Preparation And The Electrochemical Properies Of Germanium/Canbon Composite Materials

Along with the growing concerns about energy and the environment, thedevelopment and application of lithium ion battery have also been attentioned closelyby researchers, the research found that the traditional graphite carbon material can notmeet the application requirements of modern society because of its low specificcapacity, therefore the development of high capacity battery materials is in urgent need.Germanium materials have been widely studied for lithium ion battery cathodematerials due to its high specific capacity, but it has serious limitations to itscommercial application because of the huge volume expansion of germanium basematerial making cycling stability fall dramatically in the process of charging anddischarging. In this paper, the preparation of Ge/C composites is to alleviate thevolume change of electrode materials, and changing the different process parameters tofurther improve the electrochemical performance of materials.The preparation of acetylene black/germanium and carbon nanotube/germaniumcomposite materials is by the method of electrophoresis and ionic liquidelectrodeposition, and study on the influence of the surface morphology and theelectrochemical properties of the composites by changing the electrophoresis andelectrodeposition time. The study results show that2min of the electrophoretic timeand30min of the electrodeposition time is the best condition of preparation ofcomposite materials, which can obtain the better performance.The results show that the first cycle discharge specific capacity of the acetyleneblack/germanium composites is1500mAh/g due to the formation of the SEI film,coulomb efficiency is65%. And the discharge specific capacity is600mAh/g after100cycles, capacity retention of61%and the coulomb efficiency of more than98%.Composite materials improve its electrochemical performance obviously comparedwith single germanium and acetylene black electrode materials. The CNTs/Genanocomposite anode exhibits better electrochemical properties than acetyleneblack/Ge composite with superior electrochemical cycling properties of over800mAh/g at0.2C after100cycles as anode electrode materials because of its specialstructure. The composites have the initial discharge capacity of1459mAh/g and initialcoulomb efficiency of77%. We also obtain the capacity retention of71%and coulombefficiency of more than98%after100times cycling.Porous germanium/carbon composite was prepared by ionic liquids electrodeposition of germanium on the PS template and high-temperature calcination.Study on the effect of calcination temperature and time in order to obtain bettermorphology and electrochemical properties of the composite materials. Annealing at400oC for2h exhibits the best structure which is uniform formation of porousgermanium/carbon nanocomposite. And the electrochemical testing results show thatthe composite with the better performance, which exhibited initial deintercalationcapacity of988mAh/g and coulomb efficiency of57%, remaining reversible capacityof689mAh/g with the capacity retention of69%for100cycles.