Although the NASICON-type of NaV(PO) is regarded as a potential cathode candidate for advanced sodium-ion batteries (SIBs), it has an undesirable rate performance and low cyclability, which are a result of its poor electronic conductivity. Here, we utilized conductive polyaniline (PANI) grown in situ to obtain the hard carbon-coated porous NaV(PO)@C composite (NVP@C@HC) with a typically simple and effective sol-gel process. Based on the restriction of double carbon layers, the NVP size decreases distinctly, which can curtail the sodium-ion diffusion distance and enhance the electronic conductivity. As expected, the product displays good discharge capacity (111.6 mA h g at 1 C), outstanding rate capacity (60.4 mA h g at 50 C), and remarkable cycling stability (63.3 mA h g with a retention of 83.3% at 40 C over 3000 cycles). Also, it performs a long-term cycling capacity of 58.5 mA h g exceeding 15 000 cycles at 20 C (with a capacity loss of 0.24% per cycle).
Suitable
intercalation cathodes and fundamental insights into the
Zn-ion storage mechanism are the crucial factors for the booming development
of aqueous zinc-ion batteries. Herein, a novel nickel vanadium oxide
hydrate (Ni0.25V2O5·0.88H2O) is synthesized and investigated as a high-performance electrode
material, which delivers a reversible capacity of 418 mA h g–1 with 155 mA h g–1 retained at 20 A g–1 and a high capacity of 293 mA h g–1 in long-term
cycling at 10 A g–1 with 77% retention after 10,000
cycles. More importantly, multistep phase transition and chemical-state
change during intercalation/deintercalation of hydrated Zn2+ are illustrated in detail via in situ/ex situ analytical techniques
to unveil the Zn2+ storage mechanism of the hydrated and
layered vanadium oxide bronze. Furthermore, morphological development
from nanobelts to hierarchical structures during rapid ion insertion
and extraction is demonstrated and a self-hierarchical process is
correspondingly proposed. The unique evolutions of structure and morphology,
together with consequent fast Zn2+ transport kinetics,
are of significance to the outstanding zinc storage capacity, which
would enlighten the mechanism exploration of the aqueous rechargeable
batteries and push development of vanadium-based cathode materials.
Transition metal dichalcogenides (TMDs) are of great promise for various nonlinear optical (NLO) applications due to their unique electronic and optoelectronic properties, such as tunable optical bandgap, strong spin-orbit coupling, and exciton effects. However, the desired NLO performances of regular 2H-TMDs are usually restricted by their limited absorption at atomic thickness. With this regard, a structurally novel spiral MoTe 2 (s-MoTe 2 ) nanopyramids is reported with unique and superior NLO response, enabled by their broken inversion symmetry, weak interlayer coupling, exciton resonance, and strong light-matter interaction from the edge-rich 3R-like quasi-multilayer structure. The excellent NLO response over a wide spectral range from the near-infrared to visible region is demonstrated, where second-and third-order NLO responses have been simultaneously observed. Moreover, the secondorder nonlinear susceptibility of s-MoTe 2 is estimated to be around 1-2 order(s) of magnitude larger than those of most reported TMDs. The demonstration of a superior NLO response in such s-MoTe 2 not only paves a new way for designing the best NLO TMD structures, but also greatly prompts their practical applications in micro-nano NLO devices on chips in future.
High electronic conductivity, low average working voltage, and high theoretical capacities enable molybdenum carbide‐based materials as promising anodes for lithium‐ion batteries (LIBs). Apart from the increase in the number of additional active sites, further enhancement in the specific activity of the active sites is also an effective way to improve the electrochemical performance of the molybdenum carbide‐based electrodes. Here, a series of 3D cross‐linked macroporous MoxC@N‐C nanocrystals with rich incorporated Mo vacancies, high specific activity of active sites, and nitrogen‐doped carbon (N‐C) coating are designed and synthesized using a simple method. Benefitting from its 3D robust structures for the rapid transporting and additional storage of Li+, the MoxC@N‐C‐2.5 displays a high initial reversible capacity of 879.3 mAh g−1 at 0.05 A g−1. Moreover, the MoxC@N‐C‐2.5 shows a high discharge capacity of 825.3 mAh g−1 at 0.5 A g−1 with an initial capacity retention of 61.9% after 200 cycles. As expected, this facile strategy can be extended to the fabrication of other nanocomposites with rich defects, numerous porous structures, and heteroatoms doped carbon coating as electrodes toward high‐performance LIBs.
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