Author: Zhang, Songling
Title: High speed and high quality laser cutting of electrodes in mass production environment
Advisors: Man, H. C. (ISE)
Degree: Eng.D.
Year: 2020
Subject: Lasers -- Industrial applications
Laser beam cutting
Lithium ion batteries
Hong Kong Polytechnic University -- Dissertations
Department: Faculty of Engineering
Department of Industrial and Systems Engineering
Pages: xix, 174 pages : color illustrations
Language: English
Abstract: Traditional Li-ion battery electrodes die cutting can easily lead to the burring, cracking, fragmentation, deformation and efficiency problems, which seriously affect the production of and performance of batteries. This project presents an efficient and high-quality laser cutting method, establishes a process model of laser cutting with high efficiency and quality, as well as particle analysis, reduce and control method, and validates the models and technology through simulation and experiment. Specific researches are as follow: (1) Study the interaction between laser and electrodes materials, establish heat transfer model, state change effect and energy conversion effect, study the output mode of laser beam, establish the theoretical model of laser tab cutting, deeply study the methods of melting cutting and ultra-fast laser cutting, and study the influence of the cutting power, cutting speed, beam quality and focus position of on cutting quality, build the process correlation model of laser cutting parameters, math model for tab cutting, and provide guidance for mass production, to achieve high speed and quality. (2) Study the principle of dust particles generated by laser cutting, calculating the particle size, composition and amount, analyze the reason of slash, and splash speed, metal melting and cooling time, trajectory, direction of particles, and observe the result through experiment. Method for reduce and remove particles are established. Fluent is used to do the CDF simulation dust removing system. Reasonable model and simulation results are obtained, shows that the simulation with Fluent is consistent with the theoretical analysis. Experiment result shows the design of dust remove system is effective and simulation conform with the actual system. (3) Short pulse picosecond laser is studied and experiments are conducted to have a preliminary understanding the characteristics of picosecond laser cutting, and comparison the cutting quality with nanosecond laser. (4) Finally, based on the process and mathematical model established and particle analysis here, large quantity batteries are tested to verify the effectiveness of process model and particle analysis. The impedance, capacity, cycle performance, anatomy analysis under charge retention and open charge voltage drop performance are tested with batteries made using laser cut and die cut electrodes. The results show that the process model, and particle analysis and control method presented in this paper are very effective, which can bring high speed and high quality laser cutting, and great advantages over die cutting process.
Rights: All rights reserved
Access: restricted access

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