摘要
以MnO2和LiOH·H2O为原料,采用固相法分别在750和900℃温度下焙烧得到Li2MnO3正极材料,并研究Li2MnO3正极材料晶体缺陷结构和相变对电化学容量的影响。通过X射线衍射(XRD)和电子衍射(SAED)进行晶体结构分析,采用扫描电镜(SEM)和透射电镜(TEM)观察了材料形貌,并对材料进行充放电测试和微分容量分析。结果表明:在750℃下合成的Li2MnO3具有类球形结构,晶体中出现大量的层错;电化学活化后获得的139.3m A·h/g放电容量和纳米片状特征与晶体结构中存在较高的层错密度有关;在900℃下合成的Li2MnO3晶体结构完整,但电化学过程中难于活化,即使100次循环后,Li2MnO3的超晶格结构依然保持完整;在电化学循环过程中,Li2MnO3会由层状结构逐渐向尖晶石结构转变;随着循环次数增加,电池容量主要来自尖晶石的电化学容量,其余部分来自Li2MnO3的逐渐活化。
Influence of stacking fault and spinel transformation on the discharge capacity of Li2MnO3 cathode materials were studied. Li2MnO3 cathode materials were synthesized using Mn O2 and Li OH·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 m A·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.
出处
《中国有色金属学报》
EI
CAS
CSCD
北大核心
2015年第3期705-713,共9页
The Chinese Journal of Nonferrous Metals
基金
国家自然科学基金联合资助项目(U1202272)
国家自然科学基金资助项目(51464025)
