Phone Died, Responds to Charger but just shows red battery.

Hey, my 6S Iphone was on a bad charger last night (my wife and I both have had some difficulty with it) and it went ahead and died while I slept. I've tried plugging it into a better charger, and the screen actually does light up and shows a red battery when I plug it in (the icon definitely changes when I remove and replace the charger in the port). That gave me cause for hope, but it's been nearly two hours and I can't turn it on.

Also, the battery never actually turns green and says it's charging. Is it gone for good?