Carbon-encapsulated Fe3O4 composites were successfully fabricated via hydrothermal method and ex- amined by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The Fe3O4@C nanocomposite as an anode material with novel structure demonstrated excellent electrochemical performance, with enhanced specific reversible current density of 50 mA/g capacity （950 mAh/g at the after 50 cycles）, remarkable rate capability （more than 650 mAh/g even at the current density of 1,000 mAJg） and good cycle ability with less capacity fading （2.4 % after 50 cycles）. Two factors have been attributed to the ultrahigh electrochemical perfor- mance： Firstly, the 30- to 50-nm spherical structure with a short diffusion pathway and the amorphous carbon layer could not only provide extra space for buffering the volumetric change during the continuous charging-dis- charging but also improve the whole conductivity of the Fe3O4@C nanocomposite electrode; secondly, the syner- gistic effects of Fe304 and carbon could avoid Fe304 direct exposure to the electrolyte and maintain the structural stabilization of Fe3O4@C nanocomposite. It was suggested that the Fe3O4@C nanocomposite could be suitable as analternative anode for lithium-ion batteries with a high ap- plication potential.
采用原位聚合法制备锡酸钴（Co2SnO4）/聚苯胺（PANI）复合负极材料,用XRD、SEM分析物相结构与形貌,对复合材料进行恒流充放电、循环伏安及电化学阻抗谱测试。添加PANI可缓解Co2SnO4在充放电过程中的体积膨胀效应,使Co2SnO4/PANI体系的电子导电率与循环性能得到改善。以100 m A/g的电流在0.01--3.00 V循环,Co2SnO4/PANI复合材料的首次放电比容量为1 234.11 m Ah/g,第80次循环的放电比容量为817.36 m Ah/g。
As an anode material in lithium ion battery,the Sn-Co/C composite electrode materials have been successfully synthesized by hydrothermal and sol-gel methods,respectively.The resultant composites were mainly composed of Sn-based oxides,nanometer Sn-Co alloy and carbon.Carbon and Co,acting as buffer materials,can accommodate to the large volume change of active Sn during the discharge-charge process,thus improving the cycling stability.Although charge/discharge curves revealed the excellent cycle performance for samples synthesized by both methods,composites obtained by the sol-gel showed a better dispersion effect of nanoparticles on the carbon matrix and possessed much more improved stable capacity with*624.9 mAh g-1over 100 cycles and that by hydrothermal method only exhibited*299.3 mAh g-1.Therefore,the Sn-Co/C composites obtained by sol-gel synthesis method could be a perfect candidate for anode material of Li-ion storage battery.
Xiaoli ZouXianhua HouZhibo ChengYanling HuangMin YueShejun Hu
To understand the influence of structure and atom sites on the electrochemical properties of Sn-based anode materials,the lithium intercalation–deintercalation mechanisms into SnNi2Cu and SnNiCu2phases were studied using the first-principle plane wave pseudo-potential method.Calculation results showed that both SnNi2Cu and SnNiCu2were unsuitable anode materials for lithium ion batteries.The Sn-based anode structure related to the number of interstitial sites,theoretical specific capacity,and volume expansion ratio.Different atom sites led to different forces at interstitial sites,resulting in variations in formation energy,density of states,and hybrid orbital types.In order to validate the calculated model,the SnNi2Cu alloy anode material was synthesized through a chemical reduction-codeposition approach.Experimental results proved that the theoretical design was reasonable.Consequently,when selecting Snbased alloy anodes,attention should be paid to maximizing the number of interstitial sites and distributing atoms reasonably to minimize forces at these sites and facilitate the intercalation and deintercalation of lithium ion.
