Use this guide to remove the glued-in battery from your MacBook Pro. This is best done with the help of an iFixit battery replacement kit; the liquid adhesive remover in your kit will dissolve the adhesive securing the battery, allowing you to remove it with ease. Alternatively, you can use an iOpener to apply a modest amount of heat in order to soften the adhesive before prying out the battery.
'''iFixit adhesive remover is highly flammable.''' Perform this procedure in a well-ventilated area. Do not smoke or work near an open flame during this procedure.
'''For your safety, drain your MacBook Pro's battery before you begin this procedure.''' A charged lithium-ion battery can create a dangerous and uncontrollable fire if accidentally punctured.
'''Note''': The solvent used to dissolve the battery adhesive can damage certain plastics, such as the MacBook Pro's plastic speaker enclosures. Take care when applying the solvent.
If you're using the old-style iFixit adhesive remover with separate bottle and syringe (no longer sold), [https://www.ifixit.com/Guide/MacBook+Pro+13-Inch+Retina+Display+Late+2013+Battery+Replacement/110109|click here for a slightly modified set of instructions].