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The solid-solid conversion of Li2S2 to Li2S is a crucial and rate-controlling step that provides one-half of the theoretical capacity of lithium-sulfur (Li-S) batteries. The catalysts in the Li-S batteries are often useless in the solid-solid conversion due to the poor contact interfaces between solid catalysts and insoluble solid Li2S2. Considering that ultrafine nanostructured materials have the properties of quantum size effects and unconventional reactivities, we design and synthesize for the pomegranate-like sulfur nanoclusters@nitrogen-doped carbon@nitrogen-doped carbon nanospheres (S@N-C@N-C NSs) with a seed-pulp-peel nanostructure. The ultrafine S@N-C subunits (diameter ≈5 nm) and effects of a spatial structure perfectly realize the rapid conversion of ultrafine Li2S2 to Li2S. The S@N-C@N-C seed-pulp-peel NS cathodes exhibit excellent sulfur utilization, superb rate performance (760 mAh g-1 at 10.0 C), and an ultralow capacity decay rate of about 0.016% per cycle over 1000 cycles at 4.0 C. The proposed strategy based on ultrafine nanostructured materials can also inform material engineering in related energy storage and conversion fields.

The physical confinement and chemical catalysis of lithium polysulfides (LiPSs) are effective approaches to improve the performance of lithium–sulfur (Li–S) batteries. How to effectively combine physical confinement and chemical catalysis has become the focus of research. Herein, micro–mesoporous carbon (MMC) embedded with well-dispersed ultrafine CoS2 (uCoS2) nanocrystals as an efficient sulfur host is presented. As expected, the obtained S/uCoS2@MMC cathode can achieve a synergistic effect of physical confinement and chemical catalysis of LiPSs through micro–mesoporous structures and well-dispersed uCoS2 nanocrystals. Furthermore, the MMC with a high conductive specific surface area, uniform pore size and micro–mesoporous structure can realize homogeneous loading of sulfur and physical adsorption of LiPSs. Owing to these excellent qualities, the S/uCoS2@MMC cathode delivers outstanding initial capacities up to 1227 mA h g−1 at 0.1C. More significantly, a capacity of 606 mA h g−1 is maintained after 1000 cycles at 1C (a very low capacity decay rate of only 0.032% per cycle). It can be seen that the MMC embedded with well-dispersed uCoS2 nanocrystals as the sulfur host has great application prospects in Li–S batteries.

Host materials that can physically confine and chemically adsorb/catalyze lithium polysulfides (LiPSs) are currently receiving intensive research interest for developing lithium–sulfur (Li–S) batteries. Herein, a novel host material made of micro–mesoporous carbon nanospheres (MMC NSs) with well-dispersed ultrafine NiS2-ZnS (uNiS2-ZnS) heterostructures is synthesized for the first time via a simple in situ sulfuration process. The uNiS2-ZnS/MMC materials achieve the synergistic effect of physical confinement and the efficient chemical adsorption/catalysis of LiPSs through a micro–mesoporous structure and well-dispersed uNiS2-ZnS heterostructures. In addition, compared with bulk heterostructured materials, the uNiS2-ZnS heterostructures greatly enhance the adsorption and catalytic ability toward LiPSs because the catalysis interface effect and naturally formed in-plane interfaces can be magnified by the ultrafine dispersed nanoparticles. As a result, the prepared uNiS2-ZnS/MMC-S cathodes exhibit outstanding rate capacity (675.5 mA h g−1 at 5.0C) and cyclic stability (710.5 mA h g−1 at 1.0C after 1000 cycles with a low capacity decay of 0.033% per cycle). This work provides a certain reference for the application of heterostructured materials in Li–S batteries.

The solid-solid conversion of Li

Host materials that can physically confine and chemically adsorb/catalyze lithium polysulfides (LiPSs) are currently receiving intensive research interest for developing lithium-sulfur (Li-S) batteries. Herein, a novel host material made of micro-mesoporous carbon nanospheres (MMC NSs) with well-dispersed ultrafine NiS

The carbon nanostructure with heteroatom doping having well-designed porosity and a large pore volume plays a vital role in high-performance supercapacitors. Herein, we synthesize hierarchical nitrogen and sulfur-codoped micromesoporous carbon nanospheres (N,S-HPCNSs) with an ultralarge pore volume of 3.684 cm

Red phosphorus (P) has been recognized as a promising material for lithium/sodium-ion batteries (LIBs/SIBs) because of their high theoretical capacity. However, tremendous volume variation and low conductivity limit its widespread applications. Hence, we design and synthesize uniformly distributed honeycomb-like hierarchical micro-mesoporous carbon nanospheres (HHPCNSs) with ultralarge pore volume (3.258 cm3 g-1) on a large scale through a facile way. The large pore volume provides enough space for loading of P and the expansion of P, and the uniform distribution of the micro-mesopores enables the red P to load uniformly. The resulting HHPCNSs/P composite exhibits extremely high capacity (2463.8 and 2367.6 mA h g-1 at 0.1 A g-1 for LIBs and SIBs, respectively), splendid rate performance (842.2 and 831.1 mA h g-1 at 10 A g-1 for LIBs and SIBs, respectively) and superior cycling stability (1201.6 and 938.4 mA h g-1 at 2 and 5 A g-1 after 1000 cycles for LIBs and 1269.4 and 861.8 mA h g-1 at 2 and 5 A g-1 after 1000 cycles for SIBs, respectively). More importantly, when coupled with LiFePO4 and Na3V2(PO4)3 cathode, lithium/sodium-ion full batteries display high capacity and superior rate and cycling performances, revealing the practicability of the HHPCNSs/P composite. The exceptional electrochemical performance is caused by the honeycomb-like carbon network with ultralarge pore volume, uniformly distributed hierarchical micro-mesoporous nanostructure, outstanding electronic conductivity, and excellent nanostructural stability, which is much better than currently reported P/C materials for both LIBs and SIBs.

The work describes dually-emissive silicon nanoparticles (Si NPs) in aqueous dispersion with two emissions. The Si NPs respond to different solvents independently with various wavelength fluorescence emissions (red to green). The fluorescence emission wavelengths and emissive color of Si NPs can be regulated by adjustment of the solvents. Based on the effect of the solvent, a series different emission color Si NPs is obtained (Si NPs A, B, C and D), which exhibit different fluorescence emission in various solvents. Notably, the Si NP-A (dispersed in water) exhibited excellent analytical performance in sensing Cu2+ ions with amazing fluorescent response from green to brilliant blue light. The much more enhancement at 436 nm than at 500 nm was due to the changing surface chemistry of Si NPs by Cu2+, which was dependent to the concentration of Cu2+ tightly. The excellent sensitivity of Si NP-A towards Cu2+ has been testified with the detection limit as low as 0.91 μM by good linear relationship between ratio of fluorescence intensity (I436/I500) and concentration of Cu2+ (2–30 μM). The Si NP-A can be exploited as a dual-fluorescence visualization agent for latent fingerprints imaging due to the feature of dual emission. The images exhibited green emission under excited at 254 nm, and emerged green light under 365 nm, which allowed the Si NP-A applying in development of latent finger prints at complex background. These acquired fingerprints revealed the particular second-level characteristics.

Maricite NaFePO4 (NFP) as cathode for sodium-ion batteries has attracted much attention because of the high theoretical capacity (155 mA h g−1) and simple synthetic process. However, electrochemically active maricite NFP is greatly dependent on the design of the nanostructure. Highly dispersed maricite NFP nanoclusters (NFPNCs) with ultrafine NFP@C subunits (3 nm) are designed and synthesized by a facile method. The unique ultrafine NFPNCs nanostructure makes electrochemically inactive maricite NFP change to highly active amorphous phase due to the ultrafine nanosize effect. The NFPNCs based cathode displays ultrahigh capacity (149.2 mA h g−1 at 0.2C), excellent rate performance (75.7 mA h g−1 at 50C) and superior cycling performance (91.3 mA h g−1 at 10C after 5000 cycles with 95.0% retention). Even at low temperature (-10 and −20 °C), the NFPNCs still exhibit 85.5% and 75.8% capacity retention at −10 and −20 °C, respectively, in comparison to that of 25 °C. Furthermore, when coupled with hard carbon anode, the fabricated sodium-ion full batteries also exhibit high capacity, splendid cycling and rate properties. The ultrafine NFP@C subunits shorten Na+/electron diffusion pathways and provide high electrical conductivity, leading to high rate property and outstanding low temperature application.

How to construct the advanced sulfur cathode material with both high conductivity and well-defined structure is an important direction for Li–S batteries. In present study, we report a facile in situ method to prepare sulfur@nitrogen-doped carbon (S@N–C) yolk@shell nanospheres (NSs) as cathodes for Lithium–Sulfur (Li–S) batteries. The In-situ synthesis strategy eliminates the problem of diffusion of LiPSs caused by sulfur accumulated on the outer surface of N–C. Moreover, the yolk@shell structure reduces volume expansion upon lithiation through internal hollow structure and provides physical confinement and chemical adsorption of LiPSs by enclosed N–C outer shell. In addition, the electronic conductivity and reaction kinetic rate increased due to the doped nitrogen. As expected, the S@N–C NSs cathodes exhibited superior electrochemical performance for Li–S batteries (616 mAh g−1 at 1.0 C after 500 cycles).

Although lithium-sulfur (Li-S) batteries have high theoretical capacity and energy density, their practical applications have been hampered by the rapid decay of capacity caused by the shuttle effect of polysulfides. In this paper, we synthesize the MoS2/Ni3S2 yolk-shell heterostructure nanosphere (NS) and use it for the first time as the host material for Li-S batteries. The combination of yolk-shell structure and heterostructure enables MoS2/Ni3S2 NSs to have large sulfur storage space and abundant active sites, which can effectively capture polysulfides and dynamically promote the redox reaction. As the cathode of Li-S batteries, MoS2/Ni3S2@S exhibits excellent electrochemical performance and has an initial discharge capacity of 1445.4 mA h g−1 at 0.1 C. Moreover, the capacity of 739 mA h g−1 is maintained after 1000 cycles under 1 C, with an average coulomb efficiency is 97.4%. It can be seen that the multi-functional sulfur host material MoS2/Ni3S2 has great application prospects in Li-S batteries.

For the development of lithium-sulfur (Li-S) batteries, it is important to construct advanced host materials with large conductive, specific surface area and high activity exposed polar sites for adsorption of lithium polysulfides (LiPSs), which could promote uniform nucleation of lithium sulfide (Li2S) and liquid/solid conversion efficiency of sulfur species. Herein, we first reported the synthesis of ordered micro-mesoporous carbon (OMMC) nanospheres embedded with ultrafine iron carbide (Fe3C) nanocrystals by a facile one-step carbonizing process as effective sulfur host materials. As expected, the Fe3C/OMMC nanospheres (Fe3C/OMMC NSs) can realize homogeneous loading of sulfur, strong adsorption and catalysis of LiPSs with high efficiency, and promote uniform nucleation of Li2S through the ordered micro-mesoporous structures and ultrafine (average 5 nm) Fe3C nanocrystals. The Fe3C/OMMC-S NSs cathodes achieved excellent sulfur utilization, outstanding cyclic stability (700 mAh g−1 at 1.0 C after 1000 cycles with an ultralow capacity decay of 0.033% per cycle) and impressive rate performance (656 mAh g−1 at 5.0 C).

Binary transition metal oxides are recently gaining prominence as promising anode materials for next-generation Li-ion batteries (LIBs), owing to its intrinsic merits. Herein, in our work, highly dispersible ZnFe2O4 hollow nanospheres (denoted as ZFO-HNSs) assembled by ultra-small ZFO subunits (average diameter ∼15 nm) have been prepared via one-pot and cost-effective method on a large scale. Surprisingly, the results of electrochemical test show that the ZFO-HNSs possess an excellent super-long cycle performance (1044 and 900 mA h g−1 at 500 and 1000 mA g−1 over 400 cycles, respectively), which break the previous documentary records among the as reported pure ZFO anode materials, excellent electrochemical performance benefits from the unique ZFO-HNSs are assembled by ultra-small ZFO subunits, thus providing a preview of their practical applications in LIBs. More meaningfully, other binary transition metal oxides (such as ZnCo2O4, ZnMn2O4 and CoFe2O4) can be further fabricated by our strategy, which maybe promote the further application of them in adsorption, photocatalysis, supercapacitor and microwave absorption fields.

Uniform pomegranate-like nanoclusters (NCs) organized by ultrafine transition metal oxide@nitrogen-doped carbon (TMO@N–C) subunits (diameter ≈ 4 nm) are prepared on a large scale for the first time through a facile, novel, and one-pot approach. Taking pomegranate-like Fe3O4@N–C NCs as an example, this unique structure provides short Li+/electron diffusion pathways for electrochemical reactions, structural stability during cycling, and high electrical conductivity, leading to superior electrochemical performance. The resulting pomegranate-like Fe3O4@N–C NCs possess a high specific capacity (1204.3 mA h g−1 at 0.5 A g−1 over 100 cycles), a stable cycle life (1063.0 mA h g−1 at 1 A g−1, 98.4% retention after 1000 cycles), and excellent rate capacities (606.0 mA h g−1 at 10 A g−1, 92.0% retention; 417.1 mA h g−1 at 20 A g−1, 91.7% retention after 1000 cycles).