Influence of Active Material Loading on Electrochemical Reactions in Composite Solid-State Battery Electrodes Revealed by Operando 3D CT-XANES Imaging
Influence of Active Material Loading on Electrochemical Reactions in Composite Solid-State Battery Electrodes Revealed by Operando 3D CT-XANES Imaging
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DOI：
10.1021/acsaem.0c01186
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发表时间：
2020-08-24
影响因子：
6.4
通讯作者：
Amezawa, Koji
中科院分区：
文献类型：
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作者：
Kimura, Yuta;Fakkao, Mahunnop;Amezawa, Koji
设计具有最佳微观结构、成分以及活性材料（AM）和固体电解质（SE）的复合电极对于高性能固态电池（SSB）的开发至关重要。为了优化 AM 负载（包括负载量、成分和分散状态），并最大限度地提高复合 SSB 电极中 AM 的利用率，我们需要精确了解 AM 负载如何影响电极中发生的电化学反应。在这里，我们利用计算机断层扫描结合X射线吸收近边结构光谱（CT-XANES），对不同AM负载量的复合SSB电极中的电化学反应进行了操作三维（3D）观察，以了解AM负载对电化学反应的影响。在AM负载量较高的复合电极中，反应较低的区域主要出现在聚集的AM区域的内部。有人认为这种反应分布是由于 AM 颗粒之间缓慢的粒间离子传输造成的。在AM负载量较低的复合电极中，与负载量较高的复合电极相比，电化学反应进行得更加均匀。这可能是因为较低的 AM 负载减轻了 AM 聚集，并减少了锂离子必须通过的高电阻 AM-AM 界面的数量。由于 AM 颗粒之间的缓慢离子传输而形成的这种反应分布可能会严重限制复合 SSB 电极。这与传统的液基锂离子电池（LIB）电极形成鲜明对比，在传统的液基锂离子电池（LIB）电极中，大多数AM颗粒可以直接与周围的液体电解质交换锂离子。因此，复合 SSB 电极的优化设计可能与液基 LIB 的优化设计有很大不同。我们的分析技术可以为合理设计最佳复合电极提供有价值的信息，因此我们期望该技术有助于高性能SSB的进一步发展。
Designing composite electrodes with optimal microstructure, composition, and choice of active material (AM) as well as solid electrolyte (SE) is critically important for the development of high-performance solid-state batteries (SSBs). To optimize AM loading, which includes loading amount, composition, and dispersion state, and to maximize AM utilization in composite SSB electrodes, we need to precisely understand how the AM loading affects electrochemical reactions taking place in the electrodes. Here, using computed tomography combined with X-ray absorption near edge structure spectroscopy (CT-XANES), we performed operando three-dimensional (3D) observations of electrochemical reactions in composite SSB electrodes with different AM loading amounts to understand the influence of the AM loading on the electrochemical reactions. In the composite electrode with higher AM loading amount, the lower reacted regions were mainly found at the inner parts of the aggregated AM regions. It was suggested that such a reaction distribution resulted from the slow intergranular ion transport between AM particles. In the composite electrode with lower AM loading amount, the electrochemical reaction progressed more homogeneously compared to the one with higher loading. This is probably because the lower AM loading mitigated the AM aggregation and decreased the number of high-resistance AM-AM interfaces that Li ions must pass through. Such a reaction distribution formation due to the slow ion transport between the AM particles can be a serious restriction in composite SSB electrodes. This is in marked contrast to conventional liquid-based lithium ion battery (LIB) electrodes, in which a majority of AM particles can directly exchange Li ions with the surrounding liquid electrolyte. Therefore, the optimal design for composite SSB electrodes can significantly differ from that for liquid-based LIBs. Our analysis technique can provide valuable information to rationally design optimal composite electrodes, and hence we expect that this technique contributes to the further development of high-performance SSBs.