Buy a TB30 Intelligent Flight Battery from DJI. This is the original battery that DJI makes for the Matrice 30T. It is rated for up to 400 cycles and supports hot-swapping (where you can replace one battery at a time without powering down the drone). 

NOTE: New and old batteries should not be paired up and used together. For best performance, you should always number batteries, and use them as pairs. In most cases this means you should buy additional batteries in sets of two. 

The Complete Drone Deer Recovery Kit Matrice 30T includes 8 TB30 Flight Batteries. 

The battery kit is not included.