Achieving impact-buffered compressible batteries through 3D printing-assisted design of negative Poisson's ratio...

Deformable batteries with compressive and impact-buffered abilities are essential for enhancing battery safety. However, existing compressible electrodes often face limited physical deformation and generate high stress, leading to package bulges of batteries. Here, we present a metamaterial-inspired design to develop negative Poisson's ratio (NPR) structural electrodes using a directional freezing 3D printing-assisted strategy. This approach incorporates both macroscopic NPR structures and microscopic directional porous structures, which enhances ion transport, improves compressibility and provides impact resistance, effectively preventing package bulges during compression. Consequently, the electrodes demonstrate a high 50% compressible deformation and recover their original state even after 50 cycles of 25% compression. The 3D-printed lithium iron phosphate cathodes deliver a high average specific capacity of 153 mAh/g over 100 cycles and exhibit outstanding rate capability. Furthermore, the assembled full cell maintains both excellent compressibility and impact-buffered resistance, highlighting its potential applications. This innovative design of NPR metamaterial-structured electrodes provides a universal platform for developing the next generation of impact-buffered, compressible structural batteries.