CN1794496A - Hydrogen storage alloy powder surface cladded with nickel boron alloy and its preparation method - Google Patents

Abstract

The invention proposes a nickel-boron alloy coated on the surface of hydrogen storage alloy powder and its preparation method, that is, the deposition layer on the alloy powder contains 0.001-20% boron element, and the boron element is formed as NiB ₂ or Ni ₂ B in the deposition layer ₅ exists as a boron compound. The specific steps are: first configure 0.3-1.5 mol/L nickel ion, 10-140 g/L potassium sodium tartrate, 5-90 g/L sodium hydroxide and 1-30 mg/L lead nitrate mixed solution; then configure 0.015 -0.45 mol/L boron ion solution; immerse the alloy powder in the prepared mixed solution, stir with a stirrer at a speed of 50-300 rpm, and gradually add the boron ion solution to the solution, the treatment time 20-160 minutes, repeat this process 1-10 times, the temperature of the solution is 20-100°C, the pH value of the solution is 5-14, and a nickel-boron alloy layer is coated on the surface of the alloy powder. The invention significantly improves the discharge performance and cycle discharge performance of the hydrogen storage alloy electrode.

Description

Coating nickel-boron alloy on the surface of hydrogen storage alloy powder and its preparation method

Technical field

The invention relates to the technical field of nickel-hydrogen batteries, and provides a nickel-boron alloy coated on the surface of hydrogen storage alloy powder and a preparation method thereof.

Background technique

Metal hydride nickel battery (MH/Ni) is a new type of green battery developed in the 1990s. It has good interchangeability with nickel-cadmium batteries, but has no cadmium pollution and has high specific energy. Widely used in portable information equipment. In the field of electric vehicles, it also has quite optimistic application prospects. The performance of the hydrogen storage alloy electrode in the negative electrode of metal hydride nickel battery is mainly related to the bulk phase properties such as the type, composition and structure of the alloy, but the surface treatment of the hydrogen storage alloy and the modification of the electrode can significantly improve the electrochemical performance of the negative electrode. A lot of research has been done on the surface modification of alloy powders and electrodes. Some literature shows that: acid, alkali treatment, reduction and fluorination treatment on the surface of the alloy can form a nickel-rich layer on the surface of the alloy, making the electrode more High dot catalytic activity, thus improving the performance of the electrode. Coating a layer of Pd powder or Pd compound on the electrode surface can effectively reduce the oxygen partial pressure inside the electrode. Electroplating Co and Pd on the electrode surface not only plays the role of micro-collector, but also improves the electrocatalytic activity of the negative electrode surface. Coating copper on the surface of the hydrogen storage alloy powder by replacing copper plating can improve the discharge performance of the hydrogen storage alloy, and passivation treatment can improve the stability of the copper layer in the air without adverse effects on the discharge. The patent I applied for before introduced the method of coating the surface of the hydrogen storage alloy electrode with a nickel-sulfur alloy layer. This method can improve the discharge performance of the electrode and increase the life of the electrode. This patent mainly introduces another method of coating nickel-boron alloy on the surface of hydrogen storage alloy powder by chemical method, which is used to improve the high-current discharge performance and life of the electrode.

Contents of Invention

The invention proposes a nickel-boron alloy coating on the surface of hydrogen storage alloy powder and a preparation method thereof. Through the implementation of the above technology, the discharge performance and cycle discharge performance of hydrogen storage alloy electrodes are significantly improved.

In the present invention, the nickel-boron alloy is coated on the surface of the hydrogen storage alloy powder, that is, the deposited layer on the alloy powder contains 0.001-20% boron element, and the boron element exists in the deposited layer in the form of _NiB2 or _Ni2B5 boron compound _.

The preparation method of hydrogen storage alloy powder surface-coated nickel-boron alloy of the present invention, the steps are as follows:

(1) Configure 0.3-1.5 mol/liter nickel ion, 10-140 g/liter potassium sodium tartrate, 5-90 g/liter sodium hydroxide and 1-30 mg/liter lead nitrate mixed solution;

(2) configure a solution of 0.015-0.45 mol/liter of boron ions;

(3) Immerse the alloy powder in the solution prepared in (1), stir with a stirrer at a speed of 50-300 rpm, and gradually add the solution prepared in (2) to the solution, and the processing time is 20 -160 minutes, repeat this process 1-10 times, the temperature of the solution is 20-100°C, the pH value of the solution is 5-14, and a nickel-boron alloy layer is coated on the surface of the alloy powder.

The nickel ions include nickel sulfate, nickel chloride, nickel acetate, nickel sulfamate or nickel hypophosphite.

The boron ion includes sodium borohydride, potassium borohydride, dimethylamine borane or diethylamine borane and the like.

According to the above technical method, the electrode made by mixing the processed alloy powder and a certain proportion of nickel powder and nickel hydroxide electrode constitutes a battery, the mercury oxide electrode is used as a reference electrode, and 6N potassium hydroxide solution is used as an electrolyte. The low-current discharge capability of the electrode at room temperature will not be affected, but it is beneficial to the high-current discharge capability of the electrode. With the increase of the discharge current, the improvement effect becomes more and more obvious. Under 2C discharge, the electrode treated by this method The discharge capacity of the electrode before treatment is increased by 18%. In terms of lifetime, after 250 cycles of 1C, the treated electrode can maintain 79.26% of the capacity, while the untreated electrode can only maintain 13.86% of the capacity. The improvement effect is more obvious.

Detailed ways

Example 1:

Mix nickel chloride 5g/L, potassium borohydride 0.3g/L, and sodium hydroxide 10g/L into a mixed solution. The complexing agent is potassium sodium tartrate, the concentration is 20g/L. The stabilizer is lead nitrate with a concentration of 2.5mg/L. The pH value of the solution was 13, and the temperature was 90°C. Stirring with a stirrer for 35 minutes can make the surface of the alloy powder coated with an alloy layer containing NiB ₂ and Ni ₅ B ₂ , and the content of B element is more than 0.1%. The discharge capacity of the electrode made of the treated alloy powder at 0.5C, 1C, 1.5C, and 2C currents is larger than that of the untreated electrode under the same conditions, especially under the discharge condition of 2C. The capacity is 8.6% higher than that of the untreated electrode. And the cycle life can also be improved. After 250 cycles, the untreated electrode can only retain 13.57% of its capacity, while the treated electrode can retain 61.23% of its original capacity.

Example 2:

Mix nickel sulfate 10g/L, sodium borohydride 0.6g/L, and sodium hydroxide 30g/L into a mixed solution. The complexing agent is potassium sodium tartrate, the concentration is 60g/L. The temperature is 90°C. Stir with a stirrer, and the electroless plating time is 80 minutes, so that the surface of the alloy powder can be coated with an alloy layer containing NiB ₂ and Ni ₅ B ₂ , and the content of B element is more than 0.2%. The discharge capacity of the electrode made of the treated alloy powder at 0.5C, 1C, 1.5C, and 2C currents is larger than that of the untreated electrode under the same conditions, especially under the discharge condition of 2C. Compared with the untreated electrode capacity increased by 16%. And the cycle life can also be improved. After 250 cycles, the untreated electrode can only retain 13.57% of its capacity, while the treated electrode can retain 77.14% of its original capacity.

Example 3:

Mix nickel chloride 130g/L, sodium borohydride 2.6g/L, and sodium hydroxide 90g/L into a mixed solution. The complexing agent is potassium sodium tartrate, the concentration is 130g/L. The temperature is 90°C. Stir with a stirrer, and the electroless plating time is 120 minutes, so that the surface of the alloy powder can be coated with an alloy layer containing NiB ₂ and Ni ₅ B ₂ , and the content of B element is more than 0.5%. The discharge capacity of the electrode made of the treated alloy powder at 0.5C, 1C, 1.5C, and 2C currents is larger than that of the untreated electrode under the same conditions, especially under the discharge condition of 2C. Compared with the untreated electrode capacity increased by 6.3%. And the cycle life can also be improved. After 250 cycles, the untreated electrode can only retain 13.57% of its capacity, while the treated electrode can retain 42.78% of its original capacity.

The present invention discloses and proposes coating nickel-boron alloy on the surface of hydrogen storage alloy powder and its preparation method, which can be realized by those skilled in the art by referring to the content of this article and appropriately changing raw materials, process parameters, structural design and other links. The products and methods of the present invention have been described through preferred implementation examples, and those skilled in the art can obviously make changes or appropriate changes and combinations to the methods and products described herein without departing from the content, spirit and scope of the present invention to realize The technology of the present invention. In particular, it should be pointed out that all similar substitutions and modifications will be obvious to those skilled in the art, and they are all considered to be included in the spirit, scope and content of the present invention.

Claims (4)

1. at hydrogen storage alloy powder surface cladded with nickel boron alloy, it is characterized in that on alloyed powder, containing in the sedimentary deposit 0.001-20% boron element, boron element in sedimentary deposit with NiB ₂Or Ni ₂B ₅The boron compound form exist.

2. the preparation method of the hydrogen storage alloy powder surface cladded with nickel boron alloy of a claim 1 is characterized in that:

(1) configuration 0.3-1.5 mol nickel ion, 10-140 grams per liter sodium potassium tartrate tetrahydrate, the plumbi nitras mixed solution of 5-90 grams per liter NaOH and 1-30 mg/litre;

(2) the boron ion solution of configuration 0.015-0.45 mol;

(3) alloyed powder is immersed in the solution of (1) being joined, stir with blender, rotating speed is 50-300 rev/min, and in solution, dose the solution that (2) are configured to gradually, processing time is 20-160 minute, repeats this process 1-10 time, and solution temperature is 20-100 ℃, the solution pH value is 5-14, coats one deck ni-b alloy layer on the alloyed powder surface.

3. the preparation method of a kind of hydrogen storage alloy powder surface cladded with nickel boron alloy as claimed in claim 2 is characterized in that described nickel ion adopts nickelous sulfate, nickel chloride, nickel acetate, nickel sulfamic acid or nickelous hypophosphite.

4. the preparation method of a kind of hydrogen storage alloy powder surface cladded with nickel boron alloy as claimed in claim 2 is characterized in that described boron ion adopts sodium borohydride, potassium borohydride, dimethyamine borane or diethylamine borane.