Synthesis And Electrochemical Properties Research Of Li₄Ti₅O₁₂ As Anode Material For Lithium Ion Batteries

In the past few decades,the rapid development of our economy relied heavily on consumption of fossil fuels.However,the overuse and poor-efficiency of fossil fuels resulted in serious environmental problems such as global warming and air pollution.In addition,our dependence on those ever-diminishing energy resources puts us at risk of a non-sustainable future.Among all these practical solutions,electric vehicles?EVs?have attracted worldwide attention because of their potential for replacing conventional internal combustion engines to reduce greenhouse gas emission.The development and use of advanced electrochemical systems are the key to improve the use-efficiency of energies and the reduction of environmental problems.One of the most promising candidates for electrochemical storage devices is Lithium-ion batteries?LIBs?.LIBs are being widely used in portable electronics,power tools and large-scale power sources systems.As energy-storage devices,lithium-ion batteries,which generally have high energy density and long cycling performance,are particularly suitable for applications in EVs where a long cruising range is needed after each recharge in a short time.As anode materials in LIBs,Li₄Ti₅O₁₂ owns the lithium intercalation potential at 1.55 V,which can avoid the formation of SEI and inhibit of the growth of lithium dendritic,ensuring high safety.Besides,the nature of Li₄Ti₅O₁₂ is stable,and it will not react with electrolyte,thus can be widely used.However,the diffusion coefficient and electrical conductivity of Li₄Ti₅O₁₂ are low,which limits its rate performance.Synthesising nanoscale Li₄Ti₅O₁₂ and coated with non-carbon material is an effective way to improve the rate performance,because the nano structure can shorten the diffusion distance of electronic and lithium ion,coating can improve the conductivity.In this paper,with the purpose to improve the rate performance of Li₄Ti₅O₁₂,the Li₄Ti₅O₁₂ material was studied by means of nano scale.?1?Li₄Ti₅O₁₂ nanoparticles were synthesized by sol-gel method with acetic acid as complexing agent.This method will maintain the high purity and good crystallinity of Li₄Ti₅O₁₂.The reaction time was prolonged by complexing agent,so the reaction process was carried out at the molecular level,and the particle size of the sample was controlled at 40⁶0 nm.The addition of complexing agent will enhance the difussion ability of lithium ion and electrons and improve the rate performance and cycle stability of Li₄Ti₅O₁₂.At 0.1 C rate,the capacity is 168 m Ah g-1,and after 100 cycles at 1 C the capacity is about 120.5 m Ah g-1.?2?Preparing Li₄Ti₅O₁₂ nanosheet with the length and width among 200³00 nm scale and thickness of 30 nm by hydrothermal method.We proposed the nucleation and growth mechanism of the nanosheets and explored the influence of different calcination temperature on Li₄Ti₅O₁₂ nanosheets' morphology and electrochemical properties.The Li₄Ti₅O₁₂ nanosheets obtained by calcination at 600 C for 6h not only has high crystallinity,uniform morphology,but also has the highest specific capacity and the best rate performance.The dispersed and independent nanosheets structure can shorten the diffusion path of lithium ions and electrons,and is favorable for the rapid transmission of the thin films.?3?The octahedral Li₄Ti₅O₁₂ particles with a size of 100³00 nm were prepared by modified hydrothermal method using urea as additive.The results of XRD and FESEM show that the addition of urea with a mass ratio of 5% could promote the formation of Li₄Ti₅O₁₂ nanoparticles with high purity,good crystallinity and uniform particle size,and also inhibited the agglomeration of particles.?4?Dual phase nanosheet consisting of Li₄Ti₅O₁₂ and the TiO₂ nanorodes were synthesized by a simple and inexpensive hydrothermal method.The effects of different ratios on the crystal structure,morphology,specific surface area and electrochemical properties of the materials were investigated by controlling the ratio of lithium and titanium.In order to explain the formation mechanism of the dual phase materials,we us XRD,TG-DSC,FESEM and TEM to study the mechanism.The insert of TiO₂ band can act as a channel in the double phase Li₄Ti₅O₁₂-TiO₂ nanosheets,which allows the electron and lithium ions to be embedded into the Li₄Ti₅O₁₂,increasing the conductivity and the diffusion rate of lithium ions.This method provides a possibility for the manufacture of a new generation of non carbon high safety and high rate performance of the anode materials.