An important trend in electronics involves the development of materials, mechanical designs and manufacturing strategies that enable the use of unconventional substrates, such as polymer films, metal foils, paper sheets or rubber slabs. The last possibility is particularly challenging because the systems must accommodate not only bending but also stretching. Although several approaches are available for the electronics, a persistent difficulty is in power supplies that have similar mechanical properties, to allow their co-integration with the electronics. Here we introduce a set of materials and design concepts for a rechargeable lithium ion battery technology that exploits thin, low modulus silicone elastomers as substrates, with a segmented design in the active materials, and unusual ‘self-similar’ interconnect structures between them. The result enables reversible levels of stretchability up to 300%, while maintaining capacity densities of ~1.1 mAh cm−2. Stretchable wireless power transmission systems provide the means to charge these types of batteries, without direct physical contact.
This material is based upon work supported by a National Security Science and Engineering Faculty Fellowship and a grant from the US Department of Energy, Division of Materials Sciences under Award No. DEFG02-91ER45439. The experiments used facilities at the Materials Research Laboratory and Center for Microanalysis of Materials at the University of Illinois at Urbana-Champaign, supported by the US Department of Energy, Division of Materials Sciences under Award No. DE-FG02-07ER46471 and DE-FG02-07ER46453. Y.H. acknowledges NSF grant ECCS-0824129, and ISEN from Northwestern University for the support of the mechanics modelling effort. J.A.R. and U.P. acknowledge the National Research Foundation of Korea (NRF) through a grant (K2070400000307A050000310, Global Research Laboratory (GRL) Programme) provided by the Korean Ministry of Education, Science & Technology (MEST), for efforts on slurry development. We thank Dr Jon Howell of DuPont for donating the allyl amide functional Krytox used in this study, and also thank Shu Xiang for many stimulating discussions.
Supplementary Movie 1 comparing experimental measurement and finite element simulations on the deformation process of the symmetric mode for the self-similar interconnect. The top figure is from experimental measurement, and the bottom one is from finite element simulations.
Supplementary Movie 2 comparing experimental measurement and finite element simulations on the deformation process of the anti-symmetric mode for the self-similar interconnect. The top figure is from experimental measurement, and the bottom one is from finite element simulations.
Supplementary Movie 3 showing the reversible stretchability up to 300% with minimum output power decrease.