摘要
厚膜正极能够显著提高电池的面积比容量,从而满足实际应用需求。然而,电极厚度增加使锂离子的扩散受到限制,导致倍率性能降低,这是目前亟待解决的关键问题。使用515 nm波长飞秒激光在厚度为100μm的NCM811正极表面制备3D结构,研究了飞秒激光刻蚀工艺参数对刻蚀形貌的影响及刻蚀微结构特征尺寸对NCM811厚膜正极电化学性能的影响规律。研究结果表明:绿光飞秒激光刻蚀仅改变NCM811形貌,对其物相组成无明显影响;相比沟槽结构,网格结构既可提供充足的通道促进锂离子的扩散,又可避免正极材料的过度损耗。在高倍率3 C下,织构化网格正极质量比容量和面积比容量分别为92 mA·h/g和1.37 mA·h/cm^(2),显著高于原始正极比容量(27 mA·h/g和0.58 mA·h/cm^(2)),实现了NCM811厚膜正极倍率性能的提升。
Objective High-capacity lithium-ion batteries are essential to the rapid development of electric vehicles.Typically,the capacities are improved by increasing the thicknesses of electrodes,but this leads to inefficient diffusion of lithium ions,particularly at high current rates.Laser texturing of three-dimensional(3D)structures can provide channels for lithium-ion diffusion in thick-film electrodes.However,laser texturing using conventional laser sources suffers from electrode material melting,leading to failure of the active material.This is accompanied by capacity loss or a reduced number of lithium-ion diffusion paths,which limits the improvements to high-rate performance.This study proposes a method of texturing using a green femtosecond laser with a wavelength of 515 nm for high-capacity NCM811 cathodes.The effects of the green femtosecond laser on NCM811 ablation and the enhancement of the laser-textured structure on the electrochemical performance are investigated.Methods A laser texturing experiment is conducted using a green femtosecond laser with a wavelength of 515 nm and pulse width of 800 fs.A scanning galvanometer is used to control the laser-scanning paths.Laser-textured structures with various structural features are fabricated in a slurry-coated NCM811 cathode with a thickness of 100μm(Fig.1).The morphological evolution and phase constitution of the laser-textured structures are characterized by scanning electron microscopy and X-ray diffraction,respectively.The electrochemical performance is tested under a working current density of 0.1‒3.0 C(1 C=180 mA·h/g)and a voltage range of 2.8‒4.3 V.Results and Discussions The effects of the femtosecond laser parameters on the material removal of the NCM811 cathode are first investigated.With an increase in the energy density or a decrease in the scanning speed,the laser ablation depth and width gradually increase(Figs.2 and 4).The laser ablation threshold for NCM811 is determined(Fig.3),which provides a reference for selecting texturing parameters.
作者
李松原
曹利
王京博
肖荣诗
黄婷
Li Songyuan;Cao Li;Wang Jingbo;Xiao Rongshi;Huang Ting(Intelligent Photon Manufacturing Research Center,Faculty of Materials and Manufacturing,Beijing University of Technology,Beijing 100124,China)
出处
《中国激光》
EI
CAS
CSCD
北大核心
2023年第12期237-244,共8页
Chinese Journal of Lasers
基金
国家自然科学基金(51975018)。
关键词
激光技术
激光刻蚀
飞秒激光
厚膜电极
锂离子电池
laser technique
laser texturing
femtosecond laser
thick-film electrode
lithium-ion batteries
