High rate lithium slurry flow batteries enabled by an ionic exchange Nafion composite membrane incorporated with LLZTO fillers

Lithium slurry flow batteries (LSFBs) possessing decoupled energy/power density feature and high energy density are considered as the most promising next-generation energy storage devices. However, their cycling stability is depressed by the high permeability of active components through porous separator and low conductivity of lithium ion in non-porous membrane. Herein, a novel Nafion/PVDF/LLZTO ion exchange membrane (IEM) with high ion conductivity and mechanical properties is proposed. As-optimized IEM possesses an ionic conductivity of 0.29 mS cm−1. Both experimental and density functional theory (DFT) calculation studies suggest that the complementary effect between inorganic ceramic fillers LLZTO and polymer materials favor the generation of new Li+ migration expressway and dehydrofluorination. The H-bonding interactions can successfully address the poor mechanical strength issues. Moreover, the sandwich-like structure by commercialized PE buffer layer will be beneficial to the improved stability and can effectively suppress the swelling effect of membrane in organic electrolyte. Consequently, LFP//LTO slurry cells containing PE/NPL3/PE membrane exhibit extraordinary performance under 0.3 C. Assembled slurry pouch cells could be cycled stably for more than 270 h at room temperature. This ingenious strategy of introducing inorganic ceramic fillers into the composite membrane will pave a novel promising direction to the development of LSFBs.