Li-rich layered oxides (LLOs) are promising cathode candidates for next generation Li-ion batteries, as they exhibit a higher reversible capacity (>250mAh/g), enhanced safety and much lower cost. However, LLOs generally suffer from high first cycle irreversible capacity (IRC) loss, poor rate capability, and a substantial voltage decay over prolonged cycling. These major challenges are closely dependent on the surface structure and chemistry of LLO cathodes and, thus, different surfaces induce different irreversible reactions resulting in various levels of battery performance. This review presents the current understanding, as well as recent highlights, on the roles and fundamentals of surface structure in LLO cathodes, from a materials science perspective, concerning surface structural disorder in pristine LLO (antisites, composition segregation and crystallographic facets), the roles of surface structures on redox processes (oxygen evolution, cation activation and reversible anion redox reactions), surface structural evolution during the first cycle and long-term electrochemical operation, and surface modification strategies to stabilize the surface structure and to mitigate the performance degradation of LLOs. However, some fundamental problems remain yet ambiguous, especially with regard to characterization and understanding of the surface structure and chemistry in relation to synthesis conditions and composition, and charge transfer and ionic transport of the interfacial processes within LLOs. In order to exploit the potential of LLO cathodes, a clear understanding of these fundamental questions are essential to optimize the synthesis parameters and material properties.

中文翻译：

---

表面结构和化学在富锂层状氧化物阴极电化学过程中的作用

富含锂的层状氧化物（LLO）是下一代锂离子电池的有希望的阴极候选材料，因为它们具有更高的可逆容量（> 250mAh / g），增强的安全性和更低的成本。但是，LLO通常会遭受较高的第一循环不可逆容量（IRC）损失，较差的速率容量，并且在长时间循环中会出现较大的电压衰减。这些主要挑战紧密取决于LLO阴极的表面结构和化学性质，因此，不同的表面会引发不同的不可逆反应，从而导致各种级别的电池性能。这篇综述从材料科学的角度介绍了有关原始LLO中表面结构紊乱的反常现象，以及有关材料在LLO阴极中表面结构的作用和基本原理的最新认识，以及最近的重点。成分偏析和结晶学方面），表面结构在氧化还原过程中的作用（氧气逸出，阳离子活化和可逆阴离子氧化还原反应），第一周期和长期电化学操作中的表面结构演变以及稳定表面的表面改性策略结构并减轻LLO的性能下降。但是，一些基本问题仍然是模棱两可的，特别是在表征和理解与合成条件和组成有关的表面结构和化学性质以及LLO内部界面过程的电荷转移和离子迁移方面。为了开发LLO阴极的潜力，