Department of Radiation, Radionuclides and Reactors, Faculty of Applied Sciences, Delft University of Technology, Mekelweg 15, 2629 JB Delft, The Netherlands.
J Am Chem Soc. 2009 Dec 16;131(49):17786-92. doi: 10.1021/ja902423e.
The nanosized Li(4+x)Ti(5)O(12) spinel is investigated by electrochemical (dis)charging and neutron diffraction. The near-surface environment of the nanosized particles allows higher Li ion occupancies, leading to a larger storage capacity. However, too high surface lithium storage leads to irreversible capacity loss, most likely due to surface reconstruction or mechanical failure. A mechanism where the large near-surface capacity ultimately leads to surface reconstruction rationalizes the existence of an optimal particle size. Recent literature attributes the curved voltage profiles, leading to a reduced length of the voltage plateau, of nanosized electrode particles to strain and interface energy from the coexisting end members. However, the unique zero-strain property of the Li(4+x)Ti(5)O(12) spinel implies a different origin of the curved voltage profiles observed for its nanosized crystallites. It is proposed to be the consequence of different structural environments in the near-surface region, depending on the distance from the surface and surface orientation, leading to a distribution of redox potentials in the near-surface area. This phenomenon may be expected to play a significant role in all nanoinsertion materials displaying the typical curved voltage curves with reduced length of the constant-voltage plateau.
通过电化学（充/放电）和中子衍射研究了纳米级 Li(4+x)Ti(5)O(12)尖晶石。纳米颗粒的近表面环境允许更高的锂离子占据，从而实现更高的存储容量。然而，过高的表面锂离子存储会导致不可逆容量损失，这很可能是由于表面重构或机械失效。一种机制认为，较大的近表面容量最终会导致表面重构，从而合理化存在最佳颗粒尺寸。最近的文献将纳米电极颗粒弯曲的电压曲线导致电压平台长度缩短归因于共存端元的应变和界面能。然而，Li(4+x)Ti(5)O(12)尖晶石的独特零应变特性意味着其纳米晶所观察到的弯曲电压曲线具有不同的起源。这被认为是近表面区域中不同结构环境的结果，这取决于与表面的距离和表面取向，导致近表面区域中氧化还原电势的分布。这种现象可能在所有显示典型弯曲电压曲线且电压平台长度缩短的纳米嵌入材料中发挥重要作用。
