Generally not, especially if there has been no record of prior repairs.
Batteries are a funny thing where they're not really covered unless being shown as defective. Batteries degrade over time so apple will not replace a phone just because the battery will not hold a charge. At most they'll replace the battery for free
For proper maintenance of a lithium-based battery, its important to keep the electrons in it moving occasionally. Be sure to go through at least one charge cycle per month (charging the battery to 100% and then completely running it down).
Charging your iPhone while in certain carrying cases may generate excess heat, which can affect battery capacity. If you notice that your iPhone gets hot when you charge it, take it out of its case first.