The battery is connected to the motherboard with a power cable connector that has a small tab on the side that locks it in place.

Insert a spudger into the cut-out in the battery recess where the battery connector is located.

Use your spudger to squeeze the tab against the connector to release it.

Use your free hand to grab the battery cable just above the connector. Pull the connector straight up from its socket, wiggling it back and forth to loosen the clips securing it.