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.
The interface between cathode and electrolyte is a significant source of large interfacial resistance in solid‐state batteries (SSBs). Spark plasma sintering (SPS) allows densifying electrolyte and electrodes in one step, which can improve the interfacial contact in SSBs and significantly shorten the processing time. In this work, we proposed a two‐step joining process to prepare cathode (LiCoO2, LCO)/electrolyte (Li0.33La0.57TiO3, LLTO) half cells via SPS. Interdiffusion between Ti4+/Co3+was observed at the interface by SEM/STEM, resulting in the formation of the Li−Ti−La−Co−O and Li−Ti−Co−O phases in LLTO and the Li−Co−Ti−O phase in LCO. Computational modeling was performed to verify that the Li−Ti−Co−O phase has a LiTi2O4host lattice. In a study of interfacial electrical properties, the resistance of this interdiffusion layer was found to be 105 Ω, which is 40 times higher than the resistance of the individual LLTO phase. The formation of an interdiffusion layer is identified as the origin of the high interface resistance in the LLTO/LCO half‐cell.
more » « less- Award ID(s):
- 1734763
- PAR ID:
- 10229077
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- ChemElectroChem
- Volume:
- 8
- Issue:
- 10
- ISSN:
- 2196-0216
- Page Range / eLocation ID:
- p. 1847-1857
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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