I am using android for several years, I tried many apps for increased battery life. But in my experience no app served that. In fact after deep research, I found that "NO SUCH APP." !!
4 Things can improve our battery life :
01. Close Wi-Fi, and Data when not in use.
02. Close/Exit all the apps properly after usage.(In Samsung If u long press the center button, u will see the running apps)
03. Keep the brightness level optimum.
04. Dont keep ur phone silent. This will tend us to wake-up the phone very frequently which eats battery. Keep in Ring mode (for calls and notifications)