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Currently, many organic materials are being considered as electrode materials and display good electrochemical behavior. However, the most critical issues related to the wide use of organic electrodes are their low thermal stability and poor cycling performance due to their high solubility in electrolytes. Focusing on one of the most conventional carboxylate organic materials, namely lithium terephthalate Li 2 C 8 H 4 O 4 , we tackle these typical disadvantages via modifying its molecular structure by cation substitution. CaC 8 H 4 O 4 and Al 2 (C 8 H 4 O 4 ) 3 are prepared via a facile cation exchange reaction. Of these, CaC 8 H 4 O 4 presents the best cycling performance with thermal stability up to 570 °C and capacity of 399 mA·h·g -1 , without any capacity decay in the voltage window of 0.005-3.0 V. The molecular, crystal structure, and morphology of CaC 8 H 4 O 4 are retained during cycling. This cation-substitution strategy brings new perspectives in the synthesis of new materials as well as broadening the applications of organic materials in Li/Na-ion batteries.

Carboxylate-based metal organic frameworks are popular lithium storage electrode materials by using carbonyl groups as redox centers. In this study, alkaline earth metal terephthalates MC 8 H 4 O 4 (M=Ca, Sr, Ba) are prepared and applied as anodes for lithium ion batteries. The structure differences in terms of crystallography and molecular structures and electrochemical differences resulting from alkaline earth metal ionic radii are explored. It is found that electrostatic interactions between the alkaline metal cations and the terephthalate anions are important to the crystal structure, although these three organic matters consist of alternating layers of terephthalate anions and polyhedrally coordinated metal cations, but do not form isostructure. Moreover, terephthalate salt with smaller cationic radius is featured with ionic bond behavior, lower discharge potential vs. Li/Li + and higher discharge capacity with good capacity retention behavior.

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COMMUNICATION This journal isCarbon-silica composites were obtained via simply heating rice husk at 900 o C under N 2 atmosphere. This composite exhibits a high capacity and superior cycling performance as anodes for lithium ion batteries.Energy consumption is concomitantly growing with the economic growth and the world's population expansion. Due to limited fossil sources, developments of clean, alternative, and sustainable energy technologies are imperative 1 . In parallel, the intermittent renewable energies (e.g. wind, solar, hydro/geothermal) need the implementation of high efficient energy storage devices. As of today, lithium ion batteries (LIBs) are the contenders for these power source systems, which have been widely used in the portable electronics and present a promising future in the electric vehicles and hybrid electric vehicles 2 .

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摘要: 报道了对苯二甲酸镁作为钠离子电池负极材料的研究. 以对苯二甲酸和氢氧化镁为原料, 采用酸碱中 和反应制备了含结晶水的对苯二甲酸镁 (MgC8H4O4•2H2O), 该材料对钠离子电池表现出了较好的电化学活性、 优异的倍率性能以及良好的循环稳定性. 在 0.5C (1C=300 mA•g-1)倍率下循环 50 周以后, 可逆容量由 114 mAh•g-1 降至 95 mAh•g-1 , 容量保持率高达 83%; 在 2C 的倍率下有高达 90 mAh•g-1 的可逆比容量. 另外, 在氮 气气氛中, 400°C 进行后续热处理得到了不含结晶水的对苯二甲酸镁(MgC8H4O4), 探讨了结晶水对其电化学 性能的影响. 结果表明, MgC8H4O4•2H2O 的比容量、 倍率性能以及循环稳定性都明显优于不含结晶水的对苯二 甲酸镁.

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