Highly compacted TiO2/C micospheres via in-situ surface-confined intergrowth with ultra-long life for reversible Na-ion storage

Recent progress in high-voltage P2-Na x TMO2 materials and their future perspectives

P2-type layered materials (Na x TMO2) have become attractive cathode electrodes owing to their high theoretical energy density and simple preparation. However, they still face severe phase transition and low conductivity. Current research on Na x TMO2 is mostly focused on the modification of bulk materials, and the application performances have been infrequently addressed. This review summarizes the information on current common P2-Na x TMO2 materials and discusses their sodium-storage mechanisms. Furthermore, modification strategies to improve their performance are addressed for practical applications based on a range of key parameters (output voltage, specific capacity, and lifespan). We also discuss the future development trends and application prospects for P2 cathode materials.

Microwave-Assisted Rational Designed CNT-Mn3 O4 /CoWO4 Hybrid Nanocomposites for High Performance Battery-Supercapacitor Hybrid Device

Extensive research interest in hybrid battery-supercapacitor (BSH) devices have led to the development of cathode materials with excellent comprehensive electrochemical properties. In this work, carbon nanotube (CNT)-Mn3 O4 /CoWO4 triple-segment hybrid electrode is synthesized by using a two-step microwave-assisted hydrothermal route. Systematic physical characterization revealed that, with the assistance of microwave, granular Mn3 O4 and spheroid-like CoWO4 with preferred orientation, and oxygen vacancies are stacked or arranged on CNTs skeletons to construct a rational designed hybrid nanocomposite with abundant heterointerfaces and interfacial chemical bonds. Electrochemical evaluations show that the synergistic cooperation in CNT-Mn3 O4 /CoWO4 resulted in an ultra-high specific capacity (1907.5 C g-1 /529.8 mA h g-1 at 1 A g-1 ), a wide operating voltage window (1.15 V), the satisfactory rate capability (capacity maintained at 1016.5 C g-1 /282.3 mA h g-1 at 15 A g-1 ), and excellent cycling stability (117.2% initial capacity retention after 13000 cycles at 15 A g-1 ). In addition, the assembled CNT-Mn3 O4 /CoWO4 //N doped porous carbon (NC) BSH device delivered a stable working voltage of 2.05 V and superior energy density of 67.5 Wh kg-1 at power density of 1025 W kg-1 , as well as excellent stability (92.2% capacity retained at 5 A g-1 for 12600 cycles). This work provides a new and feasible tactic to develop high-performance transition metal oxide-based cathodes for advanced BSH devices.

Application of Synthesized Vanadium-Titanium Oxide Nanocomposite to Eliminate Rhodamine-B Dye from Aqueous Medium

In this study, a V@TiO₂ nanocomposite is examined for its ability to eliminate carcinogenic Rhodamine (Rh-B) dye from an aqueous medium. A simple ultrasonic method was used to produce the nanosorbent. In addition, V@TiO₂ was characterized using various techniques, including XRD, HRTEM, XPS, and FTIR. Batch mode studies were used to study the removal of Rh-B dye. In the presence of pH 9, the V@TiO₂ nanocomposite was able to remove Rh-B dye to its maximum extent. A correlation regression of 0.95 indicated that the Langmuir model was a better fit for dye adsorption. Moreover, the maximum adsorption capacity of the V@TiO₂ nanocomposite was determined to be 158.8 mg/g. According to the thermodynamic parameters, dye adsorption followed a pseudo-first-order model. Based on the results of the study, a V@TiO₂ nanocomposite can be reused for dye removal using ethanol.

Metal-organic framework derived vanadium-doped TiO2@carbon nanotablets for high-performance sodium storage

Titanium dioxide (TiO₂) as a potential anode material for sodium-ion batteries (SIBs) suffers from the intrinsic poor electronic conductivity and sluggish ionic diffusivity, thus usually leading to the inferior electrochemical performance. Herein, we demonstrate a facile strategy to enhance the sodium storage performance of TiO₂via vanadium (V) doping, using the pre-synthesized V-doped Ti-based metal-organic framework (MOF, MIL-125) as the precursor, which can be converted into the V-doped TiO₂ with simultaneous carbon hybridization and controlled V-doping amount (denote as V_xTiO₂@C, where × represents the V/Ti molar ratio (R_V/Ti)). V-doping not only affects the morphology of the MIL-125 changing from thick to thin nanotablets, but also greatly enhances the electrochemical performance of the V_xTiO₂@C. When used as an anode for SIBs, the V_0.1TiO₂@C exhibits a much higher reversible capacity of 211 mAh/g than that for the undoped TiO₂@C (only 156 mAh/g) after 150 cycles at 100 mA/g. Even after high-rate long-term cycling, the V_0.1TiO₂@C can still display a capacity of 180 mAh/g with a high capacity retention of 137% at 1000 mA/g after 4500 cycles. Structural/electrochemical measurements reveal that V-doping induces the formation of oxygen vacancies as well as Ti³⁺ species, which efficiently improve the electric conductivity and the ion diffusivity of the electrode. Meanwhile, the thinner V_0.1TiO₂@C nanotablets with porous structure and carbon hybridization could facilitate the ion/electron transfer with shortened diffusion pathways.

Dual Doping of Titania for Enhanced Na Storage Performance

The sluggish sodium-ion diffusion kinetics and low electronic conductivity have severely restricted the development of the TiO₂ anode for sodium-ion batteries. Defect engineering, such as single-heteroatom doping and oxygen vacancies, has proven to be effective methods to improve the conductivity of TiO₂, but a comprehensive understanding of the synergistic effect of dual-heteroatom doping and oxygen vacancies on the sodium storage performance of TiO₂ is still lacking. Herein, we design a synergistic strategy of dual doping via the in situ doping and hydrogenation treatment to improve conductivity and cycling stability of TiO₂. Experiments and theoretical calculations together revealed that N and C doping reduces the band gap of TiO₂, while the presence of oxygen vacancies efficiently accelerates the diffusion of sodium ions. Thus N, C, and oxygen vacancies with high concentration co-doped TiO₂, resulting in extraordinary high-rate performance, significant stable cycling, and long-term cyclability of up to 10,000 cycles. The synthesis strategy of dual doping proposed here emphasizes the importance of defect engineering in improving material conductivity and electrode cycling stability for possible practical applications in the near future.