MXPA97008403A

MXPA97008403A - A method for preparing ni-hidroxicarbonate with a high densi

Info

Publication number: MXPA97008403A
Application number: MXPA/A/1997/008403A
Authority: MX
Inventors: Lee Sangwon; Park Yongchul; Kim Sungsoo; Kim Geunbea
Original assignee: Samsung Sdi Co Ltd
Priority date: 1996-12-31
Filing date: 1997-10-31
Publication date: 1998-10-30

Abstract

A method comprising continuously injecting an aqueous solution of nickel salt, an aluminum salt solution, a solution accusing alkali and ammonia in a reactor under constant temperature by mixing the above solution and extracting continuously, Ni-Al hydroxycarbonate can be prepared. It has a high density and a globul shape

Description

A METHOD FOR PREPARING NI-M HYDROXYCARBONATE WHICH HAS A HIGH DENSITY DESCRIPTION OF THE INVENTION The present invention relates to a method for preparing Ni-M hydroxycarbonate having a high density, and particularly to a method for preparing Ni-hydroxycarbonate. M that has a high density, which can be used to prepare a cell that has a high capacity and a long life time. Recently, with the tendency to miniaturize and lighten portable electronic machines such as integrated VTR-camera systems, audio systems and lap-top personal computers and portable telephones and the like, there is a need to improve the efficiency and capacity of a cell which It is used as a power source for these machines. In particular, we also try to reduce the cost of production in economic aspects. In general, the cells are classified as follows: a primary cell, such as a manganese battery, an alkali battery, a mercury battery and a silver oxide battery, which are not electrically recharged and are therefore discarded afterwards. that is downloaded; a secondary cell such as a lead storage battery, a battery of Nil-MH (nickel-metal hydride) using metal hydride as a negative active material, a sealed nickel-cadmium battery, a lithium-metal battery, ^ a lithium-ion battery (LIB), a lithium-polymer battery (LPB), which can be electrically recharged to their original condition after use; a fuel battery; and a solar battery. The primary cell has a disadvantage since the cell has a low capacity, a short life time and is not reused. On the other hand, the secondary cell has the advantage that the cell has a long life time for the recharged and reused and has a higher voltage than a primary cell in such a way that the cell has a high performance and efficiency, and the cell It can be reused. Among the secondary cells described in the above, a nickel-based cell is desirable in environmental aspects due to the highly developed technology of Ni recycling. And the capacity of an electrode plate is increased by packing an amount by volume by packing an active paste material into a multi pore plate and an alkali resistant plate to provide a cell having a high capacity, and to be widely used now. Currently, nickel hydroxide is used as a negative active material in a nickel-based cell, and the charge-discharge reaction of the material is as follows: ß-Ni (OH) 2 < > ß-NiOOH During the reversible reaction, the nickel oxidation number changes by one (Ni (II) < > Ni (III)).

Therefore, the theoretical capacity of a cell produced using nickel hydroxide is 289 mAh / g. However, the nickel oxidation number changes from +2.3 to + 3.0-3.7 in a real charge-discharge reaction (in a nickel redox reaction), so the practical capacity of the nickel-based cell varies from 200 at 400 mAh / g (70 to 140% of the theoretical value). Regardless of the advantages described above, a high nickel oxidation number causes a decrease in the life time of a cell and an electrode, severe self-discharge, and low reversibility of the reaction. Therefore, the current available capacity varies from 250 to 280 mAh / g. In a positive electrode of a nickel cell, the main reason for the inferiority of the electrode is the swelling of the electrode due to the expansion of the electrode volume, which happens when the nickel hydroxide changes from ß-NiOOH to V-NiOOH that It has low density. The swelling of the electrode causes the separation of an active material, decreases the conductivity, and severely decreases the life time and efficiency of the electrode. The X-NiOOH having a low density is formed due to the compact crystalline structure of ß-Nickel hydroxide having a high density. The compact crystalline structure is the result of the decrease in the number of internal micropores. Therefore, hydrogen ions can not move uniformly in the crystal structure. Therefore, it is necessary to avoid the formation of X-NiOOH that has a low density in the reversible reaction of ß-Ni (OH) 2 < > ß-NiOOH, in order to improve the characteristics of an electrode. A new material, the Ni-M hydroxycarbonate which is prepared by adding elements such as cobalt, cadmium, zinc, and the like to nickel hydroxide to replace a part of the nickel when the element to maintain a stable form in an alkali electrolyte strong, so the change from ß-NiOOH to y-NiOOH is avoided. The new material, Ni-M hydroxycarbonate is used in the reversible reaction of α-NiOOH to Y-NiOOH. The method allows the transformation of a network by replacing nickel, which facilitates the movement of hydrogen ions to reduce overvoltage. Therefore, the method can effectively prevent the formation of y-NiOOH having low density from ß-NiOOH. Additionally, a method in which the conductivity of an active material is improved using cobalt-based oxide or other additional agents which form an effective network in a strong alkali solution, is widely used together with the aforementioned method.

Conventionally, a method for preparing the nickel-metal compound above is as follows: First, the Ni salt is reacted with ammonia and sodium hydroxide solution to prepare Ni-Zn hydroxide. Second, the Ni-Al hydroxycarbonate is prepared by forming precipitates in the form of a colloid at a pH of 8 to 11, as shown in reaction 1. The colloid is dried and treated to have the powder form. [Reaction 1] 8NiS04 + Al2 (S04) 3 + 22NaOH - > NigAl2 (OH) 22 + HNa2S04 Ni8Al2 (OH) 22 + Na2C03 - > NigAl2 (OH) 20CO3 + 2Na0H The material is used for a reversible reaction of a-Ni (OH) 2 < - > / -NiOOH, which has a small density change. Additionally, the nickel oxidation number changes by a large amount during the reaction, that is, the number of electrons exchanged is increased. Therefore, a cell prepared using the material has a high capacity in theory in such a way that a remarkable increase in capacity can be expected. Additionally, the swelling of an electrode can be avoided by using the material, and therefore the life time of the cell can be improved. However, practically, since the Ni-Al hydroxycarbonate prepared by the method has an irregular shape in the form of a colloid, the material has a low density and the shape of it is irregular, and it is difficult to increase the density of the material and take it to a globular shape. Therefore, when the material is used as an active material, it is very difficult to apply this to a cell due to the low density and irregular shape of the material. In order to solve the aforementioned problems of the conventional material, the present invention provides a method for preparing Ni-M hydroxycarbonate having a high density and a globular shape which can be packaged in a compact form on a positive electrode plate. In order to achieve the object, the present invention provides a method for preparing Ni-M hydroxycarbonate comprising the steps of dissolving alkali in a metal salt solution to prepare a solution including metal; mixing the solution including the metal, a nickel salt solution and a complexed agent; and allow the mixture to settle. In the present invention, it is preferred that the mixing step be carried out at 0 to 35 ° C. When the temperature exceeds 35 ° C, the core of the metal hydride forms very rapidly such that the crystal structure of the Ni-M hydroxycarbonate can not grow. The preferred pH range of the mixture is 11 to 13. When the pH range of the mixture exceeds 13 or is less than 11, Ni-M hydroxycarbonate having a low density can be formed. In the method of the present invention, the metal is preferably selected from the group consisting of Al, Co, Fe, Ga, In and Mn, and more preferably, Al. Additionally, the preferred alkali is Na 2 CO 3, and the preferred complexing agent is ammonia. It is preferred that the amount of metal salt be 5 to 20 mole% based on the total moles of Ni. When the amount of metal salt is less than 5 mole%, the effect of the metal salt does not occur. In addition, when the amount of metal salt exceeds 20 mole%, the capacity of a prepared cell decreases. Preferably, the ratio of metal to alkali salt in this invention is less than 1: 1.5. However, the preferred ratio of Ni to ammonia is less than 1: 1.5. When the ratio of Ni to ammonia exceeds 1: 1.5, the density of a prepared powder decreases and therefore the capacity of a cell prepared using the powder decreases. As described above, the solution including metal comprises metal in the form of M (OH) 4. "When the metal salt is added directly to the nickel salt solution, the result is a precipitate of M (OH) 3 which has a low density, in the form of a colloid, more than that resulting from M (OH) 4"which can occur to prepare a product having a high density. However, in the present invention, the metal is previously converted to M (OH) 4 ~, to be added to the nickel salt solution. Therefore, the present invention can avoid the problem which occurs due to the formation of M (OH) 3 from the metal. Additionally, the present invention provides a method for preparing Ni-M hydroxycarbonate having a high density comprising the step of continuously injecting a nickel salt solution, a mixture of an aqueous solution of aluminum salt and an aqueous alkali solution. , and ammonia in a reactor by keeping them under a constant temperature and continuously extracting the resulting product while stirring. It is preferred to prepare the aqueous aluminum solution by dissolving Al salt in an aqueous solution of NaOH to form Al (OH) 4. The additional objects, advantages and novel features of the invention will be indicated in part in the description which follows, and in part it will become apparent to those skilled in the art upon examination of the following or can be learned by the practice of the invention.The object and advantages of the invention can be realized and achieved by means of mediations. and particular combinations indicated in the appended claims BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a photograph of a Ni-Al hydroxycarbonate powder in the form of a globular conformation having a high density prepared by the method of the present invention. FIGURE 2 is a photograph of a Ni-Al hydroxycarbonate powder prepared by a conventional method, and FIGURE 3 is a graph a shows X-ray diffraction (XRD) of the powder prepared by this invention and the conventional method. In Figure 3, graph A shows an XRD of Ni hydroxide with 5% Zn, graph B shows an XRD of a Ni-Al hydroxycarbonate prepared by the conventional method, and graph C shows an XRD of a hydroxycarbonate of Ni-Al having a globular conformation and a high density, prepared by the method of the present invention. In the following detailed description, only the preferred embodiment of the invention has been shown and described, simply by the manner of illustration of the best mode contemplated by the inventor or inventors of carrying out this invention. As the invention is to be carried out, the invention is capable of modification in several obvious aspects, without departing from the scope of the invention. Therefore, the drawing and description are taken as illustrations in nature, and not as restrictive. The present invention is further explained in more detail with reference to the following example which is within the scope of this invention. [Example 1] 999 g of Al2 (S04) 3 • 3H20 and 2,000 g of NaOH in 100 ml of water to convert the Al ion to have the form of Al (OH) 4"and add to it 413 g of a2C03 to prepare an aluminum solution, inject the aluminum solution, the NiS04 solution to the 2.5 M and the 16M ammonia solution in a reactor at a rate of 7.14 ml per minute, 7.14 ml per minute and 1.1 ml per minute respectively, while maintaining the reactor temperature at 35 ° C. After this, the product The resultant is allowed to stand for 16 hours, while the pH is maintained at 11 to 13 to prepare Ni-Al hydroxycarbonate having a globular shape, 1.52 of take-up density and 12 μm in size. [Comparative Example 1] NiS04, A12 (S04) 3 and NaOH under the condition of a pH of 8 to 11. Na2C03 is added to the mixture and allowed to stand to prepare a precipitate in the form of a colloid, after which the precipitate is dried to dry. prepare Ni-Al hydroxycarbonate. Prepare a cell using hydroxycarbonat or Ni-Al prepared by the above method, and the capacity of the cell to be above 320 mAh is determined. [Comparative Example 2] The nickel salt, which includes 5% Zn in a reactor with a pH of 11.5 and 50 ° C, is injected simultaneously with ammonia and NaOH, and the Ni-Zn hydroxide is continuously extracted from the reactor. The SEM photographs of Ni-Al hydroxycarbonate prepared by the method of Example 1 and in Comparative Example 1 are shown in Figure 1 and Figure 2, respectively. As shown in Figure 1 and Figure 2, it is confirmed that the Ni-Al hydroxycarbonate form prepared by Example 1 has a more globular shape than that of the Ni-Al hydroxycarbonate prepared by Comparative Example 1. In addition, the XRD model of a Ni hydroxide with 5% Zn in the conventional cell is shown in graph A of Figure 3, and the XRD of the Ni-Al hydroxycarbonate prepared by the method of Example 1 are shown. comparative and example 1 in graphs B and C of figure 3, respectively. As shown in Figure 3, the intensity of the XRD peak (B) of the Ni-Al hydroxycarbonate prepared by the comparative example 1 method, and the intensity of the XRD peak (C) of the Ni-hydroxycarbonate are relatively low. The one prepared by the method of example 1 is relatively high. The result indicates that the crystallinity of the Ni-Al hydroxycarbonate of the present invention is superior to that of the conventional Ni-Al hydroxycarbonate. In particular, as shown in Figure 3, the Ni-Al hydroxycarbonate of the present invention has a different crystalline form (form) when compared to the Ni hydroxide with 5% Zn (ß form) recently used. As described above, the present invention can prepare Ni-Al hydroxycarbonate having a high density and a globular conformation. Instead of conventional Ni (OH) 2 Ni-Al hydroxycarbonate can be used as the positive active material. Additionally, when a cell is prepared using the Ni-Al hydroxycarbonate of this invention as a positive active material, the capacity of a cell can be increased and the lifetime of the cell can be increased by 15%, compared to the conventional cell prepared using Ni-Zn. On the other hand, when the cell of this invention and the conventional cell are charged-discharged at a high speed, the capacity of these cells is as follows. In a charge of 3C and a discharge of 0.2 C the capacity of the prepared cell used Ni-Zn becomes less than 80% of the initial capacity in 104 cycles, while the capacity of the cell prepared using Ni-Al hydroxycarbonate it becomes less than 80% of the initial capacity in 120 cycles. Therefore, the cell of the present invention can be charged-discharged at a high speed.

Claims

CLAIMS 1. A method for preparing Ni-M hydroxycarbonate having a high density characterized in that it comprises the steps of: dissolving an alkali in a metal salt solution to prepare a solution including metal; mix the solution, a nickel salt solution and a complexing agent; and allow the mixture to rest.
2. The method for preparing Ni-M hydroxycarbonate having a high density according to claim 1, characterized in that the mixing step is carried out from 0 to 35 ° C.
3. The method for preparing Ni-M hydroxycarbonate having a high density according to claim 1, characterized in that the pH of the mixture is adjusted to 11 to 13.
4. The method for preparing Ni-M hydroxycarbonate having a high density according to claim 1, characterized in that the metal is selected from the group consisting of Al, Co, Fe, Ga, In and Mn.
5. The method for preparing Ni-M hydroxycarbonate having a high density according to claim 4, characterized in that the metal ee Al.
6. The method for preparing Ni-M hydroxycarbonate having a high density according to claim 1, characterized in that the alkali is Na 2 CO 3.
7. The method for preparing the Ni-M hydroxycarbonate having a high density according to claim 1, characterized in that the complexing agent is ammonia.
8. The method for preparing Ni-M hydroxycarbonate having a high density according to claim 1, characterized in that the amount of metal salt to be used is 5 to 20% based on the total moles of Ni.
9. The method for preparing Ni-M hydroxycarbonate having a high density according to claim 1, characterized in that the molar ratio of the metal to alkali salt is less than 1: 1.5.
10. The method for preparing Ni-M hydroxycarbonate having a high density according to claim 1, characterized in that the molar ratio of Ni to the complexed agent is less than 1: 1.5.
11. The method for preparing Ni-M hydroxycarbonate having a high density according to claim 1, characterized in that the Ni-M hydroxycarbonate is used in a one-cell plate.
12. A method for preparing Ni-Al having a high density characterized in that it comprises the step of: continuously injecting an aqueous solution of a nickel salt, a mixture of an aqueous solution of ammonia salt and an aqueous solution of alkali, and ammonia in a reactor that is kept under a constant temperature; and continuously extracting the resulting product while stirring. The method for preparing Ni-Al hydroxycarbonate having a high density according to claim 12, characterized in that the aqueous aluminum salt solution comprises Al in the form of Al (OH) 4". preparing Ni-Al hydroxycarbonate having a high density according to claim 12, characterized in that the aqueous solution of the aluminum salt is prepared by dissolving Al salt in an aqueous solution of NaOH 15. The method for preparing Ni hydroxycarbonate - The one having a high density according to claim 12, characterized in that the amount of aluminum is 5 to 20% mol based on the total moles of Ni. 16. The method for preparing Ni-Al hydroxycarbonate having a high density according to claim 12, characterized in that the molar ratio of aluminum to alkali salt is less than 1: 1.5. 17. The method for preparing Ni-M hydroxycarbonate having a high density according to claim 12, characterized in that the molar ratio of Ni to ammonia is less than 1: 1.5. 18. The method for preparing hydroxycarbonate from Ni-Al having a high density according to claim 12, characterized in that the temperature of the reactor is 0 to 35 ° C. 19. The method for preparing Ni-Al hydroxycarbonate having a high density according to claim 12, characterized in that the Ni-Al hydroxycarbonate is used in the plate of a cell. 20. A powder of Ni-M hydroxycarbonate having a high density, a globular shape and 1.5 density of intake. 21. A Ni-Al hydroxycarbonate powder having a high density prepared by the method according to claim 1.