Your 18650 mod battery is a precision part that should be free of damage, defects and wear. If you notice physical damage, it is a good idea to replace your battery with a new one that will be more reliable in the long term.
Dents: Dents can occur if the battery is dropped, either on its own or while inside the device. Any type of deformity that changes the shape of the battery will impair its electrical properties, so you should change it out as soon as you can.
Scratches: Scratches can sometimes be superficial and will not cause major performance issues. Still, if a scratch appears particularly long or deep – or if you simply don’t like the looks of it – it is always better to be safe than sorry. If the scratch isn't too deep and it's just on the wrap, you can purchase all different types of replacement wrap to re-wrap your battery
Wrap: “Wrap” generally refers to heat shrink wrap tubing for your battery. This can come in the form of a large roll or it can be pre-cut. No matter what the case, however, you should replace the wrap that has become visibly damaged. This is essential to the battery’s thermal regulation.
Improper Storage: Batteries can become damaged as a result of improper storage. The most common issue is when the battery is stored in a location that is not dry or that receives too much direct sunlight. Storage in places that are too hot or too cold can also cause problems.