Compositionally Gradient Garnet/PVDF-HFP Hybrid Membranes for Li-Metal Batteries

Development of Li-ion conducting membranes capable of supporting Li-metal anode to enable high- performance Li-metal batteries (LiMB) is a priority for the Department of Energy (DOE). State-of- the-art membranes used for Li-ion batteries (LiB) are not suitable for LiMB and have a number of disadvantages including poor cycling performance, low Li-ion conductivity, and electrochemical stability with Li-metal anodes. Therefore, there is a critical need to develop high-performance, stable, and low-cost membranes for LiMB to meet the DOE goal of less than $100/kWh-1. We propose developing and demonstrating compositionally gradient inorganic–polymer garnet (LiLZO) and PVDF–HFP hybrid membrane with a LiF passivation layer, adaptable to Li-metal anodes. Our methods are easily scalable as roll-to-roll (R2R) process and will use interfacial polymerization (IP) method to create an engineered polymer composite to impart high mechanical strength that will inhibit dendrite breakthrough. Our proposal combines innovations in materials, chemistry, and processing methods to develop advanced membranes for LiMB. The Hazen–CU–NREL team will perform the following tasks: (1) Develop and demonstrate inorganic–organic precursors capable of forming cubic Al-doped LiLZO sub-micron sized particles through spray-pyrolysis and fluidized bed reaction methods; (2) Demonstrate fabrication and processing of LiF passivated LiLZO-(PVDF–HFP) hybrid membranes with Li-ion conductivity >10-4 S/cm at room temperature; and (3) Demonstrate full cells with the hybrid membranes in combination with Li-metal anode and high-voltage cathode with an initial capacity of >175 mAh/g, voltage stability in the 3.5–4.5 V range, coulombic efficiency of >95%, and a capacity retention of >90% over 250 cycles. The global LiB market is expected to be US$35 billion in 2018 and to grow at a compound annual growth rate of 17%. Expanding markets for electric vehicles, portable electronics, and grid storage is expected to further drive this market demand. Solid state LiMB is expected to dominate the future market because of its higher energy density, long-term cycling, and safety attributes. Our proposal to develop superior, low-cost, and stable membranes for LiMB specifically addresses this opportunity. This proposal supports the DOE’s mission to create a new US-led market for high performance LiMB.