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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]

The volume-change and poor conductivity issues of sulfur severely restrict the performance of lithium-sulfur (Li–S) batteries. Herein, we present a novel spring-shaped composite in which the sulfur is coated on helix-structured SiO 2 @hydrogel nanowires. The helix composite provides a buffer space for the volume-change of sulfur during charge and discharge; and the hydrogel polyaniline (PANI) coating improves the conductivity of the electrode and enables interaction with sulfides which is demonstrated by first-principle modelling. The prepared SiO 2 @C@PANI/S nanowires exhibit a stable capacity of 940 mAh g−1 after 120 cycles at a rate of 0.1C, along with a good Coulombic efficiency of 99.8%. The nanowires-based cathode also shows a high rate-performance even after three rounds of repeated measurements. The high performance and the general preparation method would enable the composite to be able to find significant applications for electrochemical energy-storage. Image 1 • A novel helix-structured nanowire is presented. • Composite cathodes exhibit a high electrochemical performance. • Helix structure enables stable energy-storage. • Ultra-stable rate-performance is achievable. [ABSTRACT FROM AUTHOR]

Lithium-sulfur battery cathodes still remain a challenge on capacity decay due to the shuttle effect even though a series of strategies have been tried. Here we report a novel matryoshka-like CuS@void@Co 3 O 4 architecture of double micro-cubes (μ -cubes) that locks sulfur between the CuS core and the Co 3 O 4 shell. Plenty of existing spaces between the μ -cubes suffice a high loading of sulfur and volumetric accommodation. The robust, double closed cubes configuration greatly enhances the confinement of polysulfides. In parallel, the CuS core increases the electronic conductivity and contributes to additional capacity, while the Co 3 O 4 shell ensures a better interface activity. A high Li+ ion diffusion coefficient is obtained during the sulfur and lithium sulfide transformation. The constructed battery displays an initial capacity up to 1480 mAh g−1, and a Coulombic efficiency (CE) exceeding 99%. A capacity retention higher than 500 mAh g−1 with a CE larger than 99.8% after cycling 400 times at 0.2 C are achieved. In addition, under a temperature of −5 °C, a high capacity of 700 mAh g−1 at 0.2 C after 200 cycles is achieved, indicating a good low-temperature tolerance. [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]

Current lithium‑sulfur (Li S) batteries have some severe issues such as shuttle effect of polysulfides and volumetric expansion of sulfur, even though their high theoretical energy density is attractive. Herein, we present a porous multi-walled ZnCo 2 O 4 sphere prepared by a self-reduction approach as sulfur host for Li S battery cathode. During the annealing of an inorganic-organic hybrid precursor, ZnCo 2 O 4 spheres are partially reduced by the released carbon monoxide, resulting in the formation of ZnO and CoO nanoparticles which are subsequently etched by acid, finally forming mesopores throughout the multi-walled ZnCo 2 O 4 spheres. The multi-walled ZnCo 2 O 4 provides sufficient space for accommodating the volumetric change of sulfur. The adsorption measurements show that the multi-walled ZnCo 2 O 4 can adsorb the polysulfides efficiently, which suppresses the shuttle effect. After cycling 1000 times at a rate of 0.5C, the multi-walled ZnCo 2 O 4 @S composite remains a capacity of 590 mAh g−1. The rate-performance is well recoverable during repeated tests. Moreover, the capacities at relatively low and high temperatures of − 5 and 50 °C are 654 and 619 mAh g−1 after 100 cycles, respectively, indicating a potential for applications Unlabelled Image • A novel multi-walled ZnCo 2 O 4 @S composite is presented for lithium-sulfur battery. • Porous multi-walled structure suppresses the shuttle effect of polysulfides. • Multi-walled ZnCo 2 O 4 @S cathode exhibits a long cycling life of 1000 cycles. • Stable rate-performance and capacities at low and high temperatures are achievable. [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]