I have read a lot about battery technology. They need to solvefour or fivee problems, and so far nothing addresses all the requirements.
1. size – something small
2. but powerful enough to light up a cell phone for at least 24 hours or more
3. availability of trustworthy supply for whatever chemical they use for power. (in other words, don’t be dependent on some mineral that is only available in China)
4. Safe: it can’t catch fire spontaneously, and can’t overheat, and hopefully can be receycled – think Samsung and theri Galaxy phones that caught fire 3–4 years ago.
5. recharges quickly.
As I understand it, they can do three of them – but not all. Small batteries don’t have the oomph to go more than a couple of hours under load.