701 research outputs found
Low-cost synthesis route for high-performance S/C composite with 90% S content
No full textLithium-sulfur (Li-S) batteries offer a high theoretical energy density of 2567 W?h?kg???1 by the multi-electron-transfer cathode reaction between elemental sulfur and lithium ions, and are a focus of post lithium-ion batteries technology1. Yet, there are challenging obstacles standing in the way of the large-scale application of the Li-S technology in the market, which include the potential safety risky of Li- dendrite formation, low electrical conductivity of sulfur (5*10???30 S?cm???1 at 25 ??C), the dissolution of the charge/discharge intermediates, polysulfides (Li2Sx, 4 ??? x ??? 8) in the electrolyte, and the volume change of the sulfur during lithiation/delithiation (~80%)2. Carbon materials are commonly used as the host to accommodate sulfur to address the issues relevant to the sulfur-cathode owning to their diversity, conductivity, robust stability and chemistry, and their ready abundance and cost3. A carbon host with sulfur nanoparticles adhered can conduct electrons generated by sulfur lithiation/delithiation, limit the dissolution of polysulfides, and withstand the volume change of the sulfur; it therefore can provide an improved specific capacity, rate capability, and cyclic life. However, these improvements are closely connected to both the mass ratio of sulfur in such a sulfur/carbon composite and the areal loading density of sulfur in the cathode. Higher mass ratio and areal loading density of sulfur are favored for practical Li- S battery application, but are usually accompanied by lower???sulfur utility???that yields reduced specific capacity, rate capability, and cycle life.clos
Synthesis and characterization of chemically modified graphenes
No full textThis review documents our contributions to the synthesis of chemically-modified graphene (CMG) materials. We focus on methods for the preparation of homogenous colloidal suspensions of CMGs and procedures for the chemical reduction of graphene oxide, along with techniques for the structural elucidation of graphene oxide and reduced graphene oxide materials. We conclude with an outline of the persisting chemical challenges and current limitations of practical applications.close
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