Qunying Li

Three-Dimensional Network of N-Doped Carbon Ultrathin Nanosheets with Closely Packed Mesopores: Controllable Synthesis and Application in Electrochemical Energy Storage

A flexible one-pot strategy for fabricating a 3D network of nitrogen-doped (N-doped) carbon ultrathin nanosheets with closely packed mesopores (N-MCN) via an in situ template method is reported in this research. The self-assembly soluble salts (NaCl and Na2SiO3) serve as hierarchical templates and support the formation of a 3D glucose-urea complex. The organic complex is heat-treated to obtain a 3D N-doped carbon network constructed by mesoporous nanosheets. Especially, both the mesoporous structure and doping content can be easily tuned by adjusting the ratio of raw materials. The large specific surface area and closely packed mesopores facilitate the lithium ion intercalation/deintercalation accordingly. Besides, the nitrogen content improves the lithium storage ability and capacitive properties. Due to the synergistic effect of hierarchical structure and heteroatom composition, the 3D N-MCN shows excellent characteristics as the electrode of a lithium ion battery and supercapacitor, such as ultrahigh reversible storage capacity (1222 mAh g(-1) at 0.1 A g(-1)), stable long cycle performance at high current density (600 cycles at 2 A g(-1)), and high capacitive properties (225 F g(-1) at 1 A g(-1) and 163 F g(-1) at 50 A g(-1)).

Sandwiched C@SnO2@C hollow nanostructures as an ultralong-lifespan high-rate anode material for lithium-ion and sodium-ion batteries

SnO2 is considered a promising anode candidate for both lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs), but suffers from the low electrical conductivity and severe volume variation during repetitive cycling. To circumvent these issues, we developed novel interconnected sandwiched carbon-coated hollow nanostructures, i.e., carbon–shell/SnO2–nanocrystal–layer/hollow–carbon–core (C@SnO2@C HNSs), in which ultrasmall SnO2 nanocrystals (2–5 nm) were tightly confined between the carbon shell and the hollow carbon core. Such a unique structure can not only protect the active materials from direct exposure to the electrolyte as well as restrain the migration and pulverization of the SnO2, but also offer rich void space for buffering the volume changes and complement the electron conductivity of the active materials, thus achieving remarkably enhanced electrical conductivity and structural integrity of the whole electrode. As a consequence, this C@SnO2@C HNS electrode exhibited an extremely outstanding long-life high-rate cycling stability for both LIB and SIB anodes, such as only 8% capacity loss after 1000 cycles at 10 A g−1 for LIB anode and only 10% capacity loss after 3000 cycles at 4.6 A g−1 for SIB anodes. As far as we know, this is the best high-rate cycle performance ever reported for SnO2-based SIB anodes.

N-Doped Porous Carbon Nanofibers/Porous Silver Network Hybrid for High-Rate Supercapacitor Electrode

A three-dimensional cross-linked porous silver network (PSN) is fabricated by silver mirror reaction using polymer foam as the template. The N-doped porous carbon nanofibers (N-PCNFs) are further prepared on PSN by chemical vapor deposition and treated by ammonia gas subsequently. The PSN substrate serving as the inner current collector will improve the electron transport efficiency significantly. The ammonia gas can not only introduce nitrogen doping into PCNFs but also increase the specific surface area of PCNFs at the same time. Because of its large surface area (801 m2/g), high electrical conductivity (211 S/cm), and robust structure, the as-constructed N-PCNFs/PSN demonstrates a specific capacitance of 222 F/g at the current density of 100 A/g with a superior rate capability of 90.8% of its initial capacitance ranging from 1 to 100 A/g while applied as the supercapacitor electrode. The symmetric supercapacitor device based on N-PCNFs/PSN displays an energy density of 8.5 W h/kg with power density of 250 W/kg and excellent cycling stability, which attains 103% capacitance retention after 10 000 charge-discharge cycles at a high current density of 20 A/g, which indicates that N-PCNFs/PSN is a promising candidate for supercapacitor electrode materials.