High‐capacity Li‐rich Mn‐based oxide cathodes show a great potential in next generation Li‐ion batteries but suffer from some critical issues, such as, lattice oxygen escape, irreversible transition metal (TM) cation migration, and voltage decay. Herein, a comprehensive structural modulation in the bulk and surface of Li‐rich cathodes is proposed through simultaneously introducing oxygen vacancies and P doping to mitigate these issues, and the improvement mechanism is revealed. First, oxygen vacancies and P doping elongates OO distance, which lowers the energy barrier and enhances the reversible cation migration. Second, reversible cation migration elevates the discharge voltage, inhibits voltage decay and lattice oxygen escape by increasing the Li vacancy‐TM antisite at charge, and decreasing the trapped cations at discharge. Third, oxygen vacancies vary the lattice arrangement on the surface from a layered lattice to a spinel phase, which deactivates oxygen redox and restrains oxygen gas (O2) escape. Fourth, P doping enhances the covalency between cations and anions and elevates lattice stability in bulk. The modulated Li‐rich cathode exhibits a high‐rate capability, a good cycling stability, a restrained voltage decay, and an elevated working voltage. This study presents insights into regulating oxygen redox by facilitating reversible cation migration and suppressing O2 escape.
We describe the synthesis of β-fluorinated porpholactones by oxidation of the fluorinated CC bond of the pyrrolic subunit in porphyrin using the “RuCl3 + Oxone®” protocol.
LiCoO2 (LCO) is ideal for 3C electronics due
to its
high tap density. However, the excessive O → Co charge transfer
at high delithiation leads to irreversible Co reduction, O release,
and structural degradation, deteriorating the high-voltage performance
of LCO. Herein, we propose to regulate the intrinsic Fermi level via
uneven trace Zr/Mg doping. First, the increase of electron density
in the Fermi level mitigates both the O oxidation/coupled Co reduction
through alleviating the O → Co charge transfer, restraining
the formations of Co2+ and O2. This elevates
Co redox activity and reduces O redox activity. In addition, the structural
evolution of the cathode at delithiation is simplified. The modulated
LCO delivers a high discharge capacity and a high cycling stability
with 4.5 and 4.6 V ceilings. This study sheds new light on the modulation
of Co/O redox chemistry and the reliable large-scale production of
high-voltage LiCoO2.
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