Doped And Undoped Bicontinuous Crystalline TiO₂/C Composites Used As Anode Materials In Lithium Ion Battery

Great attention is paid to lithium ion battery as clean and green energy storagedevices. Electrode materials are quite significant for batteries and for anodematerials which have to endure repeated lithium insertion and extraction processeswithout structural damage for a long recharge able lifetime. TiO₂is a promisingoption to traditional anodes, there are some reasons:（1） TiO₂can work at muchhigher voltages （～1.7V vs Li+（1M）/Li）.（2） AnataseTiO₂possess favourablecrystal type, that is TiO₆-edge sharing octahedra in the TiO₂crystal lattice structureshare vertices and edges, giving rise to a three-dimensional network which createsmany empty sites for lithium extraction. Besides, it is pollution-free and strongoxidation capability. In addition mesoporous materials with large specific area arequite favourable for batteries. From the above，the main object of this thesis is tosynthetize TiO₂mesoporous materials and use as-made materials on lithiumbatteries. According to the previous study, the pure TiO₂mesoporous structure is notstable. Then I do doping to improve the properties of the batteries.In this thesis the synthesis mechanism is researched, and the influence factorssuch as, the addition of carbon precursor, Ti precursor, experiment conditions,thickness of the films and dopant are discussed, though which, the optimalexperiment conditions are found. Then as-made materials are used as anodes andafter electrochemical property testing, if necessary, go on do doping to improve theperformance. The main achievements are as follow:（1）The addition and pH value of resols both have great effects on mesoporousmaterials. Too much or too less of the resols is unfavourable for the orderedmesoporous. The acidic resol is also hard to get ordered structure.（2） Too much addition of TiCl4is hard to get ordered structure. That is becausetoo much TiCl4means excessive HCl produced here which leads to acidic solution.（3） The thickness of the film will affect mesoporous structures. Compared withthe thick sample, the intensity of peaks in XRD is stronger in thin sample,suggesting it is high degree ordered. In the FI-IR, more–OH in thick samples butthese–OH will get out after heating, suggesting the shrinkage is more serious inthick samples.（4） Different resols doping show different electrochemical property. This isrelational with the form of the carbon. The order sp2is good to battery. In addition,the electrochemical property mainly relates to the morphology, the opening of thepores.（5） The radii of doped metal, the lattice distortion and the crystal texture will affect the mesoporous structures and the battery performances. In this thesis, theFe-doping is superior to Al-doping.