Search

Creating defects by heteroatom doping is commonly approved in respect of enhancing fast sodium‐ion storage of carbonaceous anodes ascribing to rich external defects, but the contribution of intrinsic carbon defects (e.g., vacancy) in improving rate‐capability has rarely been investigated. Here, a bio‐derived fibrous hard carbon with high‐reversible intrinsic defects is synthesized via metal‐assisted‐catalytic strategy. It is found that sp2‐hybridized carbon is united through catalytic‐tuning during thermal‐etching process along with the formation of low‐potential planar intrinsic carbon defects (vacancies and non‐hexagonal carbon rings) by sacrificing poor‐reversible carbon edges. Such integrated structures greatly improve the reversibility of defective sites and charge transfer kinetics, thus enhancing the slope sodium‐storage capacity of carbon below 1 V even at high current densities. Thus‐obtained fibrous carbon anodes enable boosted initial coulombic efficiency (≈90%) and ultrahigh‐rate capability in both half‐ (222.2 mAh g−1at 50 A g−1) and full‐cell (200 C, charged/discharged in ≈10 s). Interestingly, compared with meso‐/macroporous structures, such micropore‐dominated carbon fibers are more beneficial for fabricating high‐mass‐loading, crack‐free thick electrodes (>10 mg cm−2) with considerable areal‐capacity over 3.0 mAh cm−2. Paired with high‐loading Na3V2PO4 cathode (14.4 mg cm−2), full‐cell achieves admirable areal‐capacity over 1.4 mAh cm−2 and peak areal‐energy/power‐density of 3.2/74 mW cm−2. [ABSTRACT FROM AUTHOR]

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 GaNb 49 O 124 as a novel intercalation-type M-Nb-O anode material. GaNb 49 O 124 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, GaNb 49 O 124 microspheres could be developed as an efficient anode material for Li-ion batteries. [ABSTRACT FROM AUTHOR]

To achieve both high gravimetric and volumetric energy densities of lithium–sulfur (Li–S) batteries, it is essential yet challenging to develop low‐porosity dense electrodes along with diminishment of the electrolyte and other lightweight inactive components. Herein, a compact TiO2@VN heterostructure with high true density (5.01 g cm–3) is proposed crafted by ingenious selective nitridation, serving as carbon‐free dual‐capable hosts for both sulfur and lithium. As a heavy S host, the interface‐engineered heterostructure integrates adsorptive TiO2 with high conductive VN and concurrently yields a built‐in electric field for charge‐redistribution at the TiO2/VN interfaces with enlarged active locations for trapping‐migration‐conversion of polysulfides. Thus‐fabricated TiO2@VN–S composite harnessing high tap‐density favors constructing dense cathodes (≈1.7 g cm–3) with low porosity (<30 vol%), exhibiting dual‐boosted cathode‐level peak volumetric‐/gravimetric‐energy‐densities nearly 1700 Wh L−1cathode/1000 Wh kg−1cathode at sulfur loading of 4.2 mg cm−2 and prominent areal capacity (6.7 mAh cm−2) at 7.6 mg cm−2 with reduced electrolyte (<10 µL mg−1sulfur). Particular lithiophilicity of the TiO2@VN is demonstrated as Li host to uniformly tune Li nucleation with restrained dendrite growth, consequently bestowing the assembled full‐cell with high electrode‐level volumetric/gravimetric‐energy‐density beyond 950 Wh L−1cathode+anode/560 Wh kg−1cathode+anode at 3.6 mg cm−2 sulfur loading alongside limited lithium excess (≈50%). [ABSTRACT FROM AUTHOR]

Ti 2 Nb 2 x O 4+5 x 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 CrNb 11 O 29 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 Ti 2 Nb 2 x O 4+5 x but a high rate capability. CrNb 11 O 29 nanorods (CrNb 11 O 29 -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 Cr 3+ , CrNb 11 O 29 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 CrNb 11 O 29 -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). [ABSTRACT FROM AUTHOR]