The use of sustainable energy or electric vehicles demands effective energy conversion and storage devices. Lithium ion batteries (LIBs) have proved to be viable systems that have high energy densities and less pollutants generation. The cathode materials are the bottle neck for the development of the LIB systems because of their high cost and limited energy capacities.

In this study, spinel LMNO sub-micrometer-sized spheres were obtained from a one-step solid-state synthesis route using MnCO₃ microspheres as the precursors. They were tested as cathode materials for LIBs. Three aspects related to the materials have been mainly investigated: the selection of Mn precursors, the optimization of calcination temperatures and the effect of lithium excessive amounts on the performan...[ Read more ]

The use of sustainable energy or electric vehicles demands effective energy conversion and storage devices. Lithium ion batteries (LIBs) have proved to be viable systems that have high energy densities and less pollutants generation. The cathode materials are the bottle neck for the development of the LIB systems because of their high cost and limited energy capacities.

In this study, spinel LMNO sub-micrometer-sized spheres were obtained from a one-step solid-state synthesis route using MnCO₃ microspheres as the precursors. They were tested as cathode materials for LIBs. Three aspects related to the materials have been mainly investigated: the selection of Mn precursors, the optimization of calcination temperatures and the effect of lithium excessive amounts on the performance of the products. Different characteristics of LMNO samples were examined by various approaches, including the physical characterization methods, such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman, and the electrochemical methods including cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), charge/discharge cycling at different current rates.

It was found that MnCO₃ microspheres prepared by the hydrothermal method provided the proper self-supporting template. The best calcination temperature is 800 ℃, at which the LMNO particles could both retain the spherical morphology and show high crystallinity. A phase transition from Fd3m to P4₃32 would occur with the increment of lithium excessive amounts. The LMNO sample exhibits the best electrochemical performance with 5% (mole) lithium excess, which is caused by the comparatively high Mn³⁺ content (Mn³⁺/Mn⁴⁺ mole ratio: 0.9) in the bulk material. The product shows a discharge capacity of 121.9 mAh g^-1 and 123.0 mAh g^-1 and the corresponding capacity retention of 92.5% and 83.8% for up to 500 cycles at 2 C rate under room (25 ℃) and high (55 ℃) temperature, respectively. In addition, ~ 90 % of the original capacity could be retained at 10 C testing under room temperature.