Preparation And Electrochemical Performance Of Lithium Titanate As Anode Materials For Li-Ion Batteries

With the accelerated pace and the improved quality of people's life,electronic products with fast charging and high-power discharge are more and more popular.However,lithium ion batteries with graphite as the negative electrode have been unable to meet these requirements.Lithium titanate(Li₄Ti₅O₁₂)has a"zero strain"lattice structure and a three-dimensional lithium ion transport path,so the replacement of graphite anode with lithium titanate?LTO?can largely satisfy the rapid charging and high power discharge of electronic products.However,lithium titanate materials facing many challenges.The lower intrinsic conductivity of lithium titanate limits its rate performance,and the lower theoretical specific capacity limits its energy density,which is the two major bottlenecks that lithium titanate is facing.Therefore,it is very valuable to increase the research on improving the conductivity and energy density of lithium titanate.Therefore,it is very valuable to increase the research on the electronic conductivity and ionic conductivity of lithium titanate and to improve the energy density of the battery.In this paper,tetrabutyl titanate and lithium hydroxide are used as raw materials,and an excessive amount of lithium hydroxide is added to provide a strong alkaline chemical environment and an appropriate amount of hydrogen peroxide is added to assist the hydrothermal reaction.Lithium titanate having a flower-like hierarchical structure of about500 nm in diameter formed by self-assembly of ultrathin lithium titanate nanosheets was synthesized by controlling the time and temperature of the hydrothermal reaction.Thereafter,electrodes were prepared and assembled into batteries for electrochemical performance testing.The battery can maintain a discharge specific capacity at 138mAh/g after charge and discharge 3000 cycles at a rate of 20 C?fully charged in 3 minutes?,exhibiting excellent rate and long cycle performance.Secondly,the lithium titanate precursor was treated by a lower temperature of 200°C to obtain amorphous lithium titanate?Li-Ti-O?with non-spinel type and low crystallinity.This amorphous lithium titanate has a high first-rate discharge capacity,excellent rate and long cycle performance,but the first few cycles have a significant capacity reduction.The discharge specific capacity was maintained at 107mAh/g after 3000cycles at 20C.The relatively low processing temperature of 200°C can maintain the morphology of lithium titanate while removing the adsorbed water and crystal water of lithium titanate.It is possible to avoid damage to the material morphology caused by product roughening at high temperature calcination.Thirdly,a composite of graphene-coated lithium titanate nanosheets was prepared,which improved the conductivity of lithium titanate by using the excellent conductivity of graphene,thereby improving the rate performance and cycle performance of lithium titanate.Assembled into a battery for electrochemical performance test,the results show that after charging and discharging 5000 times at 20C,it still has a discharge specific capacity of142mAh/g,which shows excellent rate performance and cycle performance.Finally,this paper also did a deep discharge study.By reducing the discharge cut-off voltage to 0V,it is found that there is an additional reversible capacity,and the stable discharge specific capacity can be maintained between 150mAh/g and 260mAh/g at different discharge rates.The discharge specific capacity is much higher than discharge to1V at the same rate.At the same time,the increase of the voltage window also greatly increases the energy density of the battery.In addition,An increase in the active material loading per unit area can greatly increase the energy density of the battery system.Therefore,we also tried to prepare a high-capacity lithium titanate membrane electrode by vacuum filtration technique and tested the electrochemical performance.