Stretchable Lithium-Ion Battery Based on Re-Entrant Micro-Honeycomb Electrodes and Crosslinked Gel Electrolyte.

Stretchable energy storage devices are of great interest because of their potential applications in body-friendly, skin-like, wearable devices. However, stretchable batteries are very challenging to fabricate. The electrodes must have a degree of stretchability because the active materials occupy most of the volume, and the separator and packaging should also be stretchable. Here, an all-component stretchable lithium-ion battery was realized by leveraging the structural stretchability of re-entrant micro-honeycomb graphene-carbon nanotube (CNT)/active materials composite electrodes and a physically crosslinked gel electrolyte, without using an inactive elastomeric substrate or matrix. Active materials interconnected via entangled CNT and graphene sheets provided a mechanically stable porous network framework, and the inwardly protruding framework in the re-entrant honeycomb structure allowed for structural stretching during deformation. The composite network consisting solely of binder-free, highly conductive materials provided superior electron transfer, and vertically aligned microchannels enabled facile ion transport. Additionally, the physically crosslinked gel electrolyte increased mechanical stability upon deformation of the electrodes and was effective as a stretchable separator. The resulting stretchable battery showed a high areal capacity of 5.05 mAh‧cm-2, superior electrochemical performance up to 50% strain under repeated (up to 500) stretch-release cycles and long-term stability of 106% after 100 cycles in air conditions.