Structural Engineering of Nickel-Chromium Layered Double Hydroxides Through Self-Intercalated Ion Pillaring for Battery-Type Supercapacitors

Abstract

Layered double hydroxides (LDHs) are promising supercapacitor electrode materials due to their tunable layered structure and high theoretical capacitance, but their practical use is limited by poor cyclic stability. Herein, we report a binder-free electrochemical synthesis of nickel-chromium LDH (NiCr-LDH) with in situ self-intercalation of nitrate ions and water molecules, eliminating the need for external exfoliating agents or organic precursors. The engineered layered nanosheet morphology shortens ion diffusion pathways and enhances charge transfer kinetics. Optimizing Cr content in the Ni-LDH framework significantly improves electrochemical performance compared to pristine Ni-LDH and Cr-LDH. Structural and compositional analyses confirm effective nitrate and water intercalation, which act as pillars to prevent restacking and preserve structural integrity. The optimized NiCr-LDH exhibits a high specific capacitance of 1697 F g⁻¹ (679 C g⁻¹) at 1 A g⁻¹, governed mainly by a diffusion-controlled battery-type charge storage mechanism involving partial ion intercalation. A hybrid supercapacitor assembled with NiCr-LDH as the positive electrode and activated carbon as the negative electrode delivers an energy density of 21.74 Wh kg⁻¹ and a power density of 8000 W kg⁻¹, with 80% capacitance retention after 20 000 cycles. This work demonstrates a green and scalable electrodeposition strategy for high-performance LDHs-based energy storage systems.