(Invited) The ARPA-E Ionics Program: Separators to Enable the Cycling of Lithium Metal

Tuesday, 3 October 2017: 13:40
National Harbor 7 (Gaylord National Resort and Convention Center)
P. S. Albertus, S. J. Babinec (Advanced Research Projects Agency - Energy), and S. J. Litzelman (Booz Allen Hamilton)
ARPA-E has funded five themed Programs and spent >$200 million on advancing energy storage technology since its inception. Unfortunately, the ultimate impacts of some of the technical advances made within ARPA-E efforts, as well as advances developed outside of ARPA-E, are hindered by constraints arising from separator cost and performance limitations. In response to this situation, ARPA-E launched the IONICS (Integration and Optimization of Novel Ion-Conducing Solids) program in 2016. The 16 teams in the program are focused on developing breakthrough separators that would be broadly enabling in different areas of electrochemical technology, and also amenable to cost effective manufacturing. The projects include both polymer and inorganic ion conducting separators that enable electrode chemistries that have been previously unsuccessful in practical devices. Project teams are focused on overcoming property tradeoffs to achieve a full set of required attributes, including conductivity, selectivity, stability, mechanical properties, manufacturability, cost, and others. This contrasts with a common approach of optimizing a single variable at the expense of others. The IONICS focus is on solids rather than liquids, due to inherent advantages in selectivity and mechanical properties offered by solids.

The IONICS program has three areas: (1) Li+ conductors that enable the cycling of the lithium metal electrode at 25°C and at conditions required for high-energy cells, (2) highly selective polymer separators for flow batteries, and (3) anion-conducting polymer separators for use in alkaline fuel cells and electrolyzers. This talk will focus on area (1), where the cycling of lithium metal at conditions relevant to high-energy cells still has not been shown, despite decades of research. Highlights of the talk will include: (1) presentation of a new figure depicting state-of-the-art cycling of lithium metal in both industry and research institutions, which reveals tradeoffs among the critical cycling metrics relevant to high-energy cells (i.e., cumulative capacity throughput, current density, and per-cycle areal capacity), (2) suggestion of test protocols that ensure proper interpretation of cycling data, and especially that electronic and ionic currents are distinguished, (3) the economics of film manufacturing, and the pathways to achieve the aggressive IONICS cost targets (<10 $/m2) required for widespread adoption for transportation or grid applications, and (4) the technical approaches being pursued in the program, with a focus on ceramics.