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

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 Li6.1Al0.3La3Zr2O12 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 LiNi0.6Co0.2Mn0.2O2/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. [Display omitted] •Porous CSE (93 wt % garnet/7 wt % PVDF) structure•In situ formed N- and F-rich bonding stabilizes cathode/CSE interface at high voltage•NCM622/CSE/Li solid-state batteries stably cycle over 200 times from 3 to 4.8 V Wang et al. develop highly conductive garnet-based composite solid electrolyte (CSE) of porous cubic Li6.1Al0.3La3Zr2O12 (93%) and polyvinylidene difluoride, exhibiting fast Li+ migration and excellent interfacial stability. All-solid-state TiO2-coated LiNi0.6Co0.2Mn0.2O2/ceramic-based CSE/Li devices stably cycle from 3 to 4.8 V over 200 times, delivering high energy density and ultra-stable interface.