Linrui Hou

Recent progresses in high-energy-density all pseudocapacitive-electrode-materials-based asymmetric supercapacitors

Recently, asymmetric supercapacitors (ASCs) have attracted extensive research interest worldwide for their potential application in emerging energy-related fields. The smart integration of high overall cell operating voltage and large capacitance can be realized in all-pseudocapacitive-electrode-materials-based ASCs. This innovative all-pseudocapacitive-asymmetric design provides a fascinating way to obtain high-energy-density devices with high power rates and also holds huge potential to bridge the gap between dielectric capacitors and rechargeable batteries. In the present review, we mainly summarized the latest contributions and progress in aqueous/non-aqueous faradaic electrode materials including conductive polymers and/or transition metal oxides/sulfides/nitrides/carbides, the operating principles, system design/engineering, and the rational optimization of all-pseudocapacitive ASCs. The intrinsic advantages and disadvantages of these unique ASCs have been elaborately discussed and comparatively evaluated. Finally, some future trends, prospects, and challenges, especially in rate capability and cycling stability, have been presented for advanced next-generation ASCs.

Nasicon-Type Surface Functional Modification in Core–Shell LiNi0.5Mn0.3Co0.2O2@NaTi2(PO4)3 Cathode Enhances Its High-Voltage Cycling Stability and Rate Capacity toward Li-Ion Batteries

Surface modifications are established well as efficient methodologies to enhance comprehensive Li-storage behaviors of the cathodes and play a significant role in cutting edge innovations toward lithium-ion batteries (LIBs). Herein, we first logically devised a pilot-scale coating strategy to integrate solid-state electrolyte NaTi2(PO4)3 (NTP) and layered LiNi0.5Mn0.3Co0.2O2 (NMC) for smart construction of core-shell NMC@NTP cathodes. The Nasicon-type NTP nanoshell with exceptional ion conductivity effectively suppressed gradual encroachment and/or loss of electroactive NMC, guaranteed stable phase interfaces, and meanwhile rendered small sur-/interfacial electron/ion-diffusion resistance. By benefiting from immanently promoting contributions of the nano-NTP coating, the as-fabricated core-shell NMC@NTP architectures were competitively endowed with superior high-voltage cyclic stabilities and rate capacities within larger electrochemical window from 3.0 to 4.6 V when utilized as advanced cathodes for advanced LIBs. More meaningfully, the appealing electrode design concept proposed here will exert significant impact upon further constructing other high-voltage Ni-based cathodes for high-energy/power LIBs.

Recent Progresses and Development of Advanced Atomic Layer Deposition towards High-Performance Li-Ion Batteries

Electrode materials and electrolytes play a vital role in device-level performance of rechargeable Li-ion batteries (LIBs). However, electrode structure/component degeneration and electrode-electrolyte sur-/interface evolution are identified as the most crucial obstacles in practical applications. Thanks to its congenital advantages, atomic layer deposition (ALD) methodology has attracted enormous attention in advanced LIBs. This review mainly focuses upon the up-to-date progress and development of the ALD in high-performance LIBs. The significant roles of the ALD in rational design and fabrication of multi-dimensional nanostructured electrode materials, and finely tailoring electrode-electrolyte sur-/interfaces are comprehensively highlighted. Furthermore, we clearly envision that this contribution will motivate more extensive and insightful studies in the ALD to considerably improve Li-storage behaviors. Future trends and prospects to further develop advanced ALD nanotechnology in next-generation LIBs were also presented.

Sustainable rose multiflora derived nitrogen/oxygen-enriched micro-/mesoporous carbon as a low-cost competitive electrode towards high-performance electrochemical supercapacitors

Cost-efficient carbonaceous materials have been utilized extensively for advanced electrochemical supercapacitors. However, modest gravimetric/volumetric capacitances are the insuperable bottleneck in their practical applications. Herein, we develop a simple yet scalable method to fabricate low-cost micro-/mesoporous N/O-enriched carbon (NOC-K) by using natural rose multiflora as a precursor with KOH activation. The biomass-derived NOC-K is endowed with a large surface area of ∼1646.7 m2 g−1, micro-/mesoporosity with ∼61.3% microporosity, high surface wettability, and a high content of N (∼1.2 at%)/O (∼26.7 at%) species. When evaluated as an electroactive material for supercapacitors, the NOC-K electrode (5 mg cm−2) yields large gravimetric/volumetric specific capacitances of ∼340.0 F g−1 (∼238.0 F cm−3) at 0.5 A g−1, and even ∼200.0 F g−1 (∼140.0 F cm−3) at 5.0 A g−1, a low capacitance decay of ∼4.2% after 8200 consecutive cycles, and a striking specific energy of ∼8.3 W h kg−1 in aqueous KOH electrolyte, benefiting from its intrinsic structural and compositional superiorities. Moreover, a remarkable specific energy of ∼52.6 W h kg−1 and ∼96.6% capacitance retention over 6500 cycles for the NOC-K based symmetric cell are obtained with the organic electrolyte. More promisingly, the competitive NOC-K demonstrates enormous potential towards advanced supercapacitors both with aqueous and organic electrolytes as a sustainable electrode candidate.

Green and Facile Synthesis of Nitrogen and Phosphorus Co-Doped Carbon Quantum Dots towards Fluorescent Ink and Sensing Applications

Fluorescent carbon quantum dots (CQDs) have held great promise in analytical and environmental fields thanks to their congenitally fascinating virtues. However, low quantum yield (QY) and modest fluorescent stability still restrict their practical applications. In this investigation, a green hydrothermal strategy has been devised to produce water-soluble nitrogen/phosphorus (N/P) co-doped CQDs from edible Eleocharis dulcis with multi-heteroatoms. Without any additives and further surface modifications, the resultant CQDs exhibited tunable photoluminescence just by changing hydrothermal temperatures. Appealingly, they showed remarkable excitation-dependent emission, high QY, superior fluorescence stability, and long lifetime. By extending the CQDs solutions as a “fluorescent ink”, we found their potential application in the anti-counterfeit field. When further evaluated as a fluorescence sensor, the N/P co-doped CQDs demonstrated a wide-range determination capability in inorganic cations, and especially the remarkable sensitivity and selectivity for elemental Fe3+. More significantly, the green methodology we developed here can be readily generalized for scalable production of high-quality CQDs with tunable emission for versatile applications.

Foxtail millet-derived highly fluorescent multi-heteroatom doped carbon quantum dots towards fluorescent inks and smart nanosensors for selective ion detection

Carbon quantum dots (CQDs) are attracting enormous attention as a smart material owing to their congenital virtues. Unfortunately, their low quantum yield (QY) and modest fluorescence stability seriously restrain their practically versatile applications. Herein, a facile yet green strategy has been developed for synthesizing nitrogen/sulfur/phosphrous (N/S/P) co-doped CQDs via hydrothermal treatment of natural foxtail millet without any extra additives or organic agents. The resultant N/S/P co-doped CQDs were endowed with remarkable excitation-dependent emission, high QY (∼21.2%), superior fluorescence stability, and long lifetime (∼2.05 ns) owing to multi-heteroatom doping. Thanks to their strong blue-green fluorescence upon irradiation with UV light (365 nm), the water-soluble CQDs demonstrated huge potential for anticounterfeit application as a fluorescent ink. When utilized as a fluorescent sensor for cation determination, the multi-heteroatom doped CQDs especially displayed the highest sensitivity and selectivity for Fe3+ along with good linear correlation ranging from 5 to 150 μM and a low detection limit of 0.046 μM. More remarkably, our fabricated high-quality CQDs would hold great promise in analytical and/or environmental fields.

Structure-designed synthesis of yolk–shell hollow ZnFe2O4/C@N-doped carbon sub-microspheres as a competitive anode for high-performance Li-ion batteries

Spinel ZnFe2O4 (ZFO) has recently gained prominence as a fascinating anode for lithium-ion batteries (LIBs) owing to its intrinsic merits. However, serious electrode pulverization and modest electrical conductivity hugely hinder its commercial application. Herein, we describe the deliberate fabrication of a multi-functional yolk–shell hollow architecture, designated as H-ZFO–C@void@C, where hollow ZFO sub-microspheres with an internal well-distributed carbon network were prepared in a template-free manner as a yolk, along with a conductive N-doped carbon nanoshell and functional void interspace. Structural/geometric simulations and experiments confirm that the well-defined internal void and hollow interior of the yolk can efficiently accommodate volumetric expansion over lithiation without breaking the outer nanoshell while ensuring good yolk–shell electronic contact and a thin yet stable solid–electrolyte-interphase film on the outer surface. The conducting nano-carbon shell and continuous internal carbon network prevent the serious aggregation of nano-ZFO subunits, and facilitate convenient charge transfer during repeated lithiation/delithiation processes. Benefiting from the synergetic contributions of these appealing design rationales, our integrated H-ZFO–C@void@C anode delivers a high initial coulombic efficiency of ∼76.8%, a remarkable reversible capacity of ∼775 mA h g−1 at 2000 mA g−1, and long-term cyclability after 500 cycles at a high rate of 1000 mA g−1. More promisingly, our design here offers a competitive metal oxide-based anode structure for advanced LIBs.