The high current density applied to the electrode during high-speed charging/discharging, however, generates a lithium ion concentration gradient inside the electrode, which causes a variety of issues. Furthermore, one of the key reasons for the difficulties in creating energy storage materials with high high-rate qualities is the material's inherent properties, such as ion transport restriction.

We used laser processing and a dry transfer procedure to create a negative electrode plate for a lithium ion secondary battery with a surface aligned in a certain orientation. When compared to the existing electrode plate, laser-induced graphene (LIG), a porous three-dimensional nanomaterial generated by laser processing, had a higher specific surface area and a three-dimensional network structure. The fracture surface of the LIG, whose plane orientation was configured in this easy-to-transfer direction, was discovered to have a significant impact on rate capabilities.

A commercially available polyimide (PI) film (thickness: 125 µm, Kapton) was used to make the LIG-based negative plate used in this investigation, which was treated with a CO₂ laser with a wavelength of 10.6 µm. The irradiated laser had a power output of 5.4 W, and the scan speed and pitch were kept at 200 mm/s and 125 µm, respectively. Press-type roll forming was used to transfer the so produced LIG to a copper substrate with a thickness of around 20 µm, with the distance between the rolls controlled between 70 and 200 µm and the specimen feed rate controlled between 10-100 mm/s. For electrochemical evaluation, the negative plate was made up of 2032 typed coin cells, and for material evaluation, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) analysis, X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy were used.

Despite applying a high current density of 20 A/g at a loading level of around 3 mg/cm², this electrode obtained a discharge capacity of 114 mAh/g within 3 minutes, corresponding to 95 percent of the material. The great specific surface area of nanomaterials like graphene, as well as the three-dimensional structure in which the surface is oriented in a precise direction due to dry transfer, account for the unusually high rate.

In other words, the lowered internal charge transfer resistance helps to realize high rate characteristics because the holey-structured graphene with high porosity due to laser processing is well stacked in a three-dimensional structure. Furthermore, because the electrode surface is structured in a structure with multiple edge plane exposures, it was feasible to create an anode material with high rate characteristics by shortening the lithium ion transport and diffusion distance.

This method can be easily applied to the current negative electrode material and electrode manufacturing process for lithium ion secondary batteries, and it has the potential to be extended and applied to material manufacturing methods for a variety of applications that improve charge and ion transport.