That is impossible. A rechargeable lithium battery the size of a CR2025 would be useless for a device which draws so much power. Make the battery any bigger and then you'd have to increase the size of the device, which is already at the limit.
Smart watches already use rechargeable lithium batteries of a few hundred mAh which are tiny enough to fit in the watch. You just need to standardize the interface and form factors across the industry. Again, not suggesting to use CR2025 form factor, you can always define a new one. Most watches in the market already use very similar battery packs, it just isn't standardized.
