Graphene: Chemistry and Applications for Lithium-Ion Batteries

In the present era, different allotropes of carbon have been discovered, and graphene is the one among them that has contributed to many breakthroughs in research. It has been considered a promising candidate in the research and academic fields, as well as in industries, over the last decade. It has many properties to be explored, such as an enhanced specific surface area and beneficial thermal and electrical conductivities. Graphene is arranged as a 2D structure by organizing sp2 hybridized C with alternative single and double bonds, providing an extended conjugation combining hexagonal ring structures to form a honeycomb structure. The precious structure and outstanding characteristics are the major reason that modern industry relies heavily on graphene, and it is predominantly applied in electronic devices. Nowadays, lithium-ion batteries (LIBs) foremostly utilize graphene as an anode or a cathode, and are combined with polymers to use them as polymer electrolytes. After three decades of commercialization of the lithium-ion battery, it still leads in consumer electronic society due to its higher energy density, wider operating voltages, low self-discharge, noble high-temperature performance, and fewer maintenance requirements. In this review, we aim to give a brief review of the domination of graphene and its applications in LIBs.

Synthesis and Electrochemical Properties of Bi2MoO6/Carbon Anode for Lithium-Ion Battery Application

High capacity electrode materials are the key for high energy density Li-ion batteries (LIB) to meet the requirement of the increased driving range of electric vehicles. Here we report the synthesis of a novel anode material, Bi2MoO6/palm-carbon composite, via a simple hydrothermal method. The composite shows higher reversible capacity and better cycling performance, compared to pure Bi2MoO6. In 0-3 V, a potential window of 100 mA/g current density, the LIB cells based on Bi2MoO6/palm-carbon composite show retention reversible capacity of 664 mAh·g-1 after 200 cycles. Electrochemical testing and ab initio density functional theory calculations are used to study the fundamental mechanism of Li ion incorporation into the materials. These studies confirm that Li ions incorporate into Bi2MoO6 via insertion to the interstitial sites in the MoO6-layer, and the presence of palm-carbon improves the electronic conductivity, and thus enhanced the performance of the composite materials.

Crystal reconstruction of binary oxide hexagonal nanoplates: monocrystalline formation mechanism and high rate lithium-ion battery applications

Structural design and/or carbon modification are the most important strategies to improve the performance of materials in many applications, where metal (oxide)-based anode design attracts great attention in metal ion batteries due to their high capacities. However, achieving these two goals within one-step remains challenging due to the lower cost and higher efficiency needed to satisfy the demand in practical application. Herein, we report a new approach for the crystal reconstruction of metal oxides by acetylene treatment, in which a hierarchical binary oxide decorated with carbon (i.e., Mn2Mo3O8@C) is introduced. The mechanism of constructing unique monocrystalline hexagonal nanoplates and uniform carbon coating is discussed in detail. Benefiting from the uniqueness of structure and composition, the Mn2Mo3O8@C demonstrates an extremely high lithium storage capacity of 890 mA h g-1 and good rate capacities at 20 A g-1 over 1000 cycles. In addition, the high rate capabilities and long cycle lifespan are further confirmed when the Mn2Mo3O8@C anode is matched with the nickel-rich layered oxide cathode. This study not only introduces a new binary oxide anode with high performances in lithium (ion) batteries but also presents a convenient methodology to design more advanced functional materials.

Highly Crystalized Co2Mo3O8 Hexagonal Nanoplates Interconnected by Coal-Derived Carbon via the Molten-Salt-Assisted Method for Competitive Li-Ion Battery Anodes

Highly crystalized Co₂Mo₃O₈ hexagonal nanoplates interconnected by coal-derived carbon have been successfully fabricated by the molten-salt-assisted method. The formation process of the nanostructural hybrids via molten salts is proposed. The eutectic salts with low melting points act as ionic liquid solvents and "molecular templates" at high temperature, making cobalt and molybdenum salts react in the form of bare ions to get the regular Co₂Mo₃O₈ hexagonal nanoplates interconnected by conductive carbon. In addition, the crystallinity of Co₂Mo₃O₈ hexagonal nanoplates is increased with the help of molten salts. The effects of temperature on morphology and electrochemical performance of the composites were studied. Thanks to the unique structure design, the optimal composite obtained by this simple low-cost strategy exhibits remarkable electrochemical performance as anodes for lithium-ion batteries, which reveals a high reversible capacity of 1075 mA h g^-1 at 200 mA g^-1 and 596 mA h g^-1 at 1000 mA g^-1 after 100 cycles. More importantly, the sample shows good rate capability with a high capacity of 533 mA h g^-1 at a high current density of 4000 mA g^-1. The molten-salt-assisted method is also applicable to design and synthesize other metal oxide-based Li-ion battery anodes.

Electrochemistry-related aspects of safety of graphene-based non-aqueous electrochemical supercapacitors: a case study with MgO-decorated few-layer graphene as an electrode material

Composites such as MgO/few-layered graphene can be used as electrode materials in supercapacitors with aqueous electrolytes but not non-aqueous electrolytes.

Amorphous Vanadium Oxide Thin Films as Stable Performing Cathodes of Lithium and Sodium-Ion Batteries

Herein, we report additive- and binder-free pristine amorphous vanadium oxide (a-VOx) for Li- and Na-ion battery application. Thin films of a-VOx with a thickness of about 650 nm are grown onto stainless steel substrate from crystalline V₂O₅ target using pulsed laser deposition (PLD) technique. Under varying oxygen partial pressure (pO₂) environment of 0, 6, 13 and 30 Pa, films bear O/V atomic ratios 0.76, 2.13, 2.25 and 2.0, respectively. The films deposited at 6‑30 Pa have a more atomic percentage of V⁵⁺ than that of V⁴⁺ with a tendency of later state increased as pO₂ rises. Amorphous VOx films obtained at moderate pO₂ levels are found superior to other counterparts for cathode application in Li- and Na-ion batteries with reversible capacities as high as 300 and 164 mAh g^-1 at 0.1 C current rate, respectively. At the end of the 100th cycle, 90% capacity retention is noticed in both cases. The observed cycling trend suggests that more is the (V⁵⁺) stoichiometric nature of a-VOx better is the electrochemistry.

One-dimensional MoO2–Co2Mo3O8@C nanorods: a novel and highly efficient oxygen evolution reaction catalyst derived from metal–organic framework composites

One dimensional MoO₂–Co₂Mo₃O₈@C nanorods were synthesized by using MoO₃@ZIF-67 composites as a precursor and the catalyst Co₂Mo₃O₈ shows excellent OER activity.

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.