High-energy and high-power-density lithium-ion batteries are promising energy storage systems for future portable electronics and electric vehicles. Here, three-dimensional (3D) patterned electrodes are created through the paste-extrusion-based 3D printing technique realizing a trade-off between high energy density and power density. The 3D electrodes possess several distinct merits over traditional flat thick electrodes, such as higher surface area, shorter ion transport path, and improved mechanical strength. Benefiting from these advantages, the 3D-printed thick electrodes present the higher specific capacity and improved cycling stability compared with those of the conventional thick electrodes. Upon comparison to the previous studies on 3D-printed electrodes, this study investigates the influence and optimization of 3D-printed LiFePO 4 (LFP) electrodes with three different geometric shapes to achieve a high rate performance and long-term cycling stability. Accordingly, a series of 3D electrodes with different thickness were created, and an ultrathick (1500 μm) 3D-patterned electrode exhibits a high areal capacity of around 7.5 mA h cm −2 , presenting remarkable value for state-of-the-art LFP cathodes. This work demonstrates patternable 3D printing as a potential strategy to fabricate thick electrodes toward high areal energy density and power density, which holds great promise for the future development of high-performance energy storage devices. KEYWORDS: high areal energy and power density, paste extrusion, three-dimensional (3D) printing technique, 3D-patterned thick LiFePO 4 (LFP) electrodes, patternable 3D printing

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The intractable nature of conjugated polymers(CP) leads to practical limitations in the fabrication of CP-based transducers having complex three-dimensional geometries. Conventional CP device fabrication processes have focused primarily on thin-film deposition techniques; this study explores novel additive manufacturing processes specifically developed for CP with the ultimate goal of increasing the functionality of CP sensors and actuators. Herein we employ automated polymer paste extrusion processes for the direct ink writing of 3D conductive polyaniline(PANI) structures. Realization of these structures was enabled through a modified fused filament fabrication delta robot equipped with an integrated polymer paste extruder to fabricate high-resolution 3D conductive PANI structures. The required processability of PANI was achieved by means of a counterioninduced thermal doping method. The effect of thermal doping on the PANI-DBSA paste by means of a constitutive relationship to describe the paste flow as a function of the thermal doping time is explored. This relationship is incorporated within a flow model to predict the extruded track width as a function of various process parameters including: print speed, gauge pressure, nozzle diameter, and pre-extrusion thermal doping time.

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