Lanthanum nitrate as aqueous electrolyte additive for favourable zinc metal electrodeposition

Aqueous zinc batteries are appealing devices for cost-effective and environmentally sustainable energy storage. However, the zinc metal deposition at the anode strongly influences the battery cycle life and performance. To circumvent this issue, here we propose the use of lanthanum nitrate (La(NO₃)₃) as supporting salt for aqueous zinc sulfate (ZnSO₄) electrolyte solutions. Via physicochemical and electrochemical characterizations, we demonstrate that this peculiar electrolyte formulation weakens the electric double layer repulsive force, thus, favouring dense metallic zinc deposits and regulating the charge distribution at the zinc metal|electrolyte interface. When tested in Zn||VS₂ full coin cell configuration (with cathode mass loading of 16 mg cm^-2), the electrolyte solution containing the lanthanum ions enables almost 1000 cycles at 1 A g^-1 (after 5 activation cycles at 0.05 A g^-1) with a stable discharge capacity of about 90 mAh g^-1 and an average cell discharge voltage of ∼0.54 V.