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A high sulfur loading cathode is the most crucial component for lithium–sulfur batteries (LSBs) to obtain considerable energy density for commercialization applications. The major challenges associated with high sulfur loading electrodes are poor material utilization caused via the nonconductivity of the charged product (S) and the discharged product (Li2S), poor stability arisen from dissolution of lithium polysulfides (LiPSs) into most organic electrolytes and pulverization, and structural damage of the electrode caused by large volumetric expansion. A multifunctional synergistic composite enables ultrahigh sulfur content for advanced LSBs, which comprises the sulfur particle encapsulated with an ion-selective polymer with conductive carbon nanotubes and dispersed around Magnéli phase Ti4O7(MS-3) by the bottom-up method. The ion-selective polymer provides a physical shield and electrostatic repulsion against the shuttling of polysulfides with negative charge, whereas it can permit the transmission of lithium ion (Li+) through the polymer membrane, and the carbon nanotubes twined around the sulfur promote electronic conductivity and sulfur utilization as well as strong chemical adsorption of LiPSs by means of Ti4O7. Because of this hierarchical construction, the cathode possesses a lofty final sulfur loading of 72% and large sulfur areal mass loading of 3.56 mg cm–2, which displays the large areal specific capacity of 4.22 mA h cm–2. In the same time, it can provide excellent cyclic performance with the corresponding capacity attenuation ratio of 0.08% per cycle at 0.5 C after 300 cycles. Especially, while sulfur areal mass loading is sharply enhanced to 5.11 mg cm–2, the MS-3 composite exhibits a large initial areal capacity of 5.04 mA h cm–2and still keeps a high reversible capacity of 696 mA h g–1at 300th cycle even at a 1.0 C. The design of high sulfur content cathodes is a viable approach for boosting practical commercialized application of LSBs.

Construction of reasonable nanostructures for electrode materials is regarded as one critical strategy for improving capacitance and cycle life of supercapacitors (SCs). Here, self-supported, sisal-like CuCo2O4@Ni(OH)2composites were successfully synthesized on Ni foam using a hydrothermal treatment followed by the electrochemical deposition reaction. Scanning electron microscopy characterization of the composites verified that the sisal-like CuCo2O4@Ni(OH)2core–shell nanostructure comprising coating CuCo2O4nanoneedles with Ni(OH)2nanoflakes. This novel structure afforded the CuCo2O4@Ni(OH)2composites a markedly enhanced specific capacitance of 1902 F g–1at 2 A g–1and an ultralong cycle life with a captaincy retention of 87.6% after 50 000 cycles at 10 A g–1. Furthermore, an asymmetric solid-state supercapacitor comprising CuCo2O4@Ni(OH)2//activated carbon was assembled and it exhibited a high energy density of 38.6 W h kg–1at 800 W kg–1. These performances strongly suggest that the self-supported sisal-like CuCo2O4@Ni(OH)2electrode is a very promising positive material for use in SCs.

Carbon quantum dots (CQDs) as novel types of emerging materials have aroused tremendous attention in recent years. Herein, we report for the first time a new application of 3D CQD-based composite aerogels as excellent electrode materials for alkaline aqueous batteries. The scalable graphitic CQDs are prepared with high yields (>40%) and further utilized to fabricate the novel nitrogen-doped CQDs/reduced graphene oxide/porous Fe2O3(N-CQDs/rGO/Fe2O3) composite aerogels with different contents of Fe2O3. Benefiting from the unique 3D network composite aerogel structure with a high surface area and hierarchical porous structure as well as the synergistic effect of high-capacity Fe2O3and highly conductive and stable N-CQDs/rGO, the composite aerogels achieve enhanced electrochemical properties with ultrahigh specific capacity, admirable rate property, and superior cycling performance. Furthermore, the N-CQDs/rGO/Fe2O3-1 electrode (Fe2O3, 34.9 wt %) exhibits the best rate capability (72.1, 58.9, and 46.2% capacity retention at 5, 50, and 100 A g–1, respectively) and cycle performance (80.4% capacity retention at 3 A g–1over 5000 cycles), while the N-CQDs/rGO/Fe2O3-3 electrode (Fe2O3, 62.3 wt %) displays the highest specific capacity (274.1 mA h g–1at 1 A g–1). The current research provides a valuable guidance for developing high-performance 3D CQD-based composite aerogels for application in energy storage systems.

To confine the intermediate polysulfides to obstruct their dissolution from the electrolyte and increase the utilization of sulfur, a novel sulfur host for decorated nitrogen-doped carbon nanotube (NCNTs) microspheres was produced by a terse ultrasonic spraying with succedent impregnation methods. Decoration effects for Nb2O5are better than those for Sb. Nb2O5–NCNTs microspheres are woolen-like uniform balls which are twined with CNTs and infiltrated Nb2O5nanoparticles. Then Nb2O5–NCNTs microspheres deliver the high initial charge and discharge capacities of 1369.5 and 1335.3 mAh g–1, good cycle stability of 1201.7 mAh g–1at 0.1 C after 200 cycles, and outstanding long-term cycle life of 846.2 mAh g–1after 1000 cycles at 2.0 C with a very low capacity decay of 0.016% per cycle. The Nb2O5–NCNTs microspheres with remarkable effects for sulfur confinement are a potential cathode material for lithium–sulfur batteries.

To improve the electrochemical performance of commercial V2O5, its structures are rearranged and simultaneously doped by coessential and low-valence V(IV) ions via the oxalic acid reductant coupled facile hydrothermal process to achieve successfully V2O5 nanosheets. The materials were characterized by using X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy. After the structural rearrangement and V(IV)-doping, V2O5 nanosheets exhibit bigger lattice parameters and smaller grain size, but more stable structure. Compared to the commercial V2O5, V2O5 nanosheets reveal the higher specific capacity of 230.7 mAh g[?]1 at the current density of 0.2 A g[?]1 and the higher rate capacity of 216.3 mAh g[?]1 at the current density of 5 A g[?]1, maintain the more excellent capacity retention of 87.8% (189.8 mAh g[?]1) after 1000 cycles. These results indicate the structural rearrangement and V(IV) doping can greatly improve the structure and performance for commercial V2O5.

Metal selenides, as a new class of alkaline aqueous battery materials, have attracted more researchers' attention in recent years. In this work, the M0.85Se (M=Ni, Co) materials with different morphologies are successfully synthesized via a two-step hydrothermal method by using different solvents. The effects of solvents and transition metals on structure, morphology, specific surface area and pore structure and electrochemical properties of the products are systematically explored. The electrochemical measurements reveal that the Ni0.85Se products prepared by H2O and ethanol exhibit higher specific capacity (83.8 and 65.3 mAh g[?]1 at 1 A g[?]1), whereas the Co0.85Se products prepared by H2O and ethanol display better rate capability (75.1 and 69.0% of capacity retention rate at 50 A g[?]1) and cycling stability (97.6 and 94.5% of capacity retention at 5 A g[?]1 after 2000 cycles), respectively. The different electrochemical properties can be ascribed to the fact that the Ni0.85Se electrodes show diffusion-controlled faradaic chracteristic while the Co0.85Se electrodes present mixed behavior of diffusion-controlled faradaic and capacitive feature. Such work is of fundamental importance and it provides a valuable reference for the tailoring of these different properties by the use of various solvents and transition metals.

To improve the electrochemical performance of commercial V2O5, its structures are rearranged and simultaneously doped by coessential and low-valence V(IV) ions via the oxalic acid reductant coupled facile hydrothermal process to achieve successfully V2O5nanosheets. The materials were characterized by using X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy. After the structural rearrangement and V(IV)-doping, V2O5nanosheets exhibit bigger lattice parameters and smaller grain size, but more stable structure. Compared to the commercial V2O5, V2O5nanosheets reveal the higher specific capacity of 230.7 mAh g−1at the current density of 0.2 A g−1and the higher rate capacity of 216.3 mAh g−1at the current density of 5 A g−1, maintain the more excellent capacity retention of 87.8% (189.8 mAh g−1) after 1000 cycles. These results indicate the structural rearrangement and V(IV) doping can greatly improve the structure and performance for commercial V2O5.

Metal selenides, as a new class of alkaline aqueous battery materials, have attracted more researchers’ attention in recent years. In this work, the M0.85Se (M=Ni, Co) materials with different morphologies are successfully synthesized via a two-step hydrothermal method by using different solvents. The effects of solvents and transition metals on structure, morphology, specific surface area and pore structure and electrochemical properties of the products are systematically explored. The electrochemical measurements reveal that the Ni0.85Se products prepared by H2O and ethanol exhibit higher specific capacity (83.8 and 65.3 mAh g−1at 1 A g−1), whereas the Co0.85Se products prepared by H2O and ethanol display better rate capability (75.1 and 69.0% of capacity retention rate at 50 A g−1) and cycling stability (97.6 and 94.5% of capacity retention at 5 A g−1after 2000 cycles), respectively. The different electrochemical properties can be ascribed to the fact that the Ni0.85Se electrodes show diffusion-controlled faradaic chracteristic while the Co0.85Se electrodes present mixed behavior of diffusion-controlled faradaic and capacitive feature. Such work is of fundamental importance and it provides a valuable reference for the tailoring of these different properties by the use of various solvents and transition metals.