are still severe technological challenges in the wide practical applications for LOBs, such as poor round-trip efficiency, high overpotential, inferior cycle stability, and terrible rate capability. The major factor constraining the performance advantage of LOBs is the sluggish kinetics of the oxygen reduction reaction (ORR, discharge process) and the oxygen evolution reaction (OER, charge process) on the cathode. In the discharge process, the surface of cathode is gradually shrouded by Li 2 O 2 as the insulative discharging product, which reduces the conductivity of electrode system and increased the decomposed energy barrier of surface products, eventually resulting in excessive overpotential and inferior cycle performance. Furthermore, the generated superoxide radicals would attack the electrolyte and the cathode materials in the discharge/ charge process, causing the side reactions and formation of various by-products on the electrode. The development of highefficient cathode catalyst is one of the most important strategies to solve the problems of LOBs.Carbon materials were first studied as cathode materials because of the low cost and good conductivity characteristics. However, due to the superoxide radicals generated during the ORR/OER process, a large amount of side products (Li 2 CO 3 ) is produced, which contributes to the poor cycle stability. [3] Researchers have been working on the development of novel catalysts with high efficiency and their electrochemical reaction mechanisms to reduce by-products and improve cycle life and efficiency, such as precious metals (Pt, [4][5][6][7] Au, [8] Pd, [4] and Ru [9,10] ), metal oxides (CeO 2 , [11] RuO 2 , [12] NiFeO, [13] NiCo 2 O 4 , [14] etc.), metal carbides/nitrides (TiC, [15] Mo 2 C, [16] CoN, [17] etc.). High-efficient cathode catalysts could dominate the nucleation and growth kinetics, morphology, crystal states, and chemical composition of discharge products. During the ORR/OER process, LiO 2 is considered to be an important intermediate, which greatly affects the stability of catalyst and composition of discharge products. [18][19][20][21][22][23][24] The formation of discharge products could proceed through surface or solution pathway with LiO 2 species at the interface of cathode and electrolyte. Moreover, the morphology of the discharge products formed under the assistant of the cathode catalysts is strongly related to the cycle stability. Toroid like discharge products consisting of Li 2−x O 2 and Li 2 O 2 could be obtained on carbon-based material Highly-efficient cathode catalysts are the key to improve high rate cycle stability, avoid side reactions, and lower the overpotential of lithium-oxygen batteries (LOBs). MXenes are predicted to be one of the most impressive materials for energy applications. In this work, the catalytic capability of Nb 2 C MXene is demonstrated with a uniform O-terminated surface as a cathode material for LOBs. The easily fabricated uniform O-terminated surface, high catalytic activity of Nb 2 CO 2 sites, and unique re...

After optimization using percolation theory, excellent absorbing properties (90% absorption) were achieved for Ni/C nanocomposites with advantages such as thin thickness (1.75 and 1.5 mm) and light weight (25 and 30 wt%).

In the present work, combining with the Geiger-Nuttall law, a two-parameter empirical formula is proposed to study the two-proton (2p) radioactivity. Using this formula, the calculated 2p radioactivity half-lives are in good agreement with the experimental data as well as the calculated ones obtained by Goncalves et al. ([Phys. Lett. B 774, 14 (2017)]) using the effective liquid drop model (ELDM), Sreeja et al. ([Eur. Phys. J. A 55, 33 (2019)]) using a four-parameter empirical formula and Cui et al. ([Phys. Rev. C 101: 014301 (2020)]) using a generalized liquid drop model (GLDM). In addition, this two-parameter empirical formula is extended to predict the half-lives of 22 possible 2p radioactivity candidates, whose the 2p radioactivity released energy Q2p>0, obtained from the latest evaluated atomic mass table AME2016. The predicted results have good consistency with ones using other theoretical models such as the ELDM, GLDM and four-parameter empirical formula.

For lithium‐oxygen batteries (LOBs), the strong oxidant intermediate and byproducts during the charge/discharge process are the main reasons for the degradation of the electrochemical performance. Searching for highly efficient catalysts for the direct formation/decomposition of Li2O2 is essential for the development of LOBs. In this study, core–shell nanostructured MoSe2@CNT with uniform MoSe2 coating layers are purposefully synthesized through a facile hydrothermal strategy to address the negative intermediate and side‐product issues, therefore enhancing the battery performance. The continuous and multiwalled MoSe2 layers can not only work as grain promoters that induce the initial nucleation and growth of equiaxed Li2O2 grains on the cathode surface even under a high rate, but also prevent the byproducts formation from corrosive issues between carbon and electrolyte. Moreover, density functional theory (DFT) calculations reveal the intrinsic layer dependent direct formation/decomposition catalytic capability of 2D MoSe2 and the LiO2 avoidable reaction pathway during the discharge/charge process, theoretically revealing the direct epitaxial growth mechanisms of Li2O2. As a consequence, the MoSe2@CNT cathode exhibited a superior specific capacity over 32 000 mAh g−1, excellent rate capabilities, and ultralong cycle life of 280 cycles at a high rate of 500 mA g−1.

applications, especially portable electronic equipment and electric vehicles. [1][2][3][4][5][6][7] Rechargeable aprotic Li-O 2 batteries (LOBs) stand out for extremely high theoretical energy density (3623 Wh kg −1 based on the mass of oxygen and lithium), which is approaching that of gasoline and considerably ten times higher than that of current Li-ion batteries (LIBs). [8][9][10][11][12][13][14] According to previous reports, the operation of LOBs experiences the reversible formation (oxygen reduction reaction during discharge, ORR) and decomposition (oxygen evolution reaction during charge, OER) of discharge product Li 2 O 2 by means of the electrochemical reaction 2Li + + 2e − + O 2 ↔ Li 2 O 2 (2.98 V vs Li/Li + ). [15] The reactions between oxygen and lithium usually induce complicated growth pathways of Li 2 O 2 depending on the operating current density, electrolyte and catalyst, [16][17][18][19][20] which in turn resulting in a different mechanism and morphology of discharge products. The solution nucleation and growth of Li 2 O 2 particles are supposed to occur at a low current density, low overpotential, as well as in high donor number (DN) electrolyte solvent, whereas the surface growth mechanism takes place under the opposite factors then leading to quasiamorphous films on the cathode surfaces. [16,[21][22][23] For practical application of LOBs Promising lithium-oxygen batteries (LOBs) with extra-high capacities have attracted increasing attention for use in future electric devices. However, the challenges facing this complicated battery system still limit their practical applications. These challenges mainly consist of inefficient product evolution and low-activity catalysts. In present work, a cation occupying, modified 3D-architecture NiFeO cubic spinel is constructed via superassembly strategy to achieve a high rate, stable electrocatalyst for LOBs. The octahedron predominant spinel provides a stable polycrystal structure and optimized electronic structure, which dominates the discharge/charge products evolution with multiformation kinetics of crystal Li 2 O 2 and Li 2−x O 2 at low and high rate conditions and energetically favors the mass transport between the electrode/electrolyte interface. Simultaneously, the porous NiFeO framework provides adequate spaces for Li 2 O 2 accommodation and complex channels for sufficient electrolyte, oxygen, and ion transportation, which dramatically alter the cathode catalysis for an unprecedented performance. As a consequence, a large specific capacity of 23413 mAh g −1 and an excellent cyclability of 193 cycles at a high current of 1000 mA g −1 , and 300 cycles at a current of 500 mA g −1 , are achieved. The present work provides intrinsic insights into designing high-performance metal oxide electrocatalysts for Li-O 2 batteries with fine-tuned electronic and frame structure.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.