I'm confident that they may eventuate one day, the research is progressing. In just the last few days there has been research released revealing the discovery of the source of the deterioration in coulomb efficiency of SSBs. https://www.greencarcongress.com/2019/08/20190822-ucsd.html The promise of doubling the energy density and efficiency of Li ion batteries and effectively doubling EV range is exciting but it still has a long way to go.