xLi2MnO3•(1-x)LiMn0.9Cr0.1O2 (0.2 ≤ x ≤ 0.7) 正極材料的結構和電化學特性研究

Preparation and characterization of layered xLi2MnO3•(1-x)LiMn0.9Cr0.1O2 (0.2 ≤ x ≤ 0.7) cathode materials

魏聿宣(Yu-Syuan Wei)

指導教授 ： 王榮基 ； 吳溪煌

大同大學/工程學院/化學工程學系所/碩士(2011年)

摘要

利用Pechini法合成xLi2MnO3•(1-x)LiMn0.9Cr0.1O2 (0.2 ≤ x ≤ 0.7)正極粉末。以ICP-OES、XRD、EA、SEM及XANES研究合成粉末之成分組成、晶體結構、碳含量以及表面形貌。以循環充放電測試和循環伏安分析去探討所合成粉末之電化學特性。由XRD數據顯示，其生成之粉末主要為m-Li2MnO3、m-LiMnO2相 (空間群 C2/m)和少部分o- LiMnO2相 (空間群 Pmnm)。在室溫下，材料經超過4.5 V的電化學激活後，在定電流密度30 mA/g和電壓範圍2.0到4.6 V間，0.4Li2MnO3•0.6LiMn0.9Cr0.1O2的樣本展現可逆比電容量達220 mAh/g和98%的電容量保持率。採用預循環處理和不超過4.6 V的電壓範圍，有效降低在高電壓下首次循環的不可逆電容量並改善其循環穩定性。

關鍵字

鋰離子電池 ； 複合結構 ； LiMn0.9Cr0.1O2 ； Li2MnO3 ； 正極材料

並列摘要

Layered xLi2MnO3•(1-x)LiMn0.9Cr0.1O2 (0.2 ≤ x ≤ 0.7) cathode materials were synthesized by a Pechini method. The compositions, crystal structures, carbon contents, and morphologies of the as-prepared powders were investigated using ICP-OES, XRD, EA, and SEM, respectively. The electrochemical properties of the samples were studied with using cyclic voltammetric and capacity retention studies. The XRD result shows that the as-prepared powders are mainly composed of m-Li2MnO3 (space group: C2/m) and m-LiMnO2 (space group: C2/m), with a minor amount of o- LiMnO2 (space group: Pmnm). Electrode comprised of sample with targeted composition of 0.4Li2MnO3•0.6LiMn0.9Cr0.1O2 delivered reversible capacities of 220 mAh/g and 98% capacity retention at a constant current rate of 30 mA/g when cycled between 2.0 and 4.6 V after pre-cycling treatment. Pre-cycling treatment with cutoff-voltages of 2.0 and 4.6 V was employed to depress the irreversible capacities in initial cycles at high-voltage and improved cycle stability effectively.

並列關鍵字

LiMn0.9Cr0.1O2 ； Li2MnO3 ； Lithium ion battery ； Composite structure ； Cathode materials

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