Phase
transition can profoundly influence the electrochemical performances
of cathode materials for lithium ion batteries. The intricate phase
transitions upon electrochemical cycling constrain the high-rate performances
of the LiNi0.5Mn1.5O4 cathode. The
formation of the rocksalt-like phase causes the diffusion of Li ions
asymmetric in the lithiation and delithiation reactions. The evolution
of multiple cubic phases results in poor diffusivity of Li ions in
the LiNi0.5Mn1.5O4. High-resolution
XRD scans on the chemically delithiated samples reveal that the intricate
phase transitions are effectively suppressed in Cr-doped LiNi0.5Mn1.5O4. The suppression of phase
transitions not only enhances the Li ions’ diffusivity inside
the lattice, but also stabilizes the charge transfer interfaces by
reducing lattice mismatch and alleviating structural stress during
the lithiation and delithiation. Consequently, the improvement on
structure evolution endows the LiNi0.5Mn1.5O4 with enhanced diffusion coefficient of Li ions, larger accessible
capacity, and improved Coulombic efficiency.
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