Department of Chemistry, Texas A&M University, Ross@Spence Street, College Station, Texas 77845-3012, USA.
Department of Materials Science and Engineering, Texas A&M University, 575 Ross Street, College Station, Texas 77843-3003, USA.
Nat Commun. 2016 Jun 28;7:12022. doi: 10.1038/ncomms12022.
The rapid insertion and extraction of Li ions from a cathode material is imperative for the functioning of a Li-ion battery. In many cathode materials such as LiCoO2, lithiation proceeds through solid-solution formation, whereas in other materials such as LiFePO4 lithiation/delithiation is accompanied by a phase transition between Li-rich and Li-poor phases. We demonstrate using scanning transmission X-ray microscopy (STXM) that in individual nanowires of layered V2O5, lithiation gradients observed on Li-ion intercalation arise from electron localization and local structural polarization. Electrons localized on the V2O5 framework couple to local structural distortions, giving rise to small polarons that serves as a bottleneck for further Li-ion insertion. The stabilization of this polaron impedes equilibration of charge density across the nanowire and gives rise to distinctive domains. The enhancement in charge/discharge rates for this material on nanostructuring can be attributed to circumventing challenges with charge transport from polaron formation.
锂离子在阴极材料中的快速插入和提取对于锂离子电池的运行至关重要。在许多阴极材料（如 LiCoO2）中，锂化是通过固溶体形成进行的，而在其他材料（如 LiFePO4）中，锂化/脱锂伴随着富锂相与贫锂相之间的相变。我们使用扫描透射 X 射线显微镜（STXM）证明，在层状 V2O5 的单个纳米线中，在锂离子嵌入过程中观察到的锂化梯度源于电子局域化和局部结构极化。局域在 V2O5 骨架上的电子与局部结构畸变耦合，产生小极化子，作为进一步插入锂离子的瓶颈。这种极化子的稳定化阻碍了纳米线中电荷密度的平衡，并产生了独特的畴。这种材料在纳米结构化后提高充放电速率，可以归因于规避了由极化子形成引起的电荷输运挑战。
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