title: Electrochemically driven mechanical energy harvesting.
abstract: Efficient mechanical energy harvesters enable various wearable devices and auxiliary energy supply. Here we report a novel class of mechanical energy harvesters via stress-voltage coupling in electrochemically alloyed electrodes. The device consists of two identical Li-alloyed Si as electrodes, separated by electrolyte-soaked polymer membranes. Bending-induced asymmetric stresses generate chemical potential difference, driving lithium ion flux from the compressed to the tensed electrode to generate electrical current. Removing the bending reverses ion flux and electrical current. Our thermodynamic analysis reveals that the ideal energy-harvesting efficiency of this device is dictated by the Poisson's ratio of the electrodes. For the thin-film-based energy harvester used in this study, the device has achieved a generating capacity of 15%. The device demonstrates a practical use of stress-composition-voltage coupling in electrochemically active alloys to harvest low-grade mechanical energies from various low-frequency motions, such as everyday human activities.
authors.affiliation: Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Sangtae
authors.initials: S
authors.lastname: Kim
authors.affiliation: Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Soon Ju
authors.initials: SJ
authors.lastname: Choi
authors.affiliation: Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Kejie
authors.initials: K
authors.lastname: Zhao
authors.affiliation: Department of Engineering Science and Mechanics, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
authors.forename: Hui
authors.identifier: http://orcid.org/0000-0002-2628-4676
authors.initials: H
authors.lastname: Yang
authors.affiliation: Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.|Politecnico di Milano, Department of Mechanical Engineering, Milan, 20156, Italy.
authors.forename: Giorgia
authors.initials: G
authors.lastname: Gobbi
authors.affiliation: Department of Engineering Science and Mechanics, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
authors.forename: Sulin
authors.initials: S
authors.lastname: Zhang
authors.affiliation: Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.|Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Ju
authors.identifier: http://orcid.org/0000-0002-7841-8058
authors.initials: J
authors.lastname: Li
mesh_terms: D055664:Electrochemical Techniques / Q000295:instrumentation* / Q000379:methods; D004736:Energy-Generating Resources; D019563:Mechanics; D008567:Membranes, Artificial; D013816:Thermodynamics
chemical_list: D008567:Membranes, Artificial