Modified H2 V3 O8 to Enhance the Electrochemical Performance for Li-ion Insertion: The Influence of Prelithiation and Mo-Substitution

Resolving the structure of V3O7·H2O and Mo-substituted V3O7·H2O

Vanadate compounds, such as V₃O₇·H₂O, are of high interest due to their versatile applications as electrode material for metal-ion batteries. In particular, V₃O₇·H₂O can insert different ions such as Li⁺, Na⁺, K⁺, Mg²⁺ and Zn²⁺. In that case, well resolved crystal structure data, such as crystal unit-cell parameters and atom positions, are needed in order to determine the structural information of the inserted ions in the V₃O₇·H₂O structure. In this work, fundamental crystallographic parameters, i.e. atomic displacement parameters, are determined for the atoms in the V₃O₇·H₂O structure. Furthermore, vanadium ions were substituted by molybdenum in the V₃O₇·H₂O structure [(V_2.85Mo_0.15)O₇·H₂O] and the crystallographic positions of the molybdenum ions and their oxidation state are elucidated.

Nanosheet-assembled porous MnCo2O4.5 microflowers as electrode material for hybrid supercapacitors and lithium-ion batteries

Herein, the MnCo₂O_4.5 microflowers (MFs) assembled by two-dimensional (2D) porous nanosheets were prepared through an initial solvothermal reaction with a subsequent annealing process. In this architecture, many interconnected 2D thin nanosheets were self-assembled together to form a 3D hierarchical MF with plenty of open channels. Such structure endows these MnCo₂O_4.5 MFs with large specific surface area of 156.85 m²/g for energy storage and provides rich ion diffusion pathways for ion transportation, thus the as-prepared MFs can exhibit good overall electrochemical performance in both hybrid supercapacitor (HSC) and lithium-ion battery (LIB). For the utilization in supercapacitor, the MFs deliver a specific capacity of 287.02 C/g at 1 A/g as well as a rate capability with 73.3 % capacity retention at 8 A/g. The energy density of the HSC assembled by MFs and activated carbon can reach up to 30.33 W h kg^-1 at 959.35 W kg^-1. When applied as the anode for Li-ion battery, a specific capacity of 1340.8 mA h g^-1 at 0.1 A/g and cycling performance with low capacity loss of 0.73 mAh/g per cycle after 200 cycles at 0.5 A/g can be achieved. This work uncovers a repeatable and facile synthetic strategy to prepare transition metal oxides with large specific surface area and good overall electrochemical property.