Self-Reconstructed Formation of a One-Dimensional Hierarchical Porous Nanostructure Assembled by Ultrathin TiO2 Nanobelts for Fast and Stable Lithium Storage

Watermelon-like TiO2 nanoparticle (P25)@microporous amorphous carbon sphere with excellent rate capability and cycling performance for lithium-ion batteries

To overcome the inferior rate capability and cycling performance of TiO₂ nanomaterials as an anode material of lithium-ion batteries, we encapsulate TiO₂ nanoparticles (P25) in carbon spheres through a facile pyrrole polymerization and carbonization. Material characterization demonstrates TiO₂ nanoparticles are uniformly embedded in microporous amorphous carbon spheres, forming a watermelon-like structure. P25@C exhibits excellent high rate capability with average discharge capacity of 496, 416, 297, 240, 180, 99, 49 and 25 mAh g^-1 at current rate of 0.5C, 1C, 5C, 10C, 20C, 50C, 100C and 200C, which shows superior long-term cycling performance with discharge capacity of 106.9 mAh g^-1 at 20C after 5000 cycles. The capacity loss rate is only 0.008% per cycle. The outstanding lithium storage performance is ascribed to the watermelon-like composite structure, which remarkably improves electronic conductivity and structure stability of TiO₂ nanoparticles. More importantly, the agglomeration of TiO₂ nanoparticles is eliminated, and the entire surface of every TiO₂ nanoparticle participates in the electrochemical reaction, which brings about an intense capacitive Li storage effect and leads to the high specific capacity and excellent rate capability of P25@C. This is confirmed through qualitative and quantitative analysis of the contributions from surface capacitive storage and bulk intercalation storage to the total capacity of the composite.

Large-Scale Synthesis and Lithium Storage Performance of Multilayer TiO2 Nanobelts

Titanium dioxide (TiO2) has been widely investigated as the electrode material for lithium ion batteries (LIBs), due to its low cost, small volume expansion, and high environmental friendliness. However, the fading capacity and short cycle life during the cycling process lead to poor cycling performance. Herein, multilayer TiO2 nanobelts with a high specific surface area and with many pores between nanoparticles are constructed via a simple and large-scale approach. Benefiting from the multilayer nanobelt structure, as-prepared TiO2 nanobelts deliver a high reversible capacity, strong cycling stability, and ultra-long cycle life (~185mAhg−1 at 500mAg−1 after 500 cycles) as electrode materials for LIBs.

Porous Anatase-TiO2(B) Dual-Phase Nanorods Prepared from in Situ Pyrolysis of a Single Molecule Precursor Offer High Performance Lithium-Ion Storage

To overcome the problems faced by TiO₂ materials for lithium-ion batteries usage, such as easy nanoparticles agglomeration during cycling and poor cycling performance, in this study, TiO₂ nanorods with the controlled phase compositions are prepared via direct pyrolysis of single molecule precursors in combination with a simple washing process. By tuning the external cations in the single source precursors, three TiO₂ samples in a nanorod shape with the compositions of pure anatase, anatase-rutile dual phase, and anatase-TiO₂(B) dual phase are synthesized successfully. High-resolution transmission electron microscopy, X-ray powder diffraction, and Raman measurements confirm the phase structures and compositions of the three prepared samples. The electrochemical results manifest that all the three nanorod-shaped TiO₂ samples show the long-term cycling stability as negative materials for LIBs. Among them, the TiO₂ sample with the combination of the anatase and TiO₂-B phase shows the best performance, with the specific capacity of ∼184, 164, 140, 105, 80, and 60 mAh g^-1 at 0.1, 0.3, 0.5, 1.5, 3.0, and 5.0 A g^-1, respectively, and showing no capacity loss and low resistance after 1000 cycles at 1.5 A g^-1. By the analysis of the cyclic voltammetry results recorded from different scan rates, the lithium-ion storage mechanism is clarified, which is dominated by the semi-infinite linear diffusion (anatase phase) in combination with the partial surface pseudocapacitive contribution [TiO₂(B) phase]. As a result, this sample shows a great potential as a negative material for LIBs because of its electrochemical stability, high specific capacity, and superior rate capability. The proof-of-concept design of the anatase and TiO₂-B dual phase may provide a new strategy for the synthesis of high performance TiO₂-based anode material for LIBs.

Design and synthesis of interconnected hierarchically porous anatase titanium dioxide nanofibers as high-rate and long-cycle-life anodes for lithium-ion batteries

We suggest an efficient and simple synthetic strategy to prepare interconnected hierarchically porous anatase TiO2 (IHP-A-TiO2) nanofibers by two synergetic effects: phase separation between polymers and relative humidity control during electrospinning. The macro channels formed by polystyrene decomposition were interconnected by numerous mesopores that were formed by evaporation of infiltrated water vapor in the structure. The resulting IHP-A-TiO2 nanofibers showed better Li+ ion storage performances than the TiO2 materials reported in the literature. The discharge capacity of IHP-A-TiO2 nanofibers for the 3000th cycle at 1.0 A g-1 and corresponding coulombic efficiency from the 20th cycle onward were 142 mA h g-1 and >99.0%, respectively. Well-interconnected, ultrafine TiO2 nanocrystals within the nanofiber showed structural stability during cycling and facilitated facile charge transfer at the electrode-electrolyte interface.