镁掺杂改性LiMn_(0.5)Fe_(0.5)PO_(4)/C正极材料与性能研究  

Synthesis of Mg-doped LiFe_(0.5)Mn_(0.5)PO_(4)/C cathode materials for Li-ion batteries

作　　者：李晨威 徐世国 余海峰[1] 于松民 江浩[1] LI Chenwei;XU Shiguo;YU Haifeng;YU Songmin;JIANG Hao(Key Laboratory for Ultrafine Materials of Ministry of Education,School of Materials Science and Engineering,East China University of Science and Technology,Shanghai 200237,China;Wuxi Nano Energy Technology Company Limited,Wuxi 214125,Jiangsu,China)

机构地区：[1]华东理工大学材料科学与工程学院超细材料制备与应用教育部重点实验室,上海200237 [2]无锡钠科能源科技有限公司,江苏无锡214125

出　　处：《储能科学与技术》2024年第6期1767-1774,共8页Energy Storage Science and Technology

基　　金：国家自然科学基金(22308103)。

摘　　要：低成本磷酸锰铁锂正极材料相比于磷酸铁锂能量密度提升15%,近年来受到广泛关注,但是差的电子/离子电导率导致其功率性能不佳,难以满足实际应用的需求。本工作设计了一种具有多级结构的镁离子掺杂磷酸锰铁锂正极材料,该材料由纳米级一次颗粒自组装的二次球组成,且每个一次颗粒表面都具有均匀的碳包覆层。掺杂在晶格内的镁离子通过增加八面体LiO_(6)间隙提升锂离子扩散速率,表面的碳层能够在二次颗粒内构建完整的导电网络,提升电子电导率。此外,纳微多级结构不仅缩短锂离子迁移路径,还可以避免长循环过程中纳米粒子的团聚。因此,所制备的磷酸锰铁锂材料在0.1C和5C电流密度下分别具有151.8 mAh/g和113 mAh/g的高比容量,1C电流密度下循环1000次后比容量保持率高达96.2%。LiMnxFe1−xPO_(4)(LMFP)cathode materials offer higher energy density compared to LiFePO_(4),making them a subject of widespread interest.However,their practical application is hindered by low power density resulting from inferior electron/Li-ion conductivities.In this study,a Mg-doped LiMn_(0.5)Fe_(0.5)PO_(4)cathode is designed and synthesized.This cathode comprises secondary spherical particles self-assembled from nanoscale primary particles,with each nanoparticle uniformly coated by a carbon layer.The introduction of Mg-ions enhances Li-ion transfer efficiency by increasing the gap of octahedral LiO6.At the same time,the carbon coating layer improves electronic conductivity by establishing a complete conductive network within the secondary particles.Moreover,the hierarchical structure shortens the migration path of Li-ions and prevents nanoparticle aggregation during long cycling processes.Consequently,the LMFP/C-1Mg cathode exhibits a reversible specific discharge capacity of 151.8 and 113 mAh/g at 0.1C and 5C,respectively.After 1000 cycles at 1C,the capacity retention increases from 90.6%to 96.4%compared to unmodified cathodes.

关 键 词：LiMn_(0.5)Fe_(0.5)PO_(4) 镁掺杂 倍率性能 锂离子电池 

分 类 号：TB32[一般工业技术—材料科学与工程]