Pristine and boron-doped anatase TiO2 were prepared via a facile sol–gel method and the hydrothermal method for application as anode materials in sodium-ion batteries (SIBs). The sol–gel method leads to agglomerated TiO2, whereas the hydrothermal method is conducive to the formation of highly crystalline and discrete nanoparticles. The structure, morphology, and electrochemical properties were studied. The crystal size of TiO2 with boron doping is smaller than that of the nondoped crystals, which indicates that the addition of boron can inhibit the crystal growth. The electrochemical measurements demonstrated that the reversible capacity of the B-doped TiO2 is higher than that for the pristine sample. B-doping also effectively enhances the rate performance. The capacity of the B-doped TiO2 could reach 150 mAh/g at the high current rate of 2C and the capacity decay is only about 8 mAh/g over 400 cycles. The remarkable performance could be attributed to the lattice expansion resulting from B doping and the shortened Li+ diffusion distance due to the nanosize. These results indicate that B-doped TiO2 can be a good candidate for SIBs.

Bio-inspired by bone materials, hierarchical porous materials with aligned structure have been designed and applied in various fields. However, the realization of anisotropic function based on aligned structures is still a challenge. Herein, we prepare nanocomposite ionogel electrolytes with aligned porous structures via a directional freezing of BMIMPF6, PEGMA (PEGDA), and TiO2 at −18 °C and further TiO2-initiated cryopolymerization under UV irradiation. The crystals of PEG derivatives at −18 °C provide a directional template for the formation of aligned porous structures within the ionogel networks. The additional TiO2 nanoparticles, as photoinitiators and nanofillers, endow the aligned ionogels with high mechanical strength. The aligned ionogel-based supercapacitor exhibits anisotropic electrochemical performance and flexibility. The specific capacitance of the device with the vertically aligned ionogel is 172 F g−1 at the current density of 1 A g−1, which is larger than those of the parallel aligned and non-aligned devices.

Sodium-ion batteries are considered to be a promising low-cost alternative to common lithium-ion batteries in the areas where specific energy is less critical. Among all the anode materials studied so far, TiO2 is very promising due to its low operating voltage, high capacity, nontoxicity, and low production cost. Herein, we present Nb-doped anatase TiO2 nanoparticles with high capacity, excellent cycling performance, and excellent rate capability. The optimized Nb-doped TiO2 anode delivers high reversible capacities of 177 mA h g−1 at 0.1C and 108.8 mA h g−1 at 5C, in contrast to 150.4 mA h g−1 at 0.1C and only 54.6 mA h g−1 at 5C for the pristine TiO2. The good performance is likely to be associated with enhanced conductivity and lattice expansion due to Nb doping. These results, in combination with its environmental friendliness and cost efficiency, render Nb-doped TiO2 a promising anode material for high-power sodium-ion batteries.

•Binary Fe(Co) MOF is prepared by a coprecipitate process.•After calcination, the MOF precursor decomposes into CoxFe3−xO4/C composite.•The obtained CoxFe3−xO4/C exhibits good electrochemical performance for LIBs.Synthesis of binary metal oxides for high-performance lithium ion batteries is a crucial but challenging project. Herein, we presented a binary metal organic framework derived method to fabric CoxFe3−xO4/C composites. During the calcination process, the metal-oxygen coordination bonds were decomposed into CoxFe3−xO4, while the organic ligands were carbonized into carbon. When applied as anode material for lithium ion batteries, the as-obtained CoxFe3−xO4/C exhibited good rate capability and long-life cycling stability, with high capacity of 1112 and 612 mAh g−1 retained after 206 cycles at 0.1 A g−1 and 250 cycles at 1A g−1. The Coulombic efficiency levelled at near 100% during the cycling.

Li4Ti5O12/Cu2O composite was prepared by ball milling Li4Ti5O12 and Cu2O with further heat treatment. The structure and electrochemical performance of the composite were investigated via X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy, cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge–discharge tests. Li4Ti5O12/Cu2O composite exhibited much better rate capability and capacity performance than pristine Li4Ti5O12. The discharge capacity of the composite at 2 C rate reached up to 122.4 mAh g−1 after 300 cycles with capacity retention of 91.3 %, which was significantly higher than that of the pristine Li4Ti5O12 (89.6 mAh g−1). The improvement can be ascribed to the Cu2O modification. In addition, Cu2O modification plays an important role in reducing the total resistance of the cell, which has been demonstrated by the electrochemical impedance spectroscopy analysis.

•Fe2O3 modified Li4Ti5O12 was prepared by hydrolysis and further heat-treatment.•Fe2O3 particles are distributed on the surface of Li4Ti5O12.•Fe2O3 modification can improve rate capability and cycling stability of Li4Ti5O12.Spinel Li4Ti5O12/Fe2O3 composites were prepared by a facile hydrolysis method combined with further heat-treatment. The structure and electrochemical performance of the Li4Ti5O12/Fe2O3 material were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and charge–discharge tests. Electrochemical measurements demonstrated that the Fe2O3 modified Li4Ti5O12 anode material showed obviously improved high rate performance with discharge capacity of 109.4 mA h/g at 10 C. The Li4Ti5O12/Fe2O3 anode also showed superior cycling stability with an initial discharge capacity of 145.3 mA h/g at 2 C rate and maintained 93% of its initial capacity after 300 cycles.

•A facile solution-based synthesis route for preparing nanoscale Li4Ti5O12.•The route is favorable in fabricating nanoscale Li4Ti5O12 on a large scale.•The as-prepared Li4Ti5O12 has nanosheets structure.•The as-prepared Li4Ti5O12 shows good cycle stability and high specific capacity.A simple low-temperature solution-synthesis method is developed for preparing nanostructured Li4Ti5O12. Compared with normal hydrothermal synthesis (temperature > 120 °C), this low-temperature (60 °C) approach is more suitable for fabricating pure Li4Ti5O12 nanomaterials on a large scale due to its low requirements of reaction conditions and equipments. The as-prepared Li4Ti5O12 nanosheets are characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy and cyclic voltammetry. Galvanostatic testing results show that the discharging capacity of the sample still remains 148.9mAhg− 1 at 10C rates after 100 cycles, presenting excellent rate performance and cycle stability.

•Nitrogen-doped carbon coated TiO2 composite are prepared.•Polydopamine is used as nitrogen-containing carbon precursor.•An uniform carbon layer is coated on the surface of TiO2 nanoparticles.•The battery using carbon coated TiO2 anode shows excellent cycling performance.In order to improve cycle life of lithium-ion batteries, nitrogen-doped carbon coated anatase TiO2 (TiO2@C) anode materials were prepared by using polydopamine as carbon precursor. Transmission electron microscopy measurements showed that an uniform and continuous carbon layer with thickness of 4±0.5 nm was coated on the surface of the TiO2 nanoparticles. From X-ray photoelectron spectroscopy analysis, the weight content of nitrogen in the carbon coating layer was about 7.96 wt%. Thermogravimetric analysis results showed that the carbon content of the TiO2@C nanocomposite is about 4.2 wt%. Compared with the pristine TiO2 electrode, the TiO2@C nanocomposite electrode showed higher discharge retention and better cycling performance.

Bio-inspired by bone materials, hierarchical porous materials with aligned structure have been designed and applied in various fields. However, the realization of anisotropic function based on aligned structures is still a challenge. Herein, we prepare nanocomposite ionogel electrolytes with aligned porous structures via a directional freezing of BMIMPF6, PEGMA (PEGDA), and TiO2 at −18 °C and further TiO2-initiated cryopolymerization under UV irradiation. The crystals of PEG derivatives at −18 °C provide a directional template for the formation of aligned porous structures within the ionogel networks. The additional TiO2 nanoparticles, as photoinitiators and nanofillers, endow the aligned ionogels with high mechanical strength. The aligned ionogel-based supercapacitor exhibits anisotropic electrochemical performance and flexibility. The specific capacitance of the device with the vertically aligned ionogel is 172 F g−1 at the current density of 1 A g−1, which is larger than those of the parallel aligned and non-aligned devices.

Sodium-ion batteries are considered to be a promising low-cost alternative to common lithium-ion batteries in the areas where specific energy is less critical. Among all the anode materials studied so far, TiO2 is very promising due to its low operating voltage, high capacity, nontoxicity, and low production cost. Herein, we present Nb-doped anatase TiO2 nanoparticles with high capacity, excellent cycling performance, and excellent rate capability. The optimized Nb-doped TiO2 anode delivers high reversible capacities of 177 mA h g−1 at 0.1C and 108.8 mA h g−1 at 5C, in contrast to 150.4 mA h g−1 at 0.1C and only 54.6 mA h g−1 at 5C for the pristine TiO2. The good performance is likely to be associated with enhanced conductivity and lattice expansion due to Nb doping. These results, in combination with its environmental friendliness and cost efficiency, render Nb-doped TiO2 a promising anode material for high-power sodium-ion batteries.