Sadly your battery has hit its limit! Batteries wear-out by both time (years) and number of cycles.
Your battery is 6.5 years old and has 960 cycles. Here’s a bit more on the max lifespan of a battery by cycle [https://support.apple.com/en-us/HT201585|Determine battery cycle count for Mac notebooks]
Here’s the needed part [product|IF188-113-2] and here’s the guide to replace it [guide|6359]