Functionalized iron oxide nanoparticles (IONPs) are of great interest due to wide range applications, especially in nanomedicine. However, they face challenges preventing their further applications such as rapid agglomeration, oxidation, etc. Appropriate surface modification of IONPs can conquer these barriers with improved physicochemical properties. This review summarizes recent advances in the surface modification of IONPs with small organic molecules, polymers and inorganic materials. The preparation methods, mechanisms and applications of surface-modified IONPs with different materials are discussed. Finally, the technical barriers of IONPs and their limitations in practical applications are pointed out, and the development trends and prospects are discussed.

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Conversion-type cathode materials, such as transition metal halides, chalcogenides, and oxides, demonstrate high operational voltages and high specific capacities, offering high energy densities for rechargeable lithium-metal batteries. In this review, a series of low-cost, environmentally benign, and high energy density Li-free cathode materials are selected based on thermodynamic calculations. Coupled with Li/C anodes, these cathodes (e.g., S, FeF 3 , CuF 2 , FeS 2 , and MnO 2 ) have the potential to offer energy densities of 1,000-1,600 Wh kg À1 and 1,500-2,200 Wh L À1 at the cell level. Their main challenges, including capacity fading, high voltage hysteresis, large volume change, and parasitic reactions with electrolytes, are discussed. Strategies to circumvent these issues based on the state-of-the-art technologies are summarized. It seems that all of these challenges are able to be solved. We believe that with the development of practical Li-metal-based anodes and solid-state electrolytes, conversion-type cathodes have a promising future for the next-generation high energy density energy storage devices.

Massive efforts have been devoted to enhancing performances of Li–S batteries to meet the requirements of practical applications. However, problems remain in enhancing the energy density and improving the cycle life. We present a free-standing structure of walnut-shaped VS4 nanosites combine with carbon nanotubes (NTs) as cathodes. In this framework, NT arrays provide high surface area and conductivity for high sulfur loadings, and VS4 nanosites facilitate trapping and catalytic conversions of lithium polysulfides. The synergistic effects of free-standing NT arrays and VS4 nanosites have enabled high rate capability up to 6 C and long-term cycling with a low decay rate of 0.037% up to 1200 cycles at 2 C. Moreover, the designed cathode can achieve high areal capacities up to ∼13 mAh·cm–2 and estimated gravimetric energy density of 243.4 Wh·kg–1 at a system level, demonstrating great potential in practical applications of Li–S batteries.

HIGHLIGHTS• The tunable mechanisms of lateral heterostructures on both homogeneous junctions and heterogeneous junctions are summarized.• Electronic and photoelectronic devices with lateral heterostructures have been discussed.• Different types of contacts of 2D lateral heterostructures are classified. • Recent developments in synthesis and nanofabrication technologies of 2D lateral heterostructures are reviewed. ABSTRACT Recent developments in synthesis and nanofabrication technologies offer the tantalizing prospect of realizing various applications from twodimensional (2D) materials. A revolutionary development is to flexibly construct many different kinds of heterostructures with a diversity of 2D materials. These 2D heterostructures play an important role in semiconductor and condensed matter physics studies and are promising candidates for new device designs in the fields of integrated circuits and quantum sciences. Theoretical and experimental studies have focused on both vertical and lateral 2D heterostructures; the lateral heterostructures are considered to be easier for planner integration and exhibit unique electronic and photoelectronic properties. In this review, we give a summary of the properties of lateral heterostructures with homogeneous junction and heterogeneous junction, where the homogeneous junctions have the same host materials and the heterogeneous junctions are combined with different materials. Afterward, we discuss the applications and experimental synthesis of lateral 2D heterostructures. Moreover, a perspective on lateral 2D heterostructures is given at the end.