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Cathode materials are vital to the performance of alkali-ion batteries. Inorganic transitional metal oxides with insertion chemistry, such as LiCoO 2 , LiFePO 4 , and LiNi x Co y Mn 1−x−y O 2 , have been the predominant cathode materials in conventional LIBs. Constructed with heavy metallic elements, conventional inorganic cathode materials typically have restricted specific energy capacity (theoretical: <300 mAh g −1) with little room for further improvements. [1,2] Meanwhile, their applicability in SIBs and KIBs is often hindered due to kinetic and stability issues, where their rigid lattice structures can restrict diffusion/storage of Na + and K + ions of larger sizes than Li +. [7] In addition, produced from minerals with limited availabilities, the use of inorganic cathode materials is neither sustainable nor environmentally benign. In this regard, organic cathode materials have recently attracted increasing attention. Relative to conventional inorganic cathode materials, they show distinct advantages, including higher theoretical capacity due to their construction from abundant light elements, structural diversity with tunable electrochemical properties, rational synthesis from sustainable stocks and low costs. In addition, their less-rigid structures are beneficial for the storage and mobility of larger-sized Na + and K + ions. [8,9] With organic materials, energy storage is achieved through the reversible reaction of alkali ions with their redox-active functional groups. To date, a large family of organic cathode materials incorporating various redox-active functional groups have been developed, which have been well summarized in several recent comprehensive reviews. [10-16] The predominant redoxactive functional groups reported thus far include carbonyl (CO) functionalities, [8,9,17-25] imine (CN) functionalities, [26-29] disulfides (SS), [30-33] radicals, [34-39] and azo (NN), [40-42] with the first two types most heavily focused on. Despite the significant progress, the majority of organic cathode materials developed to date, however, still has restricted specific capacity (generally <300 mAh g −1), energy density (<750 Wh kg −1 for LIBs), and/or cycle life. [10-16] It is thus imperative to explore and discover new redox functionalities that render higher-energy multielectron organic cathode materials with high cyclic stability. We report in this work a new group of nitroaromatic compounds, para-, ortho-, and meta-dinitrobenzene (p-, o-, and m-DNB, respectively) containing dual two-electron accepting nitro groups, as reversible high-energy multielectron organic cathode Organic cathode materials with existing redox functionalities are attracting increasing attention for rechargeable alkali-ion batteries due to their high theoretical gravimetric capacity, molecular diversity, and sustainability. However, they are still restricted in specific capacity and energy density. The discovery of new multielectron redox-active functionalities that can impart significantly enhanced capacity and energy density i...

Carbon-coated Li2MoO4 hexagonal hollow nanotubes were fabricated via a facile sol-gel method involving the solution synthesis of Li2MoO4 with subsequent annealing under an inert atmosphere to decompose the organic carbon source. To the best of our knowledge, this is the first report on the synthesis of Li2MoO4 nanotubes. More significantly, we have found that Li2MoO4 can be used as an anode material for lithium-ion batteries (LIBs). When evaluated as an anode material, the carbon-coated Li2MoO4 hollow nanotubes show an excellent electrochemical performance with a high reversible capacity (∼550 mA h g(-1)) after 23 cycles, good rate capability and cycling stability. Meanwhile, carbon-free Li2MoO4 sample, fabricated via a solid state reaction, was also prepared for comparison. The Li storage mechanism has been investigated in-detail by advanced XPS, in situ XRD and HRTEM.

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Porous covalent triazine framework (CTF)-based carbon materials have gained increasing attention in energy-storage applications because of their tunable structure, high chemical stability, and rich heteroatom contents. However, CTFs have thus far been exclusively synthesized from small-molecular precursors and generally show unsatisfactory supercapacitive performance. We report herein the construction of a novel range of CTFs of significantly improved supercapacitive performance from polyethynylbenzonitrile (PEBN) as a unique macromolecular precursor for the first time by ionothermal synthesis. CTF-800 synthesized at the optimized condition (800 °C; ZnCl2/PEBN mass ratio of 3:1) shows a nanosheet-like morphology with a high yield (∼90%), high nitrogen content (>5.8%), high specific surface area (1954 m2 g–1), and optimized micropore to meso/macropore surface area ratio (42:58). As the electrode material for supercapacitor application, CTF-800 exhibits a high specific capacitance of 628 F g–1 at 0.5 A g–1, high-rate performance (71% of capacitance retention at 50 A g–1), and excellent cyclic stability (96% of capacitance retention over 20 000 cycles) in a three-electrode system with aqueous 1 M H2SO4 electrolyte. Symmetric supercapacitor devices have been further fabricated with CTF-800 in aqueous 1 M H2SO4, [EMIM]­[BF4], and LiPF6 electrolytes separately. The device with the aqueous electrolyte shows the highest capacitance of 448 F g–1 (at 0.5 A g–1) and a high energy density of 15.5 W h kg–1. The devices with [EMIM]­[BF4] and LiPF6 electrolytes exhibit exceptional energy densities of 70 and 78 W h kg–1, respectively, and retain energy densities of 41 and 45 W h kg–1, respectively, even at the high power density of 15 000 W kg–1, confirming their high-rate high-energy performance. Meanwhile, the device with [EMIM]­[BF4] electrolyte has also been demonstrated to operate well at various temperatures ranging from −20 to 60 °C with remarkable energy-storage performance.

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