The
high-voltage, cobalt-free spinel cathode LiNi0.5Mn1.5O4 (LNMO) is receiving extensive attention
for lithium-ion batteries due to its low cost, high operating voltage
and energy density, superior power density, and good thermal stability.
However, its high operating voltage hampers its stability with commercial
electrolytes and makes its practical viability challenging. We present
here a Mn-rich LNMO cathode to encourage the disordering of Mn and
Ni in the lattice and the incorporation of a small dose of Fe into
Mn-rich LNMO (Fe-LNMO) to improve the cycling stability. The introduction
of Fe further increases the cation disorder between Mn and Ni, thus
enabling a better rate capability. Electron energy loss spectroscopy
analysis indicates that Fe is concentrated on the surface, and X-ray
photoelectron spectroscopy analysis shows that Fe-LNMO alleviates
the aggressive reaction between the cathode surface and the electrolyte,
thus stabilizing the interface and cycle life. Furthermore, a full
cell assembled with a graphite anode with an areal capacity of 3 mA
h cm–2 displays a capacity retention of 90% over
300 cycles. The present work demonstrates an effective way to promote
cation disordering and lower the surface reactivity of LNMO with the
electrolyte, thereby enhancing the conductivity, stabilizing the cathode–electrolyte
interphase, and making LNMO promising for practical applications.