4.8-V all-solid-state garnet-based lithium-metal batteries with stable interface

Summary Garnet-type solid electrolytes with high chemical and electrochemical stabilities are uniquely suitable for high-voltage operation but suffer from poor wettability with electrodes, resulting in large interfacial impedance. Here, we design a highly conductive and interface-friendly garnet-based composite solid electrolyte (CSE) comprising a cubic Li_6.1Al_0.3La₃Zr₂O₁₂ porous framework and polyvinylidene difluoride (PVDF) with a three-dimensional continuous structure. Formation of La-N and La-F bonds between ceramic and polymer moieties promotes the dissociation of Li salt and thus leads to highly efficient transport. These coupling effects contribute to a high ionic conductivity (0.437 mS cm⁻¹) and Li transfer number t⁺ (0.72) at 25°C, while simultaneously enable high electrode/electrolyte interfacial stability. The high-voltage robustness of the developed CSE is demonstrated using TiO₂-coated LiNi_0.6Co_0.2Mn_0.2O₂/ceramic-based CSE/Li full solid-state batteries, which are stably cycled over 200 times from 3 to 4.8 V with no signs of interfacial instabilities at nanoscale.