Laser cutting method

A laser beam cutting method for cutting a first plate made of a first material, having a first melting point and having a first thickness, and for cutting a second plate made of a second material, having a second melting point and having a second thickness, the second melting point not being the same as the first melting point, the second thickness not being the same as the first thickness, by irradiating the plates with a laser beam, the laser beam cutting method comprising:

• a plate material placement process for placing the first and second plates side by side so that the laser beam can only irradiate one plate at a time and out of the first and second plates, an opposite surface of a laser beam irradiated surface of the plate material with a lower melting point extends further from the laser beam irradiated surface than an opposite surface of the laser beam irradiated surface of the plate with a higher melting point;
• a focus adjustment process for aligning a focus length of the laser beam with the opposite surface of the laser beam irradiated surface of the plate with the higher melting point of the first and second plates;
• and
• a plate material cutting process for cutting the first and second plates through irradiation with the laser beam according to a series of operations while maintaining constant the focus length of the laser beam such that when the laser beam irradiates the plate with the higher melting point it is focused at the opposite surface of the laser beam irradiated surface of the plate with the higher melting point,
• wherein out of the first and second plates, the plate with the lower melting point is a positive electrode tab of a laminated battery and the plate with the higher melting point is the negative electrode tab of the laminated battery;
• and
• the positive electrode tab and the negative electrode tab are formed to be thicker than a collector foil for use in formation of electrodes of the laminated battery.