Improvements in the Magnesium Ion Transport Properties of Graphene/CNT-Wrapped TiO2 -B Nanoflowers by Nickel Doping

Magnesium-ion batteries are widely studied for its environmentally friendly, low-cost, and high volumetric energy density. In this work, the solvothermal method is used to prepare titanium dioxide bronze (TiO2 -B) nanoflowers with different nickel (Ni) doping concentrations for use in magnesium ion batteries as cathode materials. As Ni doping enhances the electrical conductivity of TiO2 -B and promotes magnesium ion diffusion, the band gap of TiO2 -B host material can be significantly reduced, and as Ni content increases, diffusion contributes more to capacity. According to the electrochemical test, TiO2 -B exhibits excellent electrochemical performance when the Ni element doping content is 2 at% and it is coated with reduced graphene oxide@carbon nanotube (RGO@CNT). At a current density of 100 mA g-1 , NT-2/RGO@CNT discharge specific capacity is as high as 167.5 mAh g-1 , which is 2.36 times of the specific discharge capacity of pure TiO2 -B. It is a very valuable research material for magnesium ion battery cathode materials.

A High Potential Polyanion Cathode Material for Rechargeable Mg-Ion Batteries

The development of Mg-ion batteries is hindered by the lack of cathode materials that allow facile and reversible Mg²⁺ intercalation at high potential. Herein, the authors present a polyanion cathode material of K₂ (VO)₂ (HPO₄ )₂ (C₂ O₄ )⋅4.5H₂ O (KVPCH) for Mg-ion batteries. The inductive effect of polyanions ensures the high redox potential of the vanadium centers. In addition, the material contains structural water located between the layers. It helps with Mg²⁺ desolvation at the electrode-electrolyte interface and facilitates its diffusion in the structure, as confirmed by experimental analysis and theoretical calculations. Thanks to those factors, the KVPCH electrode presents excellent Mg storage capability at room temperature. It delivers 121 mAh g^-1 capacity at 1C with a high average discharge potential of 0.16 V versus Ag/Ag⁺ (3.2 V vs Mg/Mg²⁺ ). A capacity retention of 87% is realized after 1500 cycles at 5C. A rocking-chair Mg-ion full cell is also demonstrated with the KVPCH cathode and a MoO_x anode, which achieves 46 mAh g^-1 capacity (based on the total active material mass of two electrodes). This work would bring effective paths for the design of cathode materials for Mg-ion batteries.

Robust Strategy of Quasi-Solid-State Electrolytes to Boost the Stability and Compatibility of Mg Ion Batteries

Magnesium ion batteries (MIBs) have attracted a lot of attention because of the natural abundance of magnesium, high volumetric energy density, and superior safety. Nevertheless, MIBs are still in their infancy because of the significant challenge in developing a suitable electrolyte with low flammability, high ionic conductivity, and compatibility with the Mg anode. Herein, we construct rechargeable quasi-solid-state MIBs based on tailored polymer electrolytes. The quasi-solid state electrolyte of poly(vinylidene fluoride-co-hexafluoropropylene)-nanosized SiO₂-Mg(TFSI)₂ combines the outstanding dynamic property of a liquid electrolyte and the good stability of a solid-state electrolyte. It exhibits a highly reversible Mg²⁺ deposition-dissolution capability, high ion conductivity (0.83 mS cm^-1), and superior compatibility with the Mg metal and cathode. The quasi-solid-state MIBs with a layered titanic oxide cathode show a high reversible capacity of 129 mA h g^-1 at 50 mA g^-1 (150 W h kg^-1) without any decay after 100 cycles.

Graphene and Lithium-Based Battery Electrodes: A Review of Recent Literature

Graphene is a new generation material, which finds potential and practical applications in a vast range of research areas. It has unrivalled characteristics, chiefly in terms of electronic conductivity, mechanical robustness and large surface area, which allow the attainment of outstanding performances in the material science field. Some unneglectable issues, such as the high cost of production at high quality and corresponding scarce availability in large amounts necessary for mass scale distribution, slow down graphene widespread utilization; however, in the last decade both basic academic and applied industrial materials research have achieved remarkable breakthroughs thanks to the implementation of graphene and related 1D derivatives. In this work, after briefly recalling the main characteristics of graphene, we present an extensive overview of the most recent advances in the development of the Li-ion battery anodes granted by the use of neat and engineered graphene and related 1D materials. Being far from totally exhaustive, due to the immense scientific production in the field yearly, we chiefly focus here on the role of graphene in materials modification for performance enhancement in both half and full lithium-based cells and give some insights on related promising perspectives.

VOPO4·2H2O as a new cathode material for rechargeable Ca-ion batteries

VOPO₄·2H₂O, as a new cathode material for Ca-ion batteries, exhibits a discharge capacity of 100.6 mA h g^-1, excellent cycling stability (200 cycles) and good rate performance (42.7 mA h g^-1 at 200 mA g^-1). In situ X-ray diffraction and in situ Raman results demonstrate the calcium-ion-storage mechanism of VOPO₄·2H₂O is a single-phase reaction based on asymmetric Ca²⁺ insertion and deinsertion.