Effect of Electroless Ni-Co-P Alloy on Electrochemical Performance of Hydrogen Storage Electrode

Effect of Electroless NiCo-P Alloy on the Electrochemical Performance of Hydrogen Storage Electrode 1 Tang Zhiyuan, Sun Chunwen 12, Guo Hetong 1(1. Department of Applied Chemistry, School of Chemical Engineering, Tianjin University, Tianjin 300072, China; 2. Institute of Chemical Metallurgy, Chinese Academy of Sciences, Beijing 100080, China) The effect of electroless NCP coating on the performance of hydrogen storage alloy electrode. The results show that the NCP alloy coating with 1.74% Co alloying can effectively increase the utilization ratio of the active material of the negative electrode hydrogen storage alloy, and the activation performance of the MH electrode is significantly improved. The initial discharge capacity reaches 208mA4/g. The maximum discharge capacity is 295.8mA. °h/g; At the same time, the cycle life is also improved. After the hydrogen storage electrode of the electroless NCP alloy is subjected to 100 cycles of charge and discharge, the retention rate of the capacity is 88%, while the capacity of the electrode of the unplated hydrogen storage electrode is reduced to 62 %. The increase in the capacity of the NCP alloy electrode is mainly due to the dual effect of the Co oxidation current and the improvement of the micro current collector efficiency. The anti-powdering and anti-oxidation capabilities of the hydrogen storage alloy after electroless plating are improved, resulting in a large improvement in the self-discharge performance of the MH electrode, and the loss in the irreversible part is reduced from 23.2 mAh/g to 3.6 mAhh/g. The effect of the electroless NCP alloy on the performance improvement of the MH electrode was analyzed by SEM and XRD.

Hydrogen storage alloys; electroless N-Cf-P alloys; MH-Ni battery TG139 study found that the surface electroless plating of Ni-P or Fe, the maximum discharge capacity of the alloy does not increase. In order to improve the electrode's activation performance, increase its discharge capacity, reduce its cost, and absorb the advantages of both cobalt and nickel, we first tried to electrolessly plate N-Co-P alloy on the surface of hydrogen storage alloy powder particles. The author focused on the study. Effect of electroless Ni-Co-P coating on the performance of AB5-type storage alloy hydrogen electrode.

1 Experimental part 1.1 Hydrogen storage alloy electroless plating Ni-C (rP alloy and its analysis selected Tianjin company's hydrogen storage alloy powder, electroless Ni-Co-P alloy plating. Before electroless plating with 0. 1mol/LHC1 The surface of the activated alloy powder is cleaned with a solution, and then the alloy powder is washed with deionized water several times to remove the ions in the C plant.The electroless Ni-Co-P alloy is coated with sodium hypophosphite as the reducing agent, potassium sodium tartrate as the complexing agent, and the plating solution. The pH was adjusted with ammonia and 5mol/L NaOH aqueous solution.

The amount of Ni and Co in the coating weight gain can be obtained by analyzing the contents of Ni and Co in the alloy before and after electroless plating using a Vavian atomic absorption spectrometer (Model 200).

1.2 Preparation of Hydrogen Storage Electrode and Its Performance Test 0.5 g of hydrogen storage alloy powder coated with Ni-Co-P alloy prepared by the above process was mixed well with a suitable amount of a binder aqueous solution of polyvinyl alcohol (2% PVA). After homogeneously transferred into a paste, a 1.5 cm×1 cm foamed nickel substrate was uniformly filled with a spatula, and after vacuum drying (100 K 4 h), an MH electrode was pressed with an appropriate pressure. The electrochemical performance test of the MH electrode was performed in a three-electrode measurement system. The computer and the DC5 were charged, and the discharge instrument online collection system automatically collected and recorded the data. The electrolyte is 6.8 mol/L 63 mol/LLiOH, and its positive electrode has high-capacity polarization, so that the utilization of the active material is improved. On the other hand, from the figure Ni(OH)/NiOOH electrode, the reference electrode is an Hg/HgO electrode, and the test temperature is 22 to 25C. The charge/discharge system is: 1) When the discharge capacity and activation performance are tested, the charge current is 60 mA/g. At 7 h, the discharge current was 60 mA/g; when the cycle stability was tested, the charge current was 180 mA/g, charge 2.5 h, and the discharge current was 180 mA/g. The discharge cut-off potentials were both 0.6 V (vsHg/HgO). 2) The MH electrode self-discharge experiment is to discharge the well-formed MH electrode and measure the capacitance Ci; then charge the current at 80mAh/g for 5h, store it for 28d after open circuit, and then discharge at 100mA/g to test the electrode capacity C2. Recharge after discharge, measuring capacity C3. Using the X-650 scanning electron microscopy analyzer (Hitachi, Japan) to analyze the discharge curve of the cobalt-coated MH electrode in the alloy 2 after 100 cycles of charge and discharge of the MH electrode. Point, this is due to the oxidation of cobalt itself. This is basically the same as observed in China. The oxidation of cobalt was confirmed by the oxidation of Co metal electrode in 6 mol/L KOH at 0. The reaction was as follows: Geng also found that the discharge curve of the MH electrode with cobalt powder added had the degree of powdering and morphology changes. The addition of Japan's Rigaku Corp. was partly due to reactions in column 0: