Kimura Yuta, Kobayashi Shintaro, Kawaguchi Shogo, Ohara Koji, Suzuki Yasuhiro, Nakamura Takashi, Iriyama Yasutoshi, Amezawa Koji
Institute of Multidisciplinary Research for Advanced Materials, Tohoku University 2-1-1, Katahira, Aoba-Ku Sendai 980-8577 Japan
Japan Synchrotron Radiation Research Institute 1-1-1, Koto, Sayo-cho Sayo-gun Hyogo 679-5198 Japan.
RSC Adv. 2024 Jun 6;14(26):18109-18116. doi: 10.1039/d4ra03058c.
The solidification of lithium-ion batteries (LIBs) by replacing liquid electrolytes with solid electrolytes enables the development of a new class of LIBs, namely all-solid-state lithium-ion batteries (ASSLIBs), with improved safety and energy density. Such battery solidification can greatly influence the properties of battery components, as exemplified by a recent report suggesting that the (dis)charge behaviour of Fe(MoO) (FMO), a promising two-phase electrode material, differs on solid electrolytes compared to liquid electrolytes. However, its underlying mechanism remains unclear. Here we examined the (de)lithiation behaviour of FMO thin films on solid electrolytes using synchrotron X-ray diffraction (XRD) to gain insights into the influence of the solidification on the (dis)charge mechanism of electrode materials. The XRD results revealed that FMO on solid electrolytes exhibits a monotonic peak shift over a wide capacity range, accompanied by a temporary peak broadening. This suggests that FMO possesses an expanded solid-solution reaction region and a narrower two-phase reaction region in solidified batteries compared to liquid-based LIBs. The altered (dis)charge behavior was suggested to be thermodynamically driven, as it remained largely unchanged with varying rates and under open circuit conditions. Qualitative analysis considering stress-induced variations in Gibbs free energy curves demonstrated that external stress, potentially caused by the constraint of chemo-mechanical expansion, can thermodynamically narrow the two-phase region when the chemical expansion coefficients of the two phases of FMO differ. These findings highlight the significant impact of the battery solidification on electrode material properties, emphasizing the importance of considering these unique issues in the design of ASSLIBs.
通过用固体电解质替代液体电解质来实现锂离子电池（LIBs）的固态化，能够开发出一类新型的LIBs，即全固态锂离子电池（ASSLIBs），其安全性和能量密度都有所提高。这种电池固态化会极大地影响电池组件的性能，最近的一份报告就说明了这一点，该报告指出，作为一种很有前景的两相电极材料，Fe(MoO)（FMO）在固体电解质上的充放电行为与在液体电解质上有所不同。然而，其潜在机制仍不清楚。在这里，我们使用同步加速器X射线衍射（XRD）研究了FMO薄膜在固体电解质上的脱嵌锂行为，以深入了解固态化对电极材料充放电机制的影响。XRD结果表明，FMO在固体电解质上在很宽的容量范围内呈现出单调的峰位移，同时伴有暂时的峰展宽。这表明与基于液体的LIBs相比，FMO在固态电池中具有更宽的固溶体反应区域和更窄的两相反应区域。这种改变的充放电行为被认为是由热力学驱动的，因为它在不同的速率和开路条件下基本保持不变。考虑到应力引起的吉布斯自由能曲线变化的定性分析表明，当FMO两相的化学膨胀系数不同时，由化学机械膨胀的约束可能导致的外部应力会在热力学上使两相区域变窄。这些发现突出了电池固态化对电极材料性能的重大影响，强调了在ASSLIBs设计中考虑这些独特问题的重要性。
