Study On The Doping Modification Of Lithium Titanate Anode Material

In this paper, Li₄Ti₅O₁₂materials doped by the two metals and carbon coated metalelements doped Li₄Ti₅O₁₂materials were prepared by high-temperature solid state method.Effects on performance of Li₄Ti₅O₁₂material, such as different pre-burn time, differentamount of carbon, different doping metal and doping amount, were studied detailedly. Thematerial structure, morphology and electrochemical performance were characterized andanalyed by thermal analysis, XRD, EIS, CV and constant current charge and dischargemethods.Double metal-doped Li₄Ti₅O₁₂materials were synthesized by two-step calcinationsynthesis method, using Li2CO3, TiO2and a certain amount of charring agent as rawmaterial and doping two different metal elements. The electrochemical results showed thatthe sample calcined at700℃for12h has large capacity, good cycling stability. Ni,Cr-doped samples did not improve specific capacity and cycle performance. The specificcapacity of double-doped samples of Co, Mn; Al, Zn; Mn, Cr were all better than pureLi₄Ti₅O₁₂, at1C, all discharge specific capacity reached120mAh·g-1, the high ratedischarge performance of the material was improved. Li3.95Co0.05Mn0.1Ti4.9O12exhibitedthe best specific capacity and rate cycle capability, the first charge-discharge capacity couldreach168.9and205.4mAh·g-1, respectively, and corresponding charge-dischargeefficiency was82.2%at0.1C; when the rate was1C, the initial discharge specific capacitywas153.4mAh·g-1and91.9%of the initial discharge capacity was retained after20charge-discharge cycling. The initial discharge specific capacity of Li3.9Al0.05Zn0.05Ti5O12sample was157.9mAh·g-1and153.6mAh·g-1and the initial discharge specific capacitywas retained97.3%after20charge-discharge cycling at1C, which showed good specificcapacity and cycle performance.The sample of Li4Mn0.05Cr0.02Ti4.93O12only had10.1%capacity loss after20cycling at1C, Which showed high discharge specific capacity andexcellent cycle performance.The carbon-coated Li₄Ti₅O₁₂were parpered by high-temperature solid state method,using anhydrous glucose as carbon source. The best Ti: C molar ratio is5:10, the discharge capacity of sample was great, the initial discharge capacity could reach68.2mAh·g-1at2C,affter20cycles at different rate, the capacity retention rate was about90%, the dischargecapacity of the large rate and the cycle performance were improved.The different Cr, Zn, Co doped and carbon-coated Li₄Ti₅O₁₂were parpered by high-temperature solid state method at Ti: C=5:10, The results as follows: The dischargecapacity and cycle performance of Li4Cr0.2Ti4.8O12/C samples were improved and dopingCr3+to some extent reduce the discharge voltage of the material; The electrochemicalperformance of Li4Zn0.05Ti4.95O12/C samples was significantly improved compared to pureLi₄Ti₅O₁₂materials and other Zn-doped samples, its capacity retention rate was95.8%at1C; the discharge capacity and cycle characteristics of Li4Co0.1Ti4.9O12/C sample was betterthan pure Li₄Ti₅O₁₂, the cycle stability is also the best in all doped samples. The dischargecapacity of carbon-coated Li₄Ti₅O₁₂was99.7mAh·g-1at1C, the capacity retention ratewas about95%at different rate, the capacity and cycling performance were the best in allmodified samples.