My previous idea was about separating water into evaporation classes. From the easy evaporative to the desert sustainable.
From this I speculate that a battery could be improved by using sand. What if you can be picky and select the best material from within the same material. By this I mean that the sand can act as a natural separator or cleaner not only for water. Perhaps the electrolyte could also do a natural ?good and bad separation using dispersion in sand.