Tesla & GM 1Million Mile Battery - NVX to supply Graphite, Electrolyte & Cathode, page-505

Thats the million mile question, and the answer is hidden in secrecy. I suspect that the combination of silicon/grahite is superior. Pure siicon is better but degrades too quickly but pure graphite is not as good an anode so you combine the both, it is even more complex because the first charge precipitates material onto the anode. The chemistry is complex and secret so we can only guess. That is why Elon's tweet may, or may not be relevant. Time will tell and I dare say BD will help, though there are cynics in that regard. Frankly I think BD will sort things one way or tother. Feral