A general strategy for enabling Fe3O4 with enhanced lithium storage performance: Synergy between yolk-shell nanostructures and doping-free carbon

Core-shell-structured Mn2SnO4@Void@C as a stable anode material for lithium-ion batteries with long cycle life

Owing to its high theoretical specific capacity, Mn₂SnO₄ has been regarded as a promising electrode material for lithium-ion batteries. However, in suffering from huge volume expansion and pulverization amidst the alloying/dealloying processes, it presents difficulties in applications as an anode material. Herein, a core-shell-structured Mn₂SnO₄@Void@C anode material was successfully synthesized using a layer-wise assembly and selective etching method. Tetraethyl silicate (TEOS) and resorcinol formaldehyde resin, serving, respectively, as sacrificial template (SiO₂) and carbon layer sources, were coated successively onto Mn₂SnO₄ particles. Adopting an alkali etching process, the SiO₂ template was removed, and a Mn₂SnO₄@Void@C was therewith constructed. As Mn₂SnO₄ is well wrapped by a carbon shell and there are enough voids therein, its volume expansion whilst cycling can be significantly buffered. Moreover, the porous structure in Mn₂SnO₄@Void@C can provide convenient channels for ion transport and alleviate volume changes. Mn₂SnO₄@Void@C exhibits upgraded capacity and long cycling stability, since its specific capacity is maintained at 783.1 mA h g^-1 at 100 mA g^-1 after 150 cycles and at 553.3 mA h g^-1 at 1000 mA g^-1 after 1000 cycles.

Preparation of Hollow Core-Shell Fe3O4/Nitrogen-Doped Carbon Nanocomposites for Lithium-Ion Batteries

Iron oxides are potential electrode materials for lithium-ion batteries because of their high theoretical capacities, low cost, rich resources, and their non-polluting properties. However, iron oxides demonstrate large volume expansion during the lithium intercalation process, resulting in the electrode material being crushed, which always results in poor cycle performance. In this paper, to solve the above problem, iron oxide/carbon nanocomposites with a hollow core-shell structure were designed. Firstly, an Fe2O3@polydopamine nanocomposite was prepared using an Fe2O3 nanocube and dopamine hydrochloride as precursors. Secondly, an Fe3O4@N-doped C composite was obtained by means of further carbonization treatment. Finally, Fe3O4@void@N-Doped C-x composites with core-shell structures with different void sizes were obtained by means of Fe3O4 etching. The effect of the etching time on the void size was studied. The electrochemical properties of the composites when used as lithium-ion battery materials were studied in more detail. The results showed that the sample that was obtained via etching for 5 h using 2 mol L-1 HCl solution at 30 °C demonstrated better electrochemical performance. The discharge capacity of the Fe3O4@void@N-Doped C-5 was able to reach up to 1222 mA g h-1 under 200 mA g-1 after 100 cycles.

Constructing an interspace in MnO@NC microspheres for superior lithium ion battery anodes

In this work, silica nanospheres were introduced into nitrogen-carbon (NC) coated MnO microspheres and filled the gap between NC and MnO. After etching, an interspace was formed between the coating layer and the MnO microspheres. The structure not only provides a conductive NC layer, but also constructs a space to mitigate the volume effect of MnO. As expected, the specific capacity remained at 1143.93 mA h g^-1 after 200 cycles at a current density of 0.2 A g^-1, and 726.96 mA h g^-1 after 450 cycles at a high current density of 1 A g^-1. The superior performance can be attributed to the unique structure with an internal void space and the excellent protection of MnO microspheres by the surface NC layer.