My phone suddenly became almost unusable about a week ago. Started shutting down at 50% and refusing to turn back on without plugging in for 20 minutes and a hard reset (home +power).
Battery settings said the battery needed servicing, and a battery app reported the health was 60%. As much as I hated buying a new phone mid cycle, I also didn't want to mess around having it kick the bucket at an inopportune moment so I bit the bullet and replaced it.
plus I'm just accepting that unless the industry changes its practices, phones are being made to last 2-3 years so this is just an unavoidable expense.