Constructing strain and defects modulated novel germanium doped zeolitic imidazolate framework-67 derived NiCo layer double hydroxide nanocomposites for boosted supercapacitor applications

The growing demand for high gravimetric energy storage has driven the development of pseudocapacitive materials with large surface areas. Among these, hybrid layered double hydroxides (LDHs) derived from zeolitic imidazolate frameworks (ZIFs) have gained attention due to their tunable structure and porosity, high surface area, facile functionalization, and robust stability. Employing lattice strain and defect engineering has proven to be an effective strategy to tailor the electronic properties of such nanocomposites, enhancing electron transport and accelerating electrochemical reactions. In this study, we report a novel one-step solution synthesis of germanium (Ge) doped ZIF-67-derived NiCoLDH with a wrinkled sheet-like morphology, where Ge was introduced via ammonium hexafluoro germanite to induce lattice strain and defects. The wrinkled Ge/NiCoLDH nanosheets exhibited a high specific surface area of 124 m² g⁻¹ and an optimized micropore size around 4 nm. The optimized ZIF-67-based LDH demonstrated outstanding pseudocapacitive behavior, delivering a specific capacitance of 1804 F g⁻¹ at 1 A g⁻¹, along with excellent cycling stability, retaining 98 % capacity after 10,000 cycles. Furthermore, the assembled hybrid supercapacitor device achieved a notable energy density of 58 Wh kg⁻¹ at a power density of 745 W kg⁻¹ under a current density of 1 A g⁻¹, maintaining 94 % capacitance retention over 10,000 charge-discharge cycles at 20 A g⁻¹. Consequently, this works provides insight into the designing of ZIF based high performance pseudocapacitive materials to meet the challenges of energy storage.