Chaotropic Polymer Additive with Ion Transport Tunnel Enable Dendrite-Free Zinc Battery

Zn batteries are considered the new-generation candidate for large-scale energy storage systems, taking both safety and environmental problems into account. They are still restricted by unexpected dendrite/byproducts occurring on the Zn anodes. We hereby screen a powerful polymer type additive, hyaluronic acid (HA), to regulate the typical ZnSO4 electrolyte for obtaining dendrite-free Zn ion batteries. The intrinsically chaotropic property of the HA molecule can efficiently destruct the original hydrogen-bonds from H2O-H2O, thus restricting the common parasitic reactions derived from the large amount of active water molecules. Simultaneously, the abundant functional groups along the long chain from HA additives can construct an effective tunnel for transferring Zn2+ smoothly, enabling an obviously improved Zn ion transference number of 0.62. Owning to the above intriguing mechanism for regulating the solvation structure of electrolyte systems, the HA additives can greatly increase the cycling life of Zn-Zn symmetric cells to 2200 and 800 h under the conditions of 1 mA cm-2/1 mAh cm-2 and 5 mA cm-2/5 mAh cm-2, respectively. Modified performance for both Zn-Ti and Zn-MnO2 can all be realized by this valid additive, elucidating it can be potentially utilized in large-scale Zn based aqueous energy storage devices.