MacBook Air 2019 dying at 90%

My two and a half year old MacBook Air has been dying faster and faster when not plugged in to a power source, to the point where it only has about 30 minutes of battery before "dying" – it's not really dying, it's more shutting down and displaying the red battery icon when I try to turn it back on again, but when I plug it in, it often acts as though it was just in sleep mode when I turn it back on again (though it does sometimes just completely shut down). Does my battery need to be replaced or is this a fixable problem?