(Invited) Cation Transport across Interfaces in Solid-State Li Batteries

Abstract

Despite all the progress made in the development of solid-state Li batteries (SSLB), interfaces arise as the main bottleneck impeding their practical realization. In particular, the interfacial regions between the individual components of a cell comprising those formed between ceramic electrolytes and Li metal and ceramic high-voltage cathodes as well as interfaces between ceramic particles and the polymeric matrix in composite electrolytes are identified to be challenging.1 For example, current constriction that arise from inhomogeneous electrical field distributions at the Li metal | solid-electrolyte interface leads to the formation of dendritic structures at high current rates.2 Forming a good interface between the solid electrolyte and cathode material requires high temperature treatments that leads to the formation of an interphase layer that impedes the ion transport across the interface.3 To unroll the beneficial properties of a composite membrane both components, ceramic particles and polymer matrix, must contribute to the long-range ion transport. Due to the high interface resistance between the components, ionic transport does not take place in ceramic particles; hence, the ceramic has only the role of a passive filler rather than improving the membrane properties.4 Inspired by these challenges, mitigation strategies to overcome these bottlenecks will be presented. For example, strategies that (i) enable cycling at very high rates up to 6 mA cm-2 using different surface treatments and current waveforms, (ii) change the mechanical properties at the interface to potentially avoid crack formation that ultimately leads to short circuits, and (iii) lower the interfacial resistance between ceramics and polymers by orders of magnitude.5 Moreover, we show that Co interdiffusion not only lead to the formation of resistive interphases, but is also detrimental for the electrical transport properties and electrochemical stability of solid electrolytes. References (1) A. Banerjee, et al. Chem. Rev. 2020, 120, 6878–6933.(2) J. Kasemchainan, et al. Nat. Mater. 2019, 18, 1105-1111.(3) K. Park, et al. Chem. Mater. 2016, 28, 8051–8059.(4) J. Zheng, et al. Angew. Chemie Int. Ed. 2016, 55, 12538–12542.(5) E. Kuhnert, et al. Cell Reports Phys. Sci. 2020, 1, 100214. Acknowledgement Financial support by the Austrian Federal Ministry for Digital and Economic Affairs, the National Foundation for Research, Technology and Development and the Christian Doppler Research Association (Christian Doppler Laboratory for Solid-State Batteries) and the Austrian Science Fund (FWF) (project no. P25702) is gratefully acknowledged.