We know the fundamental physics and chemistry.
Your largest-scaling options are thermal storage (molten-salt thermal, not to be confused with molten-salt electric batteries), compressed air energy storage (CAES), and pumped-hydro. The last as with hydroelectric dams is limited by available sites and environmental impacts.
Any thermal storage or thermal-process generation (e.g., molten salt thermal storage, synfuel-based generation) will be limited by Carnot efficiencies, with about a 30% energy recovery to thermal input possible. Hydrolysis loses about half of input energy, hence the 15% return on synfuel storage.
Synfuels are another option. Most of these involve creating hydrogen, many (and the ones I tend to favour) will then combine that with carbon and/or oxygen to create hydrocarbon analogues or alcohol. These are very-long-term stable, and have high energy densities. They're valuable for specific uses already (portable power tools, vehicles --- especially off-road or remote, aircraft, and marine shipping). The total net energy recovery is low, on the order of 15--25%, but the storage capacity, the storage durability, the handling characteristics, safety, and extensive extant experience and capital for storage, transport, and utilisation, are all positives.
I've followed the electric battery story reasonably closely for about a decade. It's characterised by big promises and relatively low delivery. LiON is likely the best light-weight battery, for mobile and portable applications, simply based on chemistry. There are only so many light atoms, and the ones lighter than those we're using are exceedingly anti-social. (Notably flourine and chlorine.)
Air-metal, molten-salt, and molten-metal batteries might afford large-scale capabilities, though most research seems to have had limited success. All involve inconvenient behavioural properties of the electorlytes and cells themselves. None are well-suited to mobile applications. Several should be kept some distance from other infrastructure (e.g., residential/commercial zones, etc.).
Energy banking through direct thermal storage (hot water, ground/geothermal heat/cold storage, etc.) are possible, though would require considerable revisions to existing land-use and infrastructure interconnections. Reducing overall energy loads through passive designs minimising heating, cooling, lighting, and other loads, is also probably a factor.
We're headed to a future in which energy economics will be markedly different from those of the past 50, 100, 150 years. It's those economics which have shaped our activities, infrastructure, and land use. I strongly suspect all three to adapt substantially to the new regime. Assuming that the lifestyle we've become accustomed to will continue forward is probably at odds with future realities.