Preparation And Research Of Lithium Titanate Anode Materials

As a anode material for lithium batteries,the spinel-type lithium titanate(Li4Ti5O12)is a "zero strain" material.The change in the volume of the battery when lithium ions are inserted or extracted is almost negligible.Batteries with lithium titanate as lithium Ion battery anode has the advantages of good safety,light bulk density,and long cycling life-time.The 1.55 V discharge platform allows it to effectively inhibit the SEI film and lithium dendrite formation.Therefore,it has good cycle stability,thermal stability,and stable discharge platform.However,lithium titanate as a battery anode material has also the following drawbacks: low electric conductivity(10-13 S·cm-1)and lithium ion diffusion coefficient(10-9-10-16 cm2·s-1).Therefore,searching for a LTO material to has higher specific capacity and high rate capability becomes the goal of the present investigation.In this investigation,a solvothermal synthe sis method was used to synthesize tatainium ethylene glycol polymer in the presence of carbon nanotubes(CNT)in a reactor,and then in situ hydrolysis the polymer by reacting with Li OH aqueous solution to obtain a gel precursor.The as prepared gel precur sor is calcined in nitrogen atmosphere to obtain the Li4Ti5O12-carbon nanotubes(LTO-CNTs)anode material.The investigation include:In Chapter 3,LTO-CNTs discusses the preparation.LTO-CNTs is prepared through two steps: 1)the solvothermal polymerizati on reaction of tatainium tetra-isopropyloxide with ethylene glycol and 2)the hydrothermal hydrolysis of product from the first reaction and then calcination.The influence of calcination temperature on electrochemical properties of material is studied.Th e results show that LTO-CNTs sintered at 700 °C has the highest initial charge-discharge efficiency(up to 77%),specific capacity,and high rate capability(123 m Ah·g-1 at 4.0 A·g-1).The material has also long cycling life-time.After 500 cycles at 300 m A·g-1,there is no specific capacity(230 m Ah·g-1)fading.In addition,the physical properties and electrochemical properties of LTO-CNTs containing different amounts of carbon nanotubes are also studied.The results show that the lithium titanate composite has higher specific capacity and better rate performance,when containing 0.6 wt% of CNT.The investigation suggests that the addition of carbon nanotubes can significantly improve the electric conductivity of the material,and therefore greatly improve the rate capability of the material.The fourth chapter mainly studies the electrochemical performance of LTO-carbon that is prepared from different carbon sources.It is found that LTO-CNTs has the highest specific capacity and the highest rate capability.