Zirconization of LiCoO2 for enhanced stability and oxygen deactivation in all-solid-state lithium battery cathodes

Developing high-voltage LiCoO 2 (LCO) is essential in realizing practical all-solid-state lithium batteries (ASSLBs). However, high voltage-induced structural instability and oxygen evolution are crucial for the fast degradation of layered metal oxide cathodes. This study reveals that the zirconization on the near-surface region of LCO shows superior electrochemical performance at high voltage (≥ 4.5 V). High-angle annular dark field-scanning transmission electron microscopy firstly reveals the formation of sub-nanoscale Li 2 CoZrO 4 with disordered rock salt ( α -LiFeO 2 ) phase on the surface of LCO. Furthermore, zirconization could prevent the bending of the Co–O layers at high voltage, significantly inhibiting the formation of microcracks after many cycles and enhancing the structural stability of LCO, as further confirmed by high-resolution transmission electron microscopy. Further, Electron paramagnetic resonance and Electron energy loss spectroscopy provide direct experimental evidence that lattice oxygen on LCO at high voltage has greatly deactivated in sub-nanoscale zirconization (Li 2 CoZrO 4 ). Density functional theory calculations reveal that Li 2 CoZrO 4 enhances the stability of lattice oxygen. Therefore, in ASSLBs, LZSO@LCO cathode exhibits impressive electrochemical cycling stability, e.g., 78.1% capacity retention after 1000 cycles at 0.5 C and 71.2% capacity retention over 100 cycles at 0.1 C at an extremely low temperature of −20 °C.