Ge Mingyuan, Wi Sungun, Liu Xiang, Bai Jianming, Ehrlich Steven, Lu Deyu, Lee Wah-Keat, Chen Zonghai, Wang Feng
Energy and Photon Sciences Directorate, Brookhaven National Laboratory, Upton, NY, 11973, USA.
Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, IL, 60439, USA.
Angew Chem Int Ed Engl. 2021 Aug 2;60(32):17350-17355. doi: 10.1002/anie.202012773. Epub 2021 Mar 11.
High-nickel cathodes attract immense interest for use in lithium-ion batteries to boost Li-storage capacity while reducing cost. For overcoming the intergranular-cracking issue in polycrystals, single-crystals are considered an appealing alternative, but aggravating concerns on compromising the ionic transport and kinetic properties. We report here a quantitative assessment of redox reaction in single-crystal LiNi Mn Co O using operando hard X-ray microscopy/spectroscopy, revealing a strong dependence of redox kinetics on the state of charge (SOC). Specifically, the redox is sluggish at low SOC but increases rapidly as SOC increases, both in bulk electrodes and individual particles. The observation is corroborated by transport measurements and finite-element simulation, indicating that the sluggish kinetics in single-crystals is governed by ionic transport at low SOC and may be alleviated through synergistic interaction with polycrystals integrated into a same electrode.
高镍阴极因其在锂离子电池中能够提高锂存储容量并降低成本而备受关注。为了克服多晶中的晶间开裂问题，单晶被认为是一种有吸引力的替代方案，但人们越来越担心这会损害离子传输和动力学性能。我们在此报告了使用原位硬X射线显微镜/光谱对单晶LiNiMnCoO中的氧化还原反应进行的定量评估，揭示了氧化还原动力学对充电状态（SOC）的强烈依赖性。具体而言，无论是在整体电极还是单个颗粒中，氧化还原在低SOC时都很缓慢，但随着SOC的增加而迅速增加。传输测量和有限元模拟证实了这一观察结果，表明单晶中缓慢的动力学受低SOC下的离子传输控制，并且可以通过与集成在同一电极中的多晶的协同相互作用来缓解。
