Prospects of high energy Ni-based lithium-rich layered oxides

With the rapid development of electric transportation and energy storage fields, secondary battery devices with high-energy-density and long-term cycling life are urgently required to meet current market demands. Ni-based layered oxides (LiNi x M y O 2 , x ≥ y, M = Co, Mn or Al) are considered as the dominant cathode materials for the next-generation batteries owing to their high-energy-density. However, with Ni content increasing, Ni-based cathode materials undergo rapid electrochemical degradation driven by bulk structural and cathode-electrolyte interface (CEI) instability and conventional element doping strategy struggles to balance high-capacity and long-term cycling life simultaneously. According to recent studies, implanting a “Li-rich functional unit” into Ni-based layered oxides holds the potential to address the above challenges. We systematically review the latest research progress, including implanting amount, existing form, functional mechanisms and inherent limitations of these different Li-rich functional units. Furthermore, we categorize the designed / synthesized materials into “Ni-based slightly Li-rich layered oxides (Ni-sLLOs)”, “Ni-based Li-rich layered oxides (Ni-LLOs)”, and “Ni-based surface Li-rich layered oxides (Ni-fLLOs)”. Ultimately, we put forward a “dual Li-rich design” strategy for Ni-based layered oxides to solve the key issues of their application in next-generation high-energy-density and long-cycling Li-ion batteries.