1.) Rechargeable batteries have a finite life.
2.) Healthy rechargeables get warm or very warm during charging.
3.) In my experience, at least, rechargeables show that they are at end-of-life by reduced time between charges or inability to hold a charge.
4.) Lithium ion batteries can combust, though usually due to serious over-heating or impurities in manufacture.
None of that is really news.