Regulating the MXene–Zinc Interfacial Structure toward a Highly Revisable Metal Anode of Zinc–Air Batteries

Abstract

Rechargeable aqueous Zn−air batteries have been regarded as one of the most promising systems for flexible energy storage devices due to their high specific energy, safety, and cost effectiveness. However, Zn metal anodes exposed to strong alkaline electrolytes suffer from several issues such as corrosion, dissolution, and passivation, resulting in extremely poor cycle reversibility. Motivated by this challenge, we herein strategically design an MXene/Zn metal anode interfacial structure with single/few-layer Ti 3 C 2 T x MXene as a protective layer. Such a design not only isolates the direct contact between Zn metal anodes and electrolytes but also inhibits zincate dissolution due to the ion screening function of Ti 3 C 2 T x , potentially addressing the stubborn issues that Zn anodes faced with. As a result, the Ti 3 C 2 T x -protected Zn metal anode exhibits superior cycle stability (stable for more than 400 cycles) to the bare Zn counterpart (20 cycles) at a high current density of 5.0 mA cm −2 . When integrated into Zn−air coin cells, it has a high depth of discharge of 91% and operates stably for 140 cycles with small resistance. More interestingly, the excellent flexibility of the as-designed Ti 3 C 2 T x -protected Zn metal anode endows the quasi-solid-state batteries with admirable voltage stability at different bending angles from 0 to 180°.

Inhibition of Zinc Dendrite Growth by WC-Cellulose Separators for High-Performance Zinc-Ion Batteries

“…Such differences of cycling lifespan and voltage hysteresis between CNF and WCCNF separators demonstrate that the WCCNF can promote the uniform Zn nucleation and the reversible Zn plating/stripping on Zn anode. 37,38 Rate performances of Zn∥Zn cells were measured at various current densities from 0.5 to 5 mA•cm −2 . As shown in Figure 3c, the voltage hysteresis of the Zn∥Zn cell with CNF arises violent fluctuation when operated at the current density of 2.5 mA• cm −2 and short-circuits at the current density of 3.5 mA•cm −2 , indicating the poor stability of the Zn anode caused by the CNF separator especially at high current density.…”

Modification of Zinc Anodes by In Situ ZnO Coating for High-Performance Aqueous Zinc-Ion Batteries

“…14−16 Among these, constructing an artificial interphase to suppress water decomposition and regulate Zn plating emerge as key strategies for enhancing the electrochemical properties of zinc-ion batteries, including ex situ and in situ coating approaches. 17 Building a protective layer by ex situ coating inorganics (e.g., TiO 2 , 18 CaCO 3 , 19 graphene, 20 Ag, 21 Al 2 O 3 , 22 ZnF 2 , 23 HfO 2 , 24 Zn 3 (PO 4 ) 2 , 25 Si 26 ) or polymer [e.g., poly(vinyl butyral) (PVB), 5 poly(vinyl alcohol) (PVA), 27 T h i s c o n t e n t i s silk fibroin, 28 polyimide 29 ] on the surface of Zn anodes is an attractive method to regulate Zn dendrites by allowing Zn 2+ to transport but blocking water penetration to Zn surfaces. Nevertheless, this method usually requires binders and produces rough and thick coatings (>10 μm), which can increase the electrolyte−electrode interface resistance and reduce the energy density.…”

“…21 Several studies have reported the development of a ZnO architecture coating on a Zn anode. 4,32,33 For instance, a three-dimensional nanoporous ZnO coating on a Zn plate was shown to enhance the kinetics of Zn 2+ transfer and deposition due to the electrostatic attraction effect resulting from the porous structure and inert ZnO interface. 4 Another study demonstrated that the application of a ZnO interface could suppress dendrite growth, which was attributed to the reduction in local current density achieved by enlarging the surface area with the ZnO coating.…”

“…4 Another study demonstrated that the application of a ZnO interface could suppress dendrite growth, which was attributed to the reduction in local current density achieved by enlarging the surface area with the ZnO coating. 33 However, most surface modification efforts mainly focused on the electrochemical performance, while surface chemistry and interface phenomena/transformations are often neglected. Therefore, a systematic analysis to understand the reactions and evolution at the anode− electrolyte interface is highly desirable.…”

Ionic Layer Epitaxy Growth of Organic/Inorganic Composite Protective Layers for Large-Area Li and Zn Metal Anodes

“…In this inspiration, various effective strategies dedicated to promoting uniform deposition of Li and Zn ions have been developed. , One particularly successful approach involves employing an anode protection layer. Recently, various protection layers such as organic polymers, − organic–inorganic compounds, , and two-dimensional layered materials − have been developed to effectively induce uniform Li or Zn ion deposition and thus extend the cycle life. However, the thicknesses of these conventional interfacial protection layers typically range from 5 to 100 μm, imposing limitations on the overall anode energy density.…”