Synchronous Sound Recognition and Energy Harvesting by Flexible Piezoelectric PLLA/VB₂ Composites

In the present study, poling−free PLLA/VB2 piezoelectric composites are fabricated to achieve synchronous sound recognition and energy harvesting. The addition of VB2 can interact with PLLA by intermolecular hydrogen bonding, inducing the dipole orientation of C=O in PLLA. Meanwhile, VB2 can promote crystallization of PLLA through heterogeneous nucleation. The combination of the two strategies significantly improves the piezoelectric performance of PLLA/VB2 composites. The PLLA/VB2 can detect the sound frequency with an accuracy of 0.1% in the range of 0–20 kHz to recognize characteristic sounds from a specific source. PLLA/VB2 can also convert sound into electrical energy synchronously with an energy density of 0.2 W/cm−3 to power up LEDs. Therefore, PLLA/VB2 shows great potential in the field of information and energy synchronous collection.