(1. 昆明理工大學(xué) 材料科學(xué)與工程學(xué)院，昆明 650093；
2. 昆明理工大學(xué) 分析測(cè)試中心，昆明 650093)
摘 要: 以MnO2和LiOH·H2O為原料，采用固相法分別在750和900 ℃溫度下焙燒得到Li2MnO3正極材料，并研究Li2MnO3正極材料晶體缺陷結(jié)構(gòu)和相變對(duì)電化學(xué)容量的影響。通過(guò)X射線衍射(XRD)和電子衍射(SAED)進(jìn)行晶體結(jié)構(gòu)分析，采用掃描電鏡(SEM)和透射電鏡(TEM)觀察了材料形貌，并對(duì)材料進(jìn)行充放電測(cè)試和微分容量分析。結(jié)果表明：在750 ℃下合成的Li2MnO3具有類球形結(jié)構(gòu)，晶體中出現(xiàn)大量的層錯(cuò)；電化學(xué)活化后獲得的139.3 mA·h/g放電容量和納米片狀特征與晶體結(jié)構(gòu)中存在較高的層錯(cuò)密度有關(guān)；在900 ℃下合成的Li2MnO3晶體結(jié)構(gòu)完整，但電化學(xué)過(guò)程中難于活化，即使100次循環(huán)后，Li2MnO3的超晶格結(jié)構(gòu)依然保持完整；在電化學(xué)循環(huán)過(guò)程中，Li2MnO3會(huì)由層狀結(jié)構(gòu)逐漸向尖晶石結(jié)構(gòu)轉(zhuǎn)變；隨著循環(huán)次數(shù)增加，電池容量主要來(lái)自尖晶石的電化學(xué)容量，其余部分來(lái)自Li2MnO3的逐漸活化。
關(guān)鍵字: Li2MnO3；堆垛層錯(cuò)；超晶格；電化學(xué)性能
（1. College of Material Science and Engineering, Kunming University of Science and Technology, Kunming 650093, China;
2. Research Center for Analysis and Measure, Kunming University of Science and Technology, Kunming 650093, China）
Abstract:Influence of stacking fault and spinel transformation on the discharge capacity of Li2MnO3 cathode materials were studied. Li2MnO3 cathode materials were synthesized using MnO2 and LiOH·H2O as raw material by solid state reaction at the temperature of 750 and 900 ℃. Crystal structures of prepared Li2MnO3 were studied by X-ray diffraction (XRD) and electron beam diffraction (SAED). The microstructures of materials were observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and electrochemical properties were studied by charge-discharge test and differential capacity analysis. The results show that the Li2MnO3 sintered at 750 ℃ has sphere structure, which contains lots of stacking fault. The first discharge capacity of materials (139.3 mA·h/g) may be related to nano-plates and high stacking fault density. The sample sintered at 900 ℃ has good crystallinity, however, it is difficult to be activated. The superlattice structure of Li2MnO3 remains intact even after 100 cycles. Analysis results also suggest that Li2MnO3 gradually transforms to spinel during the electrochemical cycling. With increasing number of cycles, most of the increasing capacity is caused by the electrochemical activity of the spinel, and part of which comes from the progressively activation of Li2MnO3.
Key words: Li2MnO3; stacking fault; superlattice; electrochemical property
