Macbook Pro Very Slow with the Battery Disconnected

Hello,

I've a macbook late '11 which was running really fine despite battery not holding much more than 40% of its capacity. In the past few months, the battery became stewed and worried me a little bit so I decided to open my macbook and disconnect it before it explodes or something else but now my mac is running really slow - upon checking the Activity Monitor I see that the CPU has a high usage - and by that I mean 207% ( I don't know how it works but it is what is shown) and everything I do on my Macbook is very painful. Opening Chrome takes ages - any website with Javascript take even more time to load and any click freezes the Chrome \ Youtube on Safari only under 460p - anything above it does not work.

I read a few forums and it seems that I need to have the battery replaced and reconnected it to my computer so it can run properly again however the Apple Services in my country are very expensive - just for comparison an iPhone X costs around U$ 2700,00 - so I was kind of looking for a workaround which does not require me to spend too much money.

This is my Macbook's settings:

MacBook Pro (13-inch, Late 2011)

2,8 GHz Intel Core i7

8 GB 1333 MHz DDR3

Intel HD Graphics 3000 512 MB

Thank you in advance for your replies