Zn anode with hydrophobic and ferroelectric P(VDF-TrFE) layers for dendrite-free aqueous Zn-ion batteries

Abstract

Zn anodes are highly promising aqueous battery materials due to their abundant sources, environmental friendliness, and high theoretical capacity of 820 mAh/g. Nevertheless, Zn undergoes dendritic growth and side reactions in mildly acidic electrolytes, leading to shorter cycling lifetimes. Herein, a layer of poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) was spin-coated onto a Zn anode to address this issue. The coated layer physically and electrically blocked contact between the Zn surface and the electrolyte due to its hydrophobic nature. Additionally, the ferroelectric properties of crystalline P(VDF-TrFE) (c-P(VDF-TrFE)) facilitated mass transport and homogenized the electric field, resulting in consistent plating and stripping of Zn ions beneath the film. As a result, the c-P(VDF-TrFE) coating on the Zn symmetric cell led to a stable overpotential (<40 mV) and long cycling lifetimes of more than 350 h (1 mA cm(-2), 0.5 mAh cm(-2)). Even with current conditions of 5 mA cm(-2) and 0.5 mAh cm(-2), the c-P(VDF-TrFE)-coated Zn symmetric cell demonstrated stable operation for over 600 h. Furthermore, a Zn||MnO2 full cell exhibited high capacity retention after 1000 cycles.