Concrete capacitors are proven & similar batteries probable.
Some years ago a military program included a "power storage" question should a war event take out the national grid. One of the systems looked at was concrete. The team created a concrete capacitor which due to the rudimentary science was very low in efficiency & little has been done since, but it worked. Should the efficiency rate be upgraded & the focus of application be solely on pre cast units then any wall unit for domestic, commercial or hi rise plus infrastructure units (bridge sections, culverts etc.) could store electricity.
However, using existing "now" technology should slabs on ground be focused on as well & considering that in many slabs that 50%+ of their area is non-structural then the addition of integrated "cells" utilizing the robust but low tech saline battery technology could be added. Example - a typical residential house slab area is normally around 200m2 leaving approximately 100m2 of usable under slab area to install the system. A 5Kw solar system would be more than adequate to power the battery system & storage capacity would be somewhere between 5-7 days. For existing buildings simple areas such as driveways could be rebuilt to accommodate cells. So, quite possibly concrete which is the largest product by mass & volume created by man could be a robust alternative solution to the storage issues we now face & make the micro grid concept work.