Ni, Co bimetallic MOF of dual-controlled by micro-morphology and unit cell structure for biomass-based self-supporting energy storage device

Increasing the interlayer spacing of metal–organic frameworks (MOFs) through multi-metal ion doping has emerged as an effective strategy to enhance electrolyte-ion transport within the MOF unit cell, enabling the design of nickel-based MOF materials with high capacity and energy density. In this work, a series of NiCo-MOF-x (x = 1–5) were synthesized by incorporating Co2+ ions into Ni-MOF. The introduction of Co2+ modulated the unit cell structure and governed the stacking configuration of MOF nanosheets. At an optimal Ni/Co molar ratio of 4:1, the NiCo-MOF-2 sample demonstrates superior electrochemical performance, delivering a specific capacitance of 1238.6 F g−1 at 0.2 A g−1. Subsequently, NiCo-MOF-2 was grown in situ on carbonized wood (CW) to fabricate a NiCo-MOF@CW composite, which exhibits an areal capacitance of 4960 mF cm−2 at 0.6 mA cm−2. An asymmetric supercapacitor (NiCo-MOF@CW//AC) was assembled using NiCo-MOF@CW as the positive electrode and activated carbon (AC) as the negative electrode. The device achieves an areal energy density of 1.88 mWh cm−2 at a power density of 2.88 mW cm−2 (1 mA cm−2), with 83.6% capacitance retention after 2000 charge–discharge cycles. Notably, two serially connected NiCo-MOF@CW//AC devices successfully illuminate a red LED (operating voltage: 1.6–1.75 V) for 20 min. The multi-metal ion doping strategy combined with binder-free, self-supporting electrode architecture presents a novel approach for synthesizing high-performance energy storage materials.