Hydrothermal synthesis of porous hydrangea-like MnCo2O4 as anode materials for high performance lithium ion batteries

A Review of Cobalt-Containing Nanomaterials, Carbon Nanomaterials and Their Composites in Preparation Methods and Application

With the increasing demand for sustainable and green energy, electric energy storage technologies have received enough attention and extensive research. Among them, Li-ion batteries (LIBs) are widely used because of their excellent performance, but in practical applications, the electrochemical performance of electrode materials is not satisfactory. Carbon-based materials with high chemical stability, strong conductivity, high specific surface area, and good capacity retention are traditional anode materials in electrochemical energy storage devices, while cobalt-based nano-materials have been widely used in LIBs anodes because of their high theoretical specific capacity. This paper gives a systematic summary of the state of research of cobalt-containing nanomaterials, carbon nanomaterials, and their composites in LIBs anodes. Moreover, the preparation methods of electrode materials and measures to improve electrochemical performance are also summarized. The electrochemical performance of anode materials can be significantly improved by compounding carbon nanomaterials with cobalt nanomaterials. Composite materials have better electrical conductivity, as well as higher cycle ability and reversibility than single materials, and the synergistic effect between them can explain this phenomenon. In addition, the electrochemical performance of materials can be significantly improved by adjusting the microstructure of materials (especially preparing them into porous structures). Among the different microscopic morphologies of materials, porous structure can provide more positions for chimerism of lithium ions, shorten the diffusion distance between electrons and ions, and thus promote the transfer of lithium ions and the diffusion of electrolytes.

Effective regeneration of mixed composition of spent lithium-ion batteries electrodes towards building supercapacitor

Recycling of different manufacturers of spent lithium-ion batteries cathode and anode via a simple regeneration process has an opportunity to fabricate new energy devices. In this study, the different manufacturers of spent LIB cathode pieces were subjected to lixiviation process and found the best-optimized conditions such as tartaric acid concentration (2.5 M), H₂O₂ concentration (7.5 vol%), solid-liquid ratio (80 g/L), temperature (80 °C), and lixiviation time (80 min) for maximum ~ 99% extraction efficiency of metals. Further, 3D-MnCo₂O₄ (MCO) spheres were regenerated from the cathode lixivium containing metal ions via hydrothermal technique. Besides, anode graphite and Al foils after cathode lixiviation were exploited to prepare reduced graphene oxide (RGO) at room temperature in a simple method. The electrochemical performance of both regenerated electrodes from spent LIBs was explored in the half-cell configuration using the 1 M Na₂SO₄ electrolyte. Additionally, the constructed MCO//RGO asymmetric supercapacitor device offers an operational voltage of 1.8 V and displays a high energy density of ~ 23.9 Wh kg^-1 at 450 W kg^-1 with 8000 cycles. This alternative recycling method proposes the possibility to construct high-energy storage devices from different compositions of spent LIBs.

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.

Phase structure engineering of MnCo2Ox within electrospun carbon nanofibers towards high-performance lithium-ion batteries

Metal oxides are prospective alternative anode materials to the commercial graphite for lithium ion batteries (LIBs), while their practical application is seriously hampered by their poor conductivities and large volume changes. Herein, we report the controllable synthesis of amorphous/crystalline MnCo₂O_x nanoparticles within porous carbon nanofibers (marked as MCO@CNFs) through a facile electrospinning strategy and subsequent annealing reactions. The phase structures from Co/MnO_X to amorphous MnCo₂O_x and crystalline MnCo₂O_4.5 can be readily tuned by thermal reduction/oxidation under controlled atmosphere and temperature. When examined as anode for LIBs, the optimized MCO@CNFs delivers a high stable capacity of 780.3 mA h g^-1 at 200 mA g^-1 after 250 cycles, which is attributed to the synergistic effect of the distinctive amorphous structure and defective carbon nanofiber matrices. Specifically, the amorphous structure with rich defects offers more reactive sites and multiple pathways for the Li⁺ diffusion, while carbon hybridization sufficiently improves the electrode conductivities as well as buffers the volume changes. More importantly, we demonstrate a convenient synthesis strategy to control the metal-to-oxide structure evolution within carbon matrices, which is of great importance in exploring high-performance electrodes for next generation LIBs.