Superior rate capability of Zn-ion hybrid capacitor enabled by solid-state Zn2+ transport in MnFe layered double hydroxide network

The growing demand for sustainable energy storage has spurred interest in advanced electrode materials for metal-ion capacitors. Layered double hydroxides (LDH) are particularly attractive due to their tunable composition, high surface area, and efficient ion-exchange properties. In this work, manganese–iron LDH (MnFe-LDH) was directly deposited onto conductive nickel foam (NF) via electrochemical deposition to create a cost-effective electrode. The MnFe-LDH@NF delivered a high specific capacitance of 1456 mFcm −2 , energy density of 102 μWh cm −2 , and power density of 357 μWcm −2 , enabled by the NF conductive network. A zinc-ion capacitor (ZIC) assembled with MnFe-LDH@NF and a zinc plate in 1 M KOH exhibited superior performance with voltage ranging from 0.8 to 2 V , achieving 1426.7 mFcm −2 , 206 μWhcm −2 , and 1377 μWcm −2 , with 99.99 % capacitance retention and 100 % coulombic efficiency over 10,000 cycles at 8 mAcm −2 . Furthermore, a planar solid-state ZIC demonstrated 878.8 mFcm −2 , 101 μWhcm −2 , and 970 μWcm −2 , while retaining 81 % capacitance and 99 % efficiency after 2000 cycles. It successfully powered an LED for 3 min, confirming excellent practicality. • Highly active MnFe-LDH@NF synthesized using one step electrochemical deposition • Planar solid zinc-ion hybrid capacitor delivering a high areal capacitance of 878 mF cm −2 • Planar solid zinc-ion hybrid capacitor exhibits excellent cycling stability of 81 % retention after 2k cycles. • Planar solid zinc-ion hybrid capacitor successfully powering a light-emitting diode