Piezoelectric Polymer Solid Electrolyte Integrating Electromechanical Coupling and Ferroelectric Polarization Effects

The unsatisfactory lithium-ion conductivity (σ) and limited mechanical strength of polymer solid electrolytes hinder their wide applications in solid-state lithium metal batteries (SSLMBs). Here, a thin piezoelectric polymer solid electrolyte integrating electromechanical coupling and ferroelectric polarization effects has been designed and prepared to achieve long-term stable cycling of SSLMBs. The ferroelectric Bi₄Ti₃O₁₂ nanoparticle (BIT NPs) loaded poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) piezoelectric nanofibers (B-P NFs) membranes are introduced into the poly(ethylene oxide) (PEO) matrix, endowing the composite electrolyte with unique polarization and piezoelectric effects. The piezoelectric nanofiber membrane with a 3D network structure not only promotes the dissociation of lithium (Li) salts through the polarization effect but also cleverly utilizes the coupling effect of a mechanical stress-local electric field to achieve dynamic regulation of the Li electroplating process. Through the corresponding experimental tests and density functional theory calculations, the intrinsic mechanism of piezoelectric electrolytes improving σ and suppressing Li dendrites is fully revealed. The obtained piezoelectric electrolyte has achieved stable cycling of LiFePO₄ batteries over 2000 cycles and has also shown good practical application potential in flexible pouch batteries.