AB₅-type hydrogen storage alloys have been extensively studied due to their wide applications, but their degradation process is still controversial, hindering the improvement in their cycling performance. In this work, the degradation mechanism of an AB₅-type LaNi_4.75Mn_0.25 alloy with single CaCu₅-type phase structure has been investigated based on its long-term hydrogen storage properties and the structural changes during cycling. It is found that within 1000 hydrogen absorption/desorption cycles in the temperature range of 343–383 K, the P-C-T curves remain a single plateau, but the plateau slope becomes steeper and the hydrogen storage capacity decreases. These degradation phenomena are caused by the structural evolution of the alloy including particle pulverization and crystal lattice damage. The internal driving force of the structural changes is found to be the microstrains generated during hydrogen absorption/desorption. But with cycling, the isotropic parameter c/a increases, decreasing the hysteresis and slowing down the degradation process.

AB ₅型储氢合金由于其广泛的用途而被广泛研究，但是其降解过程仍存在争议，阻碍了其循环性能的提高。在这项工作中，基于其长期储氢性能和循环过程中的结构变化，研究了具有单一CaCu ₅型相结构的AB ₅型LaNi _4.75 Mn _0.25合金的降解机理。已发现，在343–383 K的温度范围内，经过1000次氢吸收/解吸循环，PCT曲线保持单一平台，但是平台斜率变得更陡并且储氢能力降低。这些降解现象是由合金的结构演变引起的，包括颗粒粉碎和晶格损坏。发现结构变化的内部驱动力是在氢吸收/解吸期间产生的微应变。但是，随着循环的进行，各向同性参数c / a增大，磁滞减小，降解过程变慢。