以水熱、共沉法二步驟製備富鋰錳基正極材料x Li2MnO3．(1-x)LiNi1/3Co1/3Mn1/3O2之電性表現

Investigation of Electrical Performance of x Li2MnO3．(1-x)LiMO2(M=Ni,Co,Mn) Prepared through a Two-stage Process of Co-precipitation and Hydrothermal Methods

賀安麗

指導教授 ： 蔡哲正

國立清華大學/工學院/材料科學工程學系/碩士(2013年)

https://doi.org/10.6843/NTHU.2013.00510

摘要

Li2MnO3與LiNi1/3Co1/3Mn1/3O2皆為層狀結構，兩者混合能形成充放電區間為2～4.8 V的固溶體富鋰材料Li2MnO3．LiNi1/3Co1/3Mn1/3O2，為一種高伏材料。此材料第一次充放電時將因Li2MnO3氧化脫出Li2O造成不可逆的電容量損失。本實驗討論pH值在共沉法製備富鋰材料前驅體時對電性的影響，此外嘗試使用水熱法與共沉法兩步驟製備活性物質：分別將兩固溶成分Li2MnO3與LiNi1/3Co1/3Mn1/3O2以水熱法與共沉法製備並調整兩製程先後順序，觀察其對電性的影響。研究發現，兩步驟製備法中以先水熱製備Li2MnO3後再共沉法製備LiNi1/3Co1/3Mn1/3O2能降低第一次充放電時的不可逆電容量損失，且具有比直接共沉法製備富鋰材料更好的電容量與循環性能。

關鍵字

富鋰材料 ； 共沉法 ； 水熱法

並列摘要

Both Li2MnO3 and LiNi1/3Co1/3Mn1/3O2 are layered structure, and they can be mixed to form a solid solution Li2MnO3．LiNi1/3Co1/3Mn1/3O2, which its charge-discharge region between 2 and 4.8 V. This material will release Li2O due to Li2MnO3 irreversible decomposition when voltage are above 4.5 V in the first charge cycle, and that’s the reson for loss of capacity in the first cycle. This experiment is composed by three part. First, I will discuss how the pH value affect the electrochemical performances when preparing Li2MnO3．LiNi1/3Co1/3Mn1/3O2 precursor through co-precipitation method. The second and the third parts will take apart Li2MnO3．LiNi1/3Co1/3Mn1/3O2 into Li2MnO3 and LiNi1/3Co1/3Mn1/3O2. We try to prepare Li2MnO3 and LiNi1/3Co1/3Mn1/3O2 through hydrothermal and co-precipitatio method, respectively, and observe how the order of these two step processes affect the electrochemical performances. In my report,process that using hydrothermal method to prepare Li2MnO3 first then co-precipitaion method to prepare LiNi1/3Co1/3Mn1/3O2 thereafter can lower the capacity loss in the first cycle, and even have higher capacity and better cycle ability comparing to Li2MnO3．LiNi1/3Co1/3Mn1/3O2 prepared by co-precipitation method.

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