Engineering an electrostatic field layer for high-rate and dendrite-free Zn metal anodes

Commercialization of zinc (Zn) metal batteries is significantly hindered by the instability of the Zn metal/electrolyte interface(s), together with concurrent parasitic reactions and dendritic growth that leads to low Coulombic efficiency (CE) and poor cycle life. Here, we report an electrostatic field layer (EFL) established via an electrolyte additive of cobalt tetraaminophthalocyanine (Co(TAPC)) to obviate these drawbacks. We confirm using judiciously combined experimental characterization and theoretical computation that Co(TAPC) with a planar and large conjugated ring structure preferentially absorbs on the Zn metal anode to form a zincophilic EFL, which prevents direct contact of Zn and water, suppresses side reaction(s), promotes desolvation and Zn²⁺ diffusion kinetics and balances the space electric field, thus enabling high-rate and dendrite-free Zn deposition. The Zn metal anode exhibits an ultra-long cycle life of >8000 cycles at a current density of 50 mA cm⁻² and high CE under harsh test conditions of 5 mA h cm⁻² and 10 mA cm⁻². Moreover, the utility of the Co(TAPC) EFL is also demonstrated in Zn||MnO₂ full cells, exhibiting outstanding cycling stability of 5000 cycles at a high current density of 2000 mA g⁻¹. Generally, the construction of a zincophilic EFL realizes uniform dendrite-free deposition in aqueous Zn metal batteries and opens an avenue for the design of stable metal anodes for high-performance metal batteries. © 2023 The Royal Society of Chemistry.