Rational Design of the Lotus-Like N-Co2 VO4 -Co Heterostructures with Well-Defined Interfaces in Suppressing the Shuttle Effect and Dendrite Growth in Lithium-Sulfur Batteries.

The shuttle effect caused by soluble lithium polysulfides (LiPSs) and intrinsic slow electrochemical transformation from LiPSs to Li2 S/Li2 S2 will induce undesirable cycling performance, which is the primary obstruct limiting the practical applications of lithium-sulfur (Li-S) batteries. Here a convenient method is designed to fabricate the 2D louts-like N-Co2 VO4 -Co heterostructures with well-abundant interfaces and oxygen vacancies (Vo ), endowing the materials with both "sulfiphilic" and "lithiophilic" features. When employed as the modification layer coated on commercial Celgard 2400 separator, the as-prepared N-Co2 VO4 -Co/PP with synergistic adsorption-electrocatalysis effects achieves desirable sulfur electrochemistry, thus showing a high initial discharge capacity of 1466.4 mAh g-1 at 0.1 C and stable cycle life with a fade rate of 0.03% per cycle over 1000 cycle at 3.0 C. Moreover, a superior areal capacity of 12.84 mAh cm-2 is preserved under high sulfur loading of 14.3 mg cm-2 .

Cobalt-Carbon nanotubes supported on V2O3 nanorods as sulfur hosts for High-performance Lithium-Sulfur batteries.

Exploring advanced sulfur cathode materials with high catalytic activity to accelerate the slow redox reactions of lithium polysulfides (LiPSs) is of great significance for lithium-sulfur batteries (LSBs). In this study, a coral-like hybrid composed of cobalt nanoparticle-embedded N-doped carbon nanotubes supported by Vanadium (III) oxide (V2O3) nanorods (Co-CNTs/C @V2O3) was designed as an efficient sulfur host using a simple annealing process. Characterization combined with electrochemical analysis confirmed that the V2O3 nanorods exhibited enhanced LiPSs adsorption capacity, and the in situ grown short-length Co-CNTs improved electron/mass transport and enhanced the catalytic activity for conversion to LiPSs. Owing to these merits, the S@Co-CNTs/C@V2O3 cathode exhibits effective capacity and cycle lifetime. Its initial capacity was 864 mAh g-1 at 1.0C and remained at 594 mAh g-1 after 800cycles with a decay rate of 0.039%. Furthermore, even at a high sulfur loading (4.5 mg cm-2), S@Co-CNTs/C@V2O3 also shows acceptable initial capacity of 880 mAh g-1 at 0.5C. This study provides new ideas for preparing long-cycle S-hosting cathodes for LSBs.

Confined Co9S8 nanocrystals into N/S-Co-doped carbon nanofibers as a chainmail-like electrocatalyst for high-performance lithium-sulfur batteries with high sulfur loading.

Accelerating phase transposition efficiency of lithium polysulfides (LiPSs) to L2S and hampering the solution of LiPSs are the keys to stabilizing lithium-sulfur (Li-S) batteries. Hence, the sulfiphilic ultrafine Co9S8 nanoparticles embedded lithiophilic N, S co-doping carbon nanofibers (Co9S8/NSCNF) are prepared via the dual-template method, which are then used as sulfur host in Li-S batteries. Particularly, the double active sites (Co9S8 and N, S) in Co9S8/NSCNF are prone to form "Co-S", "Li-O" or "Li-N" bonds, and then simultaneously improving the chemisorption and interface transposition capability of LiPSs. In case of the S@ Co9S8/NSCNF composites with high sulfur loading of 89% are employed as cathode, the cell possesses optimized "sulfiphilicity" and "lithiophilicity", which achieves remarkable sulfur electrochemistry, including outstanding reversibility of 816.8mAhg-1 over 500 cycles at 1.0C, excellent rate property of 742.2mAhg-1at 5.0C, and long-term cycling with a low attenuation of 0.011% per cycle over 1800 cycles at 3.0C. Impressively, a remarkable areal capacity of 11.51mAhcm-2 is retained under the sulfur loading of 15.3 mg cm-2 for 50 cycles. This research will deepen the understanding of the complex LiPSs interface transposition procedure and provide new ideas for the design of new host materials.

yMoO42- modified amorphous Co(PO3)2 cubes as an efficient bifunctional electrocatalyst for alkaline overall water splitting.

The exploration of efficient bifunctional electrocatalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) under alkaline conditions is an importantway to promote the development of electrolytic water technology. Herein, the reduced graphene oxide-supported MoO42- modified amorphous cobalt metaphosphate cubes (a-Co(PO3)2/MoO4/rGO) as bifunctional OER/HER catalyst is prepared by anion exchange and phosphating, using the Prussian blue analogue (PBA) as a precursor. The resulting composite exhibits the low overpotentials (η) that of 290 and 50 mV for OER and HER in 1.0 M KOH solution at 10 mA cm-2, respectively. The electrochemical test and density functional theory (DFT) results reveal that the MoO42--modified optimizes the adsorption/desorption energy of H* of Co(PO3)2, thus enhance the HER activity. Benefiting from efficient HER and OER performances, an efficient and stable alkaline water electrolysis operation using a-Co(PO3)2/MoO4/rGO used as bifunctional catalyst can be carried out, which can deliver a current density (j) of 20 mA cm-2 at 1.65 V cell voltage and work continuously for 24 h.

Amorphous CoP nanoparticle composites with nitrogen-doped hollow carbon nanospheres for synergetic anchoring and catalytic conversion of polysulfides in Li-S batteries.

The commercial viability of Li-S batteries was obstructed by short cycle life and poor capability owing to slow redox kinetics and polysulfide shuttle effect. To tackle these challenges, the amorphous CoP anchored on N-doped carbon nanospheres with hollow porous structures (CoP/HCS) has been synthesized as a superior sulfur host via a facial pyrolysis approach. The debilitating effect would be hampered during the cycling processing resulting from two reasons:(1) the powerful chemical anchoring between unsaturated Co and Li-polysulfides, (2) the remarkable adaption of volume variation originating from the hollow porous architectures. The amorphous CoP nanoparticles not only catalyze the transformation of lithium polysulfides as electrocatalyst, but also acquired a high sulfur loading as sulfur host materials. More importantly, the synergistic incorporation of CoP and HCS improved the inherit low conductivity by anchoring on the N-doped carbon hollow, thus leading to excellent performance for Li-S batteries. Benefiting from these advantages, the amorphous CoP/HCS-based sulfur electrodes exhibited outstanding rate performance (685.6 mAh g-1 at 3C), excellent long-cycling stability with a low capacity decay of only 0.03% per cycle over 1000 cycles at 2C, and a high areal capacity of 5.16 mAh cm-2 under high sulfur loading.