Siqi Zhu

Hierarchical micro-/mesoporous N- and O-enriched carbon derived from disposable cashmere: a competitive cost-effective material for high-performance electrochemical capacitors

To obtain advanced carbon materials for next-generation electrochemical capacitors (ECs), it is critical to understand the synergetic effect of versatile carbon surface functionalities and the specific pore structure on their electrochemical performance. Herein, we developed a facile yet scalable fabrication of N- and O-enriched carbon with nanoscale to mesoscale porous structures from the disposable cashmere. The hierarchical cashmere-derived micro-/mesoporous carbon (CDMMC) was endowed with a desirable specific surface area (SSA, 1358 m2 g−1), hierarchical porosity with high microporosity of ∼45.5%, and high content of heteroatom functionalities (∼4 at% N and ∼15.5 at% O). Even better electrochemical capacitance of the resulting CDMMC was obtained in 1 M H2SO4, benefiting from the hierarchical micro-/mesoporosity, large effective SSA and remarkable heteroatom (N, O) doping effects, that is, the smart combination of double layer and Faradaic contributions, compared to that in KOH. Furthermore, larger energy density (∼17.9 Wh kg−1) of the CDMMC-based symmetric device was obtained with organic electrolytes, compared to those with aqueous electrolytes.

Hollow mesoporous hetero-NiCo2S4/Co9S8 submicro-spindles: unusual formation and excellent pseudocapacitance towards hybrid supercapacitors

Hierarchical hollow porous architectures with intriguing hetero-interfaces are currently of particular interest in emerging energy-related fields. In this investigation, we report a smart template-free methodology to purposefully fabricate high-quality uniform hollow hetero-NiCo2S4/Co9S8 (NCCS) submicro-spindles with well-dispersed hetero-nanodomains at the nanoscale. High-yield hollow mesocrystal nickel cobalt carbonate spindles are first solvothermally synthesized as the intermediate, and a subsequent shape-preserving conversion into hetero-NCCS submicro-spindles via a hydrothermal anion-exchange reaction occurs. The underlying template-free formation mechanism of the hollow structures is tentatively proposed. When evaluated as a promising electrode for supercapacitors, the resultant hollow mesoporous hetero-NCCS electrode with a mass loading of 5 mg cm−2 delivers a good pseudocapacitance of ∼749 F g−1 at a current rate of 4 A g−1, and holds at approximately 620 F g−1 at 15 A g−1 as a result of intrinsic synergetic contributions from structural/compositional/componental merits. Furthermore, an asymmetric device based on hollow mesoporous hetero-NCCS achieves an encouraging energy density of around 33.5 W h kg−1 at a power density of 150 W kg−1, and exceptional cycling behavior with capacitance degradation of ∼0.007% per cycle over 5000 consecutive cycles at 5 A g−1. Comprehensive investigations unambiguously highlight that the unique hollow mesoporous hetero-NCCS submicro-spindles would be a powerful electrode platform for advanced next-generation supercapacitors.

Hierarchical Porous ZnMn2O4 Hollow Nanotubes with Enhanced Lithium Storage toward Lithium-Ion Batteries

We have purposefully developed a smart template-engaged methodology to efficiently fabricate well-defined ternary spinel ZnMn2 O4 hollow nanotubes (NTs). The procedure involves coating carbon nanotubes (CNTs) with ZnMn2 O4 nanosheets (NSs), followed by heating at high temperature in air to oxidize the CNT template. Physicochemical characterization demonstrated that the formed ZnMn2 O4 NTs with a diameter of approximately 100 nm were composed of assembled NSs and/or nanoparticles (NPs) as building blocks and possessed numerous nanopores of several nanometers in the sidewall of the NTs. In favor of the intrinsic structural advantages, the resulting ZnMn2 O4 NTs exhibited superior electrochemical lithium-storage performance with a large capacity, good rate behavior, and excellent cyclability when evaluated as promising anodes for lithium-ion batteries (LIBs). The remarkable electrochemical performance was rationally ascribed to the appealing one-dimensional (1D) porous hollow tubular architecture with nanoscale subunits and mesopores in the sidewalls, which decreased the diffusion length for the Li(+) ions, improved the kinetic process, and enhanced the structural integrity with sufficient void space to tolerate the volume variation during Li(+) -ion insertion/extraction. These results highlight the promising application of 1D ZnMn2 O4 NTs as anodes for high-performance LIBs.

Green Template‐Free Synthesis of Hierarchical Shuttle‐Shaped Mesoporous ZnFe2O4 Microrods with Enhanced Lithium Storage for Advanced Li‐Ion Batteries

In the work, a facile and green two-step synthetic strategy was purposefully developed to efficiently fabricate hierarchical shuttle-shaped mesoporous ZnFe2 O4 microrods (MRs) with a high tap density of ∼0.85 g cm(3) , which were assembled by 1D nanofiber (NF) subunits, and further utilized as a long-life anode for advanced Li-ion batteries. The significant role of the mixed solvent of glycerin and water in the formation of such hierarchical mesoporous MRs was systematically investigated. After 488 cycles at a large current rate of 1000 mA g(-1) , the resulting ZnFe2 O4 MRs with high loading of ∼1.4 mg per electrode still preserved a reversible capacity as large as ∼542 mAh g(-1) . Furthermore, an initial charge capacity of ∼1150 mAh g(-1) is delivered by the ZnFe2 O4 anode at 100 mA g(-1) , resulting in a high Coulombic efficiency of ∼76 % for the first cycle. The superior Li-storage properties of the as-obtained ZnFe2 O4 were rationally associated with its mesoprous micro-/nanostructures and 1D nanoscaled building blocks, which accelerated the electron transportation, facilitated Li(+) transfer rate, buffered the large volume variations during repeated discharge/charge processes, and provided rich electrode-electrolyte sur-/interfaces for efficient lithium storage, particularly at high rates.

Core–shell ZnO/ZnFe2O4@C mesoporous nanospheres with enhanced lithium storage properties towards high-performance Li-ion batteries

In this study, we rationally developed and explored an appealing multi-featured nanoarchitecture, core–shell mesoporous ZnO/ZnFe2O4@C (ZZFO@C) nanospheres, for highly reversible lithium storage. Physicochemical characterization revealed that the mixed ZZFO nanospheres with numerous mesopores and a yolk–shell hollow structure were coated uniformly with an ultrathin N-doped carbon shell of ∼10 nm in thickness and were endowed with an internal continuous carbon network. Benefitting from the striking synergy and interplay of intrinsic component effects and structural advantages, the as-fabricated core–shell ZZFO@C exhibited a superior electrochemical Li-storage performance with a high specific capacity, excellent cycling properties and good rate capability when evaluated as an anode material for rechargeable Li-ion batteries (LIBs). These findings further revealed that the resulting core–shell ZZFO@C would be a promising anode for high-performance LIBs. Furthermore, in-depth insights into the structure/component-Li-storage correlation of the core–shell ZZFO@C hybrid showed that it was significantly favored for optimizational design and efficient fabrication of advanced hybrid anodes for next-generation LIBs in the future.

Ultrafast spray pyrolysis fabrication of a nanophase ZnMn2O4 anode towards high-performance Li-ion batteries

In this study, a facile, ultrafast and green spray pyrolysis strategy was developed well to efficiently fabricate nanophase ZnMn2O4 (ZMO–W) with homogeneous composition from an aqueous spray solution of manganous acetate and zinc acetate. Compared with other ZMO samples prepared by utilizing absolute ethanol and ethylene glycol as solvents, the ZMO–W product displayed competitively cost-effective advantages with the comprehensive consideration of cost and performance. When evaluated as a promising anode for Li-ion batteries (LIBs), the resultant ZMO–W exhibited large initial specific capacity (∼1023 mA h g−1), good rate capability, and excellent cycling stability (average capacity degradation of only ∼4.0% per cycle) at 1 C rate. Benefiting from an ultrafast reaction process in seconds, a high yield (∼100%), environmental friendliness (no NOx emission) and simple equipment requirements (just a tubular furnace), the synthetic methodology we developed here possesses significant potential for rapid large-scale production of advanced ZMO and even other binary transition metal oxides for industrial applications of LIBs.

Metal-organic-framework-derived two-dimensional ultrathin mesoporous hetero-ZnFe2O4/ZnO nanosheets with enhanced lithium storage properties for Li-ion batteries

Mesoporous hetero-structures have drawn tremendous attention due to their unprecedented inherent advantages in advanced Li-ion batteries (LIBs). In this study, we developed a facile metal-organic-framework-engaged synthetic methodology for large-scale fabrication of two-dimensional (2D) mesoporous hetero-ZnFe2O4/ZnO nanosheets (ZFOZ NSs) with homogeneously dispersed hetero-nanodomains of spinel ZnFe2O4 and ZnO. When evaluated as a promising anode for LIB applications, the resultant 2D ultrathin mesoporous hetero-ZFOZ NSs exhibited extraordinary electrochemical Li storage performance with long-cycle behavior and large reversible capacities for next-generation LIB applications, thanks to the attractive synergetic contributions from ultrathin mesoporous architecture and electroactive bi-component hetero-interfaces at the nanoscale. Even more encouragingly, the electrode concept we developed here can be easily generalized to rational design and synthesis of other mesoporous hetero-hybrids with remarkable lithium storage capacities for LIBs.

Self-sacrificial template formation of ultrathin single-crystalline ZnMn2O4 nanoplates with enhanced Li-storage behaviors for Li-ion batteries

Ultrathin single-crystalline ZnMn2O4 nanoplates were first designed and tailored as an alternative anode for advanced Li-ion batteries via an efficient self-sacrificial template synthetic strategy, and delivered large reversible capacity and desirable stability at high C rates.

A core–shell TiO2@C nano-architecture: facile synthesis, enhanced visible photocatalytic performance and electrochemical capacitance

In this work, we elegantly devised a bottom-up solvothermal strategy coupled with subsequent controllable calcination to synthesize a core–shell TiO2@C nanohybrid with a uniform ultrathin carbon shell of ∼1–3 nm. Physicochemical investigations revealed that Rutin and ethylene glycol played a great role in successful in situ fabrication of the uniform core–shell nano-architecture. Benefiting from the appealing synergetic effect of the mesoporous core–shell structure and composition advantages, the resulting core–shell TiO2@C with remarkable visible light response exhibited enhanced photocatalytic degradation efficiency and stability for methylene blue under visible light irradiation. Furthermore, the unique core–shell TiO2@C, thanks to its large surface area, rich mesoporosity and high electronic conductivity, demonstrated excellent electrochemical capacitance with a large specific capacitance of 210 F g−1 at 0.2 A g−1, and ∼2% capacitance degradation over cycling for 1200 times in 0.5 M aqueous H2SO4 at a current rate of 1 A g−1.