Anisotropic nanoparticles, giving rise to a large number of novel physicochemical properties and functionalities, have provoked increasing attentions in nanoscience and nanotechnology. The remained challenge is to develop synthetic methods for the fabrication of anisotropic nanoparticles with less symmetry under the principle of minimum surface free energy. Here, we established a crystallization-assisted asymmetric assembly method for the synthesis of anisotropic polymer nanocrescents and their carbonaceous analogues by using triblock copolymer F127 and octadecanol in aqueous solution. With the aid of molecular dynamics (MD) simulation, we demonstrate that the observed crescent structure is caused by asymmetry distribution of octadecanol crystal within the hydrophobic core of F127 micelles, via the formation of intermediate elliptic micelles bearing hydrophobic ends that further fuse with each other end-to-end at an angle into curing nanocrescent morphology. The influences of annealing time, annealing temperature, and mole ratios of precursors that govern the kinetics of the assembly and polymerization process were systematically investigated and a series of polymer nanocrescents with tunable length of ~ 85 to ~ 262 nm and aspect ratio of ~ 1.1 to ~ 3.0 were prepared. The ability to create novel crescent-shaped polymer and carbon nanoparticles and the identification of asymmetric assembly process by combining experiment and simulation study will provide a valuable contribution both to theoretical and technological researches.

Confined nanospace pyrolysis (CNP) has attracted increasing attention as a general strategy to prepare task-specific hollow structured porous carbons (HSPCs) in the past decade. The unique advantages of the CNP strategy include its outstanding ability in control of the monodispersity, porosity and internal cavity of HSPCs. As a consequence, the obtained HSPCs perform exceptionally well in applications where a high dispersibility and tailored cavity are particularly required, such as drug delivery, energy storage, catalysis and so on. In this review, the fundamentals of the CNP strategy and its advances in structural alternation is first summarized, then typical applications are discussed by exemplifying specific synthesis examples. In addition, this review offers insights into future developments for advanced task-specific hollow structured porous materials prepared by the CNP strategy.

Porous carbon spheres with an internal gridded hollow structure and microporous shell have always been attractive as carbon hosts for electrochemical energy storage. Such carbon hosts can limit active species loss and enhance electronic conductivity throughout the entire framework. Herein, a synthesis approach of internal gridded hollow carbon spheres is developed from solid polymer spheres rather than originally gridded polymer spheres under a controlled pyrolysis micro-environment. The crucial point of this approach is the fabrication of a silica fence around solid polymer spheres, under which the free escaping of the pyrolysis gas will be partly impeded, thus offering a reconstitution opportunity for an internal structure of solid polymer spheres. As a result, the interior of carbon spheres is sculptured into a gridded hollow structure with microporous skin. Furthermore, the size and density of carbon-bridge grids can be modulated by altering the crosslinking degree of polymer spheres and varying pyrolysis conditions. Such gridded hollow carbon spheres show good performance as sulfur hosts for Li-S battery.

The commercialization of lithium-sulfur (Li-S) battery could be accelerated by designing advanced sulfur cathode with high sulfur utilization and stable cycle life at a high sulfur loading. To allow the energy density of Li-S batteries comparable to that of commercial Li-ion batteries, the areal capacity of sulfur cathode should be above 4 mA·h·cm^-2. In general, a high sulfur loading often causes rapid capacity fading by slowing electron/ion transport kinetics, catastrophic shuttle effect and even cracking the electrodes. To address this issue, herein, a multilevel structured carbon film is built by covering highly conductive CNTs and hollow carbon nanofiber together with carbon layer via chemical vapor deposition. The self-standing carbon film exhibits well-interweaved conductive network, hollow fibrous structure and abundant N, O co-doped active sites, which combine the merits of high electronic conductivity (1,200 S·m^-1), high porosity and polar characteristic in one host. Benefiting from this attractive multilevel structure, the obtained sulfur cathode based on the carbon film host shows an ultra-high areal capacity of 8.9 mA·h·cm^-2 at 0.2 C with outstanding cyclability over 60 cycles. This work shed light on designing advanced sulfur host for Li-S batteries with high areal capacity and high cycle stability, and might make a contribution to the commercialization of Li-S batteries.

Lithium sulfur battery has been identified as a promising candidate for next storage devices attributing to ultrahigh energy density. However, non-conductive nature of sulfur and shuttling effect of soluble lithium polysulfides are intractable remaining problems. Herein, we develop a highly conductive nickel-rich Ni₁₂P₅/CNTs hybrid with high specific surface area as sulfur host to address these issues. The polar nature of Ni₁₂P₅/CNTs can significantly relieve the shuttle effect by means of a strong affinity towards lithium polysulfides and enhance kinetics of polysulfides redox reactions. In addition, the Ni₁₂P₅/CNTs with a superior conductivity (500 S·m^-1) and high surface area of 395 m²·g^-1 enables the effective electron transfer and expedited interfacial reaction. As a result, Ni₁₂P₅/CNTs hosted sulfur cathode exhibits high rate capability (784 mAh·g^-1 at 4 C) and stable cycling performance with a negligible capacity fading of 0.057 % per cycle over 1, 000 cycles at 0.5 C. This work paves an alternative way for designing high performance sulfur cathodes involved metal-rich phosphides.

Designing a better carbon framework is critical for harnessing the high theoretical capacity of Li-S batteries and avoiding their drawbacks, such as the insulating nature of sulfur, active material loss, and the polysulfide shuttle reaction. Here, we report an ingenious design of hollow carbon nanofibers with closed ends and protogenetic mesopores in the shell that can be retracted to micropores after sulfur infusion. Such dynamic adjustable pore sizes ensure a high sulfur loading, and more importantly, eliminate excessive contact of sulfur species with the electrolyte. Together, the high aspect ratio and thin carbon shells of the carbon nanofibers facilitate rapid transport of Li⁺ ions and electrons, and the closed-end structure of the carbon nanofibers further blocks polysulfide dissolution from both ends, which is remarkably different from that for carbon nanotubes with open ends. The obtained sulfur-carbon cathodes exhibit excellent performance marked by high sulfur utilization, superior rate capability (1, 170, 1, 050, and 860 mA·h·g^-1 at 1.0, 2.0, and 4.0 C (1 C = 1.675 A·g^-1), respectively), and a stable reversible capacity of 847 mA·h·g^-1 after 300 cycles at a high rate of 2.0 C.

Carbon nanosheets with a tunable mesopore size, large pore volume, and good electronic conductivity are synthesized via a solution-chemistry approach. In this synthesis, diaminohexane and graphene oxide (GO) are used as the structural directing agents, and a silica colloid is used as a mesopores template. Diaminohexane plays a crucial role in bridging silica colloid particles and GO, as well as initiating the polymerization of benzoxazine on the surfaces of both the GO and silica, resulting in the formation of a hybrid nanosheet polymer. The carbon nanosheets have graphene embedded in them and have several spherical mesopores with a pore volume up to 3.5 cm³·g^–1 on their surfaces. These nuerous accessible mesopores in the carbon layers can act as reservoirs to host a high loading of active charge-storage materials with good dispersion and a uniform particle size. Compared with active materials with wide particle-size distributions, the unique proposed configuration with confined and uniform particles exhibits superior electrochemical performance during lithiation and delithiation, especially during long cycles and at high rates.

Carbon-protected magnetic nanoparticles exhibit long-term stability in acid or alkaline medium, good biocompatibility, and high saturation magnetization. As a result, they hold great promise for magnetic resonance imaging, photothermal therapy, etc. However, since pyrolysis, which is often required to convert the carbon precursors to carbon, typically leads to coalescence of the nanoparticles, the obtained carbon-protected magnetic nanoparticles are usually sintered as a non-dispersible aggregation. We have successfully synthesized discrete, dispersible, and uniform carbon-protected magnetic nanoparticles via a precise surface/interface nano-engineering approach. Remarkably, the nanoparticles possess excellent water-dispersibility, biocompatibility, a high T₂ relaxivity coefficient (384 mM^–1·s^–1), and a high photothermal heating effect. Furthermore, they can be used as multifunctional core components suited for future extended investigation in early diagnosis, detection and therapy, catalysis, separation, and magnetism.

Fe₃O₄ is a promising high-capacity anode material for lithium ion batteries, but challenges including short cycle life and low rate capability hinder its widespread implementation. In this work, a well-defined tubular structure constructed by carbon-coated Fe₃O₄ has been successfully fabricated with hierarchically porous structure, high surface area, and suitable thickness of carbon layer. Such purposely designed hybrid nanostructures have an enhanced electronic/ionic conductivity, stable electrode/electrolyte interface, and physical buffering effect arising from the nanoscale combination of carbon with Fe₃O₄, as well as the hollow, aligned and hierarchically porous architectures. When used as an anode material for a lithium-ion half cell, the carbon-coated hierarchical Fe₃O₄ nanotubes showed excellent cycling performance with a specific capacity of 1, 020 mAh·g^-1 at 200 mA·g^-1 after 150 cycles, a capacity retention of ca. 103%. Even at a higher current density of 1, 000 mA·g^-1, a capacity of 840 mAh·g^-1 is retained after 300 cycles with no capacity loss. In particular, a superior rate capability can be obtained with a stable capacity of 355 mAh·g^-1 at 8, 000 mA·g^-1. The encouraging results indicate that hierarchically tubular hybrid nanostructures can have important implications for the development of high-rate electrodes for future rechargeable lithium ion batteries (LIBs).