Cadex electronics has a website called Battery University, dedicated to everything batteries. It is a very educational site if you want to know more about batteries in general. They also have a section that gives you the answer to the very popular question "what is the best way to charge my phone?"
So what is the best way to charge your phone or what are the best methods to keep your battery healthy and long-lasting? Let's quickly dig in and see what these battery experts have to say. According to Battery University, this is what you should do (and not do) to keep your battery running at optimal performance:
Do not let your device reach low battery levels before you decide to charge it up. Deep discharges apparently wear down the battery.
Battery will last longer if kept between 65%-75%. It's not realistic to always keep your device at these levels, but this is what they deem to be the best.
Next best levels are between 45%-75%, which is definitely a little easier to do. Don't worry about charging multiple times a day to keep at these levels, as the site says "partial charges cause no harm."
Do not fully charge your phone. Apparently, fully charging your device to 100% (especially from low levels) can shorten the overall lifespan of the battery.
To go with the last bullet point, charging your smartphone overnight is not a good idea.
The folks over at Cadex seem to know a lot about batteries, so doing the steps above is at least worth a try.
Source: Business Insider via Battery University