The Emerging Layered Hydroxide Plates with Record Thickness for Enhanced High-Mass-Loading Energy Storage

The past decade has witnessed the development of layered-hydroxide-based self-supporting electrodes, but the low active mass ratio impedes its all-around energy-storage applications. Herein, the intrinsic limit of layered hydroxides is broken by engineering F-substituted β-Ni(OH)₂ (Ni–F–OH) plates with a sub-micrometer thickness (over 700 nm), producing a superhigh mass loading of 29.8 mg cm⁻² on the carbon substrate. Theoretical calculation and X-ray absorption spectroscopy analysis demonstrate that Ni–F–OH shares the β-Ni(OH)₂-like structure with slightly tuned lattice parameters. More interestingly, the synergy modulation of NH₄⁺ and F⁻ is found to serve as the key enabler to tailor these sub-micrometer-thickness 2D plates thanks to the modification effects on the (001) plane surface energy and local OH⁻ concentration. Guided by this mechanism, the superstructures of bimetallic hydroxides and their derivatives are further developed, revealing they are a versatile family with great promise. The tailored ultrathick phosphide superstructure achieves a superhigh specific capacity of 7144 mC cm⁻² and a superior rate capability (79% at 50 mA cm⁻²). This work highlights a multiscale understanding of how exceptional structure modulation happens in low-dimensional layered materials. The as-built unique methodology and mechanisms will boost the development of advanced materials to better meet future energy demands.