Hosono Eiji, Kudo Tetsuichi, Honma Itaru, Matsuda Hirofumi, Zhou Haoshen
Energy Technology Research Institute, National Institute of Advanced Industrial Science and Technology, Umezono, 1-1-1, Tsukuba, 305-8568, Japan.
Nano Lett. 2009 Mar;9(3):1045-51. doi: 10.1021/nl803394v.
How to improve the specific power density of the rechargeable lithium ion battery has recently become one of the most attractive topics of both scientific and industrial interests. The spinel LiMn2O4 is the most promising candidate as a cathode material because of its low cost and nontoxicity compared with commercial LiCoO2. Moreover, nanostructured electrodes have been widely investigated to satisfy such industrial needs. However, the high-temperature sintering process, which is necessary for high-performance cathode materials based on high-quality crystals, leads the large grain size and aggregation of the nanoparticles which gives poor lithium ion battery performance. So there is still a challenge to synthesize a high-quality single-crystal nanostructured electrode. Among all of the nanostructures, a single crystalline nanowire is the most attractive morphology because the nonwoven fabric morphology constructed by the single crystalline nanowire suppresses the aggregation and grain growth at high temperature, and the potential barrier among the nanosize grains can be ignored. However, the reported single crystalline nanowire is almost the metal oxide with an anisotropic crystal structure because the cubic crystal structure such as LiMn2O4 cannot easily grow in the one-dimentional direction. Here we synthesized high-quality single crystalline cubic spinel LiMn2O4 nanowires based on a novel reaction method using Na0.44MnO2 nanowires as a self-template. These single crystalline spinel LiMn2O4 nanowires show high thermal stability because the nanowire structure is maintained after heating to 800 degrees C for 12 h and excellent performance at high rate charge-discharge, such as 20 A/g, with both a relative flat charge-discharge plateau and excellent cycle stability.
如何提高可充电锂离子电池的比功率密度，近来已成为科学和工业领域最具吸引力的课题之一。与商用LiCoO₂相比，尖晶石LiMn₂O₄因成本低且无毒，是最有前景的阴极材料候选物。此外，为满足此类工业需求，人们已对纳米结构电极展开广泛研究。然而，基于高质量晶体的高性能阴极材料所需的高温烧结过程，会导致纳米颗粒的大晶粒尺寸和团聚，从而使锂离子电池性能不佳。因此，合成高质量的单晶纳米结构电极仍是一项挑战。在所有纳米结构中，单晶纳米线是最具吸引力的形态，因为由单晶纳米线构成的非织造织物形态可抑制高温下的团聚和晶粒生长，且纳米尺寸晶粒间的势垒可忽略不计。然而，报道的单晶纳米线几乎都是具有各向异性晶体结构的金属氧化物，因为诸如LiMn₂O₄这样的立方晶体结构不易沿一维方向生长。在此，我们基于一种新颖的反应方法，以Na₀.₄₄MnO₂纳米线为自模板，合成了高质量的单晶立方尖晶石LiMn₂O₄纳米线。这些单晶尖晶石LiMn₂O₄纳米线显示出高的热稳定性，因为在800℃加热12小时后纳米线结构仍得以保持，并且在高倍率充放电（如20 A/g）时具有优异的性能，兼具相对平坦的充放电平台和出色的循环稳定性。
