With a high-performance battery, this is a natural phenomenon of smaller sparks when connected.
But when you plugged in the battery, was the power supply unplugged?
The chip next to the processor fan is the input power circuit. Take it down and see if it has a burn mark. Was the paste not applied to the electronics? What paste did you put in? Does the paste conduct electricity? There are pastes that conduct the current and if it gets into the electronics it can cause a short circuit.
Alternatively, remove the CMOS battery while disconnecting the battery. This will reset the BIOS.
Wait for 1-2 minutes and reconnect the CMOS battery first, then the battery and then reconnect the power. The chip you shot is the motherboard control chip. If you are having problems with heat conduction, you need to replace the processor and video card paste, not this one.