Laser cutting of lithium iron phosphate battery electrodes: Characterization of process efficiency and quality

Lithium iron phosphate battery electrodes are subject to continuous-wave and pulsed laser irradiation with laser specifications systematically varied over twelve discrete parameter groups. Analysis of the resulting cuts and incisions with an optical profiler and scanning electron microscope gives insight into the dominant physical phenomena influencing laser cutting efficiency and quality. Measured incision depths are found to be piece-wise functions of average laser power, with the metallic conductor layers dominating the process due to their high thermal conductivity and low optical absorptance relative to the active coating layers. Cutting efficiency improves with shorter laser pulses and use of 532 nm radiation in place of 1064 nm. Complete electrode penetration takes place at lowest average power with pulse fluence in the ranges 35-40 J/cm2 and 100-110 J/cm2 for the cathode and anode, respectively, with 1064 nm beam wavelength. Per-pulse ablation depths are derived for the active coating layers under all tested conditions, giving new insight into the ablation behavior of each individual material. Defect size and coating layer delamination width are both found to be linked to cutting efficiency, with highest quality achieved for a given wavelength when overall cutting efficiency is optimized. Ideal parameters are found to be those maximizing the ablation efficiency of the metallic layers, as residual heat deposition in the films is minimized. © 2014 Elsevier Ltd.