Current Collector-Free Reduced Graphene Oxide Aerogel Cathode for High Energy Density Dual-Ion Batteries

Electrochemical intercalation of anions into graphite: Fundamental aspects, material synthesis, and application to the cathode of dual-ion batteries

In this review, fundamental aspects of the electrochemical intercalation of anions into graphite have been first summarized, and then described the electrochemical preparation of covalent-type GICs and application of graphite as the cathode of dual-ion battery. Electrochemical overoxidation of anion GICs provides graphite oxide and covalent-fluorine GICs, which are key functional materials for various applications including energy storage devices. The reaction conditions to obtain fully oxidized graphite has been mentioned. Concerning the application of graphite for the cathode of dual-ion battery, it stably delivers about 110 mA h g-1 of reversible capacity in usual organic electrolyte solutions. The combination of anion and solvent as well as the concentration of the anions in the electrolyte solutions greatly affect the performance of graphite cathode such as oxidation potential, rate capability, cycling properties, etc. The interfacial phenomenon is also important, and fundamental studies of charge transfer resistance, anion diffusion coefficient, and surface film formation behavior have also been summarized. The use of smaller anions, such as AlCl4 - , Br- can increase the capacity of graphite cathode. Several efforts on the structural modification of graphite and development of electrolyte solutions in which graphite cathode delivers higher capacity were also described.

An Integrated Design of Electrodes for Flexible Dual-Ion Batteries

Due to the widespread employment of carbon materials in novel dual-ion batteries (DIBs) with high energy density, they possess the potential for large-scale energy storage and are inexpensive and environmentally friendly. However, drawbacks such as Al current collector corrosion and significant self-weight, as well as lithium metal abuse and poor deposition reversibility, impair the energy density and cycle performance of lithium-graphite DIBs (Li-G DIBs), severely limiting their application potential. Therefore, an integrated electrode structure design was proposed. That is, the flexible graphite and single-walled carbon nanotubes (SWCNTs) composite cathode (GSC), which is light-weight and self-supporting, and the self-supporting lithium metal anode, which is loaded on the flexible carbon cloth (CC) derived from waste mask (Li@CC), were prepared. Not only were the impacts of current collector corrosion and active material exfoliation avoided on the electrochemical performance, but the areal loading of Li metal was also regulated and its reversibility of deposition enhanced. At a current density of 200 mA g^-1 , the constructed Li@CC//GSC full cell could release a specific capacity of 100.5 mAh g^-1 , and the capacity retention rate after 300 cycles was greater than 80 %. Moreover, the fabricated flexible Li@CC//GSC full cell is not only recyclable and produces less environmental pollution but also has potential applications in wearable devices.

Graphene Oxide of Extra High Oxidation: A Wafer for Loading Guest Molecules

We present a new modification of graphene oxide with very high content (85 wt %) of oxygen-containing functional groups (hydroxy, epoxy, lactol, carboxyl, and carbonyl groups) that forms stable aqueous dispersion in up to 9 g·L^-1 concentration solutions. A novel faster method of the synthesis is described that produces up to 1 kg of the material and allows controlling the particle size in solution. The synthesized compound was characterized by various physicochemical methods and molecular dynamics modeling, revealing a unique structure in the form of a multilayered wafer of several sheets thick, where each sheet is highly corrugated. The ragged structure of the sheets forms pockets with hindered mobility of water that leads to the possibility of trapping guest molecules.