Cold Sintering Enables the Reprocessing of LLZO‐Based Composites

Abstract

All‐solid‐state batteries have the potential for enhanced safety and capacity over conventional lithium ion batteries, and are anticipated to dominate the energy storage industry. As such, strategies to enable recycling of the individual components are crucial to minimize waste and prevent health and environmental harm. Here, we use cold sintering to reprocess solid‐state composite electrolytes, specifically Mg and Sr doped Li7La3Zr2O12 with polypropylene carbonate (PPC) and lithium perchlorate (LLZO–PPC–LiClO4). The low sintering temperature allows co‐sintering of ceramics, polymers and lithium salts, leading to re‐densification of the composite structures with reprocessing. Reprocessed LLZO–PPC–LiClO4 exhibits densified microstructures with ionic conductivities exceeding 10−4 S/cm at room temperature after 5 recycling cycles. All‐solid‐state lithium batteries fabricated with reprocessed electrolytes exhibit a high discharge capacity of 168 mA h g−1 at 0.1 C, and retention of performance at 0.2 C for over 100 cycles. Life cycle assessment (LCA) suggests that the recycled electrolyte outperforms the pristine electrolyte process in all environmental impact categories, highlighting cold sintering is a promising technology for recycling electrolytes.

Interfacial Layers to Enable Recyclability of All-Solid-State Lithium Batteries

“…All solid-state batteries that incorporate lithium iron phosphate (LFP) cathodes, Li 7–2 x + y Mg x La 3– y Sr y Zr 2 O 12 –polypropylene carbonate–lithium perchlorate solid composite electrolytes (LLZO-SE), and Li metal or lithium titanate (LTO) anodes are chosen to demonstrate recyclability. The composite electrolyte, LLZO-SE, was fabricated using the cold sintering process, which enables densification and reprocessing of composites comprised of ceramics, polymers, and salts at a low temperature with the addition of applied pressure and transient solvents. , …”

“…The failure of the full cell is dictated by evolution and degradation at interfaces, while the majority of LLZO-SE remain intact . Therefore, it is conceivable that spent battery components could be recycled without necessitating complex processes once localized interfaces are eliminated …”

“…Recovered components were then reused and incorporated into a new battery, as illustrated in Figure b. Dimethylformamide (DMF), an aprotic solvent, which is compatible with LLZO within a short duration, was used to dissolve the polymer-salt layer where undesired side reactions and secondary phases occur. In addition, DMF may react with Li metal, enabling the effective removal of a significant portion of lithium dendrites exposed to the surface of spent LLZO-SE, as depicted in Figure S11.…”

“…Recovered LLZO was reprocessed by cold-sintering, which in our previous work demonstrates the ability to reintegrate LLZO with polymer and lithium salts to form a dense bulk phase . To evaluate the electrochemical performance and stability of recovered components, fully recycled all-solid-state batteries were fabricated by integrating recovered components (fully recycled LFP/i/LLZO-SE/i/Li is incorporated with recovered LFP and recovered LLZO-SE; fully recycled LFP/i/LLZO-SE/i/LTO is incorporated with recovered LFP, recovered LLZO-SE, and recovered LTO).…”