If your phone is one of the serial numbers affected, which I assume it is if your screenshot is for that phone, then the replacement is free : https://www.apple.com/my/support/iphone6s-unexpectedshutdown/
Apple has determined that a very small number of iPhone 6s devices may unexpectedly shut down. This is not a safety issue and only affects devices within a limited serial number range that were manufactured between September and October 2015.
If you have experienced this issue, please use the serial number checker below to see if your iPhone 6s is eligible for a battery replacement, free of charge.