it’s highly unlikely that the problem is the battery, seeing as they’re lithium-ion, they’ll last longer than you will. are you sure that your charging it completely?
you might even be able to find a supplementary battery to extend the battery capacity
Aging of lithium-ion is an issue that is often ignored. A lithium-ion battery in use typically lasts between 2-3 years. The capacity loss manifests itself in increased internal resistance caused by oxidation. Eventually, the cell resistance reaches a point where the pack can no longer deliver the stored energy although the battery may still have ample charge.