An amorphous red phosphorus/carbon composite is obtained through a facile and simple ball milling process, and its electrochemical performance as an anode material for Na ion batteries is evaluated. The composite shows excellent electrochemical performance including a high specific capacity of 1890 mA h g(-1), negligible capacity fading over 30 cycles, an ideal redox potential (0.4 V vs. Na/Na(+)), and an excellent rate performance, thus making it a promising candidate for Na ion batteries.

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Disodium terephthalate and its various derivatives are synthesized via simple acid-base chemistry for anode materials in Na ion batteries. They show excellent electrochemical performance, including little capacity fading over 90 cycles, ideal redox potential, and excellent rate performance, making them promising candidates for Na ion batteries.

Lithium-ion batteries (LIBs) are considered to be key energy storage systems needed to secure reliable, sustainable, and clean energy sources. Redox-active organic compounds have been proposed as interesting candidates for electrode materials for the next-generation LIBs because of their flexible molecular design, recyclability, and low production cost. Despite wide interest, a molecular-level understanding of the electrochemical lithiations/delithiations of those materials remains rudimentary. We synthesized a set of π-conjugated dicarboxylates and discovered unprecedented excess capacities for inverse-Wurster-type nonfused aromatic compounds (dilithium terephthalate and dilithium thiophene-2,5-dicarboxylate). Molecular structural investigations based on solid-state CP/MAS (13)C NMR combined with the stable isotope labeling method and ex situ X-ray diffraction were carried out to elucidate the origin of the excess reversible capacity. Interestingly, an open-chain-type dilithium muconate did not show an analogous behavior, signifying the key role played by the cyclic moiety in the electrochemical reaction.

A new polyanion‐based compound, Na3.12M2.44(P2O7)2 (M = Fe, Fe0.5Mn0.5, Mn) is synthesized and examined as a cathode for Na ion batteries. Off‐stoichiometric synthesis induces the formation of a Na‐rich phase, Na3.32Fe2.34(P2O7)2 ‐ a member of the solid solution series Na4‐αFe2+α/2(P2O7)2 (2/3 ≤ α ≤ 7/8) ‐ which delivers a reversible capacity of about 85 mA h g−1 at ca. 3 V vs. Na/Na+ and exhibits very stable cycle performance. Above all, it shows fast kinetics for Na ions, delivering an almost constant 72% reversible capacity at rates between C/10 and 10C without the necessity for nanosizing or carbon coating. We attribute this to the spacious channel size along the a‐axis, along with a single phase transformation upon de/sodiation.

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SnSe alloy is examined for the first time as an anode for Na-ion batteries, and shows excellent electrochemical performance including a high reversible capacity of 707 mA h g(-1) and stable cycle performance over 50 cycles. Upon sodiation, SnSe is changed into amorphous NaxSn nanodomains dispersed in crystalline Na2Se, and SnSe is reversibly restored after desodiation.

4859wileyonlinelibrary.com low maintenance costs, and high energy densities, in order to replace nuclear energy or fi nite supplies of fossil fuels. Lithium-ion battery (LIB) technologies are considered to be promising candidates to meet those demands. [ 3,4 ] While most electrode materials in LIBs are based on inorganic elements or compounds, redox-active organic materials have recently gained attention as a fascinating class due to their ecofriendly production starting from renewable resources (biomass or natural compounds) and solution-phase reactions that avoid high-energy ceramic processes. [5][6][7][8][9] Moreover, the structural diversity of the organic building blocks (as scaffolds and substituents) allows the rational design of highperformance electrode materials. [10][11][12] The Chen group proposed a molecular-level engineering strategy to improve cell performance with respect to working potential, power density, rate capability, and cycling stability through the incorporation of fused heterocyclic moieties and pre-aromatic 1,2-dicarbonyl functional groups. [ 13,14 ] Ever since the fi rst demonstration of a primary battery utilizing organic molecules by Williams et al. in 1969, [ 15 ] new classes of organic materials have been developed for secondary batteries; these include conducting polymers, nitroxide-bearing radical polymers, disulfi des, and quinone derivatives. [16][17][18][19] In 2009, the seminal work of Tarascon and co-workers introduced organic anode materials on the basis of conjugated dicarboxylates including dilithium terephthalate (Li 2 TP) and dilithium trans , trans -muconate. [ 20 ] The organic salts exhibited excellent electrochemical performance in terms of enhanced thermal stability, good cyclability, and suitable redox potential. As shown in Scheme 1 a, Li 2 TP reacts with two lithium atoms to afford a conjugated enolate with a reversible capacity of about 300 mA h g −1 . According to Hünig's classifi cation, the carboxylate-enolate interconversion of Li 2 TP belongs to an inverseWurster-type system, where carboxylates are located outside a cyclic π-system that has aromaticity in the oxidized state. [ 21 ] Despite noteworthy progress, the utilization of organic-based materials involving two-electron insertion process is practically limited due to relatively low specifi c capacity values. Mechanistic Studies of Transition Metal-Terephthalate Coordination Complexes upon Electrochemical Lithiation and DelithiationHyun Ho Lee , Yuwon Park , Su Hwan Kim , Sun-Hwa Yeon , Sang Kyu Kwak , Kyu Tae Lee , * and Sung You Hong * Redox-active organic molecules are intriguing candidates as active electrode materials for next-generation rechargeable batteries due to their structural diversity, environmental friendliness, and solution-phase preparation processes. Recently, a transition metal-organic coordination approach is exploited to construct high capacity anodes for lithium-ion rechargeable batteries. Here, a family of transition metal-organic coordination complexes with terephthalate li...