Mitigating Cation Diffusion Limitations and Intercalation-Induced Framework Transitions in a 1D Tunnel-Structured Polymorph of V2O5
Mitigating Cation Diffusion Limitations and Intercalation-Induced Framework Transitions in a 1D Tunnel-Structured Polymorph of V2O5
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DOI：
10.1021/acs.chemmater.7b03800
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发表时间：
2017-12-26
影响因子：
8.6
通讯作者：
Banerjee, Sarbajit
中科院分区：
文献类型：
--
作者：
Horrocks, Gregory A.;Parija, Abhishek;Banerjee, Sarbajit
插入式电池阴极的设计需要考虑原子结构和电子结构，以促进特定过渡金属位点的氧化还原以及伴随的阳离子和电子的扩散。阳离子插入通常会导致能量耗散相变，从而导致大量的插入梯度以及多尺度相和应变的不均匀性。层状α - v2o5相被认为是一种经典的插层基质，但它的扩散动力学缓慢，而且插层引起的一系列相变需要相当大的晶格畸变。在这里，我们证明了V2O5的一维隧道结构ζ相多晶体提供了一个鲜明的对比研究，并且可以可逆地容纳锂离子，而不会对结构框架造成很大的扭曲，并且大大减轻了极化约束。在多个阴极颗粒上证明了完全均匀的锂化（与α - v2o5颗粒相反，锂化诱导的相变会导致相偏析）。与热力学稳定的α - v2o5相相比，亚稳的ζ - v2o5相对锂离子和极化子扩散的阻碍大大减少。刚性的隧道框架、嵌入锂离子在一维隧道所定义的扩散路径上的配位环境的相对较小的变化以及导带底部v3d态的简并减少了电子局域化，而电子局域化是α - v2o5中电荷输运的主要障碍。因此，1D （zeta）相促进了连续的锂化途径，这与在α - v2o5中观察到的连续插层诱导的相变明显不同。本文的结果说明了电子结构在氧化物阴极材料中介导电荷输运中的重要性，并表明具有高能量键基序的亚稳多晶可以作为一个有吸引力的插层宿主，这种亚稳多晶可以定义受挫的配位环境。
The design of cathodes for intercalation batteries requires consideration of both atomistic and electronic structure to facilitate redox at specific transition metal sites along with the concomitant diffusion of cations and electrons. Cation intercalation often brings about energy dissipative phase transformations that give rise to substantial intercalation gradients as well as multiscale phase and strain inhomogeneities. The layered alpha-V2O5 phase is considered to be a classical intercalation host but is plagued by sluggish diffusion kinetics and a series of intercalation-induced phase transitions that require considerable lattice distortion. Here, we demonstrate that a 1D tunnel-structured zeta-phase polymorph of V2O5 provides a stark study in contrast and can reversibly accommodate Li-ions without a large distortion of the structural framework and with substantial mitigation of polaronic confinement. Entirely homogeneous lithiation is evidenced across multiple cathode particles (in contrast to alpha-V2O5 particles wherein lithiation-induced phase transformations induce phase segregation). Barriers to Li-ion as well as polaron diffusion are substantially diminished for metastable zeta-V2O5, in comparison to the thermodynamically stable alpha-V2O5 phase. The rigid tunnel framework, relatively small changes in coordination environment of intercalated Li-ions across the diffusion pathways defined by the 1D tunnels, and degeneracy of V 3d states at the bottom of the conduction band reduce electron localization that is a major impediment to charge transport in alpha-V2O5. The 1D (zeta-phase thus facilitates a continuous lithiation pathway that is markedly different from the successive intercalation-induced phase transitions observed in alpha-V2O5. The results here illustrate the importance of electronic structure in mediating charge transport in oxide cathode materials and demonstrates that a metastable polymorph with higher energy bonding motifs that define frustrated coordination environments can serve as an attractive intercalation host.