Structure engineering-enabled multi-direction-reconfigurable, soft, rechargeable lithium-ion battery with tissue-compliance low modulus and high performance

The significant demand for wearable and implantable bioelectronics necessitates high-performance power units. However, conventional batteries typically comprise rigid and bulky metals, or soft materials with conductive fillers (e.g., carbon nanotubes). These materials may induce undesired immune responses and battery failures when subjected to violent deformations due to the mismatch in mechanical properties between biological tissues (<100 kPa) and batteries. Additionally, current research on tissue-compliance soft batteries is based on the material-based low modulus and stretchability, where hydrogels are used as the elastic low modulus matrix. In this study, a structure-based low modulus electrode is developed wherein one-dimension (1D) uniaxial and two-dimension (2D) biaxial Kirigami pattern electrodes were carefully designed to provide both tissue-like modulus and multi-directional reconfigurability. The resulting reconfigurable soft battery exhibits excellent compliance and softness with Young's modulus of 64.1 kPa, which, to our knowledge, is the lowest modulus achieved for batteries with decent performance. The electrochemical performance of the reconfigurable lithium-ion soft battery under various deformations, such as stretching, bending, and twisting was investigated, and a high specific capacity of 83.5 mAh/g was achieved at a current density of 0.5 A/g under 100% stretching strain. The multi-directional stretchability, long-term stability, and biocompatibility of the reconfigurable soft battery were demonstrated. This groundbreaking work paves the way for the designing and manufacturing of soft batteries specifically tailored for wearable and implantable bioelectronics.