Anbang Wang

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 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).

A high sulfur content composite with core–shell structure as cathode material for Li–S batteries

Lithium–sulfur (Li–S) batteries have received significant attention in recent years because of their high theoretical specific capacity (1675 mA h g−1) and energy density (2600 W h kg−1). Many papers focus on cells that exhibit very high capacity per gram of sulfur, which contain sulfur contents well below 50% which greatly reduces their overall energy density per gram of cathode. Moreover, they do not address the issues of practical sulfur loading and large-scale technology for commercial applications. In general, the lower the sulfur content, the higher the sulfur capacity. In this paper, a high sulfur content (80% S) carbon–sulfur (P-AB@S) material with core–shell structure has been successfully synthesized by grafting of polymer electrolyte (polyethylene glycol, PEG) chains and depositing sulfur onto the surface of electronically conductive acetylene black (AB). The PEG chains are inserted into the sulfur layer to reinforce the material’s structural stability. More importantly, with a cathode containing 66% sulfur and approximately 3 mg cm−2 sulfur loading on the electrode, P-AB@S as a cathode material for lithium sulfur batteries shows a specific capacity of 577 mA h g−1 after 500 cycles at 100 mA g−1 between 1.5 V and 2.8 V. Moreover, the preparation method of the P-AB@S composite is a facile, cost-effective and template-free method and easy to implement large-scale technology for commercial applications.

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.

Nano-CaCO3 as template for preparation of disordered large mesoporous carbon with hierarchical porosities

A series of large mesoporous carbons (LMC, 20–50 nm) with hierarchical porosities has been prepared using commercially available CaCO3 nanoparticles as a template, formaldehyde (PF) resin as carbon precursor, and HCl solution for removing the template. During the carbonization process, the CaCO3 template decomposes releasing CO2 which serves as an activating agent to active the carbon materials producing micropores and mesopores as well as enlarging pore sizes. This effect can be named as the “CO2 inner-activation effect”, which is proved by comparing the carbon yield, N2 adsorption/desorption isotherms, pore-size distribution and textual parameters of carbon materials carbonized at two critical temperatures, namely, 900 °C (higher than the pyrolysis temperature of CaCO3) and 650 °C (lower than the pyrolysis temperature of CaCO3). Our results show that the LMC samples prepared at different ratios of CaCO3 to PF have BET surface areas ranging from 503 to 1215 m2 g−1, and pore volumes ranging from 1.8 to 9.0 cm3 g−1. This one-step carbonization method with a CO2 inner-activation effect provides a novel route to prepare large mesoporous carbons and hierarchical porous carbon materials.

Multidimensional Polycation β-Cyclodextrin Polymer as an Effective Aqueous Binder for High Sulfur Loading Cathode in Lithium–Sulfur Batteries

Although the lithium-sulfur battery has attracted significant attention because of its high theoretical energy density and low cost of elemental sulfur, its real application is still hindered by multiple challenges, especially the polysulfides shuttled between the cathode and anode electrodes. By originating from β-cyclodextrin and introducing a quaternary ammonium cation into β-cyclodextrin polymer, a new multifunctional aqueous polycation binder (β-CDp-N(+)) for the sulfur cathode is obtained. The unique hyperbranched network structure of the new binder β-CDp-N(+) as well as its multidimensional noncovalent interactions and the introduced cations endowed β-CDp-N(+) with some new abilities: a sulfur-electrode-stabilized ability, a polysulfides-immobilized ability, and a volume-accommodated ability, which help to ease the primary problems of the lithium-sulfur battery, i.e., the shuttle of polysulfides and the volume change of the sulfur during charge and discharge. It is demonstrated that cycling performance and rate capability of the cathodes can be the improved by using β-CDp-N(+) as the binder compared to other well-known binders. Even with high sulfur loading of 5.5 mg cm(-2), the cathode with β-CDp-N(+) still can deliver an areal capacity of 4.4 mAh cm(-2) at 50 mA g(-1) after 45 cycles, which is much higher than that achieved using the cathode with the conventional binder (0.9 mAh cm(-2)).

Carbyne polysulfide as a novel cathode material for lithium/sulfur batteries

A novel organic sulfide named carbyne polysulfide was prepared by co-heating carbyne analogue and elemental sulfur. The carbyne analogue was obtained by dehydrochlorination of polyvinylidene chloride. By means of several characterization methods, it was proved that the carbyne polysulfide has a unique and stable structure of a conducting sp2 hybrid carbon skeleton connected to energy-storing sulfur side chains. And in terms of morphology, it has a well-developed porous structure with an uneven pore size. The elements C and S in the organic sulfide are approximately 43.4 wt% and 54.1 wt% respectively. As a cathode material for lithium/sulfur batteries, the carbyne polysulfide displays a high reversible capacity of 960 mA h gsulfur−1 after 200 cycles at 0.1 C (168 mA gsulfur−1) current rate in carbonic ester electrolyte. It also exhibits a reversible capacity as high as 705 mAh gsulfur−1 when cycled at 1 C (1680 mA gsulfur−1) current rate. This organic sulfide exhibits great potential as a promising cathode material for high performance rechargeable lithium/sulfur batteries.

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 performance lithium–sulfur batteries with a permselective sulfonated acetylene black modified separator

The lithium–sulfur (Li–S) battery is one of the most fascinating candidates for next-generation storage devices due to its remarkably high theoretical energy density of 2600 W h kg−1 and the low cost of the sulfur element. However, its actual application is still hindered by multiple challenges, such as the insulating nature of sulfur, irreversible loss of active material, and degradation of Li–metal anodes. In this paper, a functional sulfonated acetylene black (AB-SO3−) coated separator is designed to improve the overall performance of Li–S batteries. The AB-SO3− coated separator is highly permselective to lithium ions against polysulfide anions, while the incorporation of AB-SO3− coated separator does not influence the ion conductivity. Also the AB-SO3− coating could function as an upper current collector to facilitate electron transport for enhancing the electrochemical utilization of sulfur and ensuring the reactivation of the trapped active material. Therefore, the Li–S cell with the AB-SO3− coating exhibits significant improvement in both reversible capacity and cycling stability as compared to the cell with the pristine Celgard separator. When the mass of the AB-SO3− coating is counted into the whole mass of the sulfur cathode, the Li–S cell exhibits a high sulfur content of 70 wt% in the whole sulfur cathode region and 3.0 mg cm−2 sulfur mass loading. This kind of a cell delivers a high initial capacity of 1262 mA h g−1, and a superior capacity of 955 mA h g−1 was retained after 100 cycles at 0.1C. Consequently, the sulfonated carbon coated separator is promising for the construction of high performance batteries.

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.