A hydrophilic-Zn2+ conductive lanthanum phosphate interlayer toward ultra-long-life Zn anodes and zinc ion capacitors

Abstract

The detrimental interfacial side reactions and irregular Zn dendrites may reduce the cycling life of Zn anodes and Zn-based energy storage devices. Regulating the interfacial microenvironment to eliminate harmful side reactions and achieve uniform Zn deposition is vital to develop high-performance Zn anodes. Here, a “hydrophilic-Zn²⁺ conductive” lanthanum phosphate (LaPO₄) interlayer is applied to realize an ultra-long-life Zn anode (LAP-Zn) and Zn²⁺ capacitors. The hydrophilic LaPO₄ can act as a microscopic “H₂O-reservoir” by preferentially adsorbing H₂O molecules (the adsorption energy of LaPO₄–H₂O is −1.17 eV, larger than that of Zn–H₂O). Consequently, a microscopic H₂O-poor environment on the Zn anode is formed, thus eliminating harmful side reactions including H₂ evolution and Zn corrosion. Simultaneously, Zn²⁺ de-solvation is promoted, facilitating accelerated interfacial migration and uniform flux of Zn²⁺. The Zn²⁺ migration number of LAP-Zn is 0.84 which is higher than that of pure Zn, demonstrating excellent Zn²⁺ conductivity. The LAP-Zn//LAP-Zn symmetrical cell operates efficiently for over 700 h at 5 mA cm⁻² and 2 mA cm⁻². The LAP-Zn//activated carbon capacitor exhibits an ultra-long life of 30 000 cycles at 1 A g⁻¹, with continuous operation for over 3600 h while maintaining a capacity retention ratio of 95%. Therefore, this “hydrophilic-Zn²⁺ conductive” LaPO₄ interlayer enables uniform Zn deposition and a highly reversible Zn plating/stripping process. This modification strategy using a “hydrophilic-Zn²⁺ conductive” rare earth-based interfacial layer is simple, long-term effective, and microcosmic, thus boosting the commercial application of Zn-based energy storage devices.