Preparation And Electrochemical Properties Of Anode Materials For Lithium Ion Batteries

It is well known that rechargeable lithium-ion batteries (LIBs) have been widelyused in portable electronic devices as well as electric vehicles (EVs) and hybrid electricvehicles (HEVs) due to their high energy density, high power density, long lifespan,environmentally friendliness and no memory effect. The ever-growing demand for highcapacity and/or high power LIBs has prompted tremendous research efforts indeveloping advanced high-performance. The high reactivity, favourable chargetransport properties and novel structural merits of nanomaterials make them suitablealternative to effectively improve. Therefore, this dissertation focuses on the preparationand electrochemical investigation of CoMn2O4nanosubmicrorods, spinel C@Li4Ti5O12microspheres and Fe2O3@TiO2hollow fibers. The main content is as follows,（1）In this work, by using hydrothermally synthesized b-MnO2nanorods as thetemplates, we prepared single-crystalline CoMn2O4nano/submicrorods with diametersof about100nm and lengths up to tens of micrometers. The electrochemical testsshowed that the CoMn2O4products have a reversible capacity of512mA h g-1at acurrent density of200mA g-1with a coulombic efficiency of98%after100cycles. Aspecific capacity of about400mA h g-1was obtained even at a current density as highas1000mA g-1, exhibiting a high reversibility and a good capacity retention. This studysuggests that CoMn2O4nano/submicrorods are promising anode materials for highperformance lithium-ion batteries.（2）Using anatase TiO2microspheres as the self-sacrificed templates, spinelC@Li4Ti5O12microspheres have been successfully prepared via the simplehydrothermal and subsequent carbonization processes in the presence of PVP. Aftercharacterized by XRD, SEM and XPS etc., the composited microspheres were furtherstudied as anode materials in lithium-ion batteries (LIBs), which exhibited improvedreversible capacity of160mA h g-1after100discharge/charge cycles at1C andlong-term cycling stability with little performance degradation even after100discharge/charge cycles at current density of2C, much better than those of pureLi4Ti5O12microspheres. The influences of humidity and temperature on the performance of these composite microspheres were also investigated, which revealedthat the as-prepared C@Li4Ti5O12microspheres display a very stable reversible capacityof175mA h g-1at humidity ranging from50%to90%. And the capacity ofC@Li4Ti5O12can still reach as high as220mA h g-1even at high temperature. From theresults, we can confirm that the carbon coating treatment to the Li4Ti5O12microspheresincreases the whole electrical conductivity of the electrode and facilitates the lithium ioninsertion/extraction processes.（3）Titanium(Ⅳ)isopropoxide and Ferric chloride hexahydrate as raw materials,we prepared Fe2O3@TiO2hollow fibers with diameters around240nm by coaxialelectrospinning. Their structures have been studied by SEM, TEM, XRD and EDS. Theelectrochemical performance of Fe2O3@TiO2nanofibers as anode material forassembling the simulate batteries were measured. The electrochemical properties of theprepared Fe2O3@TiO2hollow fibers tested over the range of0.02-3.00V exhibited ahigh reversible capacity of780mA h g-1at a current density of200mA g-1after150cycles with a coulombic efficiency of99%. The Fe2O3@TiO2hollow fibers exhibitedgood rate performance as well. When the current density increased to800mA h g-1, theelectrode materials delivered a stable capacity of about740mA h g-1after150cycles.were Fe2O3@TiO2hollow materials can short the distance of lithium ion diffusion andbe in favor of fast diffusion of the lithium ion，so it can improve the dynamicperformance.