Spontaneous Molecule Aggregation for Nearly Single-Ion Conducting Sol Electrolyte to Advance Aqueous Zinc Metal Batteries: The Case of Tetraphenylporphyrin.

Zn metal as a promising anode of aqueous batteries faces severe challenges from dendrite growth and side reactions. Here, tetraphenylporphyrin tetrasulfonic acid (TPPS) is explored as an electrolyte additive for advanced Zn anodes. It is interesting to note that TPPS spontaneously assembles into unique aggregates. As they adsorb on the Zn anode, the aggregates enhance the resistance to electrolyte percolation and dendrite growth compared to single molecules. Meanwhile, TPPS facilitates anion association in the solvation sheath of Zn, and boosts the transference number of Zn up to 0.95. Therefore, anion-related side reactions and anion-induced electrode overpotentials are reduced accordingly. In this context, the electrolyte containing TPPS exhibits excellent electrochemical performance. Even under a high loading of MnO (25 mg cm), a limited Zn supply (N/P ratio=1.7), and a lean electrolyte (15 μL mAh), the full cells still represent a higher cumulative capacity compared to the reported data. The advantages of this electrolyte are also adapted to other cathode materials. The pouch cells of Zn||NaVO ⋅ 1.5HO realize a capacity of ~0.35 Ah at 0.4 C under harsh conditions.