Research

      Nowadays the Li-ion batteries (LIBs), which are firstly commercialized in 1991, are a popular alternative energy source due to environmental pollution and fossil fuel depletion. The LIBs have many advantages compare to other secondary batteries such as high-power density, high energy density, long lifespan, and low self-discharge rate. LIBs, which have been developed for 30 years, have various issues in performance and manufacturing processes. We are proposing a solution to various issues of conventional LIBs through laser processing. 

      We are researching on cutting electrodes by laser to reduce defects caused by wear on tools and to provide a high quality cutting edge. The LIBs have problems related to thickness and density of active material layer. 

      We tried to make 3D electrodes by laser structuring technology. The Li-ion diffusion rate of 3D electrodes is improved due to the formed groove by laser. Consequently, the reduction of power density can be minimized although the active material layer is thick and dense. 

      Currently, commercial LIBs include graphite anode, and the capacity of conventional LIBs has almost reached its limit. Therefore, an anode with a capacity higher than graphite anode is needed to obtain a higher capacity battery. Lithium metal is expected to be a material to solve this problem. We plan to control Li dendrite growth by inducing Li+ into grooves, which is formed by laser (lighting rod effect).

           The manufacturing of lithium-ion battery is raising the interest of manufacturers due to the massive demand of this battery in the power supply and energy storage system industry. Above all, joining in the battery should be considered as the most important factor because it affects not only mechanical properties but also the working duration of the battery. The existed joining technologies in the battery have shown significant drawbacks and limitations. This is due to the different materials involved as well as the characteristics of the joining technology itself. Fortunately, researchers have found the most suitable substitute method using laser beam. 

       We are conducting laser welding for the battery case and tab in cylindrical battery cells using cost-effective laser technology. 

       Another research is carried out on the laser welding of dissimilar Cu-Al. This is a typical weld in battery as the materials of Al and Cu are the most common materials used in battery. In this study, we aim to reduce the weld defects such as porosities, voids, and spatters

            Cement-based materials are prevalent materials in almost all construction fields, such as buildings, roads, bridges, dams and nuclear power plants. The cement-based materials can be deteriorated under some unfavorable circumstances, such as high chloride environments, poorly controlled concrete casting and unexpected overloading. For this reason, the demand for the removal of deteriorated parts is steadily increasing. 

            Laser scabbling has been studied to remove the surface material of concrete using a high-power laser beam.

                Laser cutting can be applied to remove the large volumes of cement-based materials. In addition, laser ablation techniques are considered as the alternative technology to remove the contaminated concrete of about 76.2 mm thickness in nuclear power plants.

                Arc welding, which is welding process using the heat of an arc as a heat source, is essential in the manufacturing field. due to the importance of production efficiency and light weight of manufactures. However, various by-products such as slag, heat tint, and oxide layer occur around the weld bead. It adversely affects the corrosion resistance and the coating quality of the product. For this reason, by-prodcut formed after arc welding should be removed to improve the performance.

                Laser cleaning is a non-contact and eco-friendly technology based on laser ablation. This technology is mainly used to improve product quality such as corrosion removal, paint peeling, and by-product removal without directly affecting the base material.

            The polymer are not easily decomposed. The developments of eco-friendly materials are actively carried out due to environmental pollution of wastes, soil degradation, and leakage of endocrine disruptors. Poly Lactic Acid (PLA), the most widely used biodegradable polymer material, is produced by chemical method for fermenting the sugar and starch obtained from plants. 

            This study applies pulsed fiber laser to PLA, and observes the effect of laser parameter on the change of microstructure and chemical properties of weld part.

            Laser ablation plays an important role in the laser application for the processing of materials. The most important aspect of using laser for the ablation process over other processes is because heat conduction produced in the surface is being processed as well as less or no collateral damage happened due to shock waves during the process. 

            The major application of the laser ablation process is used to produce complex surface patterns or to alter microstructures in high precision processing. Laser ablation is affected by laser parameters such as wavelength, power, and pulse width. Furthermore, the interaction properties between the laser and the material can be controlled by laser parameters. Laser ablation occurs when sufficient energy is absorbed into the material surface to break the bond between atoms. When energy above the characteristic threshold is irradiated during laser-material interaction, ablation occurs on the surface. However, little craters are produced when laser energy is irradiated below the threshold. In addition, no surface changes occur due to physical, chemical, or reaction. 

            In laser parameters, the ablation threshold is defined as the minimum laser energy. It plays an important role because it greatly affects laser processing depending on various variables. The laser ablation threshold increases or decreases with laser parameters, and the resulting laser ablation results vary. To predict the laser ablation threshold, you need to adjust the number of largely irradiated pulses, and you can predict the threshold by measuring the crater size according to each pulse count.

            The aviation and railway industries are experienced with attached ice on metal surface in winter season. For example, freezing airfoil of airplane causes delay and the attached ice on railways causes derailment and slow operation. Also, the attached ice and water contacted on metal surface reduce metal’ residual life. 

            Laser Surface Treatment (LST) is proposed. This research objective is the fabrication for hydrophobic surface of metal using LST. Hierarchical structures are induced by laser surface treatment, and surface free energy on the irradiated surface is reduced.