Highly pressure-resistant and high-rate ultrathick micro-Si anodes for 3D microbatteries via direct-ink-writing of directionally continuous porous microstructure

• Highly pressure-resistant and high-rate ultrathick micro-Si anodes are fabricated via an in-situ directional freezing-assisted 3D printing approach. • The 3D-printed ultrathick microelectrodes achieve a thickness of up to 2.7 mm, delivering a high areal capacity of 14 mAh cm - ². • The 3D microelectrodes feature a directionally continuous porous microstructure, effectively resisting external stress, mitigating μ-Si volumetric changes, and enhancing ion diffusion. • A structure-integrated microelectronic device is designed using a customized μ-Si||NCM microbattery. 3D microbatteries, featuring customizable and thick electrode designs, are crucial for miniaturized and specialized electronic devices. However, the practical implementation of thick 3D microelectrodes is often challenged by sluggish ion transport and mechanical instability under external and internal stresses. Here, we developed pressure-resistant ultrathick micro-Si 3D microelectrodes using an in-situ directional freezing-assisted direct-ink-writing 3D printing approach. This approach enables the construction of ultrathick electrodes up to 2.7 mm, achieving an ultrahigh areal capacity of 14.0 mAh cm -2 . The 3D-printed thick electrodes demonstrate remarkable pressure-resistant capability due to the formation of directionally continuous porous microstructure, providing a high compression modulus of ∼3.04 MPa. The directional pore microstructure not only effectively resists external stress and mitigates micro-Si volumetric changes but also significantly enhances ion diffusion, resulting in improved rate capability and cycle stability compared to the non-directional one. This study presents a reliable method for fabricating pressure-resistant ultrathick 3D microelectrodes with high mechanical and electrochemical performances, paving the way for customized 3D microbattery applications. Pressure-resistant ultrathick microelectrodes with directionally continuous porous microstructure are fabricated via an in-situ directional freezing-assisted 3D printing approach, which allows for the construction of ultrathick electrodes up to ∼2.7 mm and simultaneously achieves ultrahigh pressure resistance and ultrahigh areal capacities. The 3D-printed customized microbattery optimizes space utilization within the microelectronic devices and enables the continuous power supply to the LED, achieving seamless battery-device integration.