I'm using Coinomi currently to store all my Bitcoin cash but i want to split them and send the other half to another wallet.
Any wallet with a high security level can be used to store Bitcoin Cash ?
I would use
btc.com if you want a web wallet. They have recently launched this service and it seems pretty nice. But make sure that you do not store too much in there because ultimately, it is a web wallet, and it's less secure.
For desktop clients you can basically use any of the suggested wallets on bitcoincash.org.
Personally when i split my bitcoin cash i used electron cash and had no issues. It's just a clone of electrum, for bitcoin cash. See here for a complete list of wallets that are endorse by the bitcoin cash team:
https://www.bitcoincash.org/Honestly though i would just dump my BCH as soon as i get it...