- 學位論文
鋁摻雜對磷酸鋰鐵基正極材料循環特性之影響
Effects of Al3+ ion substitution of LiFe1-xAlxPO4/ MCMB on the cycle properties and capacity fading mechanism
摘要
以溶液法合成純相橄欖石結構LiFePO4，摻雜Al3+離子的LiFe1-xAlxPO4 (0.01 £ x £ 0.1)。在氮氣氣氛下燒結至700oC，以同步輻射01C SWLS - X-ray Powder Diffraction、ICP-OES及SEM分析合成粉末之結晶構造、材料組成及觀察粉末之表面形態。在合成的粉末中，以LiFe0.95Al0.05PO4在室溫下有最好循環充放電特性。探討Al3+離子摻雜對LiFePO4/ Li半電池和LiFePO4/ MCMB全電池循環特性之影響。從LiFePO4/ Li半電池循環特性與GSAS結果顯示，Al3+離子摻雜增加晶格常數使可逆電容量提昇。而從LiFePO4/ MCMB全電池電容衰退結果、高解析X-ray影像、和靜置試驗顯示，Al3+離子摻雜可以抑制Fe2+的溶出來提升全電池循環特性。
並列摘要
A solution method was used to synthesize LiFePO4 and Al3+-doped LiFe1-xAlxPO4 (0 £ x £ 0.1) powders. After heat-treatment at 700oC for 8 hours under N2 flowing atmosphere, the crystalline structure, compositions, and morphology of the prepared powders were investigated with the XRD patterns performed with 01C beamline of NSRRC of Taiwan, ICP-OES, and SEM. The powder with composition of LiFe0.95Al0.05PO4 shows the best cycling performance at room temperature among the prepared samples. The effects of Al3+-doping on the cycling performance of the LiFePO4/ Li coin-type cells and LiFePO4/ MCMB were investigated. From the cycling results of LiFePO4/ Li cells and the results of GSAS refinement, it was found the reversible capacity of LiFePO4 was increased by Al3+-substitution due to the enlargements of lattice parameter. From the results of capacity retention study for the LiFe1-xAlxPO4/ MCMB stacked cells, the high resolution X-ray image observation, and soaking study, it was revealed that the cycling performance of improvement in LiFe1-xAlxPO4/ MCMB cells by Al3+-substitution was attributed to the suppression of Fe2+-dissolution into LiPF6 electrolyte.