Kinetics‐Controlled Degradation Reactions at Crystalline LiPON/LixCoO2 and Crystalline LiPON/Li‐Metal Interfaces

• Published in: ChemSusChem 2018-06, Vol.11 (12), p.1956-1969
• Main Authors: Leung, Kevin, Pearse, Alexander J., Talin, A. Alec, Fuller, Elliot J., Rubloff, Gary W., Modine, Normand A.
• Format: Article
• Language: English
• Subjects: ab initio calculations; Batteries; Crystal structure; Crystallinity; Electrolytes; Electronic structure; ENERGY STORAGE; interfaces; LiPON; Lithium; Mathematical models; Oxygen atoms; Reaction kinetics; Solid electrolytes; solid-solid reactions
• ISSN: 1864-5631; 1864-564X
• DOI: 10.1002/cssc.201800027

Detailed understanding of solid–solid interface structure–function relationships is critical for the improvement and wide deployment of all‐solid‐state batteries. The interfaces between lithium phosphorous oxynitride (LiPON) solid electrolyte material and lithium metal anode, and between LiPON and LixCoO2 cathode, have been reported to generate solid–electrolyte interphase (SEI)‐like products and/or disordered regions. Using electronic structure calculations and crystalline LiPON models, we predict that LiPON models with purely P−N−P backbones are kinetically inert towards lithium at room temperature. In contrast, transfer of oxygen atoms from low‐energy LixCoO2(104) surfaces to LiPON is much faster under ambient conditions. The mechanisms of the primary reaction steps, LiPON structural motifs that readily reacts with lithium metal, experimental results on amorphous LiPON to partially corroborate these predictions, and possible mitigation strategies to reduce degradations are discussed. LiPON interfaces are found to be useful case studies for highlighting the importance of kinetics‐controlled processes during battery assembly at moderate processing temperatures. Stable faces from two sides: In solid‐state batteries, lithium/lithium phosphorous oxynitride (LiPON) and LixCoO2/LiPON interfaces are predicted to be thermodynamically unstable. Experiments suggest that more substantial disorder exists at the cathode interface. Using DFT methods and LiPON models with atomic layer deposition‐like stoichiometry, we predict much faster degradation rates at LixCoO2/LiPON interfaces. LiPON structural motifs which readily react are identified.