Characterization of Fe 2 O 3 /Graphene Composites Synthesized using an In Situ Reaction of Inexpensive Graphite Oxide and FeCl 3

A Strategy for Anode Recovery and Upgrading by In Situ Growth of Iron-Based Oxides on Microwave-Puffed Graphite

Faced with the increasing volume of retired lithium-ion batteries (LIBs), recycling and reusing the spent graphite (SG) is of great significance for resource sustainability. Here, a facile method for transforming the SG into a carbon framework as well as loading Fe2O3 to form a composite anode with a sandwich structure is proposed. Taking advantage of the fact that the layer spacing of the spent graphite naturally expands, impurities and intercalants are eliminated through microwave thermal shock to produce microwave-puffed graphite (MPG) with a distinct three-dimensional structure. Based on the mechanism of microwave-induced gasification intercalation, a Fe2O3-MPG intercalation compound (Fe2O3-MPGIC) anode material was constructed by introducing iron precursors between the framework layers and subsequently converting them into Fe2O3 through annealing. The Fe2O3-MPGIC anode exhibits a high reversible capacity of 1000.6 mAh g-1 at 200 mA g-1 after 100 cycles and a good cycling stability of 504.4 mAh g-1 at 2000 mA g-1 after 500 cycles. This work can provide a reference for the feasible recycling of SG and development of high-performance anode materials for LIBs.

Scalable solid-state synthesis of 2D transition metal oxide/graphene hybrid materials and their utilization for microsupercapacitors

Two-dimensional metal oxide (MO) nanostructures have unique properties compared with their bulk or 0D and 1D (nanoparticle and nanowire) counterparts. Their abundant surface area and atomically thin 2D structure are advantageous for their applications in catalysis and energy, as well as integration with 2D layered materials such as graphene and reduced graphene oxide (rGO). However, fast and scalable synthesis of 2D MOs and their nanocomposites remains challenging. Here, we developed a microwave-assisted solid-state synthesis method for the scalable generation of 2D MOs and 2D MO/rGO nanocomposites with tunable structure and composition. The structures and properties of 2D Fe2O3 and 2D ZnO as well as their nanocomposites with rGO were systematically investigated. The excellent electrochemical properties of such 2D MO/rGO nanocomposites also enable us to use them as electrode materials to fabricate microsupercapacitors. This work provides new insights into the scalable and solid-state synthesis of 2D nanocomposites and their potential applications in catalysis, energy conversion and storage.

Controllable Synthesis of Carbon Yolk-Shell Microsphere and Application of Metal Compound-Carbon Yolk-Shell as Effective Anode Material for Alkali-Ion Batteries

Recently, nanostructured carbon materials, such as hollow-, yolk-, and core-shell-configuration, have attracted attention in various fields owing to their unique physical and chemical properties. Among them, yolk-shell structured carbon is considered as a noteworthy material for energy storage due to its fast electron transfer, structural robustness, and plentiful active reaction sites. However, the difficulty of the synthesis for controllable carbon yolk-shell has been raised as a limitation. In this study, novel synthesis strategy of nanostructured carbon yolk-shell microspheres that enable to control morphology and size of the yolk part is proposed for the first time. To apply in the appropriate field, cobalt compounds-carbon yolk-shell composites are applied as the anode of alkali-ion batteries and exhibit superior electrochemical performances to those of core-shell structures owing to their unique structural merits. Co₃ O₄ -C hollow yolk-shell as a lithium-ion battery anode exhibits a long cycling lifetime (619 mA h g^-1 for 400 cycles at 2 A g^-1 ) and excellent rate capability (286 mA h g^-1 at 10 A g^-1 ). The discharge capacities of CoSe₂ -C hollow yolk-shell as sodium- and potassium-ion battery anodes at the 200th cycle are 311 mA h g^-1 at 0.5 A g^-1 and 268 mA h g^-1 at 0.2 A g^-1 , respectively.

Synthesis of Si/Fe2O3-Anchored rGO Frameworks as High-Performance Anodes for Li-Ion Batteries

By virtue of the high theoretical capacity of Si, Si-related materials have been developed as promising anode candidates for high-energy-density batteries. During repeated charge/discharge cycling, however, severe volumetric variation induces the pulverization and peeling of active components, causing rapid capacity decay and even development stagnation in high-capacity batteries. In this study, the Si/Fe2O3-anchored rGO framework was prepared by introducing ball milling into a melt spinning and dealloying process. As the Li-ion battery (LIB) anode, it presents a high reversible capacity of 1744.5 mAh g-1 at 200 mA g-1 after 200 cycles and 889.4 mAh g-1 at 5 A g-1 after 500 cycles. The outstanding electrochemical performance is due to the three-dimensional cross-linked porous framework with a high specific surface area, which is helpful to the transmission of ions and electrons. Moreover, with the cooperation of rGO, the volume expansion of Si is effectively alleviated, thus improving cycling stability. The work provides insights for the design and preparation of Si-based materials for high-performance LIB applications.