Electrolyte motion induced salt inhomogeneity – a novel aging mechanism in large-format lithium-ion cells,Energy & Environmental Science

当前位置： X-MOL 学术 › Energy Environ. Sci. › 论文详情

Our official English website, www.x-mol.net, welcomes your feedback! (Note: you will need to create a separate account there.)

Electrolyte motion induced salt inhomogeneity – a novel aging mechanism in large-format lithium-ion cells
Energy & Environmental Science ( IF 32.4 ) Pub Date : 2024-08-27 , DOI: 10.1039/d4ee03211j
Sophie Solchenbach ₁ , Camilla Tacconis ₁ , Aurora Gomez Martin ₁ , Verena Peters ₁ , Lea Wallisch ₁ , Anna Stanke ₁ , Johanna Hofer ₁ , Diemo Renz ₁ , Burkhard Lewerich ₁ , Georg Bauer ₁ , Moritz Wichmann ₁ , Daniel Goldbach ₁ , Alexander Adam ₁ , Markus Spielbauer ₁ , Peter Lamp ₁ , Johannes Wandt _{1,

2}

Affiliation

The electrification of the transport sector places ever-increasing demands on the energy density, fast-charging performance, and lifetime of lithium-ion cells. In this study, we investigate fast-charging of high energy density (∼ 800 W h L⁻¹) prototype cylindrical 4695 lithium-ion cells with two different (“low” and “high”) electrolyte amounts. Using pore volume calculations, computer tomography and moment of inertia measurements, we find that the volume change of the active material causes electrolyte motion into and out of the jelly roll upon cycling in the high electrolyte cells, while no electrolyte motion occurs in the low electrolyte cells. At the same time, the high electrolyte cells show a significantly worse capacity retention during fast charge cycling compared to the low electrolyte cells (24% vs. 5% capacity loss after 130 cycles). We demonstrate that a coupling of in-plane electrolyte motion with the through-plane LiPF₆ concentration gradient rapidly causes a strong LiPF₆ concentration gradient along the jelly roll height (= in-plane) on a cm-scale: after only 18 cycles, LiPF₆ concentrations at the jelly roll edges and center (as determined by ion-chromatography) deviate by more than ± 50% in comparison to the initial average value. We term this hitherto unknown effect “electrolyte motion induced salt inhomogeneity” (EMSI). This long-scale salt concentration gradient causes a loss of cell capacity, an increase in resistance, and eventually highly localized lithium plating. Finally, we discuss the far-reaching implications of the EMSI effect on cell design and testing, not only for cylindrical cells but any large-format lithium-ion cell under high compression.

中文翻译：

电解质运动引起的盐不均匀性——大型锂离子电池的一种新型老化机制

交通运输领域的电气化对锂离子电池的能量密度、快速充电性能和使用寿命提出了越来越高的要求。在这项研究中，我们研究了具有两种不同（“低”和“高”）电解质量的高能量密度（∼ 800 W h L ^-1 ）原型圆柱形 4695 锂离子电池的快速充电。通过孔体积计算、计算机断层扫描和惯性矩测量，我们发现在高电解质电池中循环时，活性材料的体积变化导致电解质运动进出果冻卷，而低电解质中则不会发生电解质运动细胞。同时，与低电解质电池相比，高电解质电池在快速充电循环过程中的容量保持率明显较差（130 次循环后容量损失为 24%对5%）。我们证明，面内电解质运动与穿过平面的 LiPF ₆浓度梯度的耦合迅速导致沿果冻卷高度（=面内）在厘米尺度上产生强 LiPF ₆浓度梯度：仅经过 18 个循环后，果冻卷边缘和中心的LiPF ₆浓度（通过离子色谱法测定）与初始平均值相比偏差超过±50%。我们将这种迄今为止未知的效应称为“电解质运动引起的盐不均匀性”（EMSI）。这种长期的盐浓度梯度会导致电池容量损失、电阻增加，并最终导致高度局部的锂沉积。最后，我们讨论了 EMSI 效应对电池设计和测试的深远影响，不仅适用于圆柱形电池，而且适用于高压缩下的任何大型锂离子电池。

更新日期：2024-08-27

点击分享查看原文

点击收藏

阅读更多本刊新发论文本刊介绍/投稿指南