Bending good beats breaking bad: phase separation patterns in individual cathode particles upon lithiation and delithiation
Bending good beats breaking bad: phase separation patterns in individual cathode particles upon lithiation and delithiation
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DOI：
10.1039/d0mh01240h
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发表时间：
2020-12-01
影响因子：
13.3
通讯作者：
Banerjee, Sarbajit
中科院分区：
文献类型：
--
作者：
Santos, David A.;Andrews, Justin L.;Banerjee, Sarbajit
锂离子电池的操作涉及质量和电荷传输过程的协调顺序，其由活性电极材料的交替膨胀/收缩支撑。几种锂离子电池失效机制可以直接追溯到局部成分不均匀性引起的晶格失配应变。影响相分离的化学-机械耦合机制和由此产生的内部应力场的复杂演化仍然没有得到充分的理解。这项工作采用X射线显微镜技术来成像的演变的组合物和应力在各个弯曲的V2 O 5颗粒。实验结果表明，晶格应变施加的变形的一个单独的阴极颗粒深刻地修改相分离模式，产生条纹丰富的锂域内的锂贫矩阵。颗粒级不均匀性在尺度上复合，导致断裂和容量衰减。耦合相场模型的域的演变表明，所观察到的图案最大限度地减少了所产生的能量成本的几何形状施加的应变梯度在锂化的材料，并说明相分离图案敏感地依赖于粒子的几何形状，尺寸，界面能量，和晶格不稳定性。在锂化和脱锂化之间观察到相分离模式的急剧差异。这项工作证明了应变工程和颗粒几何形状的承诺，以确定性地控制相分离图案，如最大限度地减少累积应力和减轻重要的降解机制。
The operation of a Li-ion battery involves a concerted sequence of mass and charge transport processes, which are underpinned by alternating dilation/contraction of the active electrode materials. Several Li-ion battery failure mechanisms can be directly traced to lattice-mismatch strain arising from local compositional heterogeneities. The mechanisms of chemo-mechanical coupling that effect phase separation and the resulting complex evolution of internal stress fields remain inadequately understood. This work employs X-ray microscopy techniques to image the evolution of composition and stress across individual bent V2O5 particles. Experimental findings show that lattice strain imposed by the deformation of an individual cathode particle profoundly modifies phase separation patterns, yielding striated Li-rich domains ensconced within a Li-poor matrix. Particle-level inhomogeneities compound across scales resulting in fracture and capacity fade. Coupled phase field modeling of the evolution of domains reveals that the observed patterns minimize the energetic costs incurred by the geometrically imposed strain gradients during lithiation of the material and illustrate that phase separation motifs depend sensitively on the particle geometry, dimensions, interfacial energetics, and lattice incommensurability. Sharp differences in phase separation patterns are observed between lithiation and delithiation. This work demonstrates the promise of strain-engineering and particle geometry to deterministically control phase separation motifs such as to minimize accumulated stresses and mitigate important degradation mechanisms.