An Ion-Sieving Janus Separator toward Planar Electrodeposition for Deeply Rechargeable Zn-Metal Anodes

The irregular and random electrodeposition of zinc has emerged as a non-negligible barrier for deeply rechargeable aqueous zinc (Zn)-ion batteries (AZIBs), yet traditional texture regulation of the Zn substrate cannot continuously induce uniform Zn deposition. Here, a Janus separator is constructed via parallelly grown graphene sheets modified with sulfonic cellulose on one side of the commercial glass fiber separator through the spin-coating technique. The Janus separator can consistently regulate Zn growth toward a locked crystallographic orientation of Zn(002) texture to intercept dendrites. Furthermore, the separator can spontaneously repel SO₄ ^2- and anchor H⁺ while allowing effective transport of Zn²⁺ to alleviate side reactions. Accordingly, the Zn symmetric cell harvests a long-term lifespan over 1400 h at 10 mA cm^-2 /10 mAh cm^-2 and endures stable cycling over 220 h even at a high depth of discharge (DOD) of 56%. The Zn/carbon nanotube (CNT)-MnO₂ cell achieves an outstanding capacity retention of 95% at 1 A g^-1 after 1900 cycles. Furthermore, the Zn/NH₄ V₄ O₁₀ pouch cell with a Janus separator delivers an initial capacity of 178 mAh g^-1 and a high capacity retention of 87.4% after 260 cycles. This work provides a continuous regulation approach to achieve crystallographic homogeneity of the Zn anode, which can be suitable for other metal batteries.