Use the solder wick to remove as much solder from the battery terminals as possible. Be quick and do not overheat the battery in the process. Assume that battery is not entirely dead and do not short the terminals with the wick.

Use a pair of tweezers or your fingers to carefully lift the battery while you apply short heat to each of the battery terminals. It will eventually come off.

Clean the terminals with the solder wick. The left pad is positive and the right is negative.