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High-capacity lithium-rich sulfide cathodes with superior conductivity over S or Li2S materials are considered for all-solid-state lithium-ion batteries (ASSLBs), yet their capacity and rate performance require further improvement. In this work, lithium-rich sulfide cathodes Li2Ti1−xSixS3 with a disordered rocksalt structure and layered structure are synthesized by high-energy ball milling and high-temperature annealing, respectively. The Si doping strategy is implemented to tune the microstructure of the lithium-rich sulfide cathode and to obtain high capacity and improved ionic conductivity. The partial replacement of Ti with Si increases the cationic disorder of rocksalt and layered Li2Ti1−xSixS3, which further activates the anionic redox activity to enable a higher capacity than Li2TiS3. Moreover, the robust Si–S bonds induce distortions in the LiS6 octahedral and adjacent tetrahedral vacancies, broadening the Li+ migration channels in the Li+ percolation network and enabling rapid Li+ migration capability. The optimized rocksalt Li2Ti1−xSixS3 exhibits a higher specific capacity of 361 mA h g−1 than rocksalt Li2TiS3 (295 mA h g−1) at 0.3 C (120 mA g−1), while the layered Li2Ti1−xSixS3 has a higher capacity of 260 mA h g−1 than the layered Li2TiS3 (140 mA h g−1) at 0.3 C. An argyrodite-type sulfide solid-state electrolyte Li5.25PS4.25ClBr0.75 with high Li+ conductivity (7.64 mS cm−1) is designed to match with the rocksalt Li2Ti1−xSixS3 cathode, and the assembled ASSLB achieves a high areal capacity density of 9.79 mA h cm−2. The Si doping to tune the disordered structure provides an effective improvement approach for high-capacity rocksalt or layered sulfide cathodes and high-energy density ASSLBs. [ABSTRACT FROM AUTHOR]

Developing active and stable electrocatalysts of earth-abundant elements towards the oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) still remains a crucial challenge. Herein, a cobalt-containing metal–organic framework using adenine as a ligand was synthesized and pyrolyzed without any other precursors, forming a cobalt nanoparticle-embedded nitrogen-doped carbon/carbon nanotube framework (Co@N-CNTF). Due to the abundant active sites of homogeneously distributed cobalt nanoparticles within nitrogen-doped graphitic layers, the resultant Co@N-CNTF catalysts exhibit an efficient and stable electrocatalytic performance as a tri-functional catalyst towards the ORR, OER and HER, including a high half-wave potential of 0.81 V vs. RHE for the ORR, and a low overpotential at 10 mA cm−2 for the OER (0.35 V) and HER (0.22 V). As a proof-of-concept, the Co@N-CNTF as an OER/HER bifunctional catalyst for full water splitting affords an alkaline electrolyzer with 10 mA cm−2 under a stable voltage of 1.71 V. Moreover, an integrated unit of a water-splitting electrolyzer using the Co@N-CNTF catalysts, which is powered with a rechargeable Zn–air battery using the Co@N-CNTF as an ORR/OER bifunctional catalyst on air electrodes, can operate under ambient conditions with high cycling stability, demonstrating the viability and efficiency of the self-powered water-splitting system. [ABSTRACT FROM AUTHOR]

Inspired by multi-scale structures mimicking Setaria viridis, herein, arrays of vertically aligned polyaniline (PANI) nanowires on MoO3/polypyrrole (PPy) core–shell nanobelts have been successfully synthesized via a two-step wet-chemistry strategy, including a simple in situ oxidative polymerization of pyrrole on MoO3 nanobelts, followed by an in situ oxidative polymerization of aniline on the MoO3/PPy core–shell nanobelts. By mimicking the hierarchically multi-scale topography of Setaria viridis for tailoring the nanostructures and functions of the electrode materials, in the resultant MoO3/PPy/PANI composites, the MoO3 nanobelt core acts as the “stalk” surrounded by conducting polymers, whereas the intermediate PPy functions as the buffer “grain” connecting the MoO3 and PANI nanowires, which provides good structural stability as well as an efficient electron transfer pathway. Moreover, the outermost PANI nanowire arrays act as the “bristles” allowing fast transport of ions and electrons between the electrodes. Due to their compositional and structural superiority, the as-obtained MoO3/PPy/PANI composites deliver excellent electrochemical energy storage performance including a high specific capacitance of 1315 F g−1 at 0.5 A g−1, a high energy density of 63 W h kg−1 and an excellent cycling stability (capacitance retention of 86% at 10 A g−1 after 20 000 cycles). The easy synthesis and excellent electrode performance of the MoO3/PPy/PANI composites make them attractive candidates as promising electrode materials for high-performance supercapacitors. [ABSTRACT FROM AUTHOR]