Ionic + Slim, ¿Security?

Hello! I am developing an Ionic App that consume WebServices developed in Slim Framework. It’s working perfect but without security.

To apply security, my idea was:

I have a Login Page. If the username and password are correct, I generate a token JWT and I add in local storage. Later, when should to access to another API method I send the token in the Authorization Header. It’s working but it’snt sure because the token is visible.

Any suggestion to improve the security in this context?