NaTi2(PO4)3 Solid‐State Electrolyte Protection Layer on Zn Metal Anode for Superior Long‐Life Aqueous Zinc‐Ion Batteries

Abstract A fast ion conductor, NaTi 2 (PO 4 ) 3 (NTP), is hydrothermally synthesized as a solid‐state electrolyte protection layer on the surface of Zn anodes (NTP@Zn). NTP has fast ionic conductivity compared with other insoluble phosphates, such as TiP 2 O 7 (TPO) and Zn 3 (PO 4 ) 2 (ZPO), which is demonstrated by the density‐functional theory calculation and cyclic voltammetry tests. X‐ray photoelectron spectrometer, X‐ray powder diffraction, and HRTEM analyses show that the internal transport/mobility of Zn 2+ can be achieved in NTP layer as an “ion passable fence.” The NTP layer with a thickness of 20–25 µm not only prevents side reactions and zinc dendrites, but also improves the reversibility of Zn deposition and electrochemical performance. The NTP@Zn/MnO 2 battery represents the best long‐life performance among Zn/MnO 2 batteries to date, which successfully retains a considerable capacity of 105 mA h g −1 with a CE nearly 100% after 10 000 charge/discharge cycles at 10 C (≈1.5 A g −1 ). Each cycle capacity attenuation rate is only 0.004%. This work represents an advanced step toward long‐life Zn metal anodes for aqueous zinc‐ion batteries.