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•Ultrahigh dispersed MoOx on N-doped hierarchically porous carbon was prepared.•It shows a high specific capacity of 742 mAh g−1 at 100 mA g−1.•A good stability was achieved with ...431 mAh g−1 after 1000 cycles at 1000 mA g−1.•MoOx and N-doped porous carbon synergistically contribute to the performance.
Transition-metal oxides based materials have recently been shown to be promising anode material for lithium ion batteries (LIBs) application to replace graphite material. In the present work, highly dispersed ultra-small MoOx nanoparticles anchored on N-doped three-dimensional (3D) hierarchically porous carbon (3D-MoOx@CN) are prepared on the basis of an efficient in-situ chelating and hard-templating strategy. The MoOx nanoparticles with particle sizes between 1.5 and 3.5 nm are observed to be anchored on the surface of the 3D N-doped carbon. The 3D-MoOx@CN composite anode electrode exhibits several appealing characteristics for lithium ion storage, including high specific capacity, good stability against cycling and fast charge transport kinetics. An optimized 3D-MoOx@CN sample (3D-MoOx@CN-700) delivers specific capacities of 742 mAh g−1 at current density of 100 mA g−1 and 431 mAh g−1 at 1000 mA g−1 after 1000 cycles, respectively. The observed excellent performance is due to the unique hierarchical pore structure with strong binding of the ultra-small MoOx nanoparticles onto N-doped carbon surface, which can avoid the agglomeration and alleviate the volume expansion of MoOx nanoparticles in the charge-discharge process. The composite electrode material described in this work holds a great potential for the development of high-performance lithium-ion batteries. Meanwhile, the synthesis method presents a common strategy to prepare other composite materials with highly dispersed metal oxide on the hierarchically porous carbon materials.
“Zero‐strain” materials with little lattice strain and volume change during long‐term cycling are ideal electrode choices for long‐life lithium‐ion batteries. However, the very limited “zero‐strain” ...materials explored generally show small capacities (<200 mAh g−1), and the origin of “zero‐strain” is still unclear. Here, Na2Ca(VO3)4 (NCVO) nanowires are explored as a new anode material capable of keeping single‐phase‐transition “zero‐strain” during large‐capacity (381 mAh g−1) Li+ intercalation. NCVO owns a crystal structure with isolated V4O124− tetracycles separated by large‐sized NaO6 octahedra and CaO8 square antiprism decahedra, generating large‐sized quadrilateral and hexagonal channels (≈3.6 Å). During lithiation, two‐electron transfer per vanadium is accomplished, introducing a large amount of Li+ into interstitial sites and increasing the size of reduced vanadium ions. The former and latter expansion effects are eliminated by the superior volume‐buffering capabilities of the sufficiently large interstitial sites and electrochemical inactive Na‐/Ca‐based polyhedra, respectively, thus achieving “zero‐strain” with the maximum volume variation of only 0.039% and mean strain of only 0.060%. Therefore, the NCVO nanowires exhibit exceptional cyclic stability, as demonstrated by 93.8%/93.2%/94.7% capacity retention over 2000/2000/7000 cycles at 1C/2C/10C. The understanding of the crystal‐structural features for “zero‐strain” provides a guide for the future designs of “zero‐strain” energy‐storage materials.
Single‐phase‐transition “zero‐strain” and a large reversible capacity (381 mAh g−1) harmoniously coexist in a new Na2Ca(VO3)4‐nanowire Li+‐storage material. Due to the volume‐buffering capabilities of the large interstitial sites and electrochemical inactive Na‐/Ca‐based polyhedra in Na2Ca(VO3)4, its volume variation and lattice strain are the smallest among the explored Li+‐storage materials, leading to its excellent cyclic stability for thousands of cycles.
Abstract
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.
Ti2Nb10O29 is an advanced anode material for lithium-ion batteries due to its large specific capacity and high safety. However, its poor electronic/ionic conductivity significantly limits its rate ...capability. To tackle this issue, a Cr3+–Nb5+ co-doping is employed, and a series of CrxTi2–2xNb10+xO29 compounds are prepared. The co-doping does not change the Wadsley–Roth shear structure but increases the unit-cell volume and decreases the particle size. Due to the increased unit-cell volumes, the co-doped samples show increased Li+-ion diffusion coefficients. Experimental data and first-principle calculations reveal significantly increased electronic conductivities arising from the formation of impurity bands after the co-doping. The improvements of the electronic/ionic conductivities and the smaller particle sizes in the co-doped samples significantly contribute to improving their electrochemical properties. During the first cycle at 0.1 C, the optimized Cr0.6Ti0.8Nb10.6O29 sample delivers a large reversible capacity of 322 mAh g−1 with a large first-cycle Coulombic efficiency of 94.7%. At 10 C, it retains a large capacity of 206 mAh g−1, while that of Ti2Nb10O29 is only 80 mAh g−1. Furthermore, Cr0.6Ti0.8Nb10.6O29 shows high cyclic stability as demonstrated in over 500 cycles at 10 C with tiny capacity loss of only 0.01% per cycle.
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•CrxTi2–2xNb10+xO29 compounds (0 ≤ x ≤ 0.6) are systematically and intensively studied.•Cr3+–Nb5+ co-doping increases the unit-cell volume and decreases the particle size.•CrxTi2–2xNb10+xO29 has large electronic conductivity and Li+ diffusion coefficient.•CrxTi2–2xNb10+xO29 has a large capacity, outstanding rate and cyclic properties.•Cr0.6Ti0.8Nb10.6O29 is promising for lithium-ion batteries of electric vehicles.
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.
A partially reduced TiNb24O62 electrode material demonstrates excellent electrochemical performance in a broad temperature range, notably at low temperatures. At −20 °C, it retains 83.3% of the reversible capacity at 25 °C, attributed to the fast electron‐ and Li+‐transport properties inherent to the Ti2Nb10O29‐type shear ReO3 crystal structure with lower‐valence cations and a large interlayer spacing.
Li4−2xNi3xTi5−xO12 (0 ≤ x ≤ 0.25) has been synthesized via solid-state reaction. X-ray diffractions (XRD) demonstrate that all doped samples have a spinel structure with Fd3¯m space group without any ...impurities. Through further Rietveld refinements, it is shown that both lattice parameter and occupancy of non-Li+ ions in the 8a sites negligibly change with the amount of Ni2+ dopants. Scanning electron microscope reveals that Ni2+ doping does not change the morphology of Li4Ti5O12. The best electronic conductivity of Ni2+ doped Li4Ti5O12 is at least one order of magnitude higher than that of the pristine one, while all samples have similar Li+ ion diffusion coefficients. The electrochemical performance of Ni2+ doped Li4Ti5O12 shows good rate capability. The specific capacity of Li3.9Ni0.15Ti4.95O12 at 5 C is as high as 72 mAh g−1, while that of the pristine one can only achieve 33 mAh g−1. This improved rate performance can be ascribed to its enhanced electronic conductivity.
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► Li4−2xNi3xTi5−xO12 (0 ≤ x ≤ 0.25) from solid-state reaction is systematically studied. ► The effects of material structure on electrochemical properties are investigated. ► The electronic conductivity is largely improved through Ni2+ doping. ► Li3.9Ni0.15Ti4.95O12 anode exhibits high rate performance.
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.
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To explore anode materials with large capacities and high rate performances for the lithium-ion batteries of electric vehicles, defective Ti2Nb10O27.1 has been prepared through a facile solid-state ...reaction in argon. X-ray diffractions combined with Rietveld refinements indicate that Ti2Nb10O27.1 has the same crystal structure with stoichiometric Ti2Nb10O29 (Wadsley-Roth shear structure with A2/m space group) but larger lattice parameters and 6.6% O(2-) vacancies (vs. all O(2-) ions). The electronic conductivity and Li(+)ion diffusion coefficient of Ti2Nb10O27.1 are at least six orders of magnitude and ~2.5 times larger than those of Ti2Nb10O29, respectively. First-principles calculations reveal that the significantly enhanced electronic conductivity is attributed to the formation of impurity bands in Ti2Nb10O29-x and its conductor characteristic. As a result of the improvements in the electronic and ionic conductivities, Ti2Nb10O27.1 exhibits not only a large initial discharge capacity of 329 mAh g(-1) and charge capacity of 286 mAh g(-1) at 0.1 C but also an outstanding rate performance and cyclability. At 5 C, its charge capacity remains 180 mAh g(-1) with large capacity retention of 91.0% after 100 cycles, whereas those of Ti2Nb10O29 are only 90 mAh g(-1) and 74.7%.
Present-day Li+ storage materials generally suffer from sluggish low-temperature electrochemical kinetics and poor high-temperature cycling stability. Herein, based on a Ca2+ substituted Mg2Nb34O87 ...anode material, we demonstrate that decreasing the ionic packing factor is a two-fold strategy to enhance the low-temperature electrochemical kinetics and high-temperature cyclic stability. The resulting Mg1.5Ca0.5Nb34O87 shows the smallest ionic packing factor among Wadsley–Roth niobate materials. Compared with Mg2Nb34O87, Mg1.5Ca0.5Nb34O87 delivers a 1.6 times faster Li+ diffusivity at −20 °C, leading to it having 56% larger reversible capacity and 1.5 times higher rate capability. Furthermore, Mg1.5Ca0.5Nb34O87 exhibits an 11% smaller maximum unit-cell volume expansion upon lithiation at 60 °C, resulting in better cyclic stability; at 10C after 500 cycles, it has a 7.1% higher capacity retention, even though its reversible capacity at 10C is 57% larger. Therefore, Mg1.5Ca0.5Nb34O87 is an all-climate anode material capable of working at harsh temperatures, even when its particle sizes are in the order of micrometers.
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•Decreasing the ionic packing factor can tackle issues arising at harsh temperatures.•The ionic packing factor can be decreased through using a substitution strategy.•Li+ diffusivity is improved, and the maximum unit-cell volume change is lowered.•The low-temperature kinetics and high-temperature cycling stability are enhanced.•Mg1.5Ca0.5Nb34O87 is an all-climate anode material that works at harsh temperatures.
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.
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