Femtosecond-pulsed laser cutting of pure lithium metal anodes with burst mode

Abstract The growing demand for electric mobility and, more generally, for high-performance batteries has driven the development of advanced technologies such as all-solid-state batteries, which employ lithium metal anodes to further increase energy density. Traditionally, lithium metal anodes have been cut to size using mechanical tools such as punch dies or scissors; however, due to the adhesive nature of lithium, the material tends to stick to the cutting tools, compromising the quality of the separation. This limitation has motivated the exploration of noncontact separation methods, among which remote laser micro-cutting has emerged as a promising alternative. In this work, femtosecond-pulsed remote laser cutting was investigated to evaluate its suitability for the processing of free-standing lithium metal anodes, with particular attention to the influence of beam spot size and pulse delivery strategy on cutting performance and process stability. Two different spot diameters were considered, and the process was tested in both pulsed and burst modes. The smaller spot enabled cutting speeds of 1.0 m/s in pulsed mode and up to 7.0 m/s in burst mode, highlighting the strong productivity enhancement provided by burst mode. Conversely, when using the larger spot diameter, cutting speeds of 4.0 m/s were achieved in pulsed and burst modes, indicating a reduced sensitivity to the pulse delivery strategy. To better understand the interaction mechanisms of ultrashort laser pulses with lithium, a two-temperature model was developed to interpret the experimental results. The model was effective in explaining the influence of burst mode in improving process productivity at fixed average power. The process instability observed at small beam sizes with the femtosecondpulsed laser was attributed to the reclosure of the opened kerf, promoted by the high fluidity of molten lithium and the low capillary pressures generated during processing.