The freestanding MXene films are promising for compact energy storage ascribing to their high pseudocapacitance and density, yet the sluggish ion transport caused by the most densely packed structure severely hinders their rate capability. Here, a reassembly strategy for constructing freestanding and flexible MXene-based film electrodes with a tunable porous structure is proposed, where the Ti 3 C 2 T x microgels disassembled from 3D structured hydrogel are reassembled together with individual Ti 3 C 2 T x nanosheets in different mass ratios to form a densely packed 3D network in microscale and a film morphology in macroscale. The space utilization of produced film can be maximized by a good balance of the density and porosity, resulting in a high volumetric capacitance of 736 F cm −3 at an ultrahigh scan rate of 2000 mV s −1 . The fabricated supercapacitor yields a superior energy density of 40 Wh L −1 at a power density of 0.83 kW L −1 , and an energy density of 21 Wh L −1 can be still maintained even when the power density reaches 41.5 kW L −1 , which are the highest values reported to date for symmetric supercapacitors in aqueous electrolytes. More promisingly, the reassembled films can be used as electrodes of flexible supercapacitors, showing excellent flexibility and integrability.
Due to outstanding electrical conductivity and excellent solution processing ability, MXenes show great potential as inks for printed/coated electronic devices. To meet the rheological requirements, an ultra‐high concentration is usually involved to formulate MXenes into versatile inks, however, low efficiency in rheology regulation, and restacking issues of MXene sheets hinder their further applications. Herein, a gelation‐assisted approach is proposed to prepare versatile MXene inks with a 3D interlinked network to well address above issues. With an effective combination of cross‐linking as well as the swelling of interlinked network, the gel ink exhibits tunable rheological properties by simply tuning the water amount within the sol‐gel system. Among various applicable printing/coating techniques ranging from painting to extrusion printing, blade coating is selected to demonstrate the advantage of MXene gel ink. The smooth coating layer with interlinked 3D structures is greatly beneficial to the uniform and dense zinc deposition with high reversibility, and endows the aqueous zinc ion batteries with a remarkable rate capability. This work provides an alternative approach to prepare versatile MXene inks and would offer MXenes new opportunities for their application in advanced printable electronic devices.
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