Gradient Electrolyte Strategy Achieving Long‐Life Zinc Anodes

Abstract Aqueous Zn‐ion batteries are plagued by a short lifespan caused by localized dendrites. High‐concentration electrolytes are favorable for dense Zn deposition but have poor performance in batteries with glass‐fiber separators. In contrast, low‐concentration electrolytes can wet the separators well, ensuring the migration of zinc ions, but the dendrites grow rapidly. In this work, we propose an electrolyte gradient strategy wherein a zinc‐ion concentration gradient is established from the anode to the separator, ensuring that the separator keeps a good wettability in low‐concentration areas and the zinc anode achieves dendrite‐free deposition in a high‐concentration area. By using this strategy in a common electrolyte, zinc sulfate, a Zn||Zn symmetric cell achieves 14 000 ultralong cycles (exceeding 8 months) at 5 mA cm −2 and 1 mAh cm −2 . When the current is further increased to 20 mA cm −2 , the symmetric cell could still run for over 10 000 cycles. Assembled Zn||NVO full cells also demonstrate prominent performance. At a high current of 16 mA cm −2 , the NVO cathode with high loading (8 mg cm −2 ) still has a capacity of 58% after 1200 cycles. Overall, the gradient electrolyte strategy provides a promising approach for practical long‐life Zn anodes with the advantages of simple operation and low cost.