Suppressing concentration polarization in lithium battery composite polymer electrolytes via piezo-assisted electromechanical coupling effect.

Abstract

The inherent limitation of Li⁺ transport and resulting severe concentration polarization in solid-state electrolytes have hindered the practical application of lithium metal batteries. Addressing this challenge, here we create a piezoelectric polymeric composite electrolyte based on poly(vinylidene fluoride) blended with 0.5Ba(Zr_0.2Ti_0.8)O₃-0.5(Ba_0.7Ca_0.3)TiO₃, which exploits volume fluctuations of lithium metal negative electrodes during cycling to activate a piezo-assisted electromechanical coupling effect. The resulting gradient piezo-field within the prepared electrolyte selectively accelerates Li⁺ while impedes anions movement, thereby effectively suppressing concentration polarization fundamentally. Consequently, the prepared electrolytes exhibit relatively low concentration polarization, enabling a high critical current density of 3.7 mA cm^-2, stable Li plating/stripping even at high current density of 2 mA cm^-2, and prolonged cycling stability of Li | |Ni_0.8Co_0.1Mn_0.1O₂ full cell over 2600 times at the specific current of 900 mA g^-1 within a potential window of 2.8 to 4.5 V. This work proposes a mechanical-electrochemical conversion strategy by constructing a piezoelectric electrolyte that actively utilizes the unavoidable volume fluctuation of lithium metal to minimize Li⁺ concentration gradient, offering a promising pathway towards high-performance lithium metal batteries.