Superior Lithium-Ion Storage Properties of Mesoporous CuO-Reduced Graphene Oxide Composite Powder Prepared by a Two-Step Spray-Drying Process

Sintering- and oxidation-resistant ultrasmall Cu(I)/(II) oxides supported on defect-rich mesoporous alumina microspheres boosting catalytic ozonation

Supported copper oxides with well-dispersed metal species, small size, tunable valence and high stability are highly desirable in catalysis. Herein, novel copper oxide (CuO_x) catalysts supported on defect-rich mesoporous alumina microspheres are developed using a spray-drying-assisted evaporation induced self-assembly method. The catalysts possess a special structure composed of a mesoporous outer layer, a mesoporous-nanosphere-stacked under layer and a hollow cavity. Because of this special structure and the defective nature of the alumina support, the CuO_x catalysts are ultrasmall in size (1 ~ 3 nm), bivalent with a very high Cu⁺/Cu²⁺ ratio (0.7), and highly stable against sintering and oxidation at high temperatures (up to 800 °C), while the wet impregnation method results in CuO_x catalysts with much larger sizes (~15 nm) and lower the Cu⁺/Cu²⁺ ratios (~0.29). The catalyst formation mechanism through the spray drying method is proposed and discussed. The catalysts show remarkable performance in catalytic ozonation of phenol wastewaters. With high-concentration phenol (250 ppm) as the model organic pollutant, the optimized catalyst delivers promising catalytic performance with 100% phenol removal and 53% TOC removal in 60 min, and a high cyclic stability. Superoxide anion free radicals (⋅O₂^-), singlet oxygen (¹O₂) and hydroxyl radicals (⋅OH) are the predominant reactive species. A detailed structure-performance study reveals the surface hydroxyl groups and Cu⁺/Cu²⁺ redox couples play cooperatively to accelerate O₃ decomposition generating reactive radicals. The plausible catalytic O₃ decomposition mechanism is proposed and discussed with supportive evidences.

Advances in the synthesis and design of nanostructured materials by aerosol spray processes for efficient energy storage

The increasing demand for energy storage has motivated the search for highly efficient electrode materials for use in rechargeable batteries with enhanced energy density and longer cycle life. One of the most promising strategies for achieving improved battery performance is altering the architecture of nanostructured materials employed as electrode materials in the energy storage field. Among numerous synthetic methods suggested for the fabrication of nanostructured materials, aerosol spray techniques such as spray pyrolysis, spray drying, and flame spray pyrolysis are reliable, as they are facile, cost-effective, and continuous processes that enable the synthesis of nanostructured electrode materials with desired morphologies and compositions with controlled stoichiometry. The post-treatment of spray-processed powders enables the fabrication of oxide, sulfide, and selenide nanostructures hybridized with carbonaceous materials including amorphous carbon, reduced graphene oxide, carbon nanotubes, etc. In this article, recent progress in the synthesis of nanostructured electrode materials by spray processes and their general formation mechanisms are discussed in detail. A brief introduction to the working principles of each spray process is given first, and synthetic strategies for the design of electrode materials for lithium-ion, sodium-ion, lithium-sulfur, lithium-selenium, and lithium-oxygen batteries are discussed along with some examples. This analysis sheds light on the synthesis of nanostructured materials by spray processes and paves the way toward the design of other novel and advanced nanostructured materials for high performance electrodes in rechargeable batteries of the future.

Nanostructural Uniformity of Ordered Mesoporous Materials: Governing Lithium Storage Behaviors

Nanostructured materials make a considerable impact on the performance of lithium-storage characteristics in terms of the energy density, power density, and cycle life. Direct experimental observation, by a comparison of controlled nanostructural uniformity of electrode materials, reveals that the lithium-storage behaviors of mesoporous MoO₂ and CuO electrodes are linearly correlated with their nanostructural uniformity. Reversible capacities of mesoporous MoO₂ and CuO electrodes with well-developed nanostructures (1569 mA h g^-1 for MoO₂ and 1029 mA h g^-1 for CuO) exceed their theoretical capacity based on the conversion reaction (838 mA h g^-1 for MoO₂ and 674 mA h g^-1 for CuO). Given that exact understanding of the origin of the additional capacity is essential in maximizing the energy density of electrode material, this work may help to gain some insights into the development of high energy-density lithium-storage materials for next-generation lithium rechargeable batteries.

Spray-Drying of Electrode Materials for Lithium- and Sodium-Ion Batteries

The performance of electrode materials in lithium-ion (Li-ion), sodium-ion (Na-ion) and related batteries depends not only on their chemical composition but also on their microstructure. The choice of a synthesis method is therefore of paramount importance. Amongst the wide variety of synthesis or shaping routes reported for an ever-increasing panel of compositions, spray-drying stands out as a versatile tool offering demonstrated potential for up-scaling to industrial quantities. In this review, we provide an overview of the rapidly increasing literature including both spray-drying of solutions and spray-drying of suspensions. We focus, in particular, on the chemical aspects of the formulation of the solution/suspension to be spray-dried. We also consider the post-processing of the spray-dried precursors and the resulting morphologies of granules. The review references more than 300 publications in tables where entries are listed based on final compound composition, starting materials, sources of carbon etc.

Design and Synthesis of Spherical Multicomponent Aggregates Composed of Core-Shell, Yolk-Shell, and Hollow Nanospheres and Their Lithium-Ion Storage Performances

Micrometer-sized spherical aggregates of Sn and Co components containing core-shell, yolk-shell, hollow nanospheres are synthesized by applying nanoscale Kirkendall diffusion in the large-scale spray drying process. The Sn₂ Co₃ -Co₃ SnC_0.7 -C composite microspheres uniformly dispersed with Sn₂ Co₃ -Co₃ SnC_0.7 mixed nanocrystals are formed by the first-step reduction of spray-dried precursor powders at 900 °C. The second-step oxidation process transforms the Sn₂ Co₃ -Co₃ SnC_0.7 -C composite into the porous microsphere composed of Sn-Sn₂ Co₃ @CoSnO₃ -Co₃ O₄ core-shell, Sn-Sn₂ Co₃ @CoSnO₃ -Co₃ O₄ yolk-shell, and CoSnO₃ -Co₃ O₄ hollow nanospheres at 300, 400, and 500 °C, respectively. The discharge capacity of the microspheres with Sn-Sn₂ Co₃ @CoSnO₃ -Co₃ O₄ core-shell, Sn-Sn₂ Co₃ @CoSnO₃ -Co₃ O₄ yolk-shell, and CoSnO₃ -Co₃ O₄ hollow nanospheres for the 200^th cycle at a current density of 1 A g^-1 is 1265, 987, and 569 mA h g^-1 , respectively. The ultrafine primary nanoparticles with a core-shell structure improve the structural stability of the porous-structured microspheres during repeated lithium insertion and desertion processes. The porous Sn-Sn₂ Co₃ @CoSnO₃ -Co₃ O₄ microspheres with core-shell primary nanoparticles show excellent cycling and rate performances as anode materials for lithium-ion batteries.

Synthesis of carbon nanotube (CNT)-entangled CuO nanotube networks via CNT-catalytic growth and in situ thermal oxidation as additive-free anodes for lithium ion batteries

We demonstrated the utility of carbon nanotubes (CNTs) as a catalyst and conductive agent to synthesize CNT-entangled copper nanowire (CuNW-CNT) networks within a melted mixture of hexadecylamine and cetyltrimethy ammounium bromide. The CuNW-CNT networks were further in situ thermally oxidized into CuO nanotube-CNT (CuONT-CNT) with the high retention of network structure. The binder- and conducting-additive-free anodes constructed using the CuONT-CNT networks exhibited high performance, such as high capability (557.7 mAh g^-1 at 0.2 °C after 200 cycles), high Coulombic efficiency (near 100%), good rate performance (385.5 mAh g^-1 at 5 °C and 310.3 mAh g^-1 at 10 °C), and long cycling life.

Preparation of Advanced CuO Nanowires/Functionalized Graphene Composite Anode Material for Lithium Ion Batteries

The copper oxide (CuO) nanowires/functionalized graphene (f-graphene) composite material was successfully composed by a one-pot synthesis method. The f-graphene synthesized through the Birch reduction chemistry method was modified with functional group “–(CH₂)₅COOH”, and the CuO nanowires (NWs) were well dispersed in the f-graphene sheets. When used as anode materials in lithium-ion batteries, the composite exhibited good cyclic stability and decent specific capacity of 677 mA·h·g⁻¹ after 50 cycles. CuO NWs can enhance the lithium-ion storage of the composites while the f-graphene effectively resists the volume expansion of the CuO NWs during the galvanostatic charge/discharge cyclic process, and provide a conductive paths for charge transportation. The good electrochemical performance of the synthesized CuO/f-graphene composite suggests great potential of the composite materials for lithium-ion batteries anodes.

Self-assembly of porous CuO nanospheres decorated on reduced graphene oxide with enhanced lithium storage performance

A Li full cell assembled by porous CuO-NSs/RGO anode and commercial LiFPO₄ cathode can light up an LED lamp.

Li(V0.5Ti0.5)S2 as a 1 V lithium intercalation electrode

Graphite, the dominant anode in rechargeable lithium batteries, operates at ∼0.1 V versus Li⁺/Li and can result in lithium plating on the graphite surface, raising safety concerns. Titanates, for example, Li₄Ti₅O₁₂, intercalate lithium at∼1.6 V versus Li⁺/Li, avoiding problematic lithium plating at the expense of reduced cell voltage. There is interest in 1 V anodes, as this voltage is sufficiently high to avoid lithium plating while not significantly reducing cell potential. The sulfides, LiVS₂ and LiTiS₂, have been investigated as possible 1 V intercalation electrodes but suffer from capacity fading, large 1st cycle irreversible capacity or polarization. Here we report that the 50/50 solid solution, Li_1+x(V_0.5Ti_0.5)S₂, delivers a reversible capacity to store charge of 220 mAhg⁻¹ (at 0.9 V), 99% of theoretical, at a rate of C/2, retaining 205 mAhg⁻¹ at C-rate (92% of theoretical). Rate capability is excellent with 200 mAhg⁻¹ at 3C. C-rate is discharge in 1 h. Polarization is low, 100 mV at C/2. To the best of our knowledge, the properties/performances of Li(V_0.5Ti_0.5)S₂ exceed all previous 1 V electrodes.

Lithium sulfides have been previously investigated as 1 V anodes for Li-ion batteries, but suffered from significant performance issues. Here, the authors report on a 1 V lithium sulfide electrode with noteworthy performance, demonstrating that sulfide-based electrodes may merit further exploration.

In situ synthesis of hierarchical CoFe2O4 nanoclusters/graphene aerogels and their high performance for lithium-ion batteries

In this article, we demonstrate a simple solvothermal method towards in situ growth of hierarchical CoFe₂O₄ nanoclusters on graphene aerogels (GAs). The CoFe₂O₄/GAs electrode exhibits high specific capacity, excellent cycling stability and superior rate capabilities in both half and full cells.