球磨时间对石墨烯复合材料电化学性能的影响

采用X射线衍射仪（XRD）、扫描电子显微镜（SEM）和电化学工作站等手段研究了球磨时间（0~60 min）对石墨烯/La₁₅Fe₂Ni₇₁Mn₆B₂Al₂复合材料微观结构和电化学性能的影响。结果表明，球磨时间为0~60 min制备的石墨烯复合储氢合金都主要由La₃Ni₁₃B₂、（Fe，Ni）、LaNi₅相组成，其中LaNi₅相的晶胞体积会随着球磨时间的增加而减小。随着球磨时间从0 min增加至60 min，石墨烯复合储氢合金的电荷转移电阻先减小后增大、交换电流密度先增大后减小、氢扩散系数和荷电保持率先增加后减小，在球磨时间为40 min时取得电荷转移电阻最小值，交换电流密度、氢扩散系数和荷电保持率最大值。此外，在相同循环次数下球磨时间为40 min制备的石墨烯复合储氢合金具有相对较高的放电比容量。适宜的石墨烯/La₁₅Fe₂Ni₇₁Mn₆B₂Al₂复合材料的球磨时间为40 min，此时氢扩散系数和荷电保持率分别为1.259×10^-8 cm²/s和97.62%，具有较好的电化学性能，这主要与此时复合材料粉末颗粒较为细小、均匀且结晶度较高等有关。

Effect of ball milling time on electrochemical properties of graphene composites

The effects of ball milling time on the microstructure and electrochemical properties of graphene/La₁₅Fe₂Ni₇₁Mn₆B₂Al₂ composites were studied by means of X-ray diffraction（XRD），scanning electron microscope（SEM） and electrochemical workstation.The results showed that the graphene composite hydrogen storage alloys milled for 0~60 min were mainly composed of La₃Ni₁₃B₂，（Fe，Ni） and LaNi₅ phases，and the cell volume of LaNi₅ phase would decrease with the increase of milling time.With the increase of ball milling time from 0 to 60 min，the charge transfer resistance of graphene composite hydrogen storage alloy was firstly decreased and then increased，the exchange current density was firstly increased and then decreased，the hydrogen diffusion coefficient and charge retention were firstly increased and then decreased.When the ball milling time was 40 min，the minimum value of charge transfer resistance and the maximum value of exchange current density，hydrogen diffusion coefficient and charge retention were obtained.In addition，graphene composite hydrogen storage alloys showed relatively high discharge capacity at the same cycle times and ball milling time of 40 min.The suitable milling time of graphene/La₁₅Fe₂Ni₇₁Mn₆B₂Al₂ composite was 40 min，and the hydrogen diffusion coefficient and charge retention were 1.259×10^-8 cm²/s and 97.62% respectively，which showed good electrochemical properties.It was mainly related to the fine and uniform powder particles and high crystallinity of the composite.