Influence of Al3+ ions on the morphology and structure of layered LiMn1–xAlxO2 cathode materials for the lithium ion battery
Influence of Al3+ ions on the morphology and structure of layered LiMn1–xAlxO2 cathode materials for the lithium ion battery
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DOI：
10.1016/j.jallcom.2013.03.187
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发表时间：
2013-08
影响因子：
6.2
通讯作者：
Yi He;Feng-ying Yuan;Hui Ma;X. Bai;Xiaojing Yang
中科院分区：
文献类型：
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作者：
Yi He;Feng-ying Yuan;Hui Ma;X. Bai;Xiaojing Yang
以Mn 2 O3和Al 2 O3为Mn源和Al源，在3.5M LiOH水溶液中于150°C水热处理，成功合成了不同形貌的正交晶系LiMn 1-xAlxO 2纳米晶（Pmmn（59），origin choice 2）.尽管引入起始水热溶液中的Al 3+离子的量很大，Al/Mn摩尔比为0 - 0.33，记为Al/Mn（HT），其中HT是指水热处理;在相纯的LiMn 1-xAlxO 2晶体中该比率低至0.05，记为Al/Mn（SS），其中SS指固溶体，当Al/Mn（HT）比大于0.5时，生成正交相LiAlO 2。随着Al/Mn（SS）的增加，平均氧化数大于3并逐渐增加，导致晶胞沿沿着a轴（金属-氧八面体层的锯齿方向）单调收缩。此外，Al 3+还对晶体的形态产生影响：（1）晶体呈长方体状（Al/Mn（SS）<0.02），沿垂直于层的方向择优生长;（2）当Al/Mn（SS）>0.02时，可以获得立方状晶体。恒电流测试表明，由Li_（0.93）Mn_（0.96）Al_（0.04）O_2组成的电极在0.1C电流密度下的放电容量可达175 mAh/g，循环25次后容量保持率为82.9%，表明Al ~（3+）通过抑制层状结构向尖晶石结构的转变而起到稳定层状结构的作用。
Orthorhombic LiMn1–xAlxO2nanocrystals (Pmmn (59), origin choice 2) with different morphologies were successfully synthesized using Mn2O3and Al2O3as Mn- and Al-sources in a 3.5M LiOH aqueous solution hydrothermally treated at 150°C. Although Al3+ions introduced into the starting hydrothermal solution was in a large amount from 0 to 0.33 of Al/Mn molar ratio, noted as Al/Mn(HT) where HT refers to hydrothermal treatment; the ratio was as low as 0.05 in the phase-pure LiMn1–xAlxO2crystals, noted as Al/Mn(SS) where SS refers to solid solution, while a Al/Mn(HT) ratio higher than 0.5 resulted in the formation of orthorhombic LiAlO2phase. With an increase of Al/Mn(SS), the average oxidation number was higher than 3 and gradually increased, leading to a monotonous shrinkage of the unit cell along a-axis (the zigzag direction of the metal-oxygen octahedron layers). Furthermore, Al3+also influenced on the morphology of the crystals: (1) cuboid shaped crystals as (Al/Mn(SS)<0.02), with the ascendant growth in the direction vertical to the layer; and (2) cubic-like crystals as Al/Mn(SS)>0.02 can be obtained. Galvanostatic measurement exhibited that the capacity of the electrode composed of Li0.93Mn0.96Al0.04O2can reach a discharge capacity of 175mAh/g at a current density of 0.1C and the capacity retention could be 82.9% after 25th cycling, showing that Al3+can stabilize the layered structure by retarding its transforming to spinel one.