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The garnet-type solid Li-ion conductor, Li6.4La3Zr1.4Ta0.6O12, is viewed as a promising solid-state electrolyte for the next-generation high-performance Li-ion battery because of its high ionic conductivity and stability. The previous researches, in order to avoid Li volatilization loss during solid-state reaction of sintering, mother powder with the same composition as green bodies was usually used to cover the samples, it would waste the expensive raw materials and increase the fabrication cost. In this study, a new method was proposed to prepare the Li6.4La3Zr1.4Ta0.6O12 ceramic solid-state electrolyte where the Li loss is compensated by the outside Li2CO3. Samples prepared by this method have pure garnet phase and compact micromorphology with few pores. These samples have a high Li-ion conductivity of 2.9×10−4 S/cm and a low activation energy of 0.37 eV at room temperature. The electronic conductivity is 1.08×10−8 S/cm, which can be neglected for solid-state electrolyte. [ABSTRACT FROM AUTHOR]

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/LiFePO 4 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. [ABSTRACT FROM AUTHOR]