Recycling method of waste nickel-hydrogen battery

Stripping the failed MH/Ni battery case, separating the negative electrode sheets from the battery core, using ultrasonic vibration and other physical methods to obtain the failed negative electrode powder, and then chemically treating the treated negative electrode powder to compress the negative electrode powder. It is repeatedly smelted 3 to 4 times in a non-consumable vacuum arc furnace. The oxide layer on the surface of the smelted ingot is removed, crushed, and uniformly mixed. The percentage of each element of the mixed rare earth, nickel, cobalt, manganese and aluminum is measured by ICP method, and nickel is used according to the loss of the hydrogen storage alloy element. The content of the element is based on the reference, supplemented with other necessary elements, and then smelted to finally obtain a recycled alloy with excellent performance.

2. Recovery of negative alloy of MH/Ni battery

The failed anode powder is chemically treated, and the surface of the alloy is etched by the treatment liquid to destroy the oxide on the surface of the alloy, but the influence of the other elements of the alloy which are not oxidized and the conductive agent are minimized. The spent alloy powder was treated with 0 5 mol·L -1 acetic acid solution at room temperature for 0.5 h, washed with distilled water and dried under vacuum. The results show that the main structure of the AB5 hydrogen storage alloy has not changed, and it still belongs to the CaCu5 type hexagonal structure, but the heterophases of Al(OH)3 and La(OH)3 in the anode powder are almost completely disappeared, indicating that these oxides are chemically oxidized. After the treatment, the oxide of the surface is almost completely dissolved. The chemically treated spent anode powder is compared with the original alloy powder for the battery and the non-chemically treated alloy powder for comparison. The discharge specific capacity of the chemically treated failed anode powder is less than that of the chemical treatment. The negative electrode powder has a height of 23 mAh·g-1, indicating that after the chemical treatment, since the surface oxide is mostly removed, the active component of the hydrogen storage alloy in the failed anode powder is increased.

XPS test results show that the concentration of nickel atoms on the surface of the anode powder is increased from 6.79% before chemical treatment to 9.30%, which indicates that after chemical treatment, the nickel-rich layer with higher electrocatalytic activity is formed on the surface of the alloy. The electrocatalytic activity of the hydrogen storage electrode is improved, and the diffusion path of the hydrogen atom is also provided, thereby improving the discharge performance of the electrode. However, the chemically treated spent anode powder is still 90 mAh·g-1 lower than the original alloy powder used to make the battery. On the one hand, the oxidation of the alloy is not limited to the surface, but may also be deep. Inside the alloy, the chemical treatment only removes the oxides on the surface, and the deep oxidation inside the particles is not completely removed. On the other hand, it may be due to the pulverization of the alloy, which increases the specific surface area and simultaneously reacts the alloy with O2. The corrosion of the electrolyte is easier, and the combination of the two causes causes the discharge performance of the alloy to decrease. Therefore, the method of chemical treatment alone does not restore the function of the failed negative electrode, and further smelting treatment is required.

The chemically treated negative electrode powder was subjected to the first smelting in a non-consumable electric arc furnace. The obtained alloy ingot is polished to remove surface impurities, and the content of each element is analyzed. As a result, it can be seen that the element content in the alloy deviates from the original alloy, and the nickel content is much larger than the nickel content in the original alloy powder because the process of making the electrode is performed. Nickel powder is added as a conductive agent, in order to use it effectively, based on it, the content of other elements is adjusted to match the composition of each element of composition MmNi3.5Co0.7Mn0.4Al0.3, and the second smelting is carried out. . After smelting, the obtained alloy ingot was crushed, and after grinding, the structure was measured to be CaCu5 type, and no other impurity phase was formed.

The charge-discharge performance test of the recovered alloy powder shows that the discharge capacity of the recovered alloy powder is about 100 mAh·g-1 higher than that of the failed anode powder, which is substantially the same as the discharge capacity of the original alloy powder, and the alloy powder is recovered. The discharge platform pressure is about 20 mV higher than that of the original alloy powder. This may be due to several smeltings during the alloy recovery process, which improves the composition and microstructure of the alloy.