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1. Decomposition of Trace Li 2 CO 3 During Charging Leads to Cathode Interface Degradation with the Solid Electrolyte LLZO

   https://doi.org/10.1002/adfm.202103716  

   Delluva, Alexander A. ; Kulberg‐Savercool, Jonas ; Holewinski, Adam ( July 2021 , Advanced Functional Materials)

   A major challenge for lithium‐containing electrochemical systems is the formation of lithium carbonates. Solid‐state electrolytes circumvent the use of organic liquids that can generate these species, but they are still susceptible to Li₂CO₃formation from exposure to water vapor and carbon dioxide. It is reported here that trace quantities of Li₂CO₃, which are re‐formed following standard mitigation and handling procedures, can decompose at high charging potentials and degrade the electrolyte–cathode interface. Operando electrochemical mass spectrometry (EC–MS) is employed to monitor the outgassing of solid‐state batteries containing the garnet electrolyte Li₇La₃Zr₂O₁₂(LLZO) and using appropriate controls CO₂and O₂are identified to emanate from the electrolyte–cathode interface at charging potentials > 3.8 V (vs Li/Li⁺). The gas evolution is correlated with a large increase in cathode interfacial resistance observed by potential‐resolved impedance spectroscopy. This is the first evidence of electrochemical decomposition of interfacial Li₂CO₃in garnet cells and suggests a need to report “time‐to‐assembly” for cell preparation methods.

    

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2. Computation‐Guided Design of LiTaSiO 5 , a New Lithium Ionic Conductor with Sphene Structure

   https://doi.org/10.1002/aenm.201803821  

   Xiong, Shan ; He, Xingfeng ; Han, Aijie ; Liu, Zhantao ; Ren, Zhensong ; McElhenny, Brian ; Nolan, Adelaide M. ; Chen, Shuo ; Mo, Yifei ; Chen, Hailong ( April 2019 , Advanced Energy Materials)

   The development of all‐solid‐state Li‐ion batteries requires solid electrolyte materials with many desired properties, such as ionic conductivity, chemical and electrochemical stability, and mechanical durability. Computation‐guided materials design techniques are advantageous in designing and identifying new solid electrolytes that can simultaneously meet these requirements. In this joint computational and experimental study, a new family of fast lithium ion conductors, namely, LiTaSiO₅with sphene structure, are successfully identified, synthesized, and demonstrated using a novel computational design strategy. First‐principles computation predicts that Zr‐doped LiTaSiO₅sphene materials have fast Li diffusion, good phase stability, and poor electronic conductivity, which are ideal for solid electrolytes. Experiments confirm that Zr‐doped LiTaSiO₅sphene structure indeed exhibits encouraging ionic conductivity. The lithium diffusion mechanisms in this material are also investigated, indicating the sphene materials are 3D conductors with facile 1D diffusion along the [101] direction and additional cross‐channel migration. This study demonstrates a novel design strategy of activating fast Li ionic diffusion in lithium sphenes, a new materials family of superionic conductors.

    

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3. Lithium Chlorides and Bromides as Promising Solid‐State Chemistries for Fast Ion Conductors with Good Electrochemical Stability

   https://doi.org/10.1002/ange.201901938  

   Wang, Shuo ; Bai, Qiang ; Nolan, Adelaide M. ; Liu, Yunsheng ; Gong, Sheng ; Sun, Qiang ; Mo, Yifei ( May 2019 , Angewandte Chemie)

   Enabling all‐solid‐state Li‐ion batteries requires solid electrolytes with high Li ionic conductivity and good electrochemical stability. Following recent experimental reports of Li₃YCl₆and Li₃YBr₆as promising new solid electrolytes, we used first principles computation to investigate the Li‐ion diffusion, electrochemical stability, and interface stability of chloride and bromide materials and elucidated the origin of their high ionic conductivities and good electrochemical stabilities. Chloride and bromide chemistries intrinsically exhibit low migration energy barriers, wide electrochemical windows, and are not constrained to previous design principles for sulfide and oxide Li‐ion conductors, allowing for much greater freedom in structure, chemistry, composition, and Li sublattice for developing fast Li‐ion conductors. Our study highlights chloride and bromide chemistries as a promising new research direction for solid electrolytes with high ionic conductivity and good stability.

    

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4. Lithium Chlorides and Bromides as Promising Solid‐State Chemistries for Fast Ion Conductors with Good Electrochemical Stability

   https://doi.org/10.1002/anie.201901938  

   Wang, Shuo ; Bai, Qiang ; Nolan, Adelaide M. ; Liu, Yunsheng ; Gong, Sheng ; Sun, Qiang ; Mo, Yifei ( May 2019 , Angewandte Chemie International Edition)

   Enabling all‐solid‐state Li‐ion batteries requires solid electrolytes with high Li ionic conductivity and good electrochemical stability. Following recent experimental reports of Li₃YCl₆and Li₃YBr₆as promising new solid electrolytes, we used first principles computation to investigate the Li‐ion diffusion, electrochemical stability, and interface stability of chloride and bromide materials and elucidated the origin of their high ionic conductivities and good electrochemical stabilities. Chloride and bromide chemistries intrinsically exhibit low migration energy barriers, wide electrochemical windows, and are not constrained to previous design principles for sulfide and oxide Li‐ion conductors, allowing for much greater freedom in structure, chemistry, composition, and Li sublattice for developing fast Li‐ion conductors. Our study highlights chloride and bromide chemistries as a promising new research direction for solid electrolytes with high ionic conductivity and good stability.

    

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5. Importance of multimodal characterization and influence of residual Li 2 S impurity in amorphous Li 3 PS 4 inorganic electrolytes

   https://doi.org/10.1039/d1ta02754a  

   Mirmira, Priyadarshini ; Zheng, Jin ; Ma, Peiyuan ; Amanchukwu, Chibueze V. ( September 2021 , Journal of Materials Chemistry A)

   Amorphous Li 3 PS 4 (LPS) solid-state electrolytes are promising for energy-dense lithium metal batteries. LPS glass, synthesized from a 3 : 1 mol ratio of Li 2 S and P 2 S 5 , has high ionic conductivity and can be synthesized by ball milling or solution processing. Ball milling has been attractive because it provides the easiest route to access amorphous LPS with a conductivity of 3.5 × 10 −4 S cm −1 (20 °C). However, achieving the complete reaction of precursors via ball milling can be difficult, and most literature reports use X-ray diffraction (XRD) or Raman spectroscopy to confirm sample purity, both of which have limitations. Furthermore, the effect of residual precursors on ionic conductivity and lithium metal cycling is unknown. In this work, we illustrate the importance of multimodal characterization to determine LPS phase and chemical purity. To determine the residual Li 2 S content in LPS, we show that (1) XRD and 31 P solid state nuclear magnetic resonance (ssNMR) are insufficient and (2) Raman loses sensitivity at concentrations below 12 mol% Li 2 S. Most importantly, we show that 7 Li ssNMR is highly sensitive. Using 7 Li ssNMR, we investigate the effect of ball milling parameters and develop a robust and highly reproducible procedure for pure LPS synthesis. We find that as the residual Li 2 S precursor content increases, LPS conductivity decreases and lithium metal batteries exhibit higher overpotentials and poor cycle life. Our work reveals the importance of multimodal characterization techniques for amorphous solid-state electrolyte characterization and will enable better synthetic strategies for highly conductive electrolytes for efficient energy-dense solid-state lithium metal batteries. 

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