Synthesis and Characterization of Ca-doped Li4Ti5O12 Using CaCO3 from Chicken Eggshell as a Dopant for Lithium-Ion Battery Anode Material

摘要

In order to improve the performance of Li4Ti5O12 (LTO) anode, this research was focused on Ca~(2+) ion doping as a substitute to Li~+ ion to form Li_(4-x)CaxTi5O12 with values of x=0, 0.05, 0.075, and 0.125 using solid-state reaction. The Ca~(2+) ion source was CaCO3 which synthesized from the chicken eggshell. The LTO was prepared by a solid-state method using TiO2 Degussa. The pristine LTO and Ca-doped LTO sample powder was characterized by XRD, SEM, and were also tested its electrochemical performance by EIS, CV and CD. The CaCO3 dopant characterization results showed CaCO3 in calcite polymorph as the main phase, with agglomerated fine particulate morphology and high purity. Characterization of LTO sample powder with XRD revealed that dopant Ca successfully enter the structure of LTO spinel, with maximum addition level x=0.05, which excessive addition led to CaTiO3 impurity forming. SEM result showed all Ca-doped LTO have almost similar morphology, which was agglomerated particulate. Ca-doped LTO samples have smaller particle size compared to pristine LTO. Electronic conductivity improvement was spotted at all of Ca-doped LTO sample, with Li3.75Ca0.125T15O12 (LCaTO-3) showed the lowest charge transfer resistance of 29.5 Q. Li3.75Ca0.125Ti5O12 (LCaTO-3) also had the highest initial discharge capacity of 168.2 mAh/g. Nevertheless, in high rate application, the best performance was showed by Li3.85Ca0.075Ti5O12 (LCaTO-2) with the discharge capacity of 30.2 mAh/g at 12 C, which capacity retention percentage of 21.43% compared to its discharge capacity at 0.2 C.