We report a facile strategy to synthesize the nanocomposite of Co3O4 nanoparticles anchored on conducting graphene as an advanced anode material for high-performance lithium-ion batteries. The Co3O4 nanoparticles obtained are 10−30 nm in size and homogeneously anchor on graphene sheets as spacers to keep the neighboring sheets separated. This Co3O4/graphene nanocomposite displays superior Li-battery performance with large reversible capacity, excellent cyclic performance, and good rate capability, highlighting the importance of the anchoring of nanoparticles on graphene sheets for maximum utilization of electrochemically active Co3O4 nanoparticles and graphene for energy storage applications in high-performance lithium-ion batteries.

Polysulfide binding and trapping to prevent dissolution into the electrolyte by a variety of materials has been well studied in Li−S batteries. Here we discover that some of those materials can play an important role as an activation catalyst to facilitate oxidation of the discharge product, Li 2 S, back to the charge product, sulfur. Combining theoretical calculations and experimental design, we select a series of metal sulfides as a model system to identify the key parameters in determining the energy barrier for Li 2 S oxidation and polysulfide adsorption. We demonstrate that the Li 2 S decomposition energy barrier is associated with the binding between isolated Li ions and the sulfur in sulfides; this is the main reason that sulfide materials can induce lower overpotential compared with commonly used carbon materials. Fundamental understanding of this reaction process is a crucial step toward rational design and screening of materials to achieve high reversible capacity and long cycle life in Li−S batteries. T he ever-increasing demand for energy storage devices with high energy density, low material cost, and long cycle life has driven the development of new battery systems beyond the currently dominant lithium ion batteries (LIBs) (1). Among alternative battery chemistries, lithium−sulfur (Li−S) batteries have attracted remarkable attention due to their high theoretical energy density of 2,600 watt hours per kilogram, 5 times higher than those of state-of-the-art LIBs (2-4). In addition, sulfur, as a byproduct of the petroleum refining process, is naturally abundant, inexpensive, and environmentally friendly (5). However, the practical application of Li−S batteries is still plagued with numerous challenges. For example, the insulating nature of sulfur and discharge products Li 2 S/Li 2 S 2 leads to low active material utilization. In addition, the easy dissolution of lithium polysulfides (LiPSs) into the electrolyte causes LiPSs shuttling between cathode and anode and uncontrollable deposition of sulfide species on the lithium metal anode, inducing fast capacity fading and low coulombic efficiency (2, 6).Tremendous efforts have been taken to circumvent these concerns, with the nanostructuring of electrodes as one of the most effective approaches to overcoming the issues facing highcapacity electrode materials (2, 7). For example, the integration of nanostructured carbon materials with sulfur is one of the primary strategies for improving the electrical conductivity of the composites and suppression of polysulfide shuttling through physical confinement (8-14). However, it was first recognized by Zheng et al. (11) that the weak interaction between nonpolar carbon-based materials and polar LiPSs/Li 2 S species leads to weak confinement and easy detachment of LiPSs from the carbon surface, with further diffusion into the electrolyte causing capacity decay and poor rate performance. Therefore, the introduction of heteroatoms into carbonaceous materials (such as nitrogen, oxygen, boron, phosphorous, sulfur, or ...

We developed two-step solution-phase reactions to form hybrid materials of Mn 3 O 4 nanoparticles on reduced graphene oxide (RGO) sheets for lithium ion battery applications. Mn 3 O 4 nanoparticles grown selectively on RGO sheets over free particle growth in solution allowed for the electrically insulating Mn 3 O 4 nanoparticles wired up to a current collector through the underlying conducting graphene network. The Mn 3 O 4 nanoparticles formed on RGO show a high specific capacity up to ~900mAh/g near its theoretical capacity with good rate capability and cycling stability, owing to the intimate interactions between the graphene substrates and the Mn 3 O 4 nanoparticles grown atop. The Mn 3 O 4 /RGO hybrid could be a promising candidate material for high-capacity, low-cost, and environmentally friendly anode for lithium ion batteries. Our growth-on-graphene approach should offer a new technique for design and synthesis of battery electrodes based on highly insulating materials.

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Lithium–sulfur batteries have attracted attention due to their six-fold specific energy compared with conventional lithium-ion batteries. Dissolution of lithium polysulfides, volume expansion of sulfur and uncontrollable deposition of lithium sulfide are three of the main challenges for this technology. State-of-the-art sulfur cathodes based on metal-oxide nanostructures can suppress the shuttle-effect and enable controlled lithium sulfide deposition. However, a clear mechanistic understanding and corresponding selection criteria for the oxides are still lacking. Herein, various nonconductive metal-oxide nanoparticle-decorated carbon flakes are synthesized via a facile biotemplating method. The cathodes based on magnesium oxide, cerium oxide and lanthanum oxide show enhanced cycling performance. Adsorption experiments and theoretical calculations reveal that polysulfide capture by the oxides is via monolayered chemisorption. Moreover, we show that better surface diffusion leads to higher deposition efficiency of sulfide species on electrodes. Hence, oxide selection is proposed to balance optimization between sulfide-adsorption and diffusion on the oxides.