Tunable Synthesis of Hierarchical Yolk/Double-Shelled SiOx @TiO2 @C Nanospheres for High-Performance Lithium-Ion Batteries

This work reports the preparation of unique hierarchical yolk/double-shelled SiO_x @TiO₂ @C nanospheres with different voids by a facile sol-gel method combined with carbon coating. In the preparation process, SiO_x nanosphere is used as a hard template. Etch time of SiO_x yolk affects the morphology and electrochemical performance of SiO_x @TiO₂ @C. With the increase in etch time, the yolk/double-shelled SiO_x @TiO₂ @C with 15 and 30 nm voids and the TiO₂ @C hollow nanospheres are obtained. The yolk/double-shelled SiO_x @TiO₂ @C nanospheres exhibit remarkable lithium-ion battery performance as anodes, including high lithium storage capacity, outstanding rate capability, good reversibility, and stable long-term cycle life. The unique structure can accommodate the large volume change of the SiO_x yolk, provide a unique buffering space for the discharge/charge processes, improve the structural stability of the electrode material during repeated Li⁺ intercalation/deintercalation processes, and enhance the cycling stability. The SiO_x @TiO₂ @C with 30 nm void space exhibits a high discharge specific capacity of ≈1195.4 mA h g^-1 at the current density of 0.1 A g^-1 after 300 cycles and ≈701.1 mA h g^-1 at 1 A g^-1 for over 800 cycles. These results suggest that the proposed particle architecture is promising and may have potential applications in improving various high performance anode materials.

Binder-Free Electrodes and Their Application for Li-Ion Batteries

Lithium-ion batteries (LIB) as energy supply and storage systems have been widely used in electronics, electric vehicles, and utility grids. However, there is an increasing demand to enhance the energy density of LIB. Therefore, the development of new electrode materials with high energy density becomes significant. Although many novel materials have been discovered, issues remain as (1) the weak interaction and interface problem between the binder and the active material (metal oxide, Si, Li, S, etc.), (2) large volume change, (3) low ion/electron conductivity, and (4) self-aggregation of active materials during charge and discharge processes. Currently, the binder-free electrode serves as a promising candidate to address the issues above. Firstly, the interface problem of the binder and active materials can be solved by fixing the active material directly to the conductive substrate. Secondly, the large volume expansion of active materials can be accommodated by the porosity of the binder-free electrode. Thirdly, the ion and electron conductivity can be enhanced by the close contact between the conductive substrate and the active material. Therefore, the binder-free electrode generally exhibits excellent electrochemical performances. The traditional manufacture process contains electrochemically inactive binders and conductive materials, which reduces the specific capacity and energy density of the active materials. When the binder and the conductive material are eliminated, the energy density of the battery can be largely improved. This review presents the preparation, application, and outlook of binder-free electrodes. First, different conductive substrates are introduced, which serve as carriers for the active materials. It is followed by the binder-free electrode fabrication method from the perspectives of chemistry, physics, and electricity. Subsequently, the application of the binder-free electrode in the field of the flexible battery is presented. Finally, the outlook in terms of these processing methods and the applications are provided.

Effect of Ni Doping Content on Phase Transition and Electrochemical Performance of TiO2 Nanofibers Prepared by Electrospinning Applied for Lithium-Ion Battery Anodes

Titanium dioxide (TiO₂), as a potential anode material applied for lithium-ion batteries (LIBs), is constrained due to its poor theoretical specific capacity (335 mAh·g⁻¹) and low conductivity (10⁻⁷-10⁻⁹ S·cm⁻¹). When compared to TiO₂, NiO with a higher theoretical specific capacity (718 mAh·g⁻¹) is regarded as an alternative dopant for improving the specific capacity of TiO₂. The present investigations usually assemble TiO₂ and NiO with a simple bilayer structure and without NiO that is immersed into the inner of TiO₂, which cannot fully take advantage of NiO. Therefore, a new strategy was put forward to utilize the synergistic effect of TiO₂ and NiO, namely doping NiO into the inner of TiO₂. NiO-TiO₂ was fabricated into the nanofibers with a higher specific surface area to further improve their electrochemical performance due to the transportation path being greatly shortened. NiO-TiO₂ nanofibers are expected to replace of the commercialized anode material (graphite). In this work, a facile one-step electrospinning method, followed by annealing, was applied to synthesize the Ni-doped TiO₂ nanofibers. The Ni doping content was proven to be a crucial factor affecting phase constituents, which further determined the electrochemical performance. When the Ni doping content was less than 3 wt.%, the contents of anatase and NiO were both increased, while the rutile content was decreased in the nanofibers. When the Ni doping content exceeded 3 wt.%, the opposite changes were observed. Hence, the optimum Ni doping content was determined as 3 wt.%, at which the highest weight fractions of anatase and NiO were obtained. Correspondingly, the obtained electronic conductivity of 4.92 × 10⁻⁵ S⋅cm⁻¹ was also the highest, which was approximately 1.7 times that of pristine TiO₂. The optimal electrochemical performance was also obtained. The initial discharge and charge specific capacity was 576 and 264 mAh·g⁻¹ at a current density of 100 mA·g⁻¹. The capacity retention reached 48% after 100 cycles, and the coulombic efficiency was about 100%. The average discharge specific capacity was 48 mAh·g⁻¹ at a current density of 1000 mA·g⁻¹. Approximately 65.8% of the initial discharge specific capacity was retained when the current density was recovered to 40 mA·g⁻¹. These excellent electrochemical results revealed that Ni-doped TiO₂ nanofibers could be considered to be promising anode materials for LIBs.

Fabrication of TiO2-Bi2WO6 Binanosheet for Enhanced Solar Photocatalytic Disinfection of E. coli: Insights on the Mechanism

TiO2-Bi2WO6 binanosheet (TBWO), synthesized by a facile two-step hydrothermal method, was used as an effective visible-light-driven photocatalyst for the inactivation of E. coli and was characterized by TEM, SEM, XRD, FTIR, XPS, and BET. A series of TBWOs with different doping ratios of TiO2 loading from 10 to 55 wt % were synthesized. Among all of the TBWOs, 40% TBWO exhibited the best bacteria disinfection efficiency, and the quantity of viable bacteria could reach 10° with 40% TBWO (100 μg/mL) after being illuminated for 4 h. Furthermore, the confocal fluorescent-based cell live/dead test and the SEM technology were applied to verify the photocatalytically lethal effect toward E. coli and the rupture of bacterial membranes. The leak of bacterial contents, including the bacterial genome represented by relevant 16srDNA, and total protein were detected by PCR and bicinchoninic acid assay. In this work, the antibacterial mechanism was studied by employing photoelectrochemical techniques, electron spin resonance (ESR), and scavengers of different reactive species, revealing the pivotal roles of electron hole (h(+)) and electron (e(-)) in the photocatalytic process. In addition, the •O2(-) and •OH radicals were also detected in the TBWOs system by ESR. It was found that the adsorption of visible light and separation of photogenerated carriers within TiO2 have been largely promoted after being coupled with Bi2WO6, which should be responsible for the improved bactericidal effect.

Synthesis of mesoporous TiO2@C@MnO2 multi-shelled hollow nanospheres with high rate capability and stability for lithium-ion batteries

Mesoporous TiO₂@C@MnO₂ multi-shelled hollow nanospheres (denoted as TiO₂@C@MnO₂ multi-shelled HNSs) prepared by a layer-by-layer deposition growth process exhibit high rate capability and stability.

Design and synthesis of one-dimensional Co3O4/Co3V2O8 hybrid nanowires with improved Li-storage properties

A new nanostructure of one-dimensional Co₃O₄/Co₃V₂O₈ hybrid nanowires directly grown on Ti substrates with improved electrochemical Li-storage properties are successfully prepared by a simple hydrothermal strategy.