Triboelectric Nanogenerators\nof the Li Salt of Adipic\nAcid-Incorporated Poly(vinyl alcohol) Composites Toward Biomechanical\nMotion Energy Harvesting and in Sports Application

Mono-Li\nsalts of adipic acid (Li-AA)-incorporated poly(vinyl\nalcohol)\n(PVA) composites were synthesized with the aim of utilizing them\nin triboelectric nanogenerators (TENGs). Fourier transform infrared\n(FTIR) spectroscopy revealed the formation of intermolecular H-bonding\nbetween the acid functional moiety of Li-AA and the hydroxyl functional\ngroup of PVA in the PVA/Li-AA composite and the simultaneous breakdown\nof interchain H-bonding of PVA. This led to a progressive decrease\nin glass transition temperature and melting temperature with a concomitant\nincrease in onset and final degradation temperatures in the PVA/Li-AA\ncomposite with increased Li-AA concentration. The dielectric properties\nof the PVA/Li-AA composite manifested the influence of strong interfacial,\ndipolar, and ionic interactions in the presence of increased Li-AA\nconcentration. Due to the higher surface roughness, flexibility, and\nincreased dielectric constant of the PVA/Li-AA composite film, the\nTENG was fabricated in a vertical-contact-separation mode. Further,\nTENG was investigated for biomotion sensing and energy harvesting\nfor various movements including knee bending, walking, jogging, etc.\nThe open-circuit voltage in the PVA/Li-AA composite-based TENG of\n15 wt % Li-AA registered ∼90 V and a short-circuit current\nof ∼45 μA. Moreover, the device showed a maximum power\ndensity of ∼2.75 W/m<sup>2</sup> at 2 MΩ resistance.\nAdditionally, the device also showed sensing output for writing and\nkeyboard typing, and the fabricated TENG exhibited sensing output\nfor boundary detection in lawn tennis sport.