Distinct functional Janus interfaces for dendrite-free Li1.3Al0.3Ti1.7(PO4)3-based lithium metal batteries

Abstract

The NASICON-type Li1.3Al0.3Ti1.7(PO4)3 (LATP) ceramic electrolyte shows promise for high-energy-density solid-state Li metal batteries (SSLMBs), but its incompatibility and poor interfacial contact with cathode/anode electrode still is a bottleneck problem of the commercial development. Herein, the compatible and effective solid-state electrolyte is devised by coating LATP pellet with distinct functional polymers dependent on respective interface necessities. Specifically, the poly (vinylene carbonate) (PVCA) + tetraethylene glycol dimethyl ether (TEGDME) protective layer is introduced into LATP/LiFePO4 interface via simple in-situ polymerization method, and the polyvinylidene fluoride hexafluoropropylene (PVDF-HFP) + TEGDME protective layer is coated to the LATP surface facing Li anode. We demonstrate that the PVCA layer on the cathode side is closely attached to LiFePO4 along with reduced impedance at LATP/LiFePO4 interface, the PVDF-HFP layer on the anode side protects LATP from being reduced, and TEGDME improves the electrochemical stability window (ESW) and ionic conductivity of the protective layers. Such Janus LATP electrolyte endows SSLMBs with extremely small interfacial impedance (188 Ω), excellent cycling stability (∼ 90% after 300 cycles) and dendritic-free Li anode (3000 h stable cycling) at 60 °C. This study implies that this double-protected interface modification strategy is brilliant in constructing high-performance and dendritic-free SSLMBs for future application.