Pacific Northwest National Laboratory, Richland, WA 99352, USA.
Phys Chem Chem Phys. 2012 Oct 21;14(39):13515-21. doi: 10.1039/c2cp43007j.
High voltage spinel LiNi(0.5)Mn(1.5)O(4) is a very promising cathode material for lithium ion batteries that can be used to power hybrid electrical vehicles (HEVs). Through careful control of the cooling rate after high temperature calcination, LiNi(0.5)Mn(1.5)O(4) spinels with different disordered phase and/or Mn(3+) contents have been synthesized. It is revealed that during the slow cooling process (<3 °C min(-1)), oxygen deficiency is reduced by the oxygen intake, thus the residual Mn(3+) amount is also decreased in the spinel due to charge neutrality. In situ X-ray diffraction (XRD) demonstrates that the existence of a disordered phase fundamentally changes the spinel phase transition pathways during the electrochemical charge-discharge process. The presence of an appropriate amount of oxygen deficiency and/or Mn(3+) is critical to accelerate the Li(+) ion transport within the crystalline structure, which is beneficial to enhance the electrochemical performance of LiNi(0.5)Mn(1.5)O(4). LiNi(0.5)Mn(1.5)O(4) with an appropriate amount of disordered phase offers high rate capability (96 mAh g(-1) at 10 °C) and excellent cycling performance with 94.8% capacity retention after 300 cycles. The fundamental findings in this work can be widely applied to guide the synthesis of other mixed oxides or spinels as high performance electrode materials for lithium ion batteries.
高压尖晶石 LiNi(0.5)Mn(1.5)O(4) 是一种非常有前途的锂离子电池正极材料，可用于混合动力电动汽车 (HEV)。通过高温煅烧后冷却速率的精细控制，可以合成具有不同无序相和/或 Mn(3+)含量的 LiNi(0.5)Mn(1.5)O(4)尖晶石。研究表明，在缓慢冷却过程中（<3°C min(-1))，通过吸氧减少氧空位，因此尖晶石中的残留 Mn(3+)量也因电荷中性而减少。原位 X 射线衍射 (XRD) 表明，无序相的存在从根本上改变了电化学充放电过程中尖晶石的相变途径。适量氧空位和/或 Mn(3+)的存在对于加速锂离子在晶体结构内的传输至关重要，这有利于提高 LiNi(0.5)Mn(1.5)O(4) 的电化学性能。具有适量无序相的 LiNi(0.5)Mn(1.5)O(4) 具有高倍率性能（在 10°C 时为 96 mAh g(-1)) 和出色的循环性能，经过 300 次循环后容量保持率为 94.8%。这项工作的基本发现可以广泛应用于指导其他混合氧化物或尖晶石的合成，作为锂离子电池的高性能电极材料。
