A.The battery tabs welding machine(http://www.espot-welder.com/cr20321865026650-battery-pack-welder-lithiumnimh-battery-welding-battery-welder-p-2.html) 

when the material is poor conductive(such as iron,steel,stainless steel,nickel),the material of electrodes need to using high 

conductive(such as copper,alumina copper, chromium Zirconium copper),but,not using the red copper,as the strength is too low 

at the high temperature.

B.When the material is high conductive(such as copper,aluminum,) the marterial of electrodes need to using poor conductive

(such as tungsten, molybdenum,tungsten copper)