Effect of vanadium doping on the electrochemical performances of sodium titanate anode for sodium ion battery application

Construction of High-performance Hybrid Supercapacitor Devices by V-doped Flower-like Fe₂(MoO₄)₃ and SnO₂/CNTs

In this work, we present for the first time an innovative strategy to construct high-performance hybrid supercapacitors through the synergistic optimization of vanadium-doped self-supported three-dimensional Flower-like Fe₂(MoO₄)₃ anodes and SnO₂/CNTs composite anodes. The V-doped Fe₂(MoO₄)₃ anode synthesized by a microwave-assisted hydrothermal method combines vanadium doping-induced oxygen vacancies, lattice distortion effects and self-supporting properties of the three-dimensional floral structure, which enhances the specific surface area of the material to 190.58 m2/g, and obtains a high specific capacitance of 2,157 F/g at a current density of 1 A/g, and undergoes a 15 A/g After 10,000 cycles at 15 A/g, the capacitance retention rate is still 98.2 %. To address the limitations of traditional anode materials, SnO₂/CNTs composites significantly reduce the charge transfer resistance (5.61 Ω) and enhance the multiplicity performance by combining the high theoretical capacity of SnO₂ with the three-dimensional conductive network of CNTs. Based on this, the V-Fe₂(MoO₄)₃//SnO₂/CNTs hybrid supercapacitor achieves a high energy density of 151 Wh/kg at 3 A/g, which is a 30-60 % enhancement over the conventional molybdate capacitor, and maintains 96.2 % capacitance stability after 10,000 cycles. This provides a new idea for the development of energy storage devices with high energy density and long cycle life.

Unlocking the Potential of Na2Ti3O7-C Hollow Microspheres in Sodium-Ion Batteries via Template-Free Synthesis

Layered sodium trititanate (Na2Ti3O7) is a promising anode material for sodium-ion batteries due to its suitable charge/discharge plateaus, cost-effectiveness, and eco-friendliness. However, its slow Na+ diffusion kinetics, poor electron conductivity, and instability during cycling pose significant challenges for practical applications. To address these issues, we developed a template-free method to synthesize Na2Ti3O7-C hollow microspheres. The synthesis began with polymerization-induced colloid aggregation to form a TiO2-urea-formaldehyde (TiO2-UF) precursor, which was then subjected to heat treatment to induce inward crystallization, creating hollow cavities within the microspheres. The hollow structure, combined with a conductive carbon matrix, significantly enhanced the cycling performance and rate capability of the material. When used as an anode, the Na2Ti3O7-C hollow microspheres exhibited a high reversible capacity of 188 mAh g-1 at 0.2C and retained 169 mAh g-1 after 500 cycles. Additionally, the material demonstrated excellent rate performance with capacities of 157, 133, 105, 77, 62, and 45 mAh g-1 at current densities of 0.5, 1, 2, 5, 10, and 20C, respectively. This innovative approach provides a new strategy for developing high-performance sodium-ion battery anodes and has the potential to significantly advance the field of energy storage.

Research progress in the preparation of sodium-ion battery anode materials using ball milling

Sodium-ion batteries are regarded as one of the most promising alternatives to lithium-ion batteries due to the greater abundance and lower cost of sodium compared to lithium. However, sodium-ion batteries have not yet been widely adopted. The main reason is that, compared to lithium-ion batteries, sodium-ion batteries have lower energy density and shorter cycle life, with the performance of anode materials directly affecting the energy density and cycle stability of sodium-ion batteries. Notably, ball milling, as an efficient material processing technique, has been widely applied in the preparation and modification of sodium-ion battery anode materials in recent years. This paper reviews the recent progress in the preparation of sodium-ion battery anode materials using ball milling. The process is categorized into ball milling mixing, ball milling exfoliation, ball milling synthesis, and ball milling doping. First, the basic principles and mechanisms of ball milling technology are introduced. Then, the preparation of different types of sodium-ion battery anode materials is discussed based on four specific categories. For various material systems, the effects of ball milling on the structure, morphology, and electrochemical performance are discussed. Additionally, the advantages and challenges of using ball milling in the preparation of sodium-ion battery anode materials are summarized. Finally, the future directions and development trends in the preparation of sodium-ion battery anode materials using ball milling are forecasted, aiming to provide insights and references for further research in this field.

Improving Low-temperature Performance and Stability of Na2 Ti6 O13 Anodes by the Ti-O Spring Effect through Nb-doping

Na2 Ti6 O13 (NTO) with high safety has been regarded as a promising anode candidate for sodium-ion batteries. In the present study, integrated modification of migration channels broadening, charge density re-distribution, and oxygen vacancies regulation are realized in case of Nb-doping and have obtained significantly enhanced cycling performance with 92 % reversible capacity retained after 3000 cycles at 3000 mA g-1 . Moreover, unexpected low-temperature performance with a high discharge capacity of 143 mAh g-1 at 100 mA g-1 under -15 °C is also achieved in the full cell. Theoretical investigation suggests that Nb preferentially replaces Ti3 sites, which effectively improves structural stability and lowers the diffusion energy barrier. What's more important, both the in situ X-ray diffraction (XRD) and in situ Raman furtherly confirm the robust spring effect of the Ti-O bond, making special charge compensation mechanism and respective regulation strategy to conquer the sluggish transport kinetics and low conductivity, which plays a key role in promoting electrochemical performance.

Low-content SnO2 nanodots on N-doped graphene: lattice-confinement preparation and high-performance lithium/sodium storage

Rational construction of nanosized anode nanomaterials is crucial to enhance the electrochemical performance of lithium-/sodium-ion batteries (LIBs/SIBs). Various anode nanoparticles are created mainly via templating surface confinement, or encapsulation within precursors (such as metal-organic frameworks). Herein, low-content SnO₂ nanodots on N-doped reduced graphene oxide (SnO₂@N-rGO) were prepared as anode nanomaterials for LIBs and SIBs, via a distinctive lattice confinement of a CoAlSn-layered double hydroxide (CoAlSn-LDH) precursor. The SnO₂@N-rGO composite exhibits the advantagous features of low-content (17.9 wt%) and uniform SnO₂ nanodots (3.0 ± 0.5 nm) resulting from the lattice confinement of the Co and Al species to the surrounded Sn within the same crystalline layer, and high-content conductive rGO. The SnO₂@N-rGO composite delivers a highly reversible capacity of 1146.2 mA h g^-1 after 100 cycles at 0.1 A g^-1 for LIBs, and 387 mA h g^-1 after 100 cycles at 0.1 A g^-1 for SIBs, outperforming N-rGO. Furthermore, the dominant capacitive contribution and the rapid electronic and ionic transfer, as well as small volume variation, all give rise to the enhancement. Precursor-based lattice confinement could thus be an effective strategy for designing and preparing uniform nanodots as anode nanomaterials for electrochemical energy storage.