Ionic Conductive Thermoplastic Polymer Welding Layer for Low Electrode/Solid Electrolyte Interface Resistance

The application of LAGP ceramic solid electrolytes is circumscribed by the large electrode/electrolyte interfacial resistance because of their rigidity and brittleness. Here, a highly cohesive composite polymer layer consisting of poly(vinylene carbonate)-thermoplastic polyurethanes (PVC-TPU) is coated onto both sides of the Li1.5Al0.5Ge1.5(PO4)(3) pellet to address the interfacial problems with the electrodes. The coated PVC-TPU acts as an ionic conductive welding layer to facilitate the interfacial contact of the LAGP pellet with both electrodes and decreases the interfacial resistance of the LAGP pellet against the cathode (from 1.4 x 10(6) to 3.8 x 10(3) Omega cm(2)) and the Li-metal anode (from 3.3 x 10(4) to 890 Omega cm(2)). The resulting composite solid-state electrolyte (CSSE) presents the synergistic effect of the LAGP ceramic pellet and the PVC-TPU layer in terms of electrochemical stability, ionic transport properties, and stable lithium plating/stripping cycling with a low overpotential for 1000 h. Consequently, the LiFePO4/Li solid-state batteries utilizing this CSSE deliver a high capacity retention of 95.3% after 100 cycles at room temperature with a high Coulombic efficiency exceeding 99.99% per cycle and lithium dendrite inhibition.