Lithium-ion batteries (LIBs) have attracted considerable attention due to their wide applications, such as in portable electronic devices, implantable medical devices, and electric vehicles (EVs). [ 1 ] To meet the constantly increasing demands of upcoming electronic devices, new LIBs require substantial improvements in energy capacity, cycling stability, and rate capability of both the cathode and anode materials. [ 2,3 ] Among cathode materials for LIBs, orthorhombic vanadium pentoxide (V 2 O 5 ) the most stable form in the vanadium oxide family, has gained great interest due to its high energy density, low cost, abundant sources, and good safety properties. [4][5][6][7] The theoretical capacity of V 2 O 5 with two Li intercalations/ deintercalations is about 294 mA h g − 1 , much higher than those of more commonly used cathode materials, making it a very promising cathode material for next-generation LIBs. However, the practical use of V 2 O 5 as cathode materials for LIBs has been hampered due to its poor cycling stability, low electronic and ionic conductivity, and slow electrochemical kinetics. [8][9][10] To overcome these problems, decreasing their particle size to nanoscale level is generally believed to be one of the most effective approaches due to the shorter transport lengths for both electrons and Li ions, larger electrode/electrolyte contact area, and better accommodation of the strain of Li intercalation/deintercalation in nanomaterials. [ 11 , 12 ] The unique performance of nanomaterials lies in their large specifi c surface and favorable structural properties. 2D nanosheets often possess large exposed surfaces and specifi c facets, which make them more attractive in energy conversion devices. [ 13 ] 2D structures are ideal frameworks for fast Li storage, which requires stability, large active surface area, and short transport path for Li intercalation/deintercalation. [ 14 ] There have been many researches on nanostructured V 2 O 5 materials for LIBs. [ 4-7 , 15-20 ] However, there are few reports on 2D nanostructured V 2 O 5 for LIBs. The only report on 2D nanostructured V 2 O 5 was that Zhang's group prepared large-area pure V 2 O 5 nanosheets by dissolution-splitting method from their parent bulk cyrstal using ammonium persulfate as intercalated compound. [ 21 ] The method is a typical top-down method. The as-prepared product exhibits enhanced lithium storage properties including high reversible capacity, good cycling, and rate performance.In this communication, we demonstrate a novel and facile green method to prepare 2D leaf-like V 2 O 5 nanosheets as illustrated in Figure 1 . V 2 O 5 powders were reacted with H 2 O 2 in combination with ultrasonic treatment to generate V 2 O 5 gel. Then the V 2 O 5 gel was diluted, freeze-dried, and further treated at 450 ° C in air to obtain V 2 O 5 nanosheets. Used as cathode material for LIBs, this 2D leaf-like V 2 O 5 nanosheets exhibits excellent Li storage properties, including high reversible capacity, high rate capability, and good capacity reten...

Abstract3D organic–inorganic and all‐inorganic lead halide perovskites have been intensively pursued for resistive switching memories in recent years. Unfortunately, instability and lead toxicity are two foremost challenges for their large‐scale commercial applications. Dimensional reduction and composition engineering are effective means to overcome these challenges. Herein, low‐dimensional inorganic lead‐free Cs3Bi2I9 and CsBi3I10 perovskite‐like films are exploited for resistive switching memory applications. Both devices demonstrate stable switching with ultrahigh on/off ratios (≈106), ultralow operation voltages (as low as 0.12 V), and self‐compliance characteristics. 0D Cs3Bi2I9‐based device shows better retention time and larger reset voltage than the 2D CsBi3I10‐based device. Multilevel resistive switching behavior is also observed by modulating the current compliance, contributing to the device tunability. The resistive switching mechanism is hinged on the formation and rupture of conductive filaments of halide vacancies in the perovskite films, which is correlated with the formation of AgIx layers at the electrode/perovskite interface. This study enriches the library of switching materials with all‐inorganic lead‐free halide perovskites and offers new insights on tuning the operation of solution‐processed memory devices.

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The porous carbons (PCs) with tunable morphologies and pore sizes were prepared by the sol–gel process via a freeze-drying technique for microwave absorption applications. The results of Raman spectroscopy and nitrogen sorption analysis showed that the graphitization degree was barely influenced as the ratio of tert-butanol (T) to resorcinol (R) decreased, while the pore morphologies changed from the disordered slit-shaped pores to the uniform cage-like pores. Dielectric properties of the as-prepared carbon samples were determined by a vector network analyzer in the frequency range of 8.2–12.4 GHz. Results showed that the effect of pore morphology on the dielectric loss of PCs was dominant in the case of similar graphitization. When the T/R ratio was 7.5, the sample with cage-like pores revealed the maximum values in the real part ε′ and the imaginary part ε″ of complex permittivity, which were 13.2–6.5 and 15.6–10.1, respectively, suggesting a better capacity of dielectric loss in the 8.2–12.4 GHz range. The proposed mechanism for the effect of the pore morphologies on microwave absorption performance was discussed.