| Nowadays the cutting process of lithium ion battery anode material is one of the most important steps of battery manufacturing in electronics industry,and the cutting quality plays a vital role in the performance and safety of materials in batteries.In recent years,the laser has been widely used in the cutting of various materials due to the high quality,speed,flexibility and good applicability.Therefore,the nanosecond laser also gives great advantage in the processing of cutting lithium-ion battery materials instead of traditional machining,and has become a major choice for cutting methods in the electrode material industry.In this thesis,nanosecond pulse laser cutting of anode composite material with three layers for lithium ion battery is studied.For the typical kerf shape formed after cutting,the corresponding kerf characteristic are defined,which are the surface ablation width,the graphite kerf width,and the copper foil kerf width measured in the horizontal direction,and the kerf depth measured in the vertical direction.For the nanosecond laser cutting process of anode material,the model of nanosecond laser cutting anode film is established by finite element numerical method,the temperature field of the cutting process is simulated and the temperature value of the material was extracted to simulate the kerf shape,so that the calculated value of kerf characteristics is determined.The calculation results show that the temperature field abruptly changed at the critical surface of the graphite layer and copper foil,leads to the special kerf characteristics of the nanosecond laser cutting anode material correspondingly,which were caused by the difference between the thermal resistance and the different thermal properties of the two materials.According to the experiments carried on the same parameters,the trend of the kerf characteristic obtained from simulation can roughly correspond to the experiment results within errors of 10%.On basis of this model,the influence of cutting parameters such as laser cutting speed,average power,pulse frequency and pulse width on kerf characteristics are investigated,the optimal process range that the anode material could be completely penetrate is obtained.The cutting experiments of anode material were carried out with nanosecond laser processing platform,the influence factors of kerf characteristics were investigated.The experimental results show that the laser power and cutting speed have a great influence on the kerf characteristics parameters.The width and depth of each layer decrease with the increase of laser cutting speed,and increase with the increase of laser power and pulse frequency,and the width of each layer decreases from top to bottom.A completely penetration of anode without quality degradation caused by excessive ablation was obtained at a laser power of 140 W,a cutting speed of 500mm/s,a pulse frequency of 150 kHz,and a pulse width of 60 ns.By comparing the kerf characteristics of the single copper foil and the anode composite material,it is found that the latter obtained a better cutting quality due to its higher absorption rate to the laser.According to the combustion,particle agglomeration and copper film edge melting in the experiment,it can be inferred that the main mechanism of nanosecond laser cutting anode material is gasification cutting of graphite and the melting,oxidative melting and gasification cutting of copper foil.This thesis provides theoretical analysis and experimental reference for nanosecond laser cutting anode material of lithium ion battery. |
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