Thanks for visiting the Apple Support Communities and asking about your iPhone battery. Let me offer some things to check for this.
First and most important will be to check out this help article about batteries: Maximizing Battery Life and Lifespan Tips for iPhone, iPad, and iPod touch
The article includes lots of great information along with multiple tips to help you maximize your battery life. Once you have gone through all the tips, if you are still experiencing issues, this help article talks about the importance of using and storing your device within the recommended temperatures: Keeping iPhone, iPad, and iPod touch within acceptable operating temperatures
If you are using your device in conditions outside of the normal recommended ambient temperatures, the device may behave differently as described in that article.
Next, I recommend checking your settings. Please review all your settings to ensure you are getting maximum life from your battery based on how you utilize your iPhone.
The last thing you can check is in Settings > Battery. This area shows everything that is using your battery, and breaks down by percentage (if you have that option enabled), the apps that are using your battery the most.
Thanks again and have a great rest of your day.