Hi,
If you can start the laptop with the charger then create a [https://www.windowscentral.com/generate-battery-report-windows-10|Win10 battery report] to check the status of the battery.
In the report compare ''Design capacity'' versus ''Full Charge capacity'' and calculate the percentage difference to get an idea of its effectiveness.
If the Full Charge capacity is <40% of Design capacity then the battery is failing and needs to be replaced.
Here’s the [https://download.lenovo.com/consumer/mobiles_pub/130-14ikb_130-15ikb_130-15ast_hmm_201805.pdf|hardware maintenance manual] for the laptop.
Go to p.35 to view the necessary pre-requisite steps and then the procedure to remove the battery.
On p.63 Item #14 you will find the spare part numbers for the various batteries used in the laptop (ensure you look in the correct column!)
Search online by typing the ''part number only'' in the search box of your browser to get results for suppliers of the part that suit you best. Sometimes the part number is printed on the battery if you wish to verify that you’re ordering the correct one by checking what it shows on the battery in your laptop.
Also on p.21 it shows how to test the charger to make sure that it is supplying the correct voltage to the laptop just in case it is the cause of the battery problem.