Co-spray printing of LiFePO4 and PEO-Li1.5Al0.5Ge1.5(PO4)3 hybrid electrodes for all-solid-state Li-ion battery applications

Abstract

LiFePO₄ (LFP) electrodes for Li-ion battery applications were prepared by spray printing. By optimising the substrate temperature, solvent ratio and electrode material concentration, a honeycomb pore structure was produced over a large area electrode. In a liquid electrolyte, the honeycomb structured LFP electrode showed improved cycling performance at high C-rate due to shortened pore pathways and improved Li mobility. In a solid-state configuration, a PEO(LITFSI)-Li_1.5Al_0.5Ge_1.5(PO₄)₃ (PEO-LAGP) based solid electrolyte was either spray printed on top of the LFP and/or interleaved within sub-layers of the LFP electrode, for both non-honeycomb and honeycomb pore morphologies. Cross-sectional scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDS) mapping combined with electrochemical impedance spectroscopy (EIS) testing showed that the honeycomb electrode with inter-leaved sub-layers of solid-state electrolyte improved interfacial contact between the electrode and electrolyte. When coupled with Li foil in a solid-state Li ion battery configuration, the honeycomb interleaved electrode also showed the best performance in terms of capacity and cycle stability at all testing temperatures, showing capability that exceeded previously reported performance.