Unveiling the Evolution of LiCoO2 beyond 4.6 V

The working mechanism of LiCoO2 beyond 4.6 V presents complicated issues: (1) the ambiguous multistructural evolutions, (2) the vague O-related anionic redox reactions (ARR) triggered by the overlap Co-O bands, and (3) the serious electrode-electrolyte interface stability challenges. The intricate relationship among them turns into a classic chicken and egg conundrum, leading to a confusing evolution process of LiCoO2. Herein, from an ingenious perspective combining stacking faults and nonhomogeneous delithiation, we originally demonstrate a series of intergrowth phase evolutions from O3 to O1, passing through the so-called H1-3 phase. Moreover, in sharp contrast to the O-O dimer formed in a traditional Li-rich layered cathode, a moderate and stable arrangement of oxidized lattice oxygen is unveiled as a manifestation of ARR in LiCoO2. Additionally, we clarify the nature that dehydrogenation and hydrolysis of electrolyte trigger the chain decompositions and intensify the surface degradation.

Automated summary

The working mechanism of LiCoO2 beyond 4.6 V presents complicated issues, including multistructural evolutions, anionic redox reactions triggered by Co-O bands, and electrode-electrolyte interface stability challenges. By combining stacking faults and nonhomogeneous delithiation, intergrowth phase evolutions from O3 to O1 are demonstrated, along with the manifestation of ARR in LiCoO2. The nature of electrolyte's role in chain decompositions and surface degradation is clarified.