More Like this

1. Observation of Elemental Inhomogeneity and Its Impact on Ionic Conductivity in Li‐Conducting Garnets Prepared with Different Synthesis Methods

   https://doi.org/10.1002/aesr.202000109  

   Weller, J. Mark ; Dopilka, Andrew ; Chan, Candace K. ( March 2021 , Advanced Energy and Sustainability Research)

   Tantalum‐doped lithium lanthanum zirconate garnet (Li_7−xLa₃Zr_2−xTa_xO₁₂[LLZTO]) has received interest as a solid electrolyte for solid‐state lithium batteries due to its good electrochemical properties and ionic conductivity. However, the source of discrepancies for reported values of ionic conductivity in nominally or nearly equivalent compositions of LLZTO is not completely clear. Herein, synthesis‐related factors that may contribute to the differences in performance of garnet electrolytes are systematically characterized. The conductivity of samples with composition Li_6.4La₃Zr_1.4Ta_0.6O₁₂prepared by various methods including solid‐state reaction (SSR), combustion, and molten salt synthesis is compared. Varying levels of elemental inhomogeneity, comprising a variation in Ta and Zr content on the level of individual LLZTO particles, are identified. The elemental inhomogeneity is found to be largely preserved even after high‐temperature sintering and correlated with reduced ionic conductivity. It is shown that the various synthesis and processing‐related variables in each of the preparation methods play a role in these compositional variations, and that even LLZTO synthesized via conventional, high‐temperature SSR can exhibit substantial variability in local composition. However, by improving reagent mixing and using LLZTO powder with low agglomeration and small particle size distribution, the compositional uniformity, and hence, ionic conductivity, of sintered garnet electrolytes can be improved.

    

   more » « less
2. Time‐Temperature‐Transformation (TTT) Diagram of Battery‐Grade Li‐Garnet Electrolytes for Low‐Temperature Sustainable Synthesis

   https://doi.org/10.1002/ange.202304581  

   Zhu, Yuntong ; Chon, Michael ; Thompson, Carl V. ; Rupp, Jennifer L. M. ( October 2023 , Angewandte Chemie)

   Efficient and affordable synthesis of Li⁺functional ceramics is crucial for the scalable production of solid electrolytes for batteries. Li‐garnet Li₇La₃Zr₂O_12−d(LLZO), especially its cubic phase (cLLZO), attracts attention due to its high Li⁺conductivity and wide electrochemical stability window. However, high sintering temperatures raise concerns about the cathode interface stability, production costs, and energy consumption for scalable manufacture. We show an alternative “sinter‐free” route to stabilize cLLZO as films at half of its sinter temperature. Specifically, we establish a time‐temperature‐transformation (TTT) diagram which captures the amorphous‐to‐crystalline LLZO transformation based on crystallization enthalpy analysis and confirm stabilization of thin‐film cLLZO at record low temperatures of 500 °C. Our findings pave the way for low‐temperature processing via TTT diagrams, which can be used for battery cell design targeting reduced carbon footprints in manufacturing.

    

   more » « less
3. Time‐Temperature‐Transformation (TTT) Diagram of Battery‐Grade Li‐Garnet Electrolytes for Low‐Temperature Sustainable Synthesis

   https://doi.org/10.1002/anie.202304581  

   Zhu, Yuntong ; Chon, Michael ; Thompson, Carl V. ; Rupp, Jennifer L. M. ( October 2023 , Angewandte Chemie International Edition)

   Efficient and affordable synthesis of Li⁺functional ceramics is crucial for the scalable production of solid electrolytes for batteries. Li‐garnet Li₇La₃Zr₂O_12−d(LLZO), especially its cubic phase (cLLZO), attracts attention due to its high Li⁺conductivity and wide electrochemical stability window. However, high sintering temperatures raise concerns about the cathode interface stability, production costs, and energy consumption for scalable manufacture. We show an alternative “sinter‐free” route to stabilize cLLZO as films at half of its sinter temperature. Specifically, we establish a time‐temperature‐transformation (TTT) diagram which captures the amorphous‐to‐crystalline LLZO transformation based on crystallization enthalpy analysis and confirm stabilization of thin‐film cLLZO at record low temperatures of 500 °C. Our findings pave the way for low‐temperature processing via TTT diagrams, which can be used for battery cell design targeting reduced carbon footprints in manufacturing.

    

   more » « less
4. Cold Sintering Enables the Reprocessing of LLZO‐Based Composites

   https://doi.org/10.1002/cssc.202301920  

   Lan, Yi‐Chen ; Ghasemi, Masoud ; Hall, Shelby_L ; Fair, Ryan_A ; Maranas, Christina ; Shi, Rui ; Gomez, Enrique_D ( March 2024 , ChemSusChem)

   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 Li₇La₃Zr₂O₁₂with 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−LiClO₄exhibits 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⁻¹at 0.1 C, and retention of performance at 0.2 C for over 100 cycles. Life cycle assessment (LCA) suggests that recycled electrolytes outperforms the pristine electrolyte process in all environmental impact categories, highlighting cold sintering as a promising technology for recycling electrolytes.

    

   more » « less
5. Uncovering the Network Modifier for Highly Disordered Amorphous Li‐Garnet Glass‐Ceramics

   https://doi.org/10.1002/adma.202302438  

   Zhu, Yuntong ; Kennedy, Ellis_R ; Yasar, Bengisu ; Paik, Haemin ; Zhang, Yaqian ; Hood, Zachary_D ; Scott, Mary ; Rupp, Jennifer_LM ( February 2024 , Advanced Materials)

   Highly disordered amorphous Li₇La₃Zr₂O₁₂(aLLZO) is a promising class of electrolyte separators and protective layers for hybrid or all‐solid‐state batteries due to its grain‐boundary‐free nature and wide electrochemical stability window. Unlike low‐entropy ionic glasses such as Li_xPO_yN_z(LiPON), these medium‐entropy non‐Zachariasen aLLZO phases offer a higher number of stable structure arrangements over a wide range of tunable synthesis temperatures, providing the potential to tune the LBU‐Li⁺transport relation. It is revealed that lanthanum is the active “network modifier” for this new class of highly disordered Li⁺conductors, whereas zirconium and lithium serve as “network formers”. Specifically, within the solubility limit of La in aLLZO, increasing the La concentration can result in longer bond distances between the first nearest neighbors of Zr─O and La─O within the same local building unit (LBU) and the second nearest neighbors of Zr─La across two adjacent network‐former and network‐modifier LBUs, suggesting a more disordered medium‐ and long‐range order structure in LLZO. These findings open new avenues for future designs of amorphous Li⁺electrolytes and the selection of network‐modifier dopants. Moreover, the wide yet relatively low synthesis temperatures of these glass‐ceramics make them attractive candidates for low‐cost and more sustainable hybrid‐ or all‐solid‐state batteries for energy storage.

    

   more » « less