A Synergistic Pretreatment–3D Printing Strategy for High-Performance Lignin-Based Porous Electrodes

Direct ink writing (DIW) technology enables the transformation of two-dimensional biomass electrodes into three-dimensional thick electrodes, thereby facilitating the development of high-performance supercapacitors (SCs). Nevertheless, the rigidity and poor rheological properties of lignin have constrained research on biomass inks, limiting advancements primarily to low-carbon cellulose. This study presents a strategy in which bamboo powder is treated in a maleic acid/water system to synthesize maleated bamboo lignin, which is subsequently formulated into printable ink and applied for the first time in the field of SCs. Maleated bamboo lignin was combined with F127 to formulate a printable ink exhibiting excellent rheological properties (storage modulus G′ = 28,471 Pa). The resulting MFLK carbon electrodes exhibit a hierarchical porous structure, a high specific surface area (1831.2 m2·g–1), pore sizes of 3–10 nm, and a mass loading up to 90 mg·cm–2. The areal capacitance is 31.67 F·cm–2, representing a 42.85% improvement over fully dense electrodes. Symmetric devices based on MFLK demonstrate superior electrochemical performance (areal capacitance of 5.3 F·cm–2, energy density of 0.73 mWh·cm–2) compared to fully dense and partially MXenes/graphene oxide electrodes. In summary, this work establishes a “pretreatment–3D printing” synergistic refinement framework, providing an efficient pathway from biomass precursors to high-performance energy storage devices.