Millions of electric vehicles (EVs) on the road are powered by lithium-ion batteries (LIBs) based on nickel-rich layered oxide (NRLO) cathodes, and they suffer from a limited driving range and safety concerns. Increasing the Ni content is a key way to boost the energy densities of LIBs and alleviate the EV range anxiety, which are, however, compromised by the rapid performance fading. One unique challenge lies in the worsening of the microstructural stability with a rising Ni-content in the cathode. In this review, we focus on the latest advances in the understanding of NLRO microstructures, particularly the microstructural degradation mechanisms, state-of-the-art stabilization strategies, and advanced characterization methods. We first elaborate on the fundamental mechanisms underlying the microstructural failures of NRLOs, including anisotropic lattice evolution, microcracking, and surface degradation, as a result of which other degradation processes, such as electrolyte decomposition and transition metal dissolution, can be severely aggravated. Afterwards, we discuss representative stabilization strategies, including the surface treatment and construction of radial concentration gradients in polycrystalline secondary particles, the fabrication of rod-shaped primary particles, and the development of single-crystal NRLO cathodes. We then introduce emerging microstructural characterization techniques, especially for identification of the particle orientation, dynamic changes, and elemental distributions in NRLO microstructures. Finally, we provide perspectives on the remaining challenges and opportunities for the development of stable NRLO cathodes for the zero-carbon future.

中文翻译：

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锂离子电池层状富镍正极的微观结构

道路上行驶的数百万辆电动汽车 (EV) 由基于富镍层状氧化物 (NRLO) 阴极的锂离子电池 (LIB) 提供动力，但它们的行驶里程有限且存在安全问题。增加镍含量是提高锂离子电池能量密度和缓解电动汽车续航里程焦虑的关键方法，但性能快速衰退却损害了这一点。一个独特的挑战在于随着阴极中镍含量的增加，微观结构稳定性恶化。在这篇综述中，我们重点关注 NLRO 微观结构理解的最新进展，特别是微观结构退化机制、最先进的稳定策略和先进的表征方法。我们首先详细阐述了 NRLO 微观结构失效的基本机制，包括各向异性晶格演化、微裂纹和表面降解，从而严重加剧其他降解过程，例如电解质分解和过渡金属溶解。随后，我们讨论了代表性的稳定策略，包括表面处理和多晶二次粒子径向浓度梯度的构建、棒状一次粒子的制造以及单晶 NRLO 阴极的开发。然后，我们介绍新兴的微观结构表征技术，特别是用于识别 NRLO 微观结构中的颗粒取向、动态变化和元素分布。最后，我们对零碳未来发展稳定的 NRLO 阴极所面临的挑战和机遇提出了看法。