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Nano-polycrystalline Sn2S3/Sn3S4/FeS/Fe7S8 sulfides anchored on graphene were synthesized via annealing SnS2 and Fe followed by homogeneously combining them with exfoliated graphite.

A robust solvothermal-driven solid-to-solid transition strategy is developed to craft tartaric acid-capped ultrafine SnO2 encapsulated in graphene with outstanding lithium and sodium storage reversibility due to effectively inhibited Sn coarsening.

As the most promising alternative to lithium-ion batteries (LIBs), sodium-ion batteries (SIBs) still face many issues that hinder their large-scale commercialization. Layered transition metal oxide cathodes have attracted widespread attention owing to their large specific capacity, high ionic conductivity, and feasible preparation conditions. However, their electrochemical properties are usually limited by the irreversible phase transition and harsh storage conditions caused by humidity sensitivity. Recently, tremendous efforts have been devoted to solving these issues toward advanced high-performance layered oxide cathodes. Herein, we summarize these remaining challenges of layered oxide cathodes and the corresponding modification strategies such as the variations in chemical compositions, the architecture of (nano)micro-structures, surface engineering, and the regulation of phase compositions. We hope that the understanding presented in this review can provide useful guidance to developing high-performance layer-structured cathode materials for advanced SIBs.

The ability to craft high-performance and cost-effective bifunctional oxygen catalysts opens up pivotal perspectives for commercialization of zinc–air batteries (ZABs). Despite recent grand advances in the development of synthetic techniques, the overall performance of electrocatalytic processes enters the bottleneck stage through focusing only on the design and modification of bifunctional catalyst materials. Herein, we report a simple yet robust strategy to markedly boost the performance of ZABs via capitalizing on the photothermal effect. Concretely, a bifunctional electrocatalyst comprising Co3O4 nanoparticles encapsulated within N-doped reduced graphene oxide (denoted as Co3O4/N-rGO) acted as both active material and photothermal component. Upon light illumination, the compelling photothermal effect of Co3O4/N-rGO rendered a localized and instant heating of the electrode with more active sites, enhanced electrical conductivity and improved release of bubbles. As such, a prominently reduced indicator ΔE of 0.635 V was realized, significantly outperforming recently reported systems (usually >0.68 V). Corresponding rechargeable ZABs based on Co3O4/N-rGO air electrodes possessed an excellent maximum power density of 299 mW cm−2 (1.8 times that of Pt/Ru-based ZABs) assisted by the photothermal effect with a superb cycling stability (over 500 cycles). This intensification strategy opens vast possibilities to ameliorate the performance of catalysts via innovatively and conveniently utilizing their photothermal feature, which may advance future application in high-performance ZABs and other energy conversion and storage systems.

A novel titanium, nitrogen co-doped carbon material was designed via a one-step solvothermal reaction at a moderate temperature. Characterization by scanning electron microscopy and transmission electron microscopy illustrates that carbon materials without titanium doping possess a morphology of porous flakes, whereas the inclusion of titanium results in the deposition/intercalation of island-shaped TiO2 nanoparticles on these carbon flakes. Both the volumetric energy density and the cycling stability are significantly improved by titanium doping. Electrochemical measurements show that the introduction of titanium leads to a high volumetric capacitance of 285.5 F cm−3 at 0.5 A g−1 current density. Electrodes prepared with the new materials also exhibit excellent cycling stability, where there is no capacitance loss after 40 000 cycles in the 6 M KOH electrolyte at a high charge/discharge current of 30 A g−1. The volumetric energy density of the as-obtained symmetrical supercapacitor reaches 11.99 W h L−1, which is competitive to that of lithium thin-film batteries (1–10 W h L−1).

The ability to extract/insert more than one Li per formula unit has made Li-rich layered oxides (LLO) one of the most promising cathode materials. However, irreversible transformations triggered by over-delithiation such as phase transitions, oxygen release and Jahn–Teller effects of Mn3+ have limited its practical application. In this work, the irreversible processes during repetitive de/lithiation were found to be diminished by establishing a gradient cationic redox couple of Mn3+/Mn4+ in Li1.2Ni0.2Mn0.6O2. As revealed by STEM, XPS and XAS measurements, the partial substitution of O2− by F− ions promoted nearby Li/transition metal mixing and reduced the valence state of Mn on the surface. Such a configuration shifted the surface redox center towards cationic redox couple (Mn3+/Mn4+), reducing the irreversible oxygen release as well as the ensuing structure and oxidation state changes. As a result of the modification, the product delivered a discharge capacity of 203.4 mA h g−1 after 80 cycles at 0.2C and achieved capacity retention of 89.6% after 100 cycles at 0.5C. The suppressed irreversible processes during repetitive cycling were investigated through ex situ X-ray absorption energy near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopy and DFT calculations, which confirmed the well-preserved oxidation states and atomic configurations in modified Li1.2Ni0.2Mn0.6O2. Overall, this research provided a new avenue to control the irreversible processes in LLO without changing the anion redox behavior of lattice O2− in the bulk area by accommodating the cationic redox couple on the surface.

The development of electric and hybrid electric vehicles has emerged as one of the most promising strategies for solving the global shortage of fossil energy problem. High-energy and high-power lithium-ion batteries are essential for achieving the large-scale commercialization of electric vehicles. Ni-rich layered-structure oxides appear to be one of the most ideal candidates for electrode materials owing to their high-energy density. However, severe degradation issues associated with chemical and structural instabilities have limited their further applications. This review summarizes recent progress toward the fundamental understanding of ternary layered-structure oxides with a particular focus on the key issues of ion intermixing, chemo-mechanical degradation, and phase evolution on the particle surface. The possible strategies, as well as perspectives for addressing these problems, are also proposed in this review as an effort to provide guidance on the further design of advanced layered-structure oxides.

Sub-5 nm monodispersed metal oxides have been attracting much attention in energy storage due to their large electrolyte ion-accessible surface areas and high specific capacities. However, the high surface free energy of ultrasmall nanoparticles inevitably results in their serious aggregation, leading to degraded electrochemical activities and poor cycling stability. Herein, a two-stage microimpinging stream reactor (TS-MISR) strategy that combines a first homogeneous premixing stage with a subsequent microimpinging stream reacting stage has been constructed for the controllable synthesis of Ni–Co–O/RGO composites (NCG). Benefiting from the enhanced micromixing efficiency and better process control of TS-MISR, monodispersed ultrasmall Ni–Co–O particles (3–4 nm) are evenly grown on the RGO flakes to generate a large specific surface area (293.2 m2 g−1), quantities of desirable mesopores (2–4 nm), as well as a strong synergistic effect between Ni–Co–O particles and conductive RGO flakes, hence providing more superficial electroactive sites, fast electron transfer and short diffusion paths for electrolyte ions to participate in faradaic redox reactions. The as-prepared NCG-MM exhibits a large specific capacity of 912.4 C g−1 (capacitance of 2281 F g−1) at the current density of 1 A g−1, good rate capability and cycling stability. Coupled with the activated carbon (AC) negative electrode, the assembled pouch-type NCG//AC asymmetric supercapacitor displays a prominent areal energy density (0.898 mW h cm−2 at 0.8 mW cm−2) and an excellent cycling stability (∼90.5% capacity retention after 8000 cycles). In addition, this strategy opens up an important prospect for the controllable synthesis of monodispersed metal oxide/graphene composites for application in batteries, sensors and catalysis.

Layered P2-type Na2/3Ni1/3Mn2/3O2 was successfully synthesized through a facile sol–gel method and subsequent heat treatment. Resulting from different phase transformation and sodium ion diffusion rates, its electrochemical performance is highly related to the cut-off voltage and the electrolyte used. When the cut-off voltage is set up to 4.5 V or lowered to 1.5 V, capacity fade happens due to the occurrence of P2–O2 transformation and electrolyte decomposition or the redox reaction of the Mn4+/Mn3+ ionic pair and P2–P2′ transformation. The electrode maintained 89.0 mA h g−1 with good cycling stability and excellent structural preservation between 4.0 and 2.0 V. The capacity retention is 71.2% even after 1200 cycles at 10C. It can be expected that P2-type Na2/3Ni1/3Mn2/3O2 is very promising as a cathode material for sodium ion batteries.

A hydrogel-embedded tight ultrafiltration membrane composed of sodium polyacrylate-modified polyacrylonitrile (PAAS-m-PAN) is fabricated by a modified phase inversion process. The as-prepared membrane with excellent anti-dye-fouling property can effectively separate dyes from salts with permeance as high as >140 L m−2 h−1 bar−1, which is several times that of traditional polymeric filtration membranes with a similar rejection performance.

Both microwave and conventional oil bath heating approaches are investigated for the fabrication of CdS nanocrystals through the thermolysis of a single source precursor cadmium diethyldithiocarbamate (CED), which allows us to gain further insight into the thermodynamic aspect of the synthesis. The analysis illustrates that nearly monodispersed sea-urchin-shaped CdS nanocrystals are obtained with the microwave method, whereas nanospheres covered by chunky protuberances are achieved with an oil bath approach. Such experiments suggest that microwave heating facilitates the growth of CdS along the [002] direction. In addition, we explored the catalytic activity of CdS in the photodegradation of rhodamine B, in which the CdS prepared through a microwave approach greatly outperformed that prepared through oil bath heating and the commercial CdS nanoparticles. Such enhancement arises from the higher specific surface area and crystallinity of the sea-urchin-shaped nanocrystals.

This research presents a template-free solvothermal method which offers selective preparation of graphene ranging from two-dimensional sheets to 3-dimensional nanospheres. The thus prepared nanospheres have size-defined mesopores with a huge surface area and, after doping with nitrogen, exhibited stronger electrocatalytic activity toward oxygen reduction than commercial Pt/C catalysts.