Vadhva Pooja, Boyce Adam M, Patel Anisha, Shearing Paul R, Offer Gregory, Rettie Alexander J E
Electrochemical Innovation Lab, Department of Chemical Engineering, University College London, London WC1E 7JE, United Kingdom.
School of Mechanical and Materials Engineering, University College Dublin, Dublin, D04 V1W8, Ireland.
ACS Appl Mater Interfaces. 2023 Sep 13;15(36):42470-42480. doi: 10.1021/acsami.3c06615. Epub 2023 Aug 30.
Solid-state batteries (SSBs) are promising alternatives to the incumbent lithium-ion technology; however, they face a unique set of challenges that must be overcome to enable their widespread adoption. These challenges include solid-solid interfaces that are highly resistive, with slow kinetics, and a tendency to form interfacial voids causing diminished cycle life due to fracture and delamination. This modeling study probes the evolution of stresses at the solid electrolyte (SE) solid-solid interfaces, by linking the chemical and mechanical material properties to their electrochemical response, which can be used as a guide to optimize the design and manufacture of silicon (Si) based SSBs. A thin-film solid-state battery consisting of an amorphous Si negative electrode (NE) is studied, which exerts compressive stress on the SE, caused by the lithiation-induced expansion of the Si. By using a 2D chemo-mechanical model, continuum scale simulations are used to probe the effect of applied pressure and C-rate on the stress-strain response of the cell and their impacts on the overall cell capacity. A complex concentration gradient is generated within the Si electrode due to slow diffusion of Li through Si, which leads to localized strains. To reduce the interfacial stress and strain at 100% SOC, operation at moderate C-rates with low applied pressure is desirable. Alternatively, the mechanical properties of the SE could be tailored to optimize cell performance. To reduce Si stress, a SE with a moderate Young's modulus similar to that of lithium phosphorous oxynitride (∼77 GPa) with a low yield strength comparable to sulfides (∼0.67 GPa) should be selected. However, if the reduction in SE stress is of greater concern, then a compliant Young's modulus (∼29 GPa) with a moderate yield strength (1-3 GPa) should be targeted. This study emphasizes the need for SE material selection and the consideration of other cell components in order to optimize the performance of thin film solid-state batteries.
固态电池（SSB）是现有锂离子技术很有前景的替代方案；然而，它们面临着一系列独特的挑战，要实现广泛应用就必须克服这些挑战。这些挑战包括固-固界面电阻高、动力学缓慢，并且容易形成界面空隙，由于断裂和分层导致循环寿命缩短。这项建模研究通过将化学和机械材料特性与其电化学响应联系起来，探究了固体电解质（SE）固-固界面处应力的演变，这可作为优化基于硅（Si）的固态电池设计和制造的指南。研究了一种由非晶硅负极（NE）组成的薄膜固态电池，由于硅锂化诱导的膨胀，该电池会在SE上施加压应力。通过使用二维化学-力学模型，利用连续介质尺度模拟来探究施加压力和C倍率对电池应力-应变响应的影响以及它们对电池整体容量的影响。由于锂在硅中的扩散缓慢，在硅电极内会产生复杂的浓度梯度，这会导致局部应变。为了在100%荷电状态下降低界面应力和应变，希望在低施加压力下以适中的C倍率运行。或者，可以调整SE的机械性能以优化电池性能。为了降低硅应力，应选择杨氏模量适中（类似于氧氮化锂磷，约77吉帕）且屈服强度低（与硫化物相当，约0.67吉帕）的SE。然而，如果更关注SE应力的降低，那么应目标是具有适中屈服强度（1 - 3吉帕）的柔顺杨氏模量（约29吉帕）。这项研究强调了选择SE材料以及考虑其他电池组件以优化薄膜固态电池性能的必要性。
