Alleviating the air sensitivity of nickel-rich LiNi0.815Co0.15Al0.035O2 cathode by Zr4+-modification for Li-ion batteries

The large-scale application of nickel-rich (Ni content > 60%) cathodes have been plagued by their inherent air sensitivity, which is detrimental to the electrochemical property. This work provides a highly effective Zr4+ modification strategy for nickel-rich LiNi0.815Co0.15Al0.035O2 (NCA) cathode material by a simple solid-state method to handle the air instability issue creatively. Zr4+ ions are proved to distribute homogeneously in the crystal lattice of NCA according to the results from EDX mapping. Investigations by transmission electron microscopy (TEM) and Fourier transformed infrared spectrum (FTIR) results reveal that Zr4+ ions work as residual lithium inhibitor for NCA under ambient conditions. XPS and XRD confirm that the reduction of Ni3+ and Li+/Ni2+ cation mixing are remarkably suppressed by Zr4+ modification for exposed samples. As a consequence, the Zr4+-modified NCA sample is greatly superior to the bare one with respect to the storage property. After exposed for 10 days, the Zr4+-modified NCA electrode still maintains 96.9% of its initial discharge capacity delivered by the fresh sample, whereas, that of bare NCA electrode is just 73.2%. Furthermore, the charge/discharge voltage profiles and electrochemical impedance spectroscopy (EIS) demonstrate that Zr4+ modification contributes to less voltage decay, lower polarization and smaller impedance growth of NCA cathode after exposure.