How to solve 'your battery needs replacement' issue on Lenovo windows 7 laptop?

Okay so I have Lenovo windows 7 laptop which I bought around 2011/2012. Yesterday night when I was browsing on my laptop, a cross mark suddenly popped up to the battery icon on the task bar and when I clicked it, it said my battery might need replacement. I tried some solutions of how to solve this issue by watching its YouTube tutorials and reading some tips on some websites, but none of them worked. My main question is, will it completely shut down my laptop even if I don't change the battery after it's warning?

I don't know about your brand, but my daughter completely removed the battery from her laptop and just plugged it in all the time to use it.

To find out if this will work with your computer, shut the computer down and remove the battery. Then plug the computer into the wall outlet with the battery still removed and try turning on the computer. If it works, then you know that you will be able to use your computer as long as you are near an outlet to plug into.

When the battery has insufficient energy to drive the laptop, the laptop will stop; if you plug it into the 120 v line until you purchase a replacement and keep it plugged in you will be fine.

This is just a salient warning to get your battery changed very soon. Once it won't charge again, your laptop will only work when plugged into the mains with its charger.

You solve the issue by buying a new battery to replace the one that is failing…

Not normally as long as the computer is plugged in. You can get replacement batteries on amazon.com pretty cheap. Just search for a "replacement battery for Model # xxxxx". Generally I've found laptop batteries under $20. If you order from the manufacturer like HP, Dell, etc. Be ready for sticker shock. You can get a 4 cell battery pretty cheap for it, and in general 8 cell batteries are a lot cheaper also. If you don't use your laptop unplugged for very long then go for the 4 cell. Hope this helps.