The wire leading into the connector is a common failure point on charging cables. When my last one started to fall apart, I used some heat shrink to reinforce it.
Step 1: Heat Shrink
Find a piece of heat shrink and trim it to size. It should go over the body of the connector, the cracked section and a bit of the wire leading in.
Step 2: Add Heat
Use a hair drier on high or a heat gun to activate the heat shrink.
Easy as pie, and your cable should last you a lot longer!