The chemical exfoliation of graphite to produce graphene and its oxide is undoubtedly an economical method for scalable production. Carbon researchers have dedicated significant resources to developing new exfoliation methods leads to graphene oxides with high quality. However, only a few studies have been dedicated to the effect of the starting graphite material on the resulting GO. Herein, we have prepared two different GOs through chemical exfoliation of graphite materials having different textural and structural characteristics. All samples have been subjected to structural investigations and comprehensive characterizations using Raman, X-ray diffraction, scanning electron microscopy, TGA, N2 physisorption, and FTIR spectroscopy. Our results provide direct evidence of how the crystallite size of the raw graphite affects the oxidation degree, surface functionality, and sheet size of the resulting GO. Building on these significant understandings, the optimized GO achieves a highly specific capacitance of 191 F.g−1 at the specific current of 0.25 A.g−1 in an aqueous electrolyte. This superior electrochemical performance was attributed to several factors, among which the specific surface area was accessible to the electrolyte ions and oxygenated functional groups on the surface, which can significantly modify the electronic structure of graphene and further enhance the surface energy.
Herein, the formulation of safe electrolytes for Li‐ion batteries based on phosphazene as a flame‐retardant (FR) is achieved. Three molecules are studied: hexafluorocyclotriphosphazene (FR1), (ethoxy)pentafluorocyclotriphosphazene (FR2), and pentafluoro(phenoxy)cyclotriphosphazene (FR3). By using a conventional electrolyte (LiPF6 salt in an ethylene carbonate/diethyl carbonate solvents mixture), FR's minimum percentages are defined to quantify their efficiency as FRs. Fluoroethylene carbonate is also added to the electrolyte (2 wt%). The surface tensions, vapor pressures, and transport properties of formulated electrolytes are measured to highlight the impact of the FR additives. Then, these electrolytes are tested in half and full electrochemical devices: Li|LiMn1.5Ni0.5O4 (LMNO) and graphite|LMNO between C/10 and C/2 at 20 °C. Flammability tests show that 3% of FR1, 5% of FR2, or 15% of FR3 are needed to make the electrolytes nonflammable. The transport properties of electrolytes based on FR1 and FR2 remain unchanged compared to the conventional electrolyte. Finally, the graphite|LMNO devices lose only 5% of the initial capacity after 100 cycles with the electrolytes based on FR1 and FR2, hence, confirming the latter's potential as an efficient FR for high‐voltage Li‐ion batteries.
Secondary Zinc-MnO2 batteries represent the climax of aqueous battery technology, earned by their high specific capacity and high-power density. However, Zinc-MnO2 batteries suffer from serious impediments such as capacity fading,...
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