Department of Physics, McGill University , 3600 rue University, Montreal, Québec H3A2T8, Canada.
Materials Engineering, McGill University , 3610 rue University, Montreal, Québec H3A0C5, Canada.
Nano Lett. 2017 Jul 12;17(7):4489-4496. doi: 10.1021/acs.nanolett.7b01857. Epub 2017 Jun 21.
One of the main challenges in improving fast charging lithium-ion batteries is the development of suitable active materials for cathodes and anodes. Many materials suffer from unacceptable structural changes under high currents and/or low intrinsic conductivities. Experimental measurements are required to optimize these properties, but few techniques are able to spatially resolve ionic transport properties at small length scales. Here we demonstrate an atomic force microscope (AFM)-based technique to measure local ionic transport on LiFePO to correlate with the structural and compositional analysis of the same region. By comparing the measured values with density functional theory (DFT) calculations, we demonstrate that Coulomb interactions between ions give rise to a collective activation energy for ionic transport that is dominated by large phase boundary hopping barriers. We successfully measure both the collective activation energy and the smaller single-ion bulk hopping barrier and obtain excellent agreement with values obtained from our DFT calculations.
提高快速充电锂离子电池的主要挑战之一是开发适用于阴极和阳极的合适活性材料。许多材料在高电流和/或低本征电导率下会发生不可接受的结构变化。需要进行实验测量来优化这些特性，但很少有技术能够在小尺度上空间分辨离子输运特性。在这里，我们展示了一种基于原子力显微镜（AFM）的技术来测量 LiFePO 上的局部离子输运，以与同一区域的结构和组成分析相关联。通过将测量值与密度泛函理论（DFT）计算进行比较，我们证明离子之间的库仑相互作用导致离子输运的集体激活能，该集体激活能主要由大的相界跳跃势垒主导。我们成功地测量了集体激活能和较小的单个离子体相跳跃势垒，并与我们的 DFT 计算值获得了极好的一致性。
