【摘要】 得益于阴离子氧化还原反应的引入,富锂材料具有较高的输出容量而被认为是下一代高能量密度电池正极材料的选择之一.然而氧相关的阴离子氧化还原反应的利用常常伴随着不可逆的晶格氧析出和严重的结构畸变.此外,由于复杂的阴阳离子氧化还原反应,使得富锂材料的电荷补偿机理也需要进一步澄清.本文报道了一种T2型Li_0.72[Li_0.12Ni_0.36Mn_0.52]O₂正极材料.研究发现,与其他典型的富锂层状正极不同,其具有不同于传统富锂材料的四面体碱金属配位环境与ABB′A′氧堆垛顺序.得益于其良好的结构稳定性和可逆的锂离子脱嵌过程,层状T2型正极材料具有良好的电化学稳定性,在较长的循环中具有较少的容量衰减和电压下降.研究人员通过详细的光谱表征,不仅标定了复杂的阴离子氧化还原行为,而且预估了相应的阳离子/阴离子氧化还原反应对应的电化学容量,这进一步阐明具有复杂氧化还原行为材料的电荷补偿机理.更多还原

【Abstract】 Coupled with anionic and cationic redox chemistry, Li-rich/excess cathode materials are prospective high-energy-density candidates for the next-generation Li-ion batteries. However, irreversible lattice oxygen loss would exacerbate irreversible transition metal migration, resulting in a drastic voltage decay and capacity degeneration. Herein, a metastable layered Li-excess cathode material, T2-type Li_0.72[Li_0.12 Ni_0.36 Mn_0.52]O₂, was developed, in which both oxygen stacking arrangement and Li coordination environment fundamentally differ from that in conventional O3-type layered structures. By means of the reversible Li migration processes and structural evolutions, not only can voltage decay be effectively restrained, but also excellent capacity retention can be achieved upon long-term cycling. Moreover, irreversible/reversible anionic/cationic redox activities have been well assigned and quantified by various in/ex-situ spectroscopic techniques, further clarifying the charge compensation mechanism associated with（de）lithiation. These findings of the novel T2 structure with the enhanced anionic redox stability will provide a new scope for the development of high-energy-density Li-rich cathode materials.更多还原