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Niobates are very promising anode materials for Li+-storage rooted in their good safety and high capacities. However, the exploration of niobate anode materials is still insufficient. In this work, we explore ~1 wt% carbon-coated CuNb13O33 microparticles (C-CuNb13O33) with a stable shear ReO3 structure as a new anode material to store Li+. C-CuNb13O33 delivers a safe operation potential (~1.54 V), high reversible capacity of 244 mAh g−1, and high initial-cycle Coulombic efficiency of 90.4% at 0.1C. Its fast Li+ transport is systematically confirmed through galvanostatic intermittent titration technique and cyclic voltammetry, which reveal an ultra-high average Li+ diffusion coefficient (~5 × 10–11 cm2 s−1), significantly contributing to its excellent rate capability with capacity retention of 69.4%/59.9% at 10C/20C relative to 0.5C. An in-situ XRD test is performed to analyze crystal-structural evolutions of C-CuNb13O33 during lithiation/delithiation, demonstrating its intercalation-type Li+-storage mechanism with small unit-cell-volume variations, which results in its capacity retention of 86.2%/92.3% at 10C/20C after 3000 cycles. These comprehensively good electrochemical properties indicate that C-CuNb13O33 is a practical anode material for high-performance energy-storage applications.

A general modification for the solid-state reaction preparation of energy-storage materials is explored through using sintering aids with redox activity.

The oxygen vacancies and micro-nano structure can optimize the electron/Li+ migration kinetics in anode materials for lithium batteries (LIBs). Here, porous micro-nano structured VNb9O25 composites with rich oxygen vacancies were reasonably prepared via a facile solvothermal method combined with annealing treatment at 800℃ for 30 h (VNb9O25-30 h). This micro-nano structure can enhance the contact of active material/electrolyte, and shorten the Li+ diffusion distance. The introduction of oxygen vacancies can further boosts the intrinsic conductivity of VNb9O25-30 h for achieving excellent LIB performance. The as-prepared VNb9O25-30 h anode showed advanced rate capability with reversible capacity of 122.2 mA h g−1 at 4 A g−1, and delivered excellent capacity retention of ∼100 % after 2000 cycles. Meanwhile, VNb9O25-30 h provides unexpected long-cycle life (i.e., reversible capacity of 165.7 mA h g−1 at 1 A g−1 with a high capacity retention of 85.6 % even after 8000 cycles). Additionally, coupled with the LiFePO4 cathode, the LiFePO4//VNb9O25-30 h full cell delivers superior LIB properties with high reversible capacities of 91.6 mA h g−1 at 5C for 1000 cycles. Thus, such reasonable construction method can assist in other high-performance niobium-based oxides in LIBs.

FeNb11O29 has a high theoretical capacity as a potential anode material for lithium-ion batteries; however, the practical capacity of FeNb11O29 reported was unsatisfactory. In this study, a simple and efficient Al3+-doping technique was demonstrated to improve the electrochemical performance of FeNb11O29 successfully. The influences of the Al3+ doping amount were investigated. It was found that the crystal structure of FeNb11O29 could be preserved when a suitable amount of Al3+ was added, and that Al0.2Fe0.8Nb11O29 demonstrated better electrochemical performance than FeNb11O29 because the structure of Al0.2Fe0.8Nb11O29 is more stable. At 0.1C, Al0.2Fe0.8Nb11O29 possessed a high reversible capacity of 318 mAh g−1 with an initial-cycle Coulombic efficiency of 95.0%. Al0.2Fe0.8Nb11O29 exhibited outstanding cycling stability with capacity retention of 92.9% at 10C over after 1000 cycles. Moreover, A LiFePO4/Al0.2Fe0.8Nb11O29 full cell was prepared successfully with a discharge capacity of 206 mAh g−1. The full cell exhibited good cycling stability showing the capacity retention of 84.2% over after 200 cycles at 1C and 89.8% over after 1000 cycles at 5C, respectively. This work suggests that Al0.2Fe0.8Nb11O29 has great application prospects in lithium-ion batteries. A suitable amount of Al3+ doping in FeNb11O29 significantly improves the electrochemical performance (especially the reversible capacity) of FeNb11O29.

An efficient and catalyst-free method for the large-scale preparation of high-purity α-Si3N4 nanowires was demonstrated by annealing absorbent cotton and silicic acid in a flowing nitrogen atmosphere. The pyrolysis of absorbent cotton generated a fluffy structure constructed by carbon microfibers, which could promote the growth of α-Si3N4 nanowires. The nanowires were characterized by XRD and XRD Rietveld refinement, SEM and TEM. The results indicated that the nanowires have diameters of 50–100 nm and lengths of tens to hundreds of microns. Vapor-solid (VS) mechanism was proposed to be responsible for the formation of nanowires. The α-Si3N4 nanowires were then applied as anode materials for lithium-ion batteries (LIBs), exhibiting good rate capability and cycling property.

Niobates are regarded as prospective Li+-storage anode candidates due to the rich chemistry of niobium and crystal-structural openness. However, the exploration of niobates is still insufficient. I...

M–Nb–O compounds are regarded as advanced anode materials of lithium-ion batteries owing to their large capacities, high safety and fast Li+ transport. However, challenges remain in the exploitation of new M–Nb–O compounds with low strains to enable superior cyclability. Here, we exploit V3Nb17O50 as a low-strain M–Nb–O anode compound, and V3Nb17O50 micron-sized particles (V3Nb17O50-MP) and submicron-sized rods (V3Nb17O50-SR) are demonstrated. V3Nb17O50 owns an open and robust shear ReO3 crystal structure, which is constructed by 3 ​× ​3 ​× ​∞ (V,Nb)O6 octahedron-blocks linked by VO4 tetrahedra. The resulting A–B–A layered structure with a large interlayer spacing enables the superior Li+ diffusivity and significant intercalation-pseudocapacitive behavior in V3Nb17O50. The maximum unit-cell volume expansion of V3Nb17O50 discharged to 0.8 ​V is only 3.46% (the smallest value among the known M–Nb–O anode compounds with shear ReO3 structures), leading to the excellent cyclability of V3Nb17O50-MP/V3Nb17O50-SR with 90.0/91.8% capacity retention over 2000 cycles at 10C. V3Nb17O50-MP/V3Nb17O50-SR further exhibits a safe operating potential of 1.736/1.724 ​V, large reversible capacity of 207/254 ​mA ​h g−1 at 0.1C, and high rate performance with 68/123 ​mA ​h g−1 at 10C. A LiMn2O4//V3Nb17O50-SR full cell also exhibits comprehensively good electrochemical properties, including excellent cyclability with 85.7% capacity retention over 500 cycles at 5C. Therefore, V3Nb17O50 can be a very promising anode compound for stable, safe, large-capacity and fast-charging Li+ storage.

In this paper, the effect of stereom structure on the mechanical behavior of the Sea Urchin Inorganic Skeleton (SUIS) has been studied. The stereom microstructure of both Anthocidaris crassispina and Tripnenstes gratilla was characterized by Scanning Electron Microscopy (SEM). Results indicate that a three-layer porous structure consisting of a growth, a support, and a resorption (GSR) layer is a common denominator for both species. The effect of GSR layer order on the mechanical behavior of the SUIS was studied by a finite element method. The results show that the GSR model could effectively reduce the maximum tensile stress on its meridional sutures under unidirectional pressure, hydrostatic pressure, and self-weight situation. For a fabricated three-layered ceramic test strips with different layer orders, the mechanical properties have a completely opposite performance compared with the compressive properties of the calculated SUIS-like models. This indicates that the GSR structure can effectively improve the mechanical properties of the SUIS, but it cannot be applied to bionics without considering its synergistic effect with the macro-structure of the SUIS. This is a typical example of bionic invalidation by single structure, where multi-level structure bionics may be an effective solution.

Highly Li+-conductive HfNb24O62 is explored as a new intercalation-type niobium-based oxide anode material for superior Li+ storage. HfNb24O62 owns a Wadsley–Roth shear structure with a large unit-cell volume, leading to a large Li+ diffusion coefficient. HfNb24O62 shows a large capacity, safe operating potential, high rate performance and good cyclability.

Cu2Nb34O87 with an inverse opal morphology is fabricated, showing highly-ordered macropores with sizes of ∼170 nm and walls with thicknesses of 20–30 nm. This first-reported Cu2Nb34O87 nanomaterial exhibits good Li+-storage properties, including a large capacity, safe operating potential, large initial coulombic efficiency, high rate performance and good cycling stability.

To meet the demand of high power and energy densities of Li-ion batteries, M-Nb-O compounds are of significance due to not only the intercalation pseudocapacitance but also the high theoretical capacities and excellent cycling stability. However, the exploration of M-Nb-O is very limited. Herein, we firstly report GaNb49O124 as a novel intercalation-type M-Nb-O anode material. GaNb49O124 microspheres (GaNbO-S) with an average diameter of ∼2 μm are fabricated through a hydrothermal method. Benefiting from the nanosized architecture, GaNbO-S delivers superior electrochemical performance in Li-ion batteries. A large reversible specific capacity of 294 mAh g−1 is obtained at 50 mA g−1, while 205 mAh g−1 is reached at 4000 mA g−1. Furthermore, GaNbO-S delivers long-term cycling life with a 72.0% capacity retention over 1800 cycles at 2000 mA g−1. Thus, GaNb49O124 microspheres could be developed as an efficient anode material for Li-ion batteries.

Hydrogen production through photocatalytic water splitting attracts great attention in fields of energy conversion. To improve the hydrogen evolution efficiency, narrowing the bandgap of photocatalysts by introducing dopant atoms is widely investigated for increasing light absorption. Herein, Mo-doped BaTiO3 samples are synthesized by a traditional solid-state reaction method and all the samples are modified with Pt by a photo-reduction method. Compared with pure BaTiO3, Mo doping into BaTiO3 samples realizes the band-to-band visible-light absorption and shows remarkable improvement in hydrogen production efficiency. Under simulated sunlight irradiation and with 0.4 wt% Pt deposition, BaTiO3 doped with 2 at% Mo exhibits a hydrogen evolution rate of 63 μmol g−1 h−1, about 2 times improvement in comparison to pure BaTiO3 (35 μmol g−1 h−1). Further first-principles calculations based on density-function theory demonstrates an apparent downward movement of the conduction band minimum due to the coupling between the Ti 3d and Mo 3d states, leading to the significant bandgap narrowing and enhancement of the visible-light photocatalytic activity.

This paper describes the syntheses and electrochemical properties of a new niobate compound, aluminum niobate (AlNb11O29), for Li+ storage. AlNb11O29-microsized particles and nanowires were synthesized based on the solid-state reaction and solvothermal methods, respectively. In situ X-ray diffraction results confirmed the intercalating mechanism of Li+ in AlNb11O29 and revealed its high structural stability against cycling. The AlNb11O29 nanowires with a novel bamboo-like morphology afforded a large interfacial area and short charge transport pathways, thus leading to the observed excellent electrochemical properties, including high reversible Li+-storage capacity (266 mA h g-1), safe operating potential (around 1.68 V), and high initial Coulombic efficiency (93.3%) at 0.1 C. At a very high rate (10 C), the AlNb11O29 nanowires still exhibited a capacity as high as 192 mA h g-1, indicating their good rate capability. In addition, at 10 C, 96.3% capacity was retained over 500 cycles, indicating superior cycling stability. A full cell fabricated with AlNb11O29 nanowires as the anode and LiNi0.5Mn1.5O4 microparticles as the cathode delivered a high energy density of 390 W h kg-1 at 0.1 C. This work suggests that the AlNb11O29 nanowires hold a great promise for the development of high-performance lithium-ion batteries for large-scale energy-storage applications.

Olive (Olea europaea L.) is internationally renowned for its high-end product, extra virgin olive oil. An incomplete genome of O. europaea was previously obtained using shotgun sequencing in 2016. To further explore the genetic and breeding utilization of olive, an updated draft genome of olive was obtained using Oxford Nanopore third-generation sequencing and Hi-C technology. Seven different assembly strategies were used to assemble the final genome of 1.30 Gb, with contig and scaffold N50 sizes of 4.67 Mb and 42.60 Mb, respectively. This greatly increased the quality of the olive genome. We assembled 1.1 Gb of sequences of the total olive genome to 23 pseudochromosomes by Hi-C, and 53,518 protein-coding genes were predicted in the current assembly. Comparative genomics analyses, including gene family expansion and contraction, whole-genome replication, phylogenetic analysis, and positive selection, were performed. Based on the obtained high-quality olive genome, a total of nine gene families with 202 genes were identified in the oleuropein biosynthesis pathway, which is twice the number of genes identified from the previous data. This new accession of the olive genome is of sufficient quality for genome-wide studies on gene function in olive and has provided a foundation for the molecular breeding of olive species.

In this work, we revisited the stability of the Cr

Intercalation-type niobium-based oxides are considered as promising anode materials for lithium-ion batteries owing to their high theoretical/practical capacities, long-term cyclability, and high safety. However, studies in this research field are still very limited. Here, we explore MoNb12O33 as the first molybdenum niobium oxide anode material, and prepare microsized MoNb12O33 particles (M-MoNb12O33) and porous MoNb12O33 microspheres (P-MoNb12O33) based on solid-state reaction and solvothermal methods, respectively. MoNb12O33 shows a Wadsley–Roth crystal structure, consisting of 3 × 4 × ∞ NbO6 octahedra linked by corner-sharing MoO4 tetrahedra. This very open and stable structure results in fast Li+ diffusivity and superior structural stability, respectively. These structural merits together with the nanosizing effects in P-MoNb12O33 lead to outstanding electrochemical properties in its half cell, including a high practical capacity (321 mA h g−1 at 0.1C), significant intercalation pseudocapacitive contribution (85.5% at 1.1 mV s−1), prominent rate capability (200 mA h g−1 at 10C), and superior cyclability (capacity retention of 95.7% after 1000 cycles at 10C). Moreover, outstanding electrochemical properties of a LiMn2O4//P-MoNb12O33 full cell are also achieved, such as a high reversible capacity (274 mA h g−1 at 0.1C), good rate capability (106 mA h g−1 at 10C), and superior cyclability (capacity retention of 93.9% after 1000 cycles at 5C). All these findings indicate that P-MoNb12O33 can be a practical anode material for high-capacity, safe, rapid and durable Li+ storage.

Conductive Nb12O29 hierarchical microspheres with nanosheet shells were synthesized based on a hydrothermal process and a high-temperature hydrogen reduction treatment. The obtained materials demonstrated comprehensively good electrochemical properties, including a significant pseudocapacitive contribution, safe operating potential, high reversible capacity, superior initial coulombic efficiency, increased rate capability, and durable cycling stability.

Low electrical conductivity and sluggish charge storage kinetics are the key issues of orthorhombic niobium pentoxide (T-Nb2O5) for sodium-ion batteries. Here, we report on an approach for improving the electrochemical properties of T-Nb2O5 using fluorine substitution and carbon modification strategies. The obtained orthorhombic niobium oxyfluoride/carbon nanobelt composite (T-Nb2O5−xFy⊂C-NBs) displayed significantly improved electrochemical properties with sodium ion storage capacity as high as 292 mA h g−1 at 0.05 A g−1, along with an excellent cycling stability over 10 000 cycles at 1 A g−1 (0.002% capacity decay per cycle) as measured using a half cell. An intercalation-pseudocapacitance mechanism (1.0–3.0 V vs. Na/Na+) for storing sodium ions was observed in T-Nb2O5−xFy⊂C-NBs, along with a conversion reaction mechanism (

W5Nb16O55 is a very promising negative electrode compound for lithium-ion storage owing to its good safety, durable cyclability and high rate performance. However, its commercialization is hindered by its limited capacity and high tungsten cost. Here, we designed a tungsten-free and niobium-rich zinc niobate (Zn2Nb34O87) with a large capacity (theoretically 389 mA h g−1) as a new insertion negative electrode compound. Micron-sized Zn2Nb34O87 blocks (Zn2Nb34O87-B) and one-dimensional Zn2Nb34O87 nanofibers (Zn2Nb34O87-N) were prepared via a solid-state reaction and electrospinning methods, respectively. Zn2Nb34O87-B and Zn2Nb34O87-N have 3 × 4 × ∞ shear ReO3 crystal structures of orthorhombic and monoclinic types, respectively. Both the Zn2Nb34O87 materials exhibited better electrochemical performance than W5Nb16O55 in terms of the capacity, lithium-ion diffusion coefficient, intercalation pseudocapacitive contribution, rate performance, and cyclability. In situ X-ray diffraction characterization demonstrated the excellent structural stability and electrochemical reversibility of Zn2Nb34O87, and revealed that lithium ions were stored in the (010) crystallographic planes. Furthermore, a LiNi0.5Mn1.5O4‖Zn2Nb34O87-N full cell exhibited outstanding electrochemical performance, including a large capacity, prominent rate performance, and especially ultra-long cyclability (96.5% capacity retention even after 1000 cycles at 5C). Therefore, Zn2Nb34O87 holds great promise as a practical negative electrode compound for large-capacity, cost-effective, rapid, durable and safe lithium-ion storage.

Nb16W5O55 is considered as a promising anode material for lithium-ion batteries (LIBs) due to its high safety, good cyclability and high rate performance. However, it has not been practically used since it suffers from its limited capacity. Here, we demonstrate the design and synthesis of a tungsten-free and niobium-rich Al0.5Nb24.5O62 anode material having a very large theoretical capacity of 400 mA h g−1 and a stable shear ReO3 crystal structure. Both Al0.5Nb24.5O62 microsized particles (Al0.5Nb24.5O62-M) and porous microspheres (Al0.5Nb24.5O62-P) were successfully synthesized. In situ X-ray diffraction indicated the intercalated characteristic of Al0.5Nb24.5O62 and revealed the Li+ insertion into/extraction from its (010) crystallographic planes with high structural stability. Consequently, Al0.5Nb24.5O62-P exhibited a large practical capacity (321 mA h g−1 at 0.1C) and good cyclability (90.0% capacity retention after 500 cycles at 10C). In addition, Al0.5Nb24.5O62-P exhibited significant intercalation pseudocapacitive behavior (86.1% pseudocapacitive contribution at 1.1 mV s−1), high rate performance (192 mA h g−1 at 10C), high initial coulombic efficiency (94.9%) and safe working potential (∼1.68 V). Al0.5Nb24.5O62 also performed well in a LiNi0.5Mn1.5O4//Al0.5Nb24.5O62-P full cell. These research results indicate that Al0.5Nb24.5O62 is a practical anode material for high-energy, stable, fast-charging and safe LIBs.

Ti2Nb2xO4+5x compounds are very popular negative-electrode materials for lithium-ion batteries due to their high specific capacities, safe operating potentials and high cycling stability. Nevertheless, their poor electronic conductivities and insufficient Li+ diffusion coefficients limit the rate capabilities. Herein, we explore highly conductive CrNb11O29 with a high theoretical capacity (401 mAh g−1) and an open Wadsley–Roth shear structure as a new intercalating negative-electrode material having the same advantages of Ti2Nb2xO4+5x but a high rate capability. CrNb11O29 nanorods (CrNb11O29-R) with lengths of 500–1000 nm and very small diameters of 30–50 nm are prepared based on a novel hydrothermal method. Due to the free electrons in Cr-3d orbitals and the large ionic radius of Cr3+, CrNb11O29 exhibits a high electronic conductivity and large Li+ diffusion coefficients, respectively. In-situ X-ray diffraction analyses confirm its high structural stability. These conductivity, structural and architectural advantages in CrNb11O29-R lead to its significant pseudocapacitive contribution (82.0% at 1.1 mV s−1), prominent rate capability (high reversible capacities of 343 mAh g−1 at 0.1C and 228 mAh g−1 at 10C), and outstanding cycling stability (only 8.9% capacity loss at 10C over 400 cycles).

M–Nb–O compounds are advanced anode materials for lithium-ion batteries (LIBs) due to their high specific capacities, safe operating potentials, and high cycling stability. Nevertheless, the found M–Nb–O anode materials are very limited. Here, Mg2Nb34O87 is developed as a new M–Nb–O material. Mg2Nb34O87 porous microspheres (Mg2Nb34O87-P) with primary-particle sizes of 30–100 nm are fabricated based on a solvothermal method. Mg2Nb34O87 has an open 3 × 4 × ∞ Wadsley–Roth shear structure and a large unit-cell volume, leading to its largest Li+ diffusion coefficients among all the developed M–Nb–O anode materials. In situ X-ray diffraction analyses reveal its high structural stability and intercalating characteristic. These architectural, conductivity, and structural advantages in Mg2Nb34O87-P lead to its most significant intercalation pseudocapacitive contribution (87.7% at 1.1 mV s–1) among the existing M–Nb–O anode materials and prominent rate capability (high reversible capacities of 338 mAh g–1 at 0.1C a...

Lithium-ion batteries (LIBs) are increasingly used in portable electronics due to their high energy densities, long cycle life, low self-discharge properties, and environmentally friendly features. To satisfy future large-scale energy storage, the development of high-performance electrode materials is highly important. Complex Ti-based oxides (such as Li4Ti5O12 and Li–M–Ti–O) have interesting properties for anode applications, including good safety performance and high cyclic stability. However, most of the complex Ti-based oxides suffer from low electronic conductivities and insufficient Li+-ion diffusion coefficients, significantly limiting their rate capabilities. In general, compositing is an effective strategy to tackle this issue. Comprehensively good electrochemical performance can be achieved in the composites arising from the complementarity and correlation of the components. This review focuses on the composite characteristics and compositing methods of the complex Ti-based oxides for high-performance lithium-ion storage. The relations among the material composition, material fabrication, material structure, material property and LIB performance are emphasized. In addition, a vista of future research and development in this research field is also presented.

Ti2Nb10O29 is a high-capacity, safe and stable anode material for lithium-ion batteries, but suffers from a poor rate capability. To tackle this issue, nanotechnology is employed, and Ti2Nb10O29 hollow nanofibers with an average fiber diameter of ∼500 nm and shell thickness of ∼90 nm are prepared by a facile co-electrospining technique followed by calcination in air. This material exhibits not only a high reversible capacity (307 mAh g−1 at 0.1 C) and durable cyclic stability (0.06% capacity loss per cycle at 10 C over 500 cycles) but also an outstanding rate capability (136 mAh g−1 at 20 C), thereby becoming a promising anode material for high-performance lithium-ion batteries.

Conductive M–NbV–O compounds are high-capacity, fast-charging, safe and stable anode materials that have potential use in lithium-ion batteries. However, their studies are very limited. Here, we facilely fabricate Nb25O62 (i.e., NbIVNbV24O62) and Nb12O29 (i.e., NbIV2NbV10O29) from high-temperature reduction of Nb2O5 in a mixed H2/Ar atmosphere. Nb25O62 shows a monoclinic shear ReO3 crystal structure with a C2 space group and a structural unit containing a 3 × 4 octahedron-block and 0.5 tetrahedron, while Nb12O29 shows a similar structure with an A2/m space group and a 3 × 4 octahedron-block. Their resulting open crystal structures lead to their large Li+-ion diffusion coefficients. Due to the unpaired 4d electrons in Nb4+, their electronic conductivities are increased by three orders of magnitude in comparison with Nb2O5. First-principles calculations even demonstrate their conductor characteristics. Hence, Nb25O62/Nb12O29 exhibits comprehensively good electrochemical performance, including a significant pseudocapacitive contribution (72.7/79.0% at 1.1 mV s−1), high specific capacity (289/287 mAh g−1 at 0.1 C), high working potential (∼1.69/∼1.72 V vs. Li/Li+), superior rate capability (133/165 mAh g−1 at 10 C) and prominent cyclic stability (only 0.3/14.5% capacity loss over 1000 cycles at 10 C). These findings demonstrate that Nb25O62 and Nb12O29 are promising anode materials for future use in high-performance lithium-ion storage.

Rare earth (RE) silicates are promising candidates for environmental and thermal barrier coating (ETBC) materials. Low thermal conductivity is one of the main concerned thermal properties in ETBC design. We herein adopted multiple phonon scattering mechanisms to lower thermal conductivity of (YxYb1-x)2SiO5 solid solutions. Bulk samples were prepared by hot pressing method and RE atomic occupations, Raman spectra, thermal conductivities were measured as well as Debye temperature was obtained from temperature dependent Young's modulus. It is interesting to note that huge mass and size misfits between Yb and Y ions dominate the decrement of thermal conductivity. Furthermore, Yb2+ increases the concentration of oxygen vacancy, and it further decreases heat conduction. This work highlights the possible defect engineering in RE silicates for their advances in ETBC applications.

The existing electrode materials for lithium‐ion batteries (LIBs) generally suffer from poor rate capability at low temperatures, severely limiting their applications in winter and cold climate area. Here, partially reduced TiNb24O62 (PR‐TNO) are reported that demonstrates excellent electrochemical performance in a broad temperature range, notably at low temperatures. Its crystal structure is similar to that of Ti2Nb10O29 upon partial reduction in H2. The titanium and niobium ions in PR‐TNO enable multielectron transfer, safe operation, and high Coulombic efficiencies. Benefiting from the increased electronic conductivity of the partially reduced phase and its robust crystal structure with a large interlayer spacing, PR‐TNO shows fast electron and Li+ transport, small volume change associated with Li+ storage, and notable capacitive behavior, resulting in good electrochemical performance even at very low temperatures. At −20 °C, a large reversible capacity of 313 mAh g−1 is obtained at 0.1C, reaching 83.3% of that at 25 °C. At 5C, high rate capability (58.3% of that at 0.5C) is achieved, only slightly lower than that at 25 °C (60.7%). Furthermore, PR‐TNO demonstrates excellent cyclic stability with 99.2% of the initial capacity after 1680 cycles, confirming its excellent suitability for low‐temperature LIBs.

Silicon (Si) is a promising anode candidate for lithium-ion batteries (LIBs) owing to its unprecedented theoretical capacity of 4200 mA h g−1 and earth-abundant supply (26.2 wt%). Nevertheless, the huge volume expansion and unstable solid-electrolyte interface (SEI) of Si in multiple cycles make it very hard to simultaneously achieve high-energy and long-term cycle life for applications in large-scale renewable energy storage. Herein, we demonstrate a new class of Si/SiOx@void@nitrogen-doped carbon double-shelled hollow superstructure (Si/SiOx-DSHS) electrodes that are capable of accommodating huge volume changes without pulverization during cycling. Benefiting from the unique double-shelled hollow superstructure, Si/SiOx-DSHSs can facilitate the formation of a highly stable SEI layer and provide superior kinetics toward Li+-ion storage. The diffusion-controlled process and the capacitance-type reaction can work together to endow Si/SiOx-DSHSs with remarkable electrochemical characteristics, especially at high current density. These important characteristics make Si/SiOx-DSHSs deliver a large reversible capacity (1290 mA h g−1 at 0.1C), high first-cycle coulombic efficiency (71.7%), superior rate capability (360 mA h g−1 at 10C), and excellent cycling behavior up to 1000 cycles with a small capacity decay of 10.2%. The Si/SiOx-DSHSs are among the best Si-based anode materials for LIBs reported to date.

As a recently developed anode material for lithium-ion batteries, Ti2Nb10O29 shows high theoretical/practical capacities and safety, but suffers from a poor rate capability due to its insulator nature and insufficient Li+-ion diffusion coefficient. To tackle this issue, a strategy combining nanosizing, Cr3+–Nb5+ co-doping and carbon nanotube (CNT) compositing is employed. A novel TiCr0.5Nb10.5O29/CNTs nanocomposite with 9.1 wt% CNTs is fabricated by a direct hydrolysis process followed by calcination in N2. The Cr3+–Nb5+ co-doping significantly improves the electronic conductivity and Li+-ion diffusion coefficient of Ti2Nb10O29 by three orders and one order of magnitude, respectively. The CNT compositing not only enhances the electrical conduction among the TiCr0.5Nb10.5O29 particles but also hinders the particle growth in the hydrolysis process, leading to the small particle sizes. Due to the synergistic effect of these advantages, the TiCr0.5Nb10.5O29/CNTs nanocomposite exhibits a high rate capability with a high capacity of 206 mAh g−1 at 20 C, surpassing those of Ti2Nb10O29 (145 mAh g−1) and TiCr0.5Nb10.5O29 nanoparticles (187 mAh g−1). Additionally, TiCr0.5Nb10.5O29/CNTs delivers a high reversible capacity (297 mAh g−1 at 0.1 C) and cyclic stability (95.0% capacity retention after 100 cycles at 10 C). This good electrochemical performance reveals that TiCr0.5Nb10.5O29/CNTs can be an advanced anode material for high-performance Li+-ion storage.

Lithium-ion batteries (LIBs) have achieved great success in portable electronics, but their applications in electric vehicles (EVs) are still very challenging owing to the lack of high-performance electrode materials with high specific capacities, safety, rate capability and cycling stability. Recently, intercalating Ti2Nb2xO4+5x anode materials have received intensive attention owing to their high specific capacities (388–402 mA h g−1), high safety, prolonged cycling stability, easy state-of-charge evaluation and significant pseudocapacitive behavior. Their limited rate capabilities can be significantly improved by various modifications, including crystal structure modification, formation of a composite conductive phase, particle size reduction, and combined methods. These modified Ti2Nb2xO4+5x materials can be promising and practical anode materials for LIBs in EVs. Here, the research history, crystal structures, characteristics, working mechanisms and various modifications of Ti2Nb2xO4+5x are comprehensively reviewed. The relations between the material composition, material fabrication, material structure, material properties and LIB performance are emphasized. An insight into future directions in this research community is also provided.

Although with a large capacity, TiNb2O7 as an anode material of lithium-ion batteries suffers from a poor rate capability. To solve this challenge, nano-TiNb2O7 and its carbon nanotube (CNT) nanocomposites were prepared by direct hydrolysis of TiNb2O7/CNTs suspension followed by calcination in air and N2, respectively. The TiNb2O7 nanoparticles in the composites have a Ti2Nb10O29-type crystal structure with O2− vacancies and lower-valence cations, leading to improved Li+-ion diffusion coefficient and increased electronic conductivity in TiNb2O7. The evenly distributed CNTs have good contact with the TiNb2O7 particles, thereby reducing their particle sizes and improving the electrical conduction. As a result of these improvements, the nanocomposites present outstanding electrochemical performances. For example, it delivers a large reversible capacity (346 mAh g−1 at 0.1 C) and a prominent rate capability (still 163 mAh g−1 at the ultra-large current rate of 30 C). Exceptional cyclic stability is also demonstrated with over 100 cycles at 10 C with large capacity retention of 97.6%. These results reveal that the nano-TiNb2O7/CNTs composites can be a promising anode material for lithium-ion batteries of electric vehicles.

M–Nb–O compounds have been considered as promising anode materials for lithium-ion batteries (LIBs) because of their high capacities, safety, and cyclic stability. However, very limited M–Nb–O anode materials have been developed thus far. Herein, GaNb11O29 with a shear ReO3 crystal structure and a high theoretical capacity of 379 mAh g–1 is intensively explored as a new member in the M–Nb–O family. GaNb11O29 nanowebs (GaNb11O29-N) are synthesized based on a facile single-spinneret electrospinning technique for the first time and are constructed by interconnected GaNb11O29 nanowires with an average diameter of ∼250 nm and a large specific surface area of 10.26 m2 g–1. This intriguing architecture affords good structural stability, restricted self-aggregation, a large electrochemical reaction area, and fast electron/Li+-ion transport, leading to a significant pseudocapacitive behavior and outstanding electrochemical properties of GaNb11O29–N. At 0.1 C, it shows a high specific capacity (264 mAh g–1) with a ...

The recently explored FeNb11O29 is an advanced anode material for lithium-ion batteries due to its high specific capacity and safety. However, it suffers from its poor rate capability. To tackle this issue, a crystal-structure modification is employed. Defective FeNb11O29 (FeNb11O27.9) is fabricated using a one-step solid-state reaction method in N2. FeNb11O27.9 has the same orthorhombic shear ReO3 crystal structure (Amma space group) as FeNb11O29 but a larger unit-cell volume and 3.8% O2- vacancies (vs. all O2- ions), which improve the Li+-ion diffusion coefficient by a factor of 88.3%. The contained Nb4+ ions with free 4d electrons significantly increase the electronic conductivity by three orders of magnitude. Consequently, FeNb11O27.9 shows an improved pseudocapacitive behaviour and electrochemical properties. In comparison with FeNb11O29, FeNb11O27.9 exhibits a higher reversible capacity of 270 mAh g-1 with a higher first-cycle Coulombic efficiency of 90.6% at 0.1 C. At 10 C, FeNb11O27.9 still retains a high capacity of 145 mAh g-1 with low capacity loss of 6.9% after 200 cycles, in contrast to the values of 99 mAh g-1 and 11.1% obtained for FeNb11O29.

Ti 2 Nb 10 O 29 has recently been reported as a promising anode material for lithium-ion batteries. However, its poor electronic conductivity and insufficient Li + -ion diffusion coefficient significantly limit its rate capability. To tackle this issue, a strategy combining nanosizing and crystal-structure modification is employed. Ti 2 Nb 10 O 29– x mesoporous microspheres with a sphere-size range of 0.5–4 μm are prepared by a one-step solvothermal method followed by thermal treatment in N 2 . These Ti 2 Nb 10 O 29– x mesoporous microspheres exhibit primary nanoparticles, a large specific surface area (22.9 m 2 g −1 ) and suitable pore sizes, leading to easy electron/Li + -ion transport and good interfacial reactivity. Ti 2 Nb 10 O 29– x shows a defective shear ReO 3 crystal structure with O 2− vacancies and an increased unit cell volume, resulting in its increased Li + -ion diffusion coefficient. Besides Ti 4+ and Nb 5+ ions, Ti 2 Nb 10 O 29– x comprises Nb 4+ ions with unpaired 4 d electrons, which significantly increase its electronic conductivity. As a result of these improvements, the Ti 2 Nb 10 O 29– x mesoporous microspheres reveal superior electrochemical performances in term of large reversible specific capacity (309 mAh g −1 at 0.1 C), outstanding rate capability (235 mAh g −1 at 40 C) and durable cyclic stability (capacity retention of 92.1% over 100 cycles at 10 C).