Yaqin Huang

Pig bone derived hierarchical porous carbon and its enhanced cycling performance of lithium–sulfur batteries

Pig bone derived carbon with a unique hierarchical porous structure was prepared by potassium hydroxide (KOH) activation. The effects of activation temperature on the textural properties of the pig bone based carbons were investigated. The hierarchical porous carbons exhibit the largest BET specific surface areas and pore volume when the activation temperature reaches 850 °C, and the carbon still maintains a highly hierarchical structure even when the temperature is up to 950 °C. The pig bone derived hierarchical porous carbon/sulfur composites have been tested as a novel cathode for lithium–sulfur batteries. The result shows that the cycle stability and the utilization of sulfur in the lithium–sulfur batteries have been largely improved. The hierarchical porous carbon/sulfur cathode has a high initial capacity of 1265 mAh g−1 and 643 mAh g−1 after 50 cycles, which is higher than that of the normal cathodes with compact structures.

A novel porous nanocomposite of sulfur/carbon obtained from fish scales for lithium–sulfur batteries

A novel porous sulfur/carbon nanocomposite was prepared as the cathode material for lithium–sulfur batteries. The porous nanostructure of the composite is beneficial for enhancing the cycle life by accommodating the volume expansion of sulfur particles and adsorbing the polysulfide produced during the electrochemical reaction. The resulting nanocomposite shows a high capacity of 1039 mA h g−1 at 1C (1C = 1675 mA g−1) in the first cycle and the reversible capacity remains high at up to 1023 mA h g−1 even after 70 cycles.

A fish scale based hierarchical lamellar porous carbon material obtained using a natural template for high performance electrochemical capacitors

A hierarchical lamellar porous carbon material was prepared with fish scale using a natural template. Electric double layer capacitors electrodes prepared from this kind of porous carbon exhibited exceptional ration ability which demonstrated that fish scale is a promising candidate precursor to prepare low cost but high performance porous carbon material.

A multi-core–shell structured composite cathode material with a conductive polymer network for Li–S batteries

A multi-core-shell with a conductive network structured C-PANI-S@PANI composite with high sulfur content up to 87% was synthesized. The composite cathode delivers higher specific capacity and excellent cycle stability, retaining a reversible discharge capacity of 835 mA h g(-1) after 100 cycles when the sulfur loading of the cathode was above 6 mg cm(-2).

Improved cycle stability and high security of Li-B alloy anode for lithium–sulfur battery

Lithium–sulfur (Li–S) batteries suffer from low capacity retention rate and high security risks, in large part because of the use of metallic lithium as anode. Here, by employing a Li-B alloy anode, we were able to enhance cycle performance and security of Li–S batteries. Li-B alloy has a unique structure with abundant free Li embedded in stable Li7B6 loofah sponge-like framework. The Li7B6 constituent functions in the following three aspects: (1) eliminates orientational crystallization of free lithium; (2) reduces effective current density and promotes the formation of SEI layers; and (3) protects alloy bulk materials from deformation, volume expansion or collapse when cycling.

Improve Rate Capability of the Sulfur Cathode Using a Gelatin Binder

The influence of discharge rate on the discharge behaviour of the Li/S battery with the cathode using a gelatin binder (SGA cathode) is investigated by X-ray diffraction and scanning electron microscopy, with the system using poly(ethylene oxide) (PEO) binder (SPA cathode) as comparison. It is found that SGA cathode shows smaller plateau potential drop trend and less discharge curve shape change with the discharge rate increasing. Detailed characterization reveals that this is due to the dispersion ability and good adhesion of gelatin, which enable complete conversion of elemental sulfur to polysulfide in the upper plateau region and stable structure of the cathode during discharge. Developing pores in the SGA cathode (the PSGA cathode) can further improve the rate capability of the battery, since porous structure provides a larger contact surface with the electrolyte, and shorter Li + ion diffusion length. The PSGA cathode shows an initial capacity of 1230 mAhg ―1 -S at 100 mAg ―1 -S, and remains 733 mAhg ―1 -S at a high discharge rate of 1600 mAg ―1 -S.

High-capacity adsorption of Cr(VI) from aqueous solution using a hierarchical porous carbon obtained from pig bone

A hierarchical porous carbon obtained from pig bone (HPC) was utilized as the adsorbent for removal of Cr(VI) from aqueous solution. The effects of solution pH value, concentration of Cr(VI), and adsorption temperature on the removal of Cr(VI) were investigated. The experimental data of the HPC fitted well with the Langmuir isotherm and its adsorption kinetic followed pseudo-second order model. Compared with a commercial activated carbon adsorbent (Norit CGP), the HPC showed an high adsorption capability for Cr(VI). The maximum Cr(VI) adsorption capacity of the HPC was 398.40 mg/g at pH 2. It is found that a part of the Cr(VI) was reduced to Cr(III) on the adsorbent surface from desorption experiment data. The regeneration showed adsorption capacity of the HPC can still achieve 92.70 mg/g even after fifth adsorption cycle.

Discharge Process of the Sulfur Cathode with a Gelatin Binder

Gelatin, a natural biologic macromolecule, was successfully used as a new binder in place of poly (ethylene oxide) (PEO) in the fabrication of sulfur cathode in lithium-sulfur batteries. The change of a gelatin binder sulfur cathode in the discharge-charge process was investigated by X-ray diffraction and differential scanning calorimetry analysis, and the results were compared with those of the sulfur cathode using PEO as a binder. Our results indicated that the gelatin binder could enhance the redox reversibility of sulfur cathode by slowing down the reducing reaction of elemental sulfur during the discharging process and reforming S 8 after the charging process.

Chitosan as a functional additive for high-performance lithium–sulfur batteries

Chitosan with abundant hydroxyl and amine groups as an additive for cathodes and separators has been proven to be an effective polysulfide trapping agent in lithium–sulfur batteries. Compared with common sulfur cathodes, the cathode with chitosan shows an enhanced initial discharge capacity from 950 to 1145 mA h g−1 at C/10. The reversible specific capacity after 100 cycles increases from 508 mA h g−1 to 680 mA h g−1 and 473 to 646 mA h g−1 at rates of C/2 and 1 C, respectively. In addition, batteries with separators that are coated with a carbon/chitosan layer can exhibit a high discharge capacity of 830 mA h g−1 at C/2 after 100 cycles and 675 mA h g−1 at 1 C after 200 cycles with the capacity fading to as low as 0.11% per cycle. This study demonstrates the benefits of using chitosan for not only lithium–sulfur batteries but also potentially other sulfur-based battery applications.

Modified Separator Using Thin Carbon Layer Obtained from Its Cathode for Advanced Lithium Sulfur Batteries

The realization of a practical lithium sulfur battery system, despite its high theoretical specific capacity, is severely limited by fast capacity decay, which is mainly attributed to polysulfide dissolution and shuttle effect. To address this issue, we designed a thin cathode inactive material interlayer modified separator to block polysulfides. There are two advantages for this strategy. First, the coating material totally comes from the cathode, thus avoids the additional weights involved. Second, the cathode inactive material modified separator improve the reversible capacity and cycle performance by combining gelatin to chemically bond polysulfides and the carbon layer to physically block polysulfides. The research results confirm that with the cathode inactive material modified separator, the batteries retain a reversible capacity of 644 mAh g(-1) after 150 cycles, showing a low capacity decay of about 0.11% per circle at the rate of 0.5C.