Synthesis And Electrochemical Properties Of Titanium Based And Tin Based Anode For Lithium Ion Battery

Recently,there has been lots of attempt to seek alternative materials for anode of Liion battery（LIB）to achieve better cycling performance including long-term cycliability and stable Li-ion storage.Nano-titanium-based and tin-based materials are widely used as anode or matrix materials for LIB due to their excellent capacity and cycling performance.In this thesis,nano titanium-based and tin-based Li-ion anode have been prepared by different nanocrystallization methods.TiC,TiO₂,SnS₂ and SnS₂ @ GF composite anode materials were prepared by mechanical alloying,hydrothermal method and single-mode microwave thermal synthesis respectively.After series of analysis including phase composation,micro morphology and electrochemical property,the results are as follows:Titanium carbide（TiC）anode for Li-ion battery has been prepared by mechanical milling with pure Ti and toluene.Anneal and re-BM treatments were applied in order to remove the impurity and achieve grain refinement.TEM observation showed that the size of TiC particle is about 20 nm.Accordingly,discharge capacity of TiC anode increases to a high point then begin to drop which probably attributed to activation process of the anode materials and the graphite-like structure.Besides,the capacity was still good at 3000 cycles,combine to the cyclic voltammograms and columbic efficiency data,ball milled TiC anode shows excellent long cyclic performance,which should be a considerable anode material or a stable matrix for other high performance anode material.Nanostructured anatase TiO₂ with controllable morphology has been fabricated via the oxidation of TiC with H₂O₂.At room temperature,the reaction of TiC with H₂O₂ leads to dissolution of TiC into H₂O₂ aqueous solution,producing an acidic solution.By drying the acidic solution at 80 oC in air,an amorphous powder of polytitanic acid with oxalate ligands is obtained,and its morphology is found to rely on the reaction time.By annealing the amorphous acidic powder at T>350oC,the nanostructured anatase TiO₂ with controllable morphology is generated.Depending on the oxidation time,the morphology can be fabricated as sponge-like shape,flower-like shape,spongy balls,etc.The nanostructured anatase TiO₂ is stable under the heating treatments until 900 oC,and its morphology can be tuned to the nanocrystalline grains.In addition to the annealing way,rice-shaped anatase nanocrystals can be directly formed by aging the acidic solution under ambient conditions.Anatase TiO₂ electrode shows good capacity,high rate capability and long cycling life for lithium ion battery.The Anatase TiO₂ electrode exhibits a good reversible specific capacity of 299mAh/g and a long cycling life with a high capacity of 75.4mAh/g after 200 cycles at 1A/g.SnS₂,SnS₂ nanoflakes anchored three dimensional graphene foam（SnS₂@GF）as flexible lithium ion battery anodes has been fabricated via a single mode microwave hydrothermal technique.TEM observation indicates the size of SnS₂ is about 10 nm.The flexible SnS₂@GF electrode shows high capacity,high rate capability and long cycling life for lithium ion battery.The SnS₂@GF electrode exhibits a high reversible specific capacity 1386.7 mAh/g at 0.1 A/g and a long cycling life with a high capacity of 818.4mAh/g after 500 cycles at 1A/g.The excellent performance of flexible SnS₂@GF electrode is attributes to the reduced strain during intercalation/extraction process,shortened ion transport distance,higher conductivity and more electrode/electrolyte contact area.