How do I change the battery of a T631 Logitech ultrathin mouse?

How do I change the battery of a T631 Logitech ultrathin mouse? My ultrathin mouse battery, after a long life, is unable to hold a charge. I’ve seen replacement batteries on the web but no instructions on how to open and replace the battery. Does anyone have a step-by-step guide to replacing the battery? Thanks for your time and interest.