Lithium Titanate As High-capacity Lithium-ion Battery Anode Materials

Graphite is used as the main commercial anode materials for lithium-ion batteries in nowdays, and it has a theoretical capacity of 372mAh/g. However, it generally owns a bad stability, low capacity, which cannot meet the requirement of the high specific energy storage device; What’s more, it’s easy to form lithium dendrite while under the high rate charge and over charge,thus cause short circuit that may be lead to an explosion, there are so many potential safety hazards. Therefore research and find the security, high energy density, great performance, good stability, long service life of lithium ion battery is very necessary. Spinel lithium titanate was known as the "zero strain" material, and has a very stable charge and discharge platform, is considered to be one of the ideal anode materials; Silicon owns a very high theoretical specific capacity, considered as one of the ideal alternative materials to replace graphite. To improve the electrochemical performance of materials, embarks from the nano and new type of composite structure, the systematic study of hydrothermal synthesis of nano lithium titanate process parameters; Chemical vapor deposition of silicon carbon composite prepared by the nanotube arrays of controllable and into. The main researches are as follows:(1)Static hydrothermal synthesis of lithium titanate and assemble battery testing, the results showed that the proportion of titanium and lithium, pH value, reaction temperature, reaction time, calcination temperature on the synthesis of lithium titanate influential role. Among them, the calcination temperature on the synthesis of lithium titanate effect is the largest. In the 800 oC heat treatment after lithium titanate particle size uniformity, high crystallinity, high purity; After a 100-cycle coulomb efficiency is about 100%, almost every time capacity attenuation rate is less than 0.35%, has a good retention capacity. Through to the particle size control and analysis, the method of synthesis of lithium titanate mechanism is in situ displacement reaction.(2) Dynamic hydrothermal synthesis of lithium titanate.On the basis of the static hydrothermal method, stir in magnetic driving force, the synthesis of large specific surface area of lithium titanate nanotubes. This material has high electrochemical reactivity, under the current density of 0.5C, first put the specific capacity of 174.1mAh/g, at 5C capacity remains of 135mAh/g, has a good ratio performance; In 100 after cycle capacity is 167mAh/g, still coulomb efficiency remained stable after 10 cycles and close to 100%.(3) Use of chemical vapor deposition method and synthetic silicon carbon nanotubes with lithium titanate compound. In anodic alumina template, chemical vapor deposition method of synthesis of silicon carbide composite nanotube arrays, by regulating the silicon carbon source proportion, adjusting pipe diameter and wall thickness control nanotubes arrays. Composite carbon nanotubes lateral transfer charge, inside of the gap buffer silicon volume expansion, improve circulation performance and stability of the battery. At 0.5C first put the specific capacity is 1800mAh/g, reach the theoretical specific capacity, specific capacity after 50 cycles remain more than 1300mAh/g.