Tradeoff between the Ion Exchange-Induced Residual Stress and Ion Transport in Solid Electrolytes
Tradeoff between the Ion Exchange-Induced Residual Stress and Ion Transport in Solid Electrolytes
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DOI：
10.1021/acs.chemmater.2c01806
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发表时间：
2022-09-19
影响因子：
8.6
通讯作者：
Qi, Yue
中科院分区：
文献类型：
--
作者：
Jagad, Harsh D.;Harris, Stephen J.;Qi, Yue
锂的快速枝晶生长限制了固态锂金属负极电池的商业化。近期的研究表明，锂枝晶会生长到固态电解质中预先存在的或新生的裂纹中，这表明提高固态电解质的断裂韧性将抑制枝晶穿透。有人提出，在固态电解质表面引入残余压应力可以提供这种额外的断裂韧性。诱导这些残余压应力的方法之一是用较大的等价离子（如钾离子（K⁺））与锂离子（Li⁺）进行交换。另一方面，过多的钾掺入会改变锂离子的扩散路径并降低扩散率，从而限制固态电解质的性能。利用多尺度建模方法，我们对这种权衡进行了优化，并预测在Li₇La₃Zr₂O₁₂固态电解质中，将钾离子交换至两倍晶粒尺寸的深度且交换量为3.4%时，可诱导出约1.1 GPa的最大残余压应力，这相当于断裂强度提高了约8倍，同时在室温下使离子交换区域的扩散率降低5倍。锂离子扩散率的降低是由于K⁺诱导的应力以及（主要是）浅离子交换层中锂离子通道的堵塞。
Rapid filament growth of lithium is limiting the commercialization of solid-state lithium metal anode batteries. Recent work demonstrated that lithium filaments grow into pre-existing or nascent cracks in the solid electrolyte, suggesting that increasing the fracture toughness of the solid electrolytes will inhibit filament penetration. It has been suggested that introducing residual compressive stresses at the surface of the solid electrolyte can provide this additional fracture toughness. One of the ways to induce these residual compressive stresses is by exchanging lithium ions (Li+) with larger isovalent ions such as potassium (K+). On the other hand, incorporation of too much potassium can alter the lithium-ion diffusion pathway and lower the diffusivity, thus limiting the performance of the solid-state electrolyte. Using multiscale modeling methods, we optimize this tradeoff and predict that exchanging 3.4% potassium ions up to a depth twice the grain sizes in Li7La3Zr2O12 solid electrolyte can induce a maximum residual compressive stress of around 1.1 GPa, corresponding to an increase in fracture strength by & SIM;8 times, while lowering the diffusivity in the ion-exchanged region by a factor of 5 at room temperature. The reduction of lithium diffusivity is due to K+-induced stress and (mainly) blockage of lithium ion pathways in the shallow ion-exchanged layer.