Electrochemical studies of few-layered graphene as an anode material for Li ion batteries

10.1007/s10008-013-2338-2Journal of Solid State Electrochemistry184941-94

Synthesis of Nickel Fumarate and Its Electrochemical Properties for Li-Ion Batteries

Metal–organic frameworks (MOFs) have found a potential application in various domains such as gas storage/separation, drug delivery, catalysis, etc. Recently, they have found considerable attention for energy storage applications such as Li- and Na-ion batteries. However, the development of MOFs is plagued by their limited energy density that arises from high molecular weight and low volumetric density. The choice of ligand plays a crucial role in determining the performance of the MOFs. Here, we report a nickel-based one-dimensional metal-organic framework, NiC4H2O4, built from bidentate fumarate ligands for anode application in Li-ion batteries. The material was obtained by a simple chimie douce precipitation method using nickel acetate and fumaric acid. Moreover, a composite material of the MOF with reduced graphene oxide (rGO) was prepared to enhance the lithium storage performance as the rGO can enhance the electronic conductivity. Electrochemical lithium storage in the framework and the effect of rGO on the performance have been investigated by cyclic voltammetry, galvanostatic charge–discharge measurements, and EIS studies. The pristine nickel formate encounters serious capacity fading while the rGO composite offers good cycling stability with high reversible capacities of over 800 mAh g−1

Fe2Mo3O8/exfoliated graphene oxide : solid-state synthesis, characterization and anodic application in Li-ion batteries

An Fe2Mo3O8/exfoliated graphene oxide (EG) composite with unique morphology is synthesized by a novel solid-state reduction method. Graphene oxide (GO), FeC2O4·2H2O and MoO3 are heated together at 750 °C for 8 h under an Ar atmosphere to obtain Fe2Mo3O8/EG as the resultant material. The morphology of the as-synthesized Fe2Mo3O8/EG powder as observed in electron micrographs confirmed the presence of layer-like EG and densely populated Fe2Mo3O8 hexagonal platelets. Thermogravimetric analysis showed that Fe2Mo3O8 and EG are in the composite at 98 and 2 wt%, respectively. The structural analysis of the as-synthesized Fe2Mo3O8/EG confirmed that Fe2Mo3O8 platelets are crystallized in the hcp crystal system. Raman scattering analysis further confirmed the presence of Fe2Mo3O8 and EG in the as-synthesized Fe2Mo3O8/EG composite. X-ray photoelectron spectroscopy confirmed that Fe and Mo elements are in the II and IV oxidation states in the as-synthesized Fe2Mo3O8/EG composite, which when tested as an anode material of a half-cell Li-ion battery, exhibited a high reversible capacity of 945 mA h g−1 at 50 mA g−1 current rate. This work paves the way to synthesize other graphene–metal oxide composites (with unique metal oxide morphologies) for their use as anode materials in Li-ion batteries.MOE (Min. of Education, S’pore

Sustainable Graphenothermal Reduction Chemistry to Obtain MnO Nanonetwork Supported Exfoliated Graphene Oxide Composite and its Electrochemical Characteristics

Exfoliated graphene oxide (EG)/manganese­(II) oxide (MnO) composite powder is synthesized by simple solid state graphenothermal reduction process. Structural, chemical, and morphological studies confirm the formation of EG/MnO composite in which cubic MnO crystallites are found to anchor onto EG surfaces. The as-synthesized EG/MnO composite is constituted with 65 and 35 wt % of MnO and EG, respectively. The EG/MnO composite exhibits a specific surface area of ∼82 m² g^–1 and an average pore size of ∼12 nm. As an anode in lithium-ion batteries, the EG/MnO composite shows a high reversible capacity of 936 mAh g^–1 at a current rate of 75 mA g^–1. Capacity retention of ∼84% (784 mAh g^–1) is observed even at the 100th cycle which corresponds to a Coulombic efficiency of ∼99%. Cyclic voltammetry studies on the composite show that Li storage is owing to reversible conversion reactions of MnO and electrochemical absorption/desorption by EG. Electrochemical impedance spectroscopy studies clearly show easy lithiation kinetics. Owing to the electrochemical performance of EG/MnO composite and its easy, reproducible, and scalable synthesis procedure, it is an excellent addition to this class of similar materials

Experimental Elucidation of a Graphenothermal Reduction Mechanism of Fe₂O₃: An Enhanced Anodic Behavior of an Exfoliated Reduced Graphene Oxide/Fe₃O₄ Composite in Li-Ion Batteries

The graphenothermal reduction mechanism of Fe₂O₃ by graphene oxide (GO) is elucidated through careful experimental analysis. The degree of oxidation (DO) of GO plays a key role in controlling the reduction of Fe₂O₃ by GO. GO with low DO follows a conventional three-stage reaction path, i.e., ′2GO + Fe₂O₃ → EG/Fe₃O₄ (Stage I) → EG/FeO (Stage II) → EG/Fe (Stage III)′ (where EG is exfoliated reduced graphene oxide), at temperatures 650 and 750 °C to reduce Fe₂O₃, whereas the GO with higher DO transforms rapidly and ceases the reduction at Stage I, i.e., with the formation of EG/Fe₃O₄ at 650 °C. It is also found that slow thermal treatment of GO continues the reduction to Stage II and further to Stage III depending on time of heating and temperature. EG/Fe₃O₄ (synthesized at 550 °C, 5 h) by using GO with low DO showed superior cycling performance as an anode of Li-ion battery than its counterpart prepared (at 650 °C, 5 h) from GO with high DO owing to good contacts between EG and Fe₃O₄. EG/Fe₃O₄ (synthesized at 550 °C, 5 h) exhibited reversible capacity as high as 860 mAh/g which is greater than the specific capacity of EG/Fe₃O₄ synthesized (at 650 °C, 5 h) by 150 mAh/g. Overall, EG/Fe₃O₄ (synthesized at 550 °C, 5 h) outperformed its counterpart (i.e., EG/Fe₃O₄ synthesized at 650 °C, 5 h) by exhibiting excellent cycling stability and rate capability at current rates ranging from 0.5 to 3.0 C

MgO-decorated few-layered graphene as an anode for Li-ion batteries

10.1021/am5064712ACS Applied Materials and Interfaces742301-230