Looks like the Norwegians may take the crown this year for finally figuring out how to crack (pun intended) the tendency of Silicon to break down when used in batteries. If it pans out, expect 3-5x energy density. And even better news, if they can simply swap out the part in existing factories (i.e. just sell the anodes) then factories like Teslas will remain relevant for at least another decade.
https://cleantechnica.com/2018/07/12/researchers-in-norway-claim-lithium-ion-battery-breakthrough/