Preparation Of Li₄Ti₅O₁₂ By Solid-State Method And Recycleing Of The Scrapped Li₄Ti₅O₁₂

]The spinel Li₄Ti₅O₁₂ is a zero strain material , which has good cyclingperformance, good reversibility, safety performance and excellent high rate charge-discharge performance. Because of its simple process, low cost and goodenvironmental properties, it is currently regarded as the most promising anode materialfor lithium ion batteries. However, the electronic conductivity and ionic conductivity ofbare Li₄Ti₅O₁₂ are relatively low, which impact on the high rate charge-dischargeperformance. In this paper, the Li₄Ti₅O₁₂ anode materials were synthesized bysolid-state method.We optimize the synthesis process and study the effect of carboncoated and ion doping on the material properties of Li₄Ti₅O₁₂. Moreover,the wasteLi₄Ti₅O₁₂ /Li batteries recycling process was carried out preliminarily.Firstly, we studied the effects of lithium sources, temperature and Li:Ti on theproperties of Li₄Ti₅O₁₂ which were prepared by solid-state method. The results showthat Li₂CO₃ and TiO₂ are raw materials. 650℃(14h sintering) ,Li: Ti = 0.86 canobtain the best performance of Li₄Ti₅O₁₂ materials. After the optimization process, at0.5C, 1C, 2C, 3C and 5C of charge and discharge current density ,the capacityreached 132 mAh g^-1, 125 mAh g^-1, 119 mAh g^-1, 110 mAh g^-1 and 90 mAhg^-1respectively,which shows the large charge-discharge capacity decreased. So we needsome modification to improve the performance of its large charge or discharge.Secondly, the study of metal ion doping on Li₄Ti₅O₁₂ materials was carried onto improve high rate charge - discharge performance. The results show that, whenV5 + doped(x = 0.04), Li4Ti5-xVxO12 has the fine particle size and distribution and arelatively excellent electrochemical performance.And at 0.5C, 1C, 2C, 3C and 5C ofdischarge current density,the capacity reached 145 mAh g^-1, 140 mAh g^-1, 130mAhg^-1, 120 mAh g^-1 and 100 mAh g^-1 respectively, which show that theincorporation of a certain amount of V5 + can improve the conductivity of Li₄Ti₅O₁₂materials. The incorporation of Ti3 + reduced the performance of materials. WhenNa⁺ doping(x = 0.06 ) is employed, Li4-xNaxTi5O12 rate capability is better. At 3C ofcharge and discharge current density, the specific capacity still be kept at120mAhg^-1 around.In addition, we used four carbon sources (sucrose,activated carbon,stearicacid and citric acid ) to modifie Li₄Ti₅O₁₂ . The results show that the particle sizewas uniform and the specific capacity reached 145 mAhg^-1 at 1C of charge anddischarge current demsity, when the sucrose amount was 5mass%. At 2C, 3C and 5C of charge and discharge current demsity, specific capacitances were 120 mAhg^-1,110 mAhg^-1 and 90 mAhg^-1 respectively. When activated carbon was employed ascarbon, the particle size of Li₄Ti₅O₁₂ / C composite material is relatively large andelectrochemical properties is relatively poor; when stearic acid was employed ascarbon source, the electronic conductivity of Li₄Ti₅O₁₂ / C composite material didnot be improved, but many of its electrochemical performance was reduced due tohigh temperature sintering process in the presence of this carbon source, and TiO₂can not respond fully; when 3mass% citric acid was added, , its capacitance reached158 mAh g^-1,152 mAh g^-1 and 110 mAh g^-1 at 0.5C, 1C and 5C of current density,which shows that large charge or discharge performance has been improvedFinally, we study on the recycling of used cathode material Li₄Ti₅O₁₂.Theresults show that when we soaked the scrapped materials with NaOH solution andthen sintered it at 650℃for 7h, the Li₄Ti₅O₁₂ with good performance can besynthesised. After 20 cycles, its capacitance was about 80 mAh g^-1 at 0.5C ofdischarge current , and the capacity can be kept 75mAh g^-1 at 1C of dischargecurrent.