Design of Open Ion Transport Channels in Thick Electrodes through Directional Freezing-Assisted 3D Printing: Enhancing the Electrochemical Performance of High-Load Electrodes

Aqueous zinc ion batteries (AZIBs) offer advantages such as low cost and high safety but suffer from a relatively low energy density, which limits their practical applications. The thick electrodes with a high loading capacity can significantly enhance the energy density of AZIBs. However, in traditional thick electrodes, the accumulation of active materials leads to blockage of electrochemically active sites, which hinders the transmission of ions and electrons, thereby substantially reducing the electrochemical performance of AZIBs. Herein, 3D printing technology is used to construct a thick electrode with open ion transmission channels using the AC/GO/PEDOT:PSS active material. Moreover, the pore structure of a thick electrode is optimized by integrating directional freezing technology to create open channels with both directionality and porosity. This design promotes the efficient transmission of ions and electrons while fully exposing the active sites at the microstructural level, ultimately enhancing the ion diffusion rate and electrochemical reaction efficiency of the electrode. The results demonstrate that the optimized thick electrode achieves 140% of the original specific and superior cycling stability with a retention rate of 93.4% after 2000 cycles. The specific capacity increases from 46 to 64 mAh g^-1, effectively activating a greater number of active sites within the thick electrode. After directional freezing treatment, the pores in the electrode are predominantly interconnected, with the proportion increasing from 63.32% to 85.75%. Furthermore, the optimized pore structure results in enhanced ion transport kinetics with a rate capability that improved from 70.35% to 81.42%, while delivering both a high energy density of 1.49 mWh cm^-2 and a power density of 19.66 mW cm^-2. This work presents a novel design strategy for high-capacity electrodes and paves the way for performance enhancement in advanced energy storage devices, including batteries and supercapacitors.