In 2010 I experimented with Graphene as the Anode of a Li Ion battery. The results at the time were pretty promising but we (the lab at my uni) were synthesizin

In 2010 I experimented with Graphene as the Anode of a Li Ion battery. The results at the time were pretty promising but we (the lab at my uni) were synthesizing all of the material ourselves - there was no graphene supply chain and it was very expensive. We always talked about specific capacity (q, charge per unit weight) so all the numbers I'm quoting will be in that - you can multiply by voltage to convert. We were obtaining specific capacities around 500 mAh/g. Vs q= ~370 mAh/g max for graphite anode. I recall based on theoretical modelling ~660 MAh/g could have been achievable with graphene. This pales in comparison to tin or cobalt anodes, which back in 2010 had q = 990 or so. We were not really optimizing for energy density. Rather with carbon based anodes we would see much better cyclical performance due to the lower volume expansion during Li intercalation. So you would be able to get much more charge/discharge cycles without the loss of performance you'd typically see in a higher energy density metal based anode. I work in a different industry now and have not followed battery development closely. I'd speculate a similar thing has happened in the "real world" the energy density may not have improved significantly since 2006 but the cycle life is probably better.