Dual interface layers for solid-state Li metal battery with low interfacial resistance and small polarization based on garnet electrolyte

Abstract Garnet-type electrolyte gains extensive attention because of high Li-ion conductivity and excellent stability with Li anode. However, the two major bottlenecks hindering its practical application are high interfacial resistance and fast Li dendrite growth in solid-state Li metal battery. Here we prepare highly dense garnet electrolyte by hot-press sintering and introduce dual interface layers consisting of polydopamine (PDA) film and poly(ethylene oxide)-based composite electrolyte layer at the electrode/garnet interface. The adhesive PDA film helps to realize tight interface bonding. The composite electrolyte layer improves the garnet/electrode interfacial contact and promotes Li+ transport across the interface. The Li/garnet interfacial resistance decreases to 171 Ω cm2. Correspondingly, the symmetric cell exhibits flat voltage plateau and small polarization voltage for over 500 h without Li dendrite formation, indicating the stable Li/garnet interface during cycling. The solid-state Li/garnet/LiFePO4 battery exhibits high initial capacity (161.4 mA h g−1) with a high coulombic efficiency of 99.6% and small overpotential of 0.04 V at 80 °C. This work provides a feasible option to address the interfacial challenge and promotes the development of high performance solid-state Li metal battery.