Regeneration of the Ni-H Cathode Active Material in Rechargeable Battery by Calciothermic Reduction Flexing Process

研究人员提出了一种利用钙热还原法和助熔法在废旧可充电电池中再生Ni-H阴极活性物质的有效工艺。为了开发所提出的工艺，本研究以钙为还原剂，在废电池中以氧化稀土（RE_2O_3）为原料，用钙热还原法直接合成Ni-RE（稀土）贮氢合金，研究了反应机理和工艺因素的影响。研究了RE_2O_3与CaO或MgO在B_2O_3基助熔剂中的溶解度，寻找用残余RE_2O_3和CaO或MgO助熔剂合成Ni-RE合金的最佳条件。结果表明，在900℃下，用1.5等量Ca在30min的极短时间内完成了钙热还原和Ni-RE合金的生成。PCT测试表明，合成的合金颗粒具有与市售Ni-RE储氢合金几乎相同的吸氢性能。在1350℃下熔炼4h，合金中钙和氧的含量分别从0.5和1.2 wt%降低到0.1和0.3wt%。在1350℃下实验测定了B_2O_3-CaO-RE_2O_3（RE: La和Nd）体系和B_2O_3-MgO-RE_2O_3体系的相图，证实了固相与液相平衡的是一种摩尔比为1/1的RE_2O_3-B_2O_3化合物，不含CaO和MgO。MgO-B_2O_3和CaP-B_2O_3碱助熔剂均能有效助熔合稀土氧化物。

The investigators have proposed an efficient process to regenerate the Ni-H cathode active material in the spent rechargeable battery by using calciothermic reduction and fluxing methods. to develop the proposed process, the reaction mechanism and the effect of process factors in the calciothermic reduction method to directly synthesize the Ni-RE(rare earth) hydrogen storage alloy from the rave earth oxide (RE_2O_3) in the spent battery with calcium as a reductant were investigated in the present study. Solubility of RE_2O_3 and CaO or MgO in the B_2O_3 base flux was also investigated to look for the optimum condition in the fluxing method to synthesized Ni-RE alloy from the residual RE_2O_3 and CaO or MgO.It was found that calciothermic reduction and the resultant formation of Ni-RE alloy were completed in a very short time of 30min with 1.5 equivalents of Ca at 900℃. The PCT measurement has clarified that the synthesized alloy particles have the hydrogen-absorbing properties which are nearly same as those of commercial Ni-RE hydrogen storage alloys. The contents of calcium and oxygen in the synthesized alloy could be decreased from 0.5 and 1.2 wt% to 0.1 and 0.3wt%, respectively, by melting for 4 hrs at 1350℃.Phase diagrams for the B_2O_3-CaO-RE_2O_3(RE: La and Nd) and B_2O_3-MgO-RE_2O_3 systems were experimentally determined at 1350℃ It was clarified that the solid phase equilibrating with the liquid phase is a RE_2O_3-B_2O_3 compound with a mole ratio of 1/1 without CaO or MgO. Both of the MgO-B_2O_3 and CaP-B_2O_3 base fluxes were found to be amenable for efficiently fluxing the rare earth oxides.