The third wire of some lithium-ion batteries is a temperature protection wire, and some are battery information checking wires (for example, if a non-original battery is replaced, an alarm will be triggered) .
Lithium-ion batteries are both batteries + protection boards. The 3 wires will only appear on the protection board, and the battery will still only have 2 wires.
There are two types of lithium-ion batteries. Obviously the 3.7V one is not iron phosphate and can be replaced directly.
Replacement is very simple (pay attention to the positive and negative poles):
1: Remove the original battery packaging, then separate the protection plate and the battery with iron solder.
2: Likewise, remove the protection plate from your new battery and connect the battery to the old protection plate.