If overheating is being caused by malfunctioning of internal components, my knowledge of computers doesn't go that far. However, a common cause is that the air vents underneath a laptop are being blocked by dust and need a vacuum hose, gently run over them. Another cause is thinking that, because it is called a laptop, it can be used whilst perched on one's knees.
Under no circumstance should it be used on any soft material surfaces. If one is sitting in an easy chair it can be used on a coffee table.
I don't know what to say about the Battery, unless overheating is damaging it.
Perhaps Howard will return to this thread and give a second opinion.
Ron.