Preparation And Structural Properties Of Negative Electrode Materials For Lithium Ion Batteries Based On Titanium Dioxide

Lithium-ion battery is become one of the most popular among a wide varieties of energy storage devices because of its high voltage, low self-discharge rate, wild temperature range, low pollution and security. TiO₂, as a kind of lithium ion battery anode material of transition metal oxides, which has the advantages of safety,abundance in nature, chemical stability and non-toxicity is a kind of potential material of lithium ion battery anode materials. However, TiO₂ has relatively poor electrical conductivity. To improve its electrical conductivity,there are three methods which are production of nano materials,synthesis of composite materials using conductive materials and doping metal ions into TiO₂。This paper used renewable sodium alginate as carbon source, to prepare carbon aerogel coated TiO₂ nanofibers by pyrolysis and studied the structure and electrochemical performance of the materials at different heat treatment temperature. This paper also researched the relationship between synthetic methods, the structure and electrochemical performance. The results show that the structure of the composites is made up of two crystal phases. TiO₂ nanofibers are evenly coated by carbon aerogel. The first discharge capacity is 513.1 mAh g-1 at the current density of 335 mA g-1, the reversible capacity can reach 370 mAh g-1 which reaches 72% of the initial capacity even after 400 cycles. The synthetic process extract sodium alginate from brown algae as the carbon source which is environment friendly,healthy and non-toxic. This synthetic method is simple and novel.In addition, this paper also used the method of metal ion doping to prepare tin ions doped TiO₂ nanofibers as anode materials of lithium ion battery. This method is simple, novel,non-toxic and environmental friendly. After doping tin ions, the diameter of TiO₂ is also about 50¹00nm. The electrochemical testing results show that the materials which the ratio of tin ions and TiO₂ nanofibers is 1/15 shows the excellent electrochemical properties. The reversible capacity can reach 220 mAh g-1 at the current density of 100 mA g-1 even after 100 cycles. The reversible capacity can reach 180 mAh g-1 even at the current density of 2000 mA g-1. In addition, this paper also prepare copper ions doped TiO₂ nanofibers. The electrochemical testing results show that the materials which the ratio of copper ions and TiO₂ nanofibers is 1/15 shows the excellent electrochemical properties. The reversible capacity can reach 180 mAh g-1 at the current density of 100 mA g-1 even after 100 cycles. The reversible capacity can reach 150 mAh g-1 even at the current density of 2000 mA g-1. The method of ion doping can improve theelectrochemical properties of TiO₂ nanofibers to some extent without the change of volumetric enegy density.