To achieve a circular economy for next-generation energy storage technologies such as solid-state batteries (SSBs), it is important to develop component materials that can be easily processed to form cells, as well as recycled and/or repurposed with ease. Yet current SSB manufacturing often requires high-temperature and high-pressure processing to create conformal interfaces between electrolyte particles and active materials in electrodes. Not only do such high-intensity conditions increase processing difficulties, but the resultant high adhesion between battery components also causes disassembly issues in SSB recycling. Now, Brett Helms and colleagues at Lawrence Berkeley National Laboratory demonstrate low-intensity thermal processing for SSB fabrication as well as a closed-loop SSB cathode recycling concept, through a supramolecular electrolyte design.
The researchers fabricate solid electrolytes by ball milling a tetrafunctional zwitterionic supramolecular building unit with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), 1,2-dimethoxyethane (DME), and poly(sulfobetaine methacrylate)s (PSBMA). The strong interaction between SO3− in the supramolecular building unit and Li+ in LiTFSI ensures the formation of the supramolecule-based network structure; DME and PSBMA adjust the SO3−−Li+ coordination chemistry and the electrolyte’s viscoelastic properties, respectively. In addition to possessing a good Li+ conductivity that is essential for SSB applications, the electrolyte mixture also displays a temperature-responsive property: it is a viscoelastic solid from −40 °C to 45 °C but a liquid above 100 °C. To fabricate their full cell, Helms and team therefore raised the temperature to 100 °C so that the liquid electrolyte infiltrated the cathode while also conforming to the anode surface, before cooling to ambient temperature until the electrolyte solidified. They also showed that their cell can be easily disassembled by immersing it in DME to dissolve the electrolyte from the cathode and that the recycled cathode can be directly used again in new cells.
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