iFixit sells a handy product that helps remove battery, screen and glass adhesive. It should help you out in this scenario. Just use a 1-2 drops per inch and that adhesive should go kaput.
[product|IF145-400-4]
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=== Update (10/10/2018) ===
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The adhesive remover is your best option when it comes to softening the adhesive. You can try <90% Isopropyl Alcohol with some heat, but if that doesn’t work the adhesive remover will be your best bet.
iFixit sells a handy product that helps remove battery, screen and glass adhesive. It should help you out in this scenario. Just use a 1-2 drops per inch and that adhesive should go kaput.
[product|IF145-400-4]