Suppressing H evolution by using a hydrogel for reversible Na storage in NaV(PO).

We report a low-cost hydrogel electrolyte by adding 3 wt% poly(acrylate sodium) (PAAS) into 1 M NaSO aqueous electrolyte, which achieves a widened electrochemical stability window (ESW) of 2.45 V on stainless steel current collector from 2.12 V in 1 M NaSO aqueous electrolytes (AE).