Synergy Between Zn Current Collector and K+ Shielding Additives for High‐Performance Na Plating/Stripping

The electrostatic shielding of Na dendrites using a trace amount of KPF₆ additive shows superior plating/stripping efficiency on a bare Zn current collector. The K⁺ ionic shield arrests the accelerated growth of dendrite tips by homogenizing the Na⁺ flux. The low overpotential during plating/stripping promotes higher current collector coverage and uniform morphology.

The direct plating/stripping of Na on bare current collectors often results in poor cycling stability and uncontrolled dendrite growth. These two factors significantly hinder the development of high-energy-density and fast-charging energy storage devices. Herein, the synergistic effect between the highly reversible Na plating/stripping on Zn current collectors and a controlled dendrite growth enabled by KPF6$_{6}$ electrostatic shielding additives is harnessed. A uniform morphology with lower growth/dissolution overpotential is observed for 20 mM KPF6$_{6}$ additives. The cycle stability enhances from 218 to 376 cycles in the presence of such additives at an areal current density of 0.5 mA cm-2$$ {}^{-2}$$ and capacity of 1.0 mAh cm-2$$ {}^{-2}$$. Theoretically, a multicomponent phase-field model is developed to bring insights into the Na electrodeposition in the presence of 0, 5, 10, and 20 mM KPF6$_{6}$ additives. The model successfully correlates the shield formation and predicts its healing effect on Na dendrites. Further, the effectiveness of the electrostatic shield at high overpotential fails due to the large accumulation of Na+$^{+}$ ions at the interface. The work strives toward the use of metallic Zn current collectors with electrostatic shielding additives to streamline the cell assembly process.

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