The aim of this study was to explore the effect of cerium ions on the formation and structure of hydroxyapatite (HAP). All particles, prepared by hydrothermal method, were synthesized at varied X(Ce) = Ce/(Ca + Ce) (from 0 to 10%) with the atomic ratio (Ce + Ca)/P fixed at 1.67. Their morphology, composition and crystal structure were characterized by TEM, EPMA, XRD and FTIR. The results showed that in this composition range the apatite structure is maintained, Ce3+ ions could enter the crystal lattice of apatite and substitute Ca2+ ions. The doping of Ce3+ ions resulted in the decrease of the crystallite size with increase in X(Ce). The HAP particles without doping were short rods having a diameter from 10 to 20 nm and a length from 30 to 50 nm. They grew into long needles upon increasing X(Ce).
For
this work, a Mg2+-doped LiFePO4 (LFP)
cathode material was prepared using a solid-state method with Mg(CH3COO)2 as the Mg2+ dopant. X-ray diffraction
and refinement data suggested that an appropriate doping amount of
Mg2+ can reduce the cell volume of LFP, shorten the Fe–O
and P–O bonds, and elongate the Li–O bond, thereby facilitating
the diffusion of Li+. X-ray photoelectron spectroscopy
test results revealed that Mg2+ doping prevents the formation
of Li–Fe antisite defects while also promoting the formation
of Fe2P, thereby improving the electronic conductivity
of the LFP. The electronic conductivity was measured using a four-probe
teste, and the Li+ diffusion rate was fitted and calculated
according to the electrochemical impedance spectroscopy test results.
The results found that electron conductivity expanded by 275 times
and the Li+ diffusion coefficient increased by 3.6 times
following LFP being doped with Mg2+. Charge/discharge curves
and cyclic voltammetry test reveal that LFP with Mg2+ doping
has superior reversibility, rate performance, and cycle stability,
and the capacity can be maintained at 162 mA h g–1 following 300 cycles at 0.1 C.
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