In situ built interphase with high interface energy and fast kinetics for high performance Zn metal anodes

Abstract

An in-situ SEI with Zn ₃(PO ₄) ₂ and ZnF ₂ was built on Zn anode via KPF ₆-induced chemical strategy. With high interface energy and fast kinetics, it leads to record cumulative capacity and the product of largest current density and areal capacity.

Abstract

In situ construction of a multifunctional solid electrolyte interphase (SEI) for Zn anodes is promising to address the dendrite growth and side reactions (corrosion and hydrogen evolution) in aqueous Zn-ion batteries. However, there is a lack of constructive methods for choosing suitable SEI compounds and feasible implementation routes. Here, inspired by the SEI-design for Li-metal batteries, we identified that Zn ₃(PO ₄) ₂ with high interface energy could suppress Zn dendrite growth effectively and ZnF ₂ could accelerate the kinetics of Zn ²⁺ transference and deposition, and thus constructing a composite SEI mainly composed of Zn ₃(PO ₄) ₂ and ZnF ₂ (ZCS) is likely to improve interface deposition and electrode kinetics comprehensively. However, the high redox potential of Zn/Zn ²⁺ and H ₂/H ⁺ makes it difficult to develop an in situ SEI for Zn anodes in aqueous electrolytes via traditional electrochemical routes. Considering this dilemma, we take advantage of the instability of KPF ₆ in an aqueous environment and build in situ ZCS on the Zn anode through the PF ₆ ⁻ anion-induced chemical strategy. Surprisingly, ZCS-Zn exhibits enhanced reversibility with a smooth and compact structure during long-term cycling. Both cumulative capacity (2020 mA h cm ⁻²) and the product of the largest current density and areal capacity (10 mA cm ⁻² × 20 mA h cm ⁻²) applied to ZCS-Zn reach the highest levels compared with those reported in recent reports under mildly acidic conditions. This work paves a new way for designing a desirable SEI on the Zn anode and may also guide the interface engineering of other systems to overcome the intrinsic defects in constructing favorable interphases.