Fluorination modification method for AB3-type hydrogen storage alloy

Abstract

The invention discloses a fluorination modification method for AB3-type hydrogen storage alloy. Under the protection of argon gas, raw materials, namely alloy ingots, of the AB3-type hydrogen storage alloy which contains 0.35 stoichiometric proportion of lanthanum, 0.30 stoichiometric proportion of praseodymium, 0.35 stoichiometric proportion of magnesium, 2.90 stoichiometric proportion of nickel and 0.30 stoichiometric proportion of aluminum are prepared through a vacuum induction melting method ; after the alloy ingots are ground mechanically, a ball mill is used for milling the ground alloy ingots for 30-60 minutes at the rotation speed of 225-250 revolutions per minute to obtain milled hydrogen storage alloy used for surface modification treatment, and the milled hydrogen storage alloy is sieved through a sieve with 200-300 meshes to obtain hydrogen storage alloy powder containing the 0.35 stoichiometric proportion of lanthanum, the 0.30 stoichiometric proportion of praseodymium, the 0.35 stoichiometric proportion of magnesium, the 2.90 stoichiometric proportion of nickel and the 0.30 stoichiometric proportion of aluminum; then the hydrogen storage alloy powder is placed into a beaker containing a solution of ammonium fluoride (NH4F) with the concentration of 0.1-0.2 mole per liter and then stirred for 8-12 minutes at the temperature of 40-60 DEG C, and then a solution of sodium borohydride with the concentration of 0.05-0.06 mole per liter is added to the mixture dropwise until hydrogen bubbles disappear completely; and after the mixture is subjected to ultrasound for 0.5-1.5 hours, the hydrogen storage alloy powder containing the 0.35 stoichiometric proportion of lanthanum, the 0.30 stoichiometric proportion of praseodymium, the 0.35 stoichiometric proportion of magnesium, the 2.90 stoichiometric proportion of nickel and the 0.30 stoichiometric proportion of aluminum is washed repeatedly with deionized water and then dried for 18-22 hours in a vacuum state at the temperature of 70-90 DEG C. The circulatory stability performance and the dynamics performance of alloy electrodes, which are modified through the fluorination modification method for the AB3-type hydrogen storage alloy, are both improved.

Description

technical field [0001] The present invention relates to the field of metallurgical science and electrochemical research, and to AB as Ni / MH battery negative electrode material 3 Type hydrogen storage alloy La 0.35 PR 0.30 Mg 0.35 Ni 2.90 al 0.30 A method for fluorinated modification. Background technique [0002] Hydrogen storage alloys are the most widely used in Ni / MH secondary batteries, commercialized AB 5 The discharge capacity of the alloy electrode is 300-320 mAh / g, which is close to the theoretical capacity of 348 mAh / g. It is difficult to increase its capacity and cannot meet the development requirements of Ni / MH batteries to further increase the energy density. The current novel AB with advantages of high volume, high-quality hydrogen storage density and low cost 3 The type La-Mg-Ni based alloy is favored by researchers because of its high discharge capacity (360 ~ 410 mAh / g), which is higher than the commercial AB 5 The type alloy is improved by about 30...

AI Technical Summary

Problems solved by technology

However, during the use of nickel-metal hydride batteries, the surface of the AB3 type hydrogen storage alloy used as the negative electrode material is corroded and oxidized due to long-term direct contact with KOH. , due to the entry and exit of hydrogen atoms, the metal lattice expands and contracts, causing cracks on the surface of the alloy particles, pulverization, and the increase of fresh surfaces, which aggravates the corrosion and oxidation of the alloy and rapidly decays the capacity.