The
violent side reactions of Zn metal in aqueous electrolyte
lead to sharp local-pH fluctuations at the interface, which accelerate
Zn anode breakdown; thus, the development of an optimization strategy
to accommodate a wide pH range is particularly critical for improving
aqueous Zn metal batteries. Herein, we report a pH-adaptive electric
double layer (EDL) tuned by glycine (Gly) additive with pH-dependent
ionization, which exhibits excellent capability to stabilize Zn anodes
in wide-pH aqueous electrolytes. It is discovered that a Gly-ionic
EDL facilitates the directed migration of charge carriers in both
mildly acidic and alkaline electrolytes, leading to the successful
suppression of local saturation. It is worth mentioning that the regulation
effect of the additive concentration on the inner Helmholtz plane
(IHP) structure of Zn electrodes is clarified in depth. It is revealed
that the Gly additives without dimerization can develop orderly and
dense vertical adsorption within the IHP to effectively reduce the
EDL repulsive force of Zn2+ and isolate H2O
from the anode surface. Consequently, they Zn anode with tunable
EDL exhibits superior electrochemical performance in a wide range
of pH and temperature, involving the prodigious cycle reversibility
of 7000 h at Zn symmetric cells with ZnSO4-Gly electrolytes
and an extended lifespan of 50 times in Zn symmetric cells with KOH-Gly
electrolytes. Moreover, acidic Zn powder||MnO2 pouch cells,
and alkaline high-voltage Zn||Ni0.8Co0.1Mn0.1O2 cells, and Zn||NiCo-LDH cells also deliver
excellent cycling reversibility. The tunable EDL enables the ultrahigh
depth of discharge (DOD) of 93%. This work elucidates the design of
electrolyte additives compatible in a wide range of pH and temperature,
which might cause inspiration in the fields of practical multiapplication
scenarios for Zn anodes.