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

In order to improve the performance of Li₄Ti₅O₁₂ (LTO) anode, this research was focused on Ca²⁺ion doping as a substitute to Li⁺ ion to form Li_4-xCa_xTi₅O₁₂with values of x=0, 0.05, 0.075, and 0.125 using solid-state reaction. The Ca²⁺ion source was CaCO₃which 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 Li_3.75Ca_0.125Ti₅O₁₂ (LCaTO-3) showed the lowest charge transfer resistance of 29.5. Li_3.75Ca_0.125Ti₅O₁₂(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 Li_3.85Ca_0.075Ti₅O₁₂(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.