锂离子电池正极材料LiNi_(0.5)Co_(0.2)Mn_(0.3)O_2和LiNi_(0.5)Co_(0.2)Mn_(0.3)O_2/LiFePO_4容量衰减原因分析  

Capacity Fading Analyses of LiNi_(0.5)Co_(0.2)Mn_(0.3)O_2 and LiNi_(0.5)Co_(0.2)Mn_(0.3)O_2/LiFePO_4 Cathode Materials for Lithium-Ion Battery

作　　者：胡燚[1] 何湘柱[1] 邓忠德 孔令涌 尚伟丽 

机构地区：[1]广东工业大学轻工化工学院,广东广州510006 [2]深圳市德方纳米科技股份有限公司,广东深圳518055

出　　处：《电化学》2017年第6期675-683,共9页Journal of Electrochemistry

摘　　要：采用湿法球磨法制备了锂离子电池混合正极材料LiNi_(0.5)Co_(0.2)Mn_(0.3)O_2/LiFePO_4(NMC532/LFP).通过X射线衍射(XRD)、扫描电子显微镜(SEM)、充放电测试和电化学阻抗谱测试(EIS)等方法研究对比了LiNi_(0.5)Co_(0.2)Mn_(0.3)O_2(NMC532)和LiNi_(0.5)Co_(0.2)Mn_(0.3)O_2/LiFePO_4(NMC532/LFP)的容量衰减机理.结果表明,循环50次和60 o C高温存储后,NMC532/LFP的容量保持率分别为97.80%、86.48%,其循环和高温存储性能较好.循环和高温存储后NMC532和NMC532/LFP的电荷传递阻抗Rct明显增大,但NMC532/LFP的Rct较小.NMC532和NMC532/LFP的I(003)/I(104)值都有所减小,但NMC532/LFP的I(003)/I(104)值比NMC532的大,即NMC532/LFP材料的阳离子混排现象有所改善.循环后NMC532、NMC532/LFP颗粒没有出现明显的表面开裂和链接断裂现象,但NMC532颗粒有部分发生粉化.高温储存后NMC532颗粒表面出现裂纹,且颗粒之间的链接断裂,NMC532/LFP颗粒表面出现轻微粉化.材料结构规整度下降,阳离子混排程度加剧,电荷传递阻抗增大是NMC532和NMC532/LFP容量衰减的主要原因.The LiNi0.5Co0.2Mn0.3O2/LiFePO4（NMC532/LFP） composite cathode material for lithium-ion battery was prepared by wet ball-milling.The capacity fading behaviors of LiNi0.5Co0.2Mn0.3O2（NMC532） and LiNi0.5Co0.2Mn0.3O2/LiFePO4（NMC532/LFP）were analyzed by X-ray diffraction（XRD）,scanning electron microscope（SEM）,charge/discharge and electrochemical impedance spectroscopy（EIS） tests.The results indicated that the capacity retention values of NMC532/LFP were 97.80% and 86.48%,respectively,after 50 cycles and 60 °C high temperature storage.The NMC532/LFP exhibited better cycle performance and high temperature storage performance.Charge transfer impedance（Rct） values increased obviously after 50 cycles and high temperature storage,in particular,the Rctvalue of NMC532/LFP was smaller.The I（003）/I（104） values of NMC532 and NMC532/LFP were reduced,while that of NMC532/LFP became larger,illustrating the cation mixed phenomenon was improved.There were no apparent particle cracking and particle fracture phenomena observed after 50 cycles,however,some NMC532 powder particles were obtained.The cracks were obaerved on the surface of NMC532 particles and among particles after high temperature storage,and the slight pulverization occurred on the surface of NMC532/LFP particles.Less ordered material structure,higher degree of cation mixing and increased charge transfer resistance might be mainly responsible for the capacity fading behaviors of NMC532 and NMC532/LFP.

关 键 词：湿法球磨法 锂离子电池 混合正极材料 LiNi0.5Co0.2Mn0.3O2/LiFePO4 容量衰减机理 

分 类 号：TM912[电气工程—电力电子与电力传动]