Accordion-like stretchable Li-ion batteries with high energy density

High-performance stretchable batteries are key components for stretchable devices. However, it is challenging to have both high stretchability and high energy density simultaneously. Herein, we report a design of accordion-like stretchable lithium ion batteries, where the rigid energy storage units are connected by wrinkled and stretchable components. Simulation results show that such accordion-like design and the tape/metal/tape sandwiched structure reduces maximum stress of Al foil in the structure from 31.2 MPa to only 17.1 MPa, which significantly enhance the cell stability. Meanwhile, as the volume of rigid segments are larger than the stretchable part, such design can achieve stretchability of 29% while maintaining 77% (233 Wh L⁻¹) of volumetric energy density of that in conventional packing. Experimentally, the cell shows a high capacity retention of 95.4% even after stretching by 22% for 10,000 times, bending for 20,000 times, and 100 cycles at 0.5 C. It also provides steady power output during continuous dynamic mechanical tests. The corresponding average discharge voltage is only reduced by 1 mV. This accordion-like battery provides an alternative strategy to design stretchable batteries for stretchable devices.