Co–Zn/N–C polyhedral nanocages: porous bimetallic Co/Zn embedded N-doped carbon (Co–Zn/N–C) polyhedral nanocages have been synthesized through annealing a ZIF-8@ZIF-67 precursor for the first time. The excellent lithium-storage ability is attributed to the unique structure of Co–Zn/N–C.

The exploration of inexpensive, facile, and large‐scale methods to prepare carbon scaffolds for high sulfur loadings is crucial for the advancement of Li–S batteries (LSBs). Herein, the authors report a new nitrogen and oxygen in situ dual‐doped nonporous carbonaceous material (NONPCM) that is composed of a myriad of graphene‐analogous particles. Importantly, NONPCM could be fabricated on a kilogram scale via inexpensive and green hydrothermal‐carbonization‐combined methods. Many active sites on the NONPCM surface are accessible for the efficient surface‐chemistry confinement of guest sulfur and its discharge product; this confinement is exclusive of physical entrapment, considering the low surface area. Electrochemical examination demonstrates excellent cycle stability and rate performance of the NONPCM (K)/S composite, even with a sulfur loading of 80 or 90 wt%. Hence, the scaffolds for LSBs exhibit potential for industrialization through further optimization and expansion of the present synthesis.

used as a cathode material. However, there are many shortcomings to hinder the development of Li-S batteries. First, insulating nature of sulfur and its discharge products (Li 2 S) lead to the poor electrochemical activity and low utilization of sulfur. On the other hand, during the charge/discharge process, the long-chain lithium polysulfides (Li 2 S x , 4 ≤ x ≤ 8) are very easily dissolved in the organic electrolyte [4,5] and diffuse toward the anode conductive bone, which results in undesired shuttle reactions, a rapid fading of capacity and lower Coulombic efficiency. [6] In order to promote the development of Li-S batteries, many researchers have tried attempts to solve these problems. For example, a variety of carbon materials have been designed as the host of sulfur with good electrical conductivity such as graphite or graphene, [7][8][9][10] meso-/ microporous carbon, [11,12] carbon nanotubes (CNTs)/nanofibers, [13][14][15] hollow carbon nanospheres, [16,17] and so on. Furthermore, porous carbon materials could effectively alleviate the dissolution and shuttle reactions of intermediate polysulfides by physical absorbability of pores. [11] By means of combination with chemical functionality, N-rich porous carbon materials have extensively attracted researchers' attention. For instance, Zhang and co-workers have presented a facile integration of high-quality aligned CNTs and graphene (ACNT/G hybrids) without barrier layers, followed by the process of nitrogen doping (N-ACNT/G hybrids). After combination with sulfur, electrochemical tests fully verify the superior cathode performance of N-ACNT/G hybrids to pristine ACNT/G. [18] According to the documents, pyridinic and pyrrolic nitrogen atoms can well provide abundant active sites and relieve "sulfur shuttling" by strong Li-N chemical interactions with soluble polysulfides. [19,20] Our group has reported dual N/O-doped carbon materials and explored it as carbon hosts. Because of the surficial chemical absorption function of heteroatoms for long-chain polysulfides, the related cells achieve a stable cyclic performance, even though the carbon matrix exhibits a low surface area. [19] More recently, Zheng and co-workers have proposed the derivation from metal-organic frameworks (MOFs), i.e., a synergistic composite containing cobalt and N-doped graphitic carbon (Co-N-GC), which demonstrates doped carbon facilitating S redox process and a remarkable enhancement of performance. [20] As we all known, nitrogen atoms doped in carbon matrix are beneficial for Herein, a flexible method is designed to engineer nitrogen-doped carbon materials (NC) with different functional and structural specialties involving N-doping level, graphitization, and surface area via tuning the carbonization temperature of the pre-prepared zeolitic imidazolate framework-8 (ZIF-8 ) crystals. With the aim to unveil the effect of these features on the electrochemical performance of sulfur cathode, these samples are evaluated as sulfur host and comprehensively investigated. NC-800 (800 °C, 10.45%N...

Well-distributed graphene sheets doped with nitrogen (NGS) were prepared via a thermal annealing strategy with the existence of cyanamide. The cyanamide can efficiently restrain the conglomeration of the resultant graphene sheets and synchronously make sure the doping of nitrogen. Followed by the next-step of low-temperature solvothermal route, uniform ultrasmall tin sulfide (SnS 2 ) nanocrystals were readily grown on the preformed NGS (denoted as SnS 2 -NGS).Benefiting from the synergistic function between NGS and SnS 2 , the resultant composites exhibit excellent electrochemical performance. In case of estimation as anode materials for lithium-ion batteries (LIBs), SnS 2 -NGS with moderate weight ratio of SnS 2 deliver outstanding electrochemical outcomes giving the high reversible capacity of 1407 mA h g -1 at 200 mA g -1 after 120 cycles. The composites can also maintain a reversible capacity of about 200 mA h g -1 at a high current density of 10 A g -1 . The lithium-ion storage ability of prepared SnS 2 -NGS electrode is at the top rank in comparison with the other works. The obtained composites also achieve good sodium storage ability.

The proposal herein is based on an effi cient sulfur host, namely hierarchical microporous-mesoporous carbonaceous nanotubes (denoted as HMMCNT) that feature a thick microporous wall and inner hollow channel. The electrochemical performance of the composite (HMMCNT-S) is studied systematically at different discharge cut-off voltages and at varying sulfur content. The cycling behavior in different voltage windows is compared and the highest specifi c capacity is shown for HMMCNT-S-50 in the range of 1.4-2.8 V. These results imply that better energy densities can be achieved by controlling the discharge cut-off voltage. Moreover, we show that when the sulfur loading is 50% (HMMCNT-S-50), the cycling and rate performance is better than that of the composite loaded with 40% sulfur (HMMCNT-S-40). Benefi ting from the attractive hierarchical micro/mesoporous confi guration, the obtained hybrid structure not only promotes electron and ion transfer during the charge/discharge process, but also effi ciently impedes polysulfi de dissolution. More specifi cally, the electrode can deliver a specifi c capacity of 558 mA h g −1 even after 150 cycles at a high rate of 1600 mA g −1 with a decay rate of only 0.13% per cycle. Considering the benefi cial structure of these carbon nanotubes, it is very feasible that these structures may also be used in other research fi elds, including in catalysis, as supercapacitors, in drug-delivery applications, for absorption, and so on.

Graphene-like N,S-codoped bio-carbon nanosheets (GNSCS) were prepared by a facile and environment-friendly NaCl non-aqueous ionic liquid route to house sulfur for lithium-sulfur battery. The natural nori powder was calcined at 900°C for 3 h under Ar, in which NaCl non-aqueous ionic liquid can exfoliate carbon aggregates into nanosheets. The structural characterization of GNSCS by a series of techniques demonstrates the graphene-like feature. When evaluated as the matrix for sulfur cathode, GNSCS/S exhibits more prominent cycling stability and rate capability. A discharge capacity of 548 mA h g −1 at a current density of 1.6 A g −1 after 400 cycles was delivered with a capacity fade rate of only 0.13% per cycle and an initial Coulombic efficiency (CE) as high as 99.7%. When increasing the areal sulfur loading up to 3 mg cm −2 , the discharge capacity can still be retained at 647 mA h g −1 after more than 100 cycles with a low capacity degradation of only~0.30% per cycle. The features of N/S dual-doping and the graphene-like structure are propitious to the electron transportation, lithium-ion diffusion and more active sites for chemically adsorbing polysulfides. It is anticipated that other functional biochar carbon can also be attained via the low-cost, sustainable and green method.

Sodium-ion batteries (SIBs) attract extensive attention as a promising alternative to lithium-ion batteries (LIBs) owing to their abundant reserves and low cost for large-scale energy storage systems. Among the electrode...

Na 3 V 2 O 2 (PO 4 ) 2 F (marked as NVOPF) is a promising cathode material for sodium-ion batteries owing to its high voltage and theoretical energy density, while the low electrical conductivity hinders its practical applications. Ion-doping could effectively improve electronic conductivity and structural stability of these materials. In this study, Mn-doping Na 3 V 2À x Mn x O 2 (PO 4 ) 2 F (0 � x � 0.15) hollow microspheres were successfully synthesized by hydrothermal method in the presence of H 2 O 2 . Among these obtained materials, NVMOPF-0.050 exhibits the best electrochemical performance with initial discharge capacity of 118 mAh g À 1 and 61 mAh g À 1 at 0.1 C and 2 C as cathode material for sodium ion batteries. Excellent performance can be attributed to the hollow spherical architecture, and good structural stability.