XRD peak in its plane (001) is more than 1/26, the maximum density is 1.6 g / cm-3 , eepecific surface area ee of 5 ~ 50m2 / g, and its globular shape.
2. 2. The active material according to claim 1, characterized in that M ee selects from the group that you have of Al, Co, Fe, In, Mn and dream mixes.
3. 3. The active material according to claim 1, characterized in that the content of M is 10 ~ 25 mol% of the total molar of the active materials.
4. 4. 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, a viscosity enhancing agent, and a conductive agent; (b) spreading the paste on a metal support; Y (c) pour and compress the metallic support.
5. 5. The method in accordance with the claim 4, characterized in that the conductive agent is selected from the group consisting of Co, CoO and Co (.OH) 2 and the content of the conductive agent is 6 ~ 18% by weight of the mass of the total active material.