Extended support does not cover the battery, but if your purchase included a warranty on the system, contact the seller for a battery replacement.
I bought an used XPS 9575 (still under Dell support until July 2022).I´m told the battery was renewed in October 2021. I freshly installed WIn10 and Win11 from Microsoft Media. Now I´m facing the problem that the battery suddenly runs empty: I shut down Windows at e.g. 70% battery level and after reboot the notebook shows only 4% or 2% remaining battery. I found this article which may help: [URL]  but sadly no info is given within this article which is the correct version of graphics driver to download and no direct link to the driver download. I tried SupportAssist, but the graphics driver loaded and installed by it don´t cure my problem.
XPS 9575 2-in-1 Battery (new 4 month old) suddenly empty