Enamel-like Layer of Nanohydroxyapatite Stabilizes Zn Metal Anodes by Ion Exchange Adsorption and Electrolyte pH Regulation

Abstract

The instability of Zn anode caused by severe dendrite growth and side reactions has restricted the practical applications of aqueous zinc-ion batteries (AZIBs). Herein, an enamel-like layer of nanohydroxyapatite (Ca5(PO4)3(OH), nano-HAP) is constructed on Zn anode to enhance its stability. Benefiting from the ion exchange between Zn2+ and Ca2+, the adsorption for Zn2+ in enamel-like nano-HAP (E-nHAP) layer can effectively guide Zn deposition, ensuring homogeneous Zn2+ flux and even nucleation sites to suppress Zn dendrites. Meanwhile, the low pH of acidic electrolyte can be regulated by slightly soluble nano-HAP, restraining electrolyte corrosion and hydrogen evolution. Moreover, the E-nHAP layer features high mechanical flexibility due to its enamel-like organic–inorganic composite nanostructure. Hence, symmetric cells assembled by E-nHAP@Zn show superior stability of long-term cycling at different current densities (0.1, 0.5, 1, 5, and 10 mA cm–2). The E-nHAP@Zn∥E-nHAP@Cu cell exhibits an outstanding cycling life with high Coulombic efficiency of 99.8% over 1000 cycles. Notably, the reversibility of full cell based on CNT/MnO2 cathode can be effectively enhanced. This work shows the potential of drawing inspiration from biological nanostructure in nature to develop stable metal electrodes.

Regulating Uniform Zn Deposition via Hybrid Artificial Layer for Stable Aqueous Zn-Ion Batteries

“…The NTP-C@Zn symmetrical cells can maintain stable cycling within 200 h and 160 h at 10 mA cm −2 and 20 mA cm −2 , respectively, followed by significant polarization increase. The phenomenon of the voltage increasing has also been observed and reported in the previous articles [48][49][50], which is mainly attributed to the occurrence of side reactions [51]. As for the cycling performance at a low current density, a stable cycling of Zn plating/stripping lasts over 860 h with a low overpotential (20 mV) at 0.5 mA cm −2 /0.5 mAh cm −2 , as shown in Figure 8(d).…”

Building Metal‐Molecule Interface towards Stable and Reversible Zn Metal Anodes for Aqueous Rechargeable Zinc Batteries

“…While the Zn anode using pure ZnSO 4 electrolyte shows severe CE fluctuations in the whole cycles, implying the poor reversibility induced by the water‐induced side reactions and dendrite formation. [ 33 ] Additionally, the lower overpotential and overlapped voltage curves for the selected cycles of the Zn|Ti cell using the electrolyte with TU additive further indicates the reversible Zn stripping/plating process at the electrode/electrolyte interface (Figure 4h,i). The above cell testing performance validate the effectiveness of the metal‐molecule interface on improving the Zn anode stability and reversibility.…”

A Facile Candle-Soot Nanoparticle Decoration Enables Dendrite-Free Zn Anodes for Long-Cycling Aqueous Batteries

“…In addition, the CS-Zn||Ti cell showed smaller hysteresis values, as shown in the enlarged voltage profiles (Figure S12a,b). This serves as another evidence that the CS coating layer can lower the energy barrier for Zn nucleation/dissolution . Considering all results, the enhanced mechanisms for the CS coating are schematically summarized in Figure .…”

“…This serves as another evidence that the CS coating layer can lower the energy barrier for Zn nucleation/dissolution. 50 Considering all results, the enhanced mechanisms for the CS coating are schematically summarized in Figure 5. On one hand, the tight CS coating layer averted active water/anions attack on Zn foils, effectively preventing parasitic reactions and mitigating byproduct accumulation.…”