Lithium ion batteries (LIBs) have attracted considerable attentions as the effective energy conversion and storage devices of sustainable energy or electric vehicles due to their high energy densities and less pollutants generation during usage. Anode material is one of the most important components for LIBs. Comparing with conventional graphitic anodes, Mn-based oxides/carbonate as novel anode materials have many merits, such as high specific capacity, safety, environmental friendliness and low cost.

In this study, phase-pure manganese carbonate microspheres with different diameters were synthesized by facile solvothermal and precipitation routes, respectively. Mn₂O₃ with different morphologies and particles size were obtained by thermal decomposing the obtained MnCO₃ microsph...[ Read more ]

Lithium ion batteries (LIBs) have attracted considerable attentions as the effective energy conversion and storage devices of sustainable energy or electric vehicles due to their high energy densities and less pollutants generation during usage. Anode material is one of the most important components for LIBs. Comparing with conventional graphitic anodes, Mn-based oxides/carbonate as novel anode materials have many merits, such as high specific capacity, safety, environmental friendliness and low cost.

In this study, phase-pure manganese carbonate microspheres with different diameters were synthesized by facile solvothermal and precipitation routes, respectively. Mn₂O₃ with different morphologies and particles size were obtained by thermal decomposing the obtained MnCO₃ microspheres with/without mechanical grinding, respectively. Physical characterizations, such as X-ray diffraction (XRD), scanning electron microscopy (SEM) and infra-red spectrum (IR) as well electrochemical tests like cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and discharge/charge cycling were carried out to investigate characteristics, electrochemical performances and lithium insertion/deinsertion mechanisms of these materials.

The initial discharge of MnCO₃ demonstrated a high specific capacity of 1495 and 1642 mAh g^-1 for big spheres (~ 5μm) and small spheres (~ 1μm), respectively. Their capacities were found to be 459 and 455 mAh g^-1 after 100 cycles. However, the higher specific capacity of MnCO₃ small spheres before 80th cycle was attributed to its larger non-faradaic contribution because of its higher surface areas.

Mn₂O₃ nanoparticles show the best performance among the three Mn₂O₃ samples tested with a reversible specific capacity of 583 mAh g^-1 after 100 cycles obtained. The shortest lithium diffusion path and the lowest impedances may explain its best electrochemical performance. During discharge/charge processes, Mn₃O₄ and MnO were generated as intermediate products. Besides, a series of tests for the Mn₂O₃ electrodes with different conductive additives (acetylene black, super-P or carbon nanotubes) demonstrated that sample with CNTs (multi-wall, diameter: 8-15 nm, length: > 5μm) showed the best capacity retention rate of 89 % after 100 cycles, which is attributed to an effective three-dimensional conductive network and low resistance in the electrode.