Regulating solvation structure and inducing Zn (0 0 2) plane by a multifunctional electrolyte additive toward dendrite suppression and long-life zinc ion hybrid capacitors

The side reactions of dendrites growth and hydrogen evolution occur inevitably in the aqueous system of Zn anode, which is the fundamental culprits cause of the limited lifespan and Coulomb efficiency (CE) of Zn-based energy storage devices. Herein, for weakening and reconstruction of the solvated structure of hydrated Zn2+ and promote parallel Zn deposition, a cost-effective and green D-trehalose dihydrate (DT) additive is proposed to stabilize the Zn anode by adding it to the aqueous ZnSO4 electrolyte. The results of experiment and theoretical calculation proved that DT additive can effectively disrupt the original Zn2+ solvated sheaths and reconstruct hydrogen bond networks in the ZnSO4 electrolyte, thereby increasing the decomposition potential of H2O molecules and induced (0 0 2) crystal plane to form horizontally ordered and densely stacked Zn deposition, leading to significantly reducing the generation of sharp dendrites during the Zn plating and stripping process. In this way, the Zn anodes in optimized ZnSO4 + DT electrolyte exhibit enhanced the cycling stability with lifespan over 650 h and high CE of 99%, which is nearly 10 times more stable than that in pure ZnSO4 electrolyte. Moreover, Zn-ion hybrid capacitors (ZICs) assembled with ZnSO4 + DT electrolyte and N, P co-doped hard carbon (NPHC) as cathode exhibits a high discharge capacity of 123.5 mAh/g at 0.1 A/g and superior capacity retention (over 90% after ultra-long 20,000 cycles at 5 A/g), along with about 100% CE.