Abstract
Spherical Ni x Co (1−2 x) Mn x (OH) 2 ( x = 0.333, 0.4, 0.416, 0.45) precursors with Co concentration-gradient were prepared by co-precipitation from sulfate solutions using NaOH and NH 4OH as precipitation and complexing agents. Then, well-ordered spherical LiNi x Co (1−2 x) Mn x O 2 was synthesized by sintering the mixture of as-prepared precursor and Li 2CO 3 at 950 °C for 16 h in air. EDXS results indicated that the concentration of cobalt decreased gradually inside out of the spherical precursor particle, and it was uniform in spherical LiNi x Co (1−2 x) Mn x O 2 particle obtained by sintering with Li 2CO 3. According to Rietveld refinement of XRD patterns, the LiNi x Co (1−2 x) Mn x O 2 synthesized from Co gradient precursor showed lower degree of cation disorder than that prepared from conventional precursor. The well-ordered LiNi x Co (1−2 x) Mn x O 2 from Co gradient precursor delivered much better high-rate capability than conventional one. The decrease of cation disorder of LiNi x Co (1−2 x) Mn x O 2 is attributed to the cobalt-rich in core of the precursor particles. Both abundant Co 3+ and Li + can restrain cation mixing effectively. Since Li + needs long time to reach core during calcining, cobalt-rich in core of the precursor particle is very important for restraining cation mixing. Concentration-gradient precursor is helpful to prepare well-ordered LiNi x Co (1−2 x) Mn x O 2 with good high-rate capability, and the total content of expensive and toxic cobalt does not need to be increased.
Published Version
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