Mg₂VO₄/VO₂ Nanocomposites as Aqueous Zinc Ion Battery Cathodes with High Capacity and High Ion Diffusion Rate

As one of the representative vanadium-based electrode materials for aqueous zinc ion batteries (AZIBs), VO2(B) owns excellent cycling stability and specific capacity, but the strong interlattice interactions lead to poor rate performance. Herein, multiphase, high ion diffusion rate Mg2VO4/VO2 (MVO/VO) heterostructures composed of nanoparticles were introduced and constructed based on a solid preinsertion method. The electrochemical results show that the MVO/VO electrode has excellent cycling stability and impressively high capacity and ion diffusion rate compared with pure VO2(B) (VO) and Mg2VO4 (MVO). Moreover, the reversible capacity of MVO/VO is found to be 393.6 mA h g–1 at a relatively low current density (0.3 A g–1). The MVO/VO electrode still exhibits a capacity retention of 83.6% even after 1000 charge/discharge applications, which indicates a stable performance. Finally, this contribution offers insights into the design of high-capacity and high ion diffusion rate AZIB cathode materials

Facile Synthesis of Na_0.33V₂O₅ Nanosheet-Graphene Hybrids as Ultrahigh Performance Cathode Materials for Lithium Ion Batteries

Na_0.33V₂O₅ nanosheet-graphene hybrids were successfully fabricated for the first time via a two-step route involving a novel hydrothermal method and a freeze-drying technique. Uniform Na_0.33V₂O₅ nanosheets with a thickness of about 30 nm are well-dispersed between graphene layers. The special sandwich-like nanostructures endow the hybrids with high discharge capacity, good cycling stability, and superior rate performance as cathodes for lithium storage. Desirable discharge capacities of 313, 232, 159, and 108 mA·h·g^–1 can be delivered at 0.3, 3, 6, and 9 A·g^–1, respectively. Moreover, the Na_0.33V₂O₅-graphene hybrids can maintain a high discharge capacity of 199 mA·h·g^–1 after 400 cycles even at an extremely high current density of 4.5 A·g^–1, with an average fading rate of 0.03% per cycle

Self-Assembly of Parallelly Aligned NiO Hierarchical Nanostructures with Ultrathin Nanosheet Subunits for Electrochemical Supercapacitor Applications

Parallelly aligned NiO hierarchical nanostructures were fabricated using a templated self-assembly method followed by calcinations, where rationally employed pluronic triblock copolymers (P123) are acting as molecular templates for geometrical manipulation of nanocrystals and short-chain alcohols are acting as cosolvents and cosurfactants. Such aligned nanostructure is constructed orderly with several ultrathin two-dimensional (2D) nanosheet subunits with an exceptionally small thickness of only 3 nm in a high degree of orientation and separation. Moreover, the number of assembled nanosheets in a unit can be tuned by changing the concentration of the involving P123. This is the first time to synthesize highly hierarchically ordered and bilaterally symmetrical nanostructures, distributed in diameter of around 200–300 nm, via self-assembly in the liquid phase without solid substrates. The as-synthesized NiO delivered high capacitances of 418 F/g at the current density of 2 A/g with well cycling stability (still maintained 85% after 2000 cycles) and 333 F/g at 10 A/g in rates performance after 60 cycles. These fine electrochemical performances are supposed to be attributed to the hierarchical structures with high specific surface area (SSA, ∼164.87 m²/g) and ordered multilevel mesopores, which facilitate the electrolyte accessibility and provide more active sites for redox reaction

Novel Amorphous MoS₂/MoO₃/Nitrogen-Doped Carbon Composite with Excellent Electrochemical Performance for Lithium Ion Batteries and Sodium Ion Batteries

A novel amorphous MoS₂/MoO₃/nitrogen-doped carbon composite has been successfully synthesized for the first time. The synthesis strategy only involves a facile reaction that partially sulfurizes organic–inorganic hybrid material Mo₃O₁₀ (C₂H₁₀N₂) (named as MoO_<i>x</i>/ethylene­diamine) nanowire precursors at low temperature (300 °C). It is more interesting that such amorphous composites as lithium ion battery (LIB) and sodium ion battery (SIB) anode electrodes showed much better electrochemical properties than those of most previously reported molybdenum-based materials with crystal structure. For example, the amorphous composite electrode for LIBs can reach up to 1253.3 mA h g^–1 at a current density of 100 mA g^–1 after 50 cycles and still retain 887.5 mA h g^–1 at 1000 mA g^–1 after 350 cycles. Similarly, for SIBs, it also retains 538.7 mA h g^–1 after 200 cycles at 300 mA g^–1 and maintains 339.9 mA h g^–1 at 1000 mA g^–1 after 220 cycles, corresponding to a capacity retention of nearly 100%. In addition, the amorphous composite electrode exhibits superior rate performance for LIBs and SIBs. Such superior electrochemical performance may be attributed to the following: (1) The carbonaceous matrix can enhance the conductivity of the amorphous composite. (2) Heteroatom, such as N, doping within this unique compositional feature can increase the active ion absorption sites on the amorphous composite surface benefitting the insertion/extraction of lithium/sodium ions. (3) The hybrid nanomaterials could provide plenty of diffusion channels for ions during the insertion/extraction process. (4) The 1D chain structure reduces the transfer distance of lithium/sodium ions into/from the electrode