Kinetics-Controlled Degradation Reactions at Crystalline LiPON/Li(x)CoO(2) and Crystalline LiPON/Li-metal Interfaces

TL;DR

This study uses computational models to analyze the reaction mechanisms at LiPON interfaces with lithium metal and LiCoO2, revealing kinetic factors that influence degradation and suggesting strategies to improve solid-state battery stability.

Contribution

It provides the first detailed kinetic analysis of LiPON interfaces, highlighting the role of reaction pathways and proposing mitigation strategies for interface degradation.

Findings

LiPON with P-N-P backbones is inert to lithium at room temperature.

Oxygen transfer from LiCoO2 to LiPON occurs rapidly under ambient conditions.

Kinetics-controlled processes are crucial during battery assembly.

Abstract

Detailed understanding of solid-solid interface structure-function relations 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, between LiPON and Li(x)CoO(2) cathode surfaces, have been reported to generate solid electrolyte interphase ("SEI")-like products and/or disordered regions. Using electronic structure calculations and crystalline LiPON models with atomic-layer-deposition-like stoichiometry, we predict 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 Li(x)CoO(2) (104) surfaces to LiPON is much faster under ambient conditions. The mechanisms of the primary reaction steps, LiPON motifs that readily react 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.