辊压温度对锂离子电池正极微观结构及性能的影响

Effect of calendaring temperature on microstructure and properties for Li-ion batteries cathode

为探究电极制备工艺中辊压温度对锂电池正极极片微观结构与电极性能间的关系,利用二辊轧机,制备了辊压温度为25℃和150℃两种正极极片,研究了辊压温度对正极极片微观结构、厚度一致性、力学性能及电化学性能的影响。结果表明,随着辊压温度的提高,极片涂层颗粒压实密度显著提高,孔径较小,炭胶相均匀分布黏附在活性颗粒上,涂层颗粒破碎、裂纹及孔洞等缺陷减少,涂层更容易形成导电/黏结网络的电极结构。相比于室温辊压极片,热辊压极片辊压厚度一致性提高,回弹率降低了50%,极片结合强度由182.77 N/m提高至237.37 N/m,提高了29.87%;抗拉强度由20.47 MPa提高至24.44 MPa,提高了19.39%;极片电阻率由158.05Ω·cm降低至119.41Ω·cm,降低了24.45%;电导率由0.63 S/m提高至0.84 S/m,提高了33.33%。两种极片所组装的电池,热辊压极片的电化学性能优于室温辊压极片,循环容量保持率提高了18.65%。本研究通过调控辊压温度等工艺参数来优化电极性能,可以适度提高极片性能,对锂电池极片工业化制备过程中优化电极性能提供了研究依据。

To investigate the relationship between calendaring temperature and the microstructure and performance of cathode for Li-ion batteries(LIBs),two kinds of cathodes at calendaring temperatures of 25℃and 150℃were prepared by two-high rolling mill,respectively.The effects of calendaring temperature on microstructure,thickness consistency,mechanical,and electrochemical properties of cathode were studied.The results show that with the increasing calendaring temperature,the compaction density of cathode coating particles increases significantly,the pore size is smaller,the carbon adhesive phase is uniformly distributed on the active particles,the coating particles are broken,cracks,holes,and other defects decrease,and the cathode structure of conductive/bonding network is easier to form.Compared with the room-temperature calendaring cathode,the thickness consistency of hot calendaring cathode is improved,the rebound rate is reduced by 50%,and the pole sheet bond strength increases from 182.77 N/m to 237.37 N/m,increasing 29.87%.The tensile strength increases from 20.47 MPa to 24.44 MPa,increasing 19.39%.The electrode resistivity decreases from 158.05Ω·cm to 119.41Ω·cm,decreasing 24.45%.The electrical conductivity increases from 0.63 S/m to 0.84 S/m,increasing 33.33%.After being assembled as LIBs,the electrochemical performance of the hot calendaring cathode is better than that of the room-temperature calendaring cathode.The cycling capacity retention increases by 18.65%.The cathode performance can be improved moderately by adjusting the calendaring temperature and other technological parameters,providing a research basis for optimizing cathode performance during the LIBs electrodes industrial preparation.