球形尖晶石LiMn2O4掺杂钇的性能研究

利用控制结晶方法, 在前驱体碳酸锰中共沉淀掺杂适量的钇, 得到球形掺杂钇的碳酸锰, 在540 ℃预烧后, 与锂盐一起焙烧, 可以得到高活性的掺钇球形尖晶石LiMn₂O₄. XRD分析表明, 产物中无杂相产生. 研究表明, 掺杂钇与掺杂其它金属离子的特性不一样, 钇具有催化特性, 掺杂钇可以提高尖晶石LiMn₂O₄中锰的活性. 掺钇使得更多的Mn^3＋参加电化学反应, 增加容量; 但同时也使更多的锰与电解液反应, 造成锰的溶解, 容量损失. 掺钇量越多, 锰的溶解量越大. 因此, 合适的掺杂量对于保证产品良好的电化学性能至关重要. 实验证明, 掺钇0.5%的产品Li(Y_0.005Mn_0.995)₂O₄具有较好的电化学性能. 其常温初始比容量为130 mAh?g^－1, 大于纯相的锰酸锂的125 mAh?g^－1, 100次循环后比容量为120 mAh?g^－1, 容量保持率为92.3%.

Yttrium Doping of Spherical Spinel LiMn2O4 Cathode Materials for Lithium Ion Batteries

A controlled crystallization process was proposed for synthesis of yttrium doped spherical spinel LiMn₂O₄ particles. Its successful preparation started with a carefully controlled crystallization of yttrium doped MnCO₃ by co-precipitation of MnSO₄ and YCl₃ with NH₄HCO₃ and NH₃?H₂O. Mn₂O₃ was obtained by heating MnCO₃ and mixed with Li₂CO₃ to produce yttrium doped spinel LiMn₂O₄. As-prepared samples were characterized by SEM and XRD. Dissolution of manganese in electrolyte was also investigated, resulting in that the dissolution was enhanced by dopant of yttrium. The more yttrium, the larger dissolution, indicating that manganese was activated by yttrium. The activation of manganese led to both enhancement of electrochemical activity and reactivity with electrolyte of manganese. The former improved the elec-trochemical performance of spinel LiMn₂O₄. Contrarily, the latter worsened its performance. 0.5% was a proper amount of doping, and such yttrium doped sample Li(Y_0.005Mn_0.995)₂O₄ had an initial capacity of 130 mAh?g^－1 over that of un-doped one with the capacity retention to reach 92.3% exceeding that of un-doped one at 100th cycle.