Sodium-ion batteries are an alternative to lithium-ion batteries for large-scale applications. However, low capacity and poor rate capability of existing anodes are the main bottlenecks to future developments. Here we report a uniform coating of antimony sulphide (stibnite) on graphene, fabricated by a solution-based synthesis technique, as the anode material for sodium-ion batteries. It gives a high capacity of 730 mAh g À 1 at 50 mA g À 1 , an excellent rate capability up to 6C and a good cycle performance. The promising performance is attributed to fast sodium ion diffusion from the small nanoparticles, and good electrical transport from the intimate contact between the active material and graphene, which also provides a template for anchoring the nanoparticles. We also demonstrate a battery with the stibnite-graphene composite that is free from sodium metal, having energy density up to 80 Wh kg À 1 . The energy density could exceed that of some lithium-ion batteries with further optimization.

The subject of sol-gel electrochemistry is introduced, starting with a brief account of milestones in its evolution. Then, the types of sol-gel materials that are useful for electrochemistry are presented, followed by a description of recent advances in the various fields of sol-gel electrochemistry. Modified electrodes, solid electrolytes, electrochromic devices, and corrosion protection coatings are described. Emerging fields such as RuO 2 supercapacitors and electrochemical synthesis of sol-gel precursors are also addressed.

A new approach based on rapid, chemical derivatization in a single phase was used to determine the disproportionation constants and the underlying thermodynamics of inorganic polysulfides in aqueous solutions. This method resolves the dispute over the existence of hexasulfide in aqueous solutions and establishes the presence of even higher polysulfide chains in water. The Gibbs free energies of formation (G(Sn)(o)2-) for the polysulfide species are 77.4, 71.6, 67.4, 66.1, 67.2, 70.5, and 73.6 kJ/mol for n = 2-8, respectively. Our approach is based on single phase, fast methylation of polysulfides with methyl trifluoromethanesulfonate (methyl triflate) and subsequent determination of the dimethylpolysulfides by HPLC. Two independent methods were used in order to confirm quantitative equivalence between the observed distribution of dimethylpolysulfides and the polysulfide distribution in the water: (i) Kinetic studies of each competing reaction step showed that the kinetics of the derivatization are faster than each of the competing reactions that may lead to disproportionation and deviation of the observed distribution of dimethylpolysulfides from that of the aqueous polysulfides. (ii) Determination of isotope mixing during the derivatization of a mixture of two solutions, one containing polysulfide of natural isotopic distribution and the second containing 34S-rich polysulfide revealed that polysulfide mixing during derivatization is rather low. The systematic error due to redistribution of pentasulfide during derivatization is 3% based on isotope dilution tests and less than 5% of total zero-valent sulfur based on kinetic considerations.

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