Lift the Li-ion battery gently.

Pull out the flat cable gently and then remove the Li-ion battery completely.

Background: About the flat cable. Generally speaking, the red thick line is the "+" power line; the black thick line is the "-" power line; other thin lines are signal lines.

CAUTION: Don't damage the Li-ion battery or something bad will happen, such as gas leakage, electrolyte leakage, fire, and explosion. REF: https://doi.org/10.31224/osf.io/swcyg