Search

The slow redox kinetics and shuttling behavior of the intermediate lithium polysulfides constrain the further development of lithium–sulfur (Li–S) electrochemistry. A yolk–shell In2S3@void@carbon hybrid engineered to host the sulfur for Li–S batteries is prepared by using a multi-layered assembly method. The In2S3/electrolyte interface acted as powerful adsorption and activation sites for soluble polysulfides, which is demonstrated using density functional theory (DFT) calculations. Moreover, the carbon shell provides redundancy for volume-changes during the cycles. The results indicate that yolk–shell In2S3@S@C hybrid cathode shows good reversibility and rate capability, which preserves 563.6 mA h g−1 after 500 cycles at 0.5 C, indicating the potential for developing high-performance battery systems. [ABSTRACT FROM AUTHOR]

Metal-organic-frameworks-derived nanostructures have received broad attention for secondary batteries. However, many strategies focus on the preparation of dispersive materials, which need complicated steps and some additives for making electrodes of batteries. Here, we develop a novel free-standing Co9S8 polyhedron array derived from ZIF-67, which grows on a three-dimensional carbon cloth for lithiumâ€"sulfur (Liâ€"S) battery. The polar Co9S8 provides strong chemical binding to immobilize polysulfides, which enables efficiently suppressing of the shuttle effect. The free-standing S@Co9S8 polyhedron array-based cathode exhibits ultrahigh capacity of 1079 mAh gâˆ'1 after cycling 100 times at 0.1 C, and long cycling life of 500 cycles at 1 C, recoverable rate-performance and good temperature tolerance. Furthermore, the adsorption energies towards polysulfides are investigated by using density functional theory calculations, which display a strong binding with polysulfides. [ABSTRACT FROM AUTHOR]

High-energy-density secondary batteries are required for many applications such as electric vehicles. Lithium–sulfur (Li-S) batteries are receiving broad attention because of their high theoretical energy density. However, the large volume change of sulfur during cycling, poor conductivity, and the shuttle effect of sulfides severely restrict the Li-storage performance of Li-S batteries. Herein, we present a novel core–shell nanocomposite consisting of a sulfur core and a hydrogel polypyrrole (PPy) shell, enabling an ultra-high sulfur content of about 98.4% within the composite, which greatly exceeds many other conventional composites obtained by coating sulfur onto some hosts. In addition, the void inside the core–shell structure effectively accommodates the volume change; the conductive PPy shell improves the conductivity of the composite; and PPy is able to adsorb polysulfides, suppressing the shuttle effect. After cycling for 200 cycles, the prepared S@void@PPy composite retains a stable capacity of 650 mAh g−1, which is higher than the bare sulfur particles. The composite also exhibits a fast Li ion diffusion coefficient. Furthermore, the density functional theory calculations show the PPy shell is able to adsorb polysulfides efficiently, with a large adsorption energy and charge density transfer. [ABSTRACT FROM AUTHOR]

Simultaneously achieving a high conductivity and a good volume-change accommodation for sulfur cathode in lithium‑sulfur batteries is highly required. Herein, we present a unique porous sulfur composite consisting of a porous sulfur particle coating with conductive hydrogel polypyrrole, which is prepared through a templated method. The pores inside the sulfur particles offer a good buffering space for the volume expansion of sulfur upon lithiation; while the external polypyrrole coating improves the conductivity and suppress the transfer of polysulfides. The porous sulfur@polypyrrole composite exhibits a capacity of about 900 mAh g−1 after cycling for 100 times at 0.12 C, along with a good Coulombic efficiency around 99.9%, which is much better than the polypyrrole-coated non-porous sulfur particles and pure sulfur particles. When cycled for 500 times, the capacity fading rate is as low as 0.09% per cycle. After three rounds of rate-performance measurements, the capacity retention of the sulfur@polypyrrole at different rates remain above 97%. The density functional theory calculations and electrochemical impedance spectra demonstrate a polysulfide-adsorptive and a stable electric transportation surface of the sulfur@polypyrrole composite, respectively. Unlabelled Image • A novel porous sulfur@hydrogel composite cathode is reported. • The Li-S batteries exhibit high electrochemical performance. • The cathodes enable accommodable volume-change and improved conductivity. • High proportion of capacitive contribution in overall capacity is achievable. • Density functional theory calculations demonstrate polysulfides adsorption. [ABSTRACT FROM AUTHOR]

A polysulfides-adsorptive and conductive host for sulfur (S) cathode is highly required for Li S batteries. Herein, we present a unique ternary S/C@SnO 2 composite consisting of a 3D tubular core-shell structure in which a carbon matrix as the core is coated by a porous SnO 2 shell. Sulfur is coated on carbon inside the tubes. The S/C@SnO 2 exhibits a good electrochemical performance including a stable capacity of 730 mAh g−1 after cycling for 500 times at 0.1C, along with a fading rate as low as 0.07% per cycle. The capacities recover well during two rounds of rate-performance measurements, exhibiting a recovery rate exceeding 96.3%. The composite also delivers stable capacities when cycling at different charge vs. discharge rates. The polysulfides-adsorptive capability of the SnO 2 shell as an efficient protection shield is demonstrated through density functional theory calculation, which confirms a high surface-energy of SnO 2 towards Li 2 S 4 , Li 2 S 6 , and Li 2 S 8. The porous carbon matrix inside the SnO 2 tubes provides a good conductivity for sulfur and spaces for the volume-change of sulfur. Those features of the ternary S/C@SnO 2 enable it to be a promising cathode candidate for Li S batteries. Unlabelled Image • A unique ternary sulfur/carbon@tin dioxide composite is reported. • Polysulfides-adsorptive shell and conductive core are achieved. • Ternary composite exhibits a high performance for Li S battery. • First-principle modeling confirms a high surface energy of SnO 2 shell. [ABSTRACT FROM AUTHOR]

• A novel polysulfides-immobilized composite is presented for Li-S battery. • The TiO 2 @PANI@S composite exhibits a high electrochemical performance. • Strong adsorption between the composite and polysulfides is presented. • Enhanced electron transfer and ion diffusion are achievable. Li-S batteries are promising new energy-storage systems owing to their high theoretical energy density. However, the volume-change and poor conductivity of S, and shuttle effect severely restrict applications. Here, we present a novel semispherical composite consisting of sulfur and polyaniline (PANI) hydrogel coating on a bowl-shaped hollow TiO 2. The TiO 2 @PANI@S composites show an excellent performance with a high capacity of 1058 mAh g−1 after 200 cycles at 0.2 C, and a stable Columbic efficiency of 99.8%. The composites also possess a recoverable rate-performance under repeated tests. The Li+ ion diffusion co-efficiency is studied, which indicates that the semispherical composite enables a rapid Li+ ion transportation. In addition, the density functional theory calculations confirm a strong adsorption of TiO 2 towards polysulfides including for Li 2 S 4 , Li 2 S 6 , and Li 2 S 8 , which efficiently suppress the shuttle effect. [ABSTRACT FROM AUTHOR]