An organic additive assisting with high ionic conduction and dendrite resistance of polymer electrolytes

High-performance polymer electrolytes are desirable for developing solid-state lithium (Li) metal batteries (SSLMBs) with enhanced safety and high energy density; however, their applications are hindered by low ionic conductivity and uncontrolled Li-dendrite growth. Here, a poly(vinylidene fluoride) (PVDF)-based polymer electrolyte with an organic additive, 2-acrylamido-2-methylpropane sulfonic acid (AMPS), is synthesized. First, AMPS improves the Li+ conduction by reducing the crystallinity of PVDF and immobilizing the anions. Second, AMPS assists with the formation of a LiF/Li₂S_x/Li₂SO₃/Li₃N-rich interface between Li metal and the AMPS-PVDF polymer electrolyte (AP-PE), which effectively suppresses the growth of Li dendrites. Consequently, the AP-PE with a thickness of ∼28 μm shows a high ionic conductivity of 2.2 × 10⁻⁴ S cm⁻¹ at 26 °C, corresponding to an ultrahigh areal conductance of 78.6 mS cm⁻². Meanwhile, the AP-PE shows a large Li⁺ transference number of ∼0.49, good electrochemical stability against a Li metal anode, and improved cycling stability in LiFePO₄- and LiCoO₂-based SSLMBs.