Shaozhong Zeng

Facile and tailored synthesis of ultrahigh-surface-area clews of carbon nanobelts for high-rate lithium-sulfur batteries

Hierarchical clews of carbon nanobelts (CsCNBs) with surface area up to 3445 m2 g−1 have been synthesized by a template-free method from low cost raw materials. The composite of CsCNBs/sulfur displays high initial capacities of 1476, 1021 and 838 mA h g−1 at 1, 3 and 5C, respectively, and ultraslow capacity decay rate of 0.052% per cycle during 300 cycles.

Conducting polymer-coated MIL-101/S composite with scale-like shell structure for improving Li–S batteries

Lithium–sulfur batteries are regarded as a promising energy storage system. However, they are plagued by rapid capacity decay, low coulombic efficiency, a severe shuttle effect and low sulfur loading in cathodes. To address these problems, effective carriers are highly demanded to encapsulate sulfur in order to extend the cycle life. Herein, we introduced a doped-PEDOT:PSS-coated MIL-101/S multi-core–shell structured composite. The unique structure of MIL-101, large specific area and conductive shell ensure high dispersion of sulfur in the composite and minimize the loss of polysulfides to the electrolyte. The doped-PEDOT:PSS-coated sulfur electrodes exhibited an increase in initial capacity and an improvement in rate characteristics. After 192 cycles at the current density of 0.1C, a doped-PEDOT:PSS-coated MIL-101/S electrode maintained a capacity of 606.62 mA h g−1, while the MIL-101/S@PEDOT:PSS electrode delivered a capacity of 456.69 mA h g−1. The EIS measurement revealed that the surface modification with the conducting polymer provided a lower resistance to the sulfur electrode, which resulted in better electrochemical behaviors in Li–S battery applications. Test results indicate that the MIL-101/S@doped-PEDOT:PSS is a promising host material for the sulfur cathode in the lithium–sulfur battery applications.

Facile synthesis of high-surface-area nanoporous carbon from biomass resources and its application in supercapacitors

It is critical for nanoporous carbons to have a large surface area, and low cost and be readily available for challenging energy and environmental issues. The pursuit of all three characteristics, particularly large surface area, is a formidable challenge because traditional methods to produce porous carbon materials with a high surface area are complicated and expensive, frequently resulting in pollution (commonly from the activation process). Here we report a facile method to synthesize nanoporous carbon materials with a high surface area of up to 1234 m2 g−1 and an average pore diameter of 0.88 nm through a simple carbonization procedure with carefully selected carbon precursors (biomass material) and carbonization conditions. It is the high surface area that leads to a high capacitance (up to 213 F g−1 at 0.1 A g−1) and a stable cycle performance (6.6% loss over 12 000 cycles) as shown in a three-electrode cell. Furthermore, the high capacitance (107 F g−1 at 0.1 A g−1) can be obtained in a supercapacitor device. This facile approach may open a door for the preparation of high surface area porous carbons for energy storage.

Facile Synthesis of Nitrogen and Oxygen Co-Doped Clews of Carbon Nanobelts for Supercapacitors with Excellent Rate Performance

Facile synthesis of carbon materials with high heteroatom content, large specific surface area (SSA) and hierarchical porous structure is critical for energy storage applications. In this study, nitrogen and oxygen co-doped clews of carbon nanobelts (NCNBs) with hierarchical porous structures are successfully prepared by a carbonization and subsequent activation by using ladder polymer of hydroquinone and formaldehyde (LPHF) as the precursor and ammonia as the activating agent. The hierarchical porous structures and ultra-high SSA (up to 2994 m2 g−1) can effectively facilitate the exchange and transportation of electrons and ions. Moreover, suitable heteroatom content is believed to modify the wettability of the carbon material. The as-prepared activated NCNBs-60 (the NCNBs activated by ammonia at 950 °C for 60 min) possess a high capacitance of 282 F g−1 at the current density of 0.25 A g−1, NCNBs-45 (the NCNBs are activated by ammonia at 950 °C for 45 min) and show an excellent capacity retention of 50.2% when the current density increase from 0.25 to 150 A g−1. Moreover, the NCNBs-45 electrode exhibits superior electrochemical stability with 96.2% capacity retention after 10,000 cycles at 5.0 A g−1. The newly prepared NCNBs thus show great potential in the field of energy storage.

Facile Synthesis of Ultrahigh‐Surface‐Area Hollow Carbon Nanospheres and their Application in Lithium‐Sulfur Batteries

Hollow carbon nanospheres (HCNs) with specific surface areas up to 2949 m2  g-1 and pore volume up to 2.9 cm3  g-1 were successfully synthesized from polyaniline-co-polypyrrole hollow nanospheres by carbonization and CO2 activation. The cavity diameter and wall thickness of HCNs can be easily controlled by activation time. Owing to their large inner cavity and enclosed structure, HCNs are desirable carriers for encapsulating sulfur. To better understand the effects of pore characteristics and sulfur contents on the performances of lithium-sulfur batteries, three composites of HCNs and sulfur are prepared and studied in detail. The composites of HCNs with moderate specific surface areas and suitable sulfur content present a better performance. The first discharge capacity of this composite reaches 1401 mAh g-1 at 0.2 C. Even after 200 cycles, the discharge capacity remains at 626 mAh g-1 .

A Universal Strategy To Prepare Sulfur-Containing Polymer Composites with Desired Morphologies for Lithium–Sulfur Batteries

Lithium-sulfur (Li-S) batteries are probably the most promising candidates for the next-generation batteries owing to their high energy density. However, Li-S batteries face severe technical problems where the dissolution of intermediate polysulfides is the biggest problem because it leads to the degradation of the cathode and the lithium anode, and finally the fast capacity decay. Compared with the composites of elemental sulfur and other matrices, sulfur-containing polymers (SCPs) have strong chemical bonds to sulfur and therefore show low dissolution of polysulfides. Unfortunately, most SCPs have very low electron conductivity and their morphologies can hardly be controlled, which undoubtedly depress the battery performances of SCPs. To overcome these two weaknesses of SCPs, a new strategy was developed for preparing SCP composites with enhanced conductivity and desired morphologies. With this strategy, macroporous SCP composites were successfully prepared from hierarchical porous carbon. The composites displayed discharge/charge capacities up to 1218/1139, 949/922, and 796/785 mA h g-1 at the current rates of 5, 10, and 15 C, respectively. Considering the universality of this strategy and the numerous morphologies of carbon materials, this strategy opens many opportunities for making carbon/SCP composites with novel morphologies.