Upon the emergence of electric vehicles, accurate and non-destructive monitoring of battery electrode materials during operation is highly desirable. Structural degradation of widely adopted intercalation-based materials constitutes the origin of their capacity fading and safety deterioration. Here, we introduce entropymetry to monitor the structural changes of LiCoO₂ (LCO) and its nickel (Ni)-doped derivatives at different states of charge (SOC). While simple lithium (Li) extraction on charging gives a monotonic decline of entropy change (ΔS) based on progressive vacancy occupation over Li sites, the presence of a monoclinic intermediate phase inverses the slope of the ΔS profile to reflect its limited atomic configurations with high ordering. Furthermore, Ni-doping lessens the ordering of the monoclinic phase, decreasing the height amplitude of ΔS profile in the monoclinic regime. The increased disorder by Ni-doping enhances the stability of the lattice framework, extending the cycle life with high voltage cut-off (4.6 V vs. Li/Li⁺). The present study highlights entropymetry as a unique, non-destructive tool in monitoring the structural ordering and relevant degradation of electrode materials in lithium-ion batteries.

中文翻译：

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熵分析法用于LiCoO2阴极的无损结构分析

随着电动车辆的出现，非常需要在操作过程中对电池电极材料进行准确且无损的监控。广泛采用的基于插层的材料的结构退化是其容量下降和安全性下降的根源。在这里，我们介绍了熵分析法，以监测LiCoO ₂（LCO）及其掺杂镍（Ni）的衍生物在不同电荷状态（SOC）时的结构变化。充电时简单提取锂（Li）会根据锂位点上的逐渐空位占据产生熵变（ΔS）的单调下降，但单斜中间相的存在会使ΔS的斜率倒置轮廓以反映其有限的原子构型并具有较高的有序性。此外，镍掺杂降低了单斜晶相的有序性，降低了单斜晶相中ΔS轮廓的高度幅度。镍掺杂增加的无序度提高了晶格框架的稳定性，并在高电压截止（4.6 V vs. Li / Li ⁺）的情况下延长了循环寿命。本研究强调了熵法作为监测锂离子电池中电极材料的结构有序性和相关降解的一种独特的非破坏性工具。