Research On The Preparation And Doping Modification Of Lithium Titanate

Due to the poor safety of graphite-based carbon anode materials,researchers have been looking for new anode materials to replace commercial graphite-based carbon anode materials in recent years.Lithium titanate is a promising anode material for lithium ion batteries that is expected to replace graphite-based carbon anode materials in the future.Lithium titanate neither reacts with electrolyte to form solid electrolyte interface membrane?SEI membrane?nor forms lithium dendrite to cause safety hazard.In addition,lithium titanate is in a state of zero strain during the phase transition process of charge and discharge,and the cycle efficiency is very good.However,the low intrinsic conductivity of lithium titanate leads to serious polarization of the electrode under large electric current and poor ability of quick charging and discharging,which limits its application in fast charging mobile devices.Doping modification is an effective method to improve the conductivity of lithium titanate among many modification methods.In this article,through regulation of three kinds of influence factors on the solid-phase method and hydrolysis method for synthesis of lithium titanate preparation technology is optimized,and the hydrolysis method of optimized samples preparation of lithium titanate by the Ce³⁺,Y³⁺,Er³⁺,Y³⁺single element doping modification and Ce³⁺/Y³⁺,Er³⁺/Y³⁺doping modification of research,using TG,XPS,XRD and SEM microscopic characterization and constant current charge and discharge,cyclic voltammograms and electrochemical performance test.?1?By electrochemical properties and XRD phase analysis in laboratory solid-phase method and hydrolysis method of synthesis of lithium titanate preparation process conditions optimization,finally confirmed in the calcination temperature is800?calcination time is 16 h at Li/Ti ratio of 0.85 at the same time with solid phase of lithium titanate sample prepared by the crystallinity is best,the most excellent electrochemical performance,the sample charge and discharge capacity and coulomb efficiency were 169.4 mAh·g^-1,162.1 mAh·g^-1,95.7%.And relative to the solid phase method,hydrolysis method can get the samples on smaller energy consumption,just in the calcination temperature is 700?calcination time is 4 h at Li/Ti ratio of0.8375 at the same time can obtain good performance of lithium titanate sample,the sample after a 100 cycle still has a capacity of 124.0 mAh·g^-1,is 97.8%of the initial capacity.?2?And then select a series of lithium titanate more likely to affect the conductivity of trivalent ions(Ce³⁺,Y³⁺,Er³⁺,Y³⁺)to a single element doped lithium titanate modified research,found trivalent ions doped lithium titanate improved the electrode.At 10C,the samples doped with Ce³⁺,Y³⁺,Er³⁺and Y³⁺had the reversible capacity of 121.1 mAh·g^-1,125.6 mAh·g^-1,125.3 mAh·g^-11 and 123.4 mAh·g^-1,respectively.Meanwhile,the volume retention rate after 500 cycles was 91.8%,91.0%,93.4%and 89.9%,respectively.At the same time,the"synergistic effect"of multi-element co-doping on the performance of lithium titanate was studied.?3?The synergistic effect of Ce³⁺/Y³⁺and Er³⁺/Y³⁺co-doping enables more ions to be doped into the lattice,which improves the conductivity of lithium titanate more than that of single element doping.The electrochemical properties of doped samples are obviously better than those of undoped samples,and also better than those of single element doped samples.The reversible capacities of Ce³⁺/Y³⁺,Er³⁺/Y³⁺codoped samples at 5 C,10 C,and 20 C were 145.2 mAh·g^-1,139.2 mAh·g^-1,123.1mAh·g^-1,143.6 mAh·g^-1,138.6 mAh·g^-1,and 120.1 mAh·g^-1,respectively.