Organic carbonyl compounds show potential as cathode materials for lithium‐ion batteries (LIBs) but the limited capacities (<600 mA h g−1) and high solubility in electrolyte restrict their further applications. Herein we report the synthesis and application of cyclohexanehexone (C6O6), which exhibits an ultrahigh capacity of 902 mA h g−1 with an average voltage of 1.7 V at 20 mA g−1 in LIBs (corresponding to a high energy density of 1533 Wh kg−1normalC6normalO6 ). A preliminary cycling test shows that C6O6 displays a capacity retention of 82 % after 100 cycles at 50 mA g−1 because of the limited solubility in high‐polarity ionic liquid electrolyte. Furthermore, the combination of DFT calculations and experimental techniques, such as Raman and IR spectroscopy, demonstrates the electrochemical active C=O groups during discharge and charge processes.
Organic electrode materials suffer from low electronic conductivity and poor structure stability.H erein, ametal-organic polymer,Ni-coordinated tetramino-benzoquinone (Ni-TABQ), is synthesized via d-p hybridization. The polymer chains are stitched by hydrogen bonds to feature as arobust two-dimensional (2D) layered structure.Itoffers both electron conduction and Na + diffusion pathwaysa long the directions of the polymer chains and the hydrogen bonds.With both the conjugated benzoidcarbonyls and imines as the redox centers for the insertion and extraction of Na + ,t he Ni-TABQ delivers high capacities of about 469.5 mAh g À1 at 100 mA g À1 and 345.4 mAh g À1 at 8Ag À1 .The large capacities are sustained for 100 cycles with almost 100 %c oulombic efficiencies.T he exceptional electrochemical performance is attributed to the unique 2D electron conduction and Na + diffusion pathways enabled by the robust Ni-N and hydrogen bonds.
In contrast to traditional rechargeable rock-chairm etal-ion batteries, dual-ion batteries( DIBs) involve redoxr eactions with anions rather than cations in p-type cathodes.I np rinciple, regulating the electrochemical performance of the DIB by different anion species is highly feasible. Herein, the anion effect on the electrochemical performance of aD IB, the aqueous Znorganic radical battery (Zn-ORB), consisting of ap oly(2,2,6,6tetramethylpiperidinyloxy-4-yl vinyl ether) cathode andaZn anode,w as investigated by DFT calculations. SO 4 2À ,C F 3 SO 3 À , and ClO 4 À with different molecular electrostaticp otential values were selected as anion models. DFT calculations revealed that as tronger electrostatic interaction of the anion with the organicr adicalr esulted in ah ighero perating voltage of the Zn-ORB, which was consistent with experimental results. These results bring new insighti nto the redox chemistry of ptype organic radicals with anions andw ill promote the development of high-power aqueous Zn-ORBs as well as inspire more investigations into the anion effect towards novel battery designs.Battery technologies for energy storagea re of increasing importance for the future of society. [1] Traditional rechargeable rock-chairm etal-ion batteries are fabricatedb yc ation-insertion electrode materials, in which cation chargec arriers shuttle between anode and cathode and predominate the electrochemical behavior of batteries whereas anion chargec arriers work as coordinating counterpart for ionicc onduction in the electrolyte. [2] In contrastt or ock-chairm etal-ion batteries, dual-ion batteries (DIBs) involve redox reactions with anions rathert han cations in p-type cathodes. [3] They usually present high redox potentialo wing to the low electron energy level of p-type cathodes. [4] In theory,d ifferent anion species interacting with the same p-type materials hould contribute different reaction energy levels,l eading to different operating voltages given by the Nernste quation. [5] This suggests that regulating the electrochemical performance of DIBs by different anion speciesi s highly feasible. However,t he anion effect on the electrochemical performance of DIBs hasbeen ignored for along time.Aqueous batteries have attracted tremendous attention for their merits of low cost and high safety. [6] Low cost, high volumetric energy density (5855 mA hcm À3 ), and suitable equilibrium potential (À0.763 Vv s. standard hydrogen electrode) make Zn metal ap romising anode for aqueous batteries. [7] However, reported cathodes of aqueousz inc-ionb atteries (ZIBs) encounter limited operating voltages and inferior rate capability.F or instance, average dischargev oltages have been reported to be 0.7-0.9 Vf or vanadium-based oxides, [8] 0.8-1.0 Vf or carbonyl organic compounds, [9] and 1.3-1.4 Vf or manganese-based oxides. [10] In addition, powerd ensitieso ft hese zinc-ion insertion cathodes are limited to 1000-8000 Wkg À1 owing to sluggish diffusion kinetics of divalent Zn 2 + .T od ate, only af ew zinc-based dua...
Honeycomb structure endows graphene with extraordinary properties. But could a honeycomb monolayer superlattice also be generated via self-assembly of colloids or nanoparticles? Here we report the construction of mono- and multilayer molecular films with honeycomb structure that can be regarded as self-assembled artificial graphene (SAAG). We construct fan-shaped molecular building blocks by covalently connecting two kinds of clusters, one polyoxometalate and four polyhedral oligomeric silsesquioxanes. The precise shape control enables these complex molecules to self-assemble into a monolayer 2D honeycomb superlattice that mirrors that of graphene but on the mesoscale. The self-assembly of the SAAG was also reproduced via coarse-grained molecular simulations of a fan-shaped building block. It revealed a hierarchical process and the key role of intermediate states in determining the honeycomb structure. Experimental images also show a diversity of bi- and trilayer stacking modes. The successful creation of SAAG and its stacks opens up prospects for the preparation of novel self-assembled nanomaterials with unique properties.
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