Synthesis And Modification Of Spherical Lithium Titanate With High Performance As Anode Materials For Lithium-ion Batteries

With the consumption of non-renewable energy fuel,like oil and coal, there is anurgent need in searching for new alternative energy sources and ways to improveresource utilization. Against this background, lithium was discovered by peoplebecause of its low mass,low redox potential,large density qualities. Based on theseadvantages, lithium ion batteries was born.And after the born,lithium ion batterieshave been widely used in the production and life on the account of large density,highoutput voltage,perfact fast charge and discharge abilities,outstanding cyclicperformance and long service life.Nowadays,the lithium ion battery cathode materials are made in carbon mostly.But the carbon materials have many defects such as low reversible capacity, poorsafety performance and circulation performance,which has limited the developing oflithium battery property.In order to overcome these shortcomings, spinel lithiumtitanate (Li4Ti5O12) is respected by people as a new type of lithium ion battery anodematerials gradually. Spinel lithium titanate is well known as the "zero strain"material,because its cell parameter’s change,just from0.836nm to0.837nm,is smallduring charge and discharge cycle. And benefit from that, spinel lithium titanate(Li4Ti5O12) have perfect cycle stability and safety performance and become one of thenew lithium-ion battery cathode materials which have great potentials.Using titanium isopropoxide (TTIP) as the titanium source, lithium hydroxide(LiOH· H2O) as the lithium source,we successfully prepared spherical nanometerlithium titanate material,which has excellent electrochemical performance,inhydrothermal synthesis method. Then by means of X-ray diffraction(XRD), Scanningelectron microscope(SEM), battery testing system and other instruments,we brifilycharacterized the properties of the sample.Through comparison testing in the ratio of raw materials,hydrothermal time andcalcinations temperature,we evaluated the properties and selected the optimalsynthetic route.The spinel lithium titanate prepared in that route was proved to have high charge and discharge specific capacity and good cycle stability.It has a stablevoltage platform in1.5V and its first discharge capacity reachs158.7mAh/g(in0.2C),circulation capacity remains97.35%after10laps’ cycle.The sample also showsgood fast charge and discharge properties and cycle stability in20C. The firstdischarge capacity reachs93.3mAh/g,circulation capacity remains93.78%after5laps’cycle.Spinel lithium titanate also has some defects. That mostly restricting theelectrochemical properties of the material is its low conductivity ability. In thispaper,we used silver nitrate (AgNO3) as a substrate successfully prepared Ag dopedLi4Ti5O12.And through that doping, Li4Ti5O12’s electrical conductivity and specificcapacity had been improved a large scale. We also investigated the influences ofdifferent Ag doping amount, and selected the optimal doping ratio.And under thisoptimal situation, the first discharge capacity of the doped sample reachs207.5mAh/gin0.2C, circulation capacity remains97.83%after10laps’ cycle.When increased to20C, the first discharge capacityof the doped sample also reachs124.6mAh/g. Dopingmodification effect is outstanding, and mainly reached the expected goal.