(Invited) Mechanism of Conduction in the Novel Nano-Solid Composite Electrolytes with High Li-Ion Conductivity
Authors: Barde Fanny , Chen Xubin , Gandrud Knut Bjarne , Put Brecht , Sagara Akihiko , Yabe Hiroki , Murata Mitsuhiro , Arase Hidekazu , Kaneko Yukihiro , Steele Julian , Roeffaers Maarten , Mees Maarten J. , Vereecken Philippe M. 
Published: December 2020

To increase the energy densities of batteries beyond 800Wh/L determined by the currently available cathode and anode materials used in combination with liquid type electrolytes, next generations solid-state electrolytes are investigated. Combined with the Li metal anode, they should enable safe (i.e. free of dendrites), long life (i.e. low to no consumption of Li metal during cycling) and high-performance solid-state batteries reaching energy density above 1000Wh/L.
Over the last years, an increasing number of studies have been dedicated to the research and development of various classes of solid-state electrolytes. New materials have emerged enriching the diversity of the type of solid-state battery concepts. Indeed, besides the classical sulfidic, oxidic and polymer type solid-state battery systems, several concepts based on hybridization of materials and technologies have been proposed [1, 2]. While obviously the ionic conductivity of the Li-ion conductor is a pre-requisite to enable all solid-state battery, other criteria such as stability and compatibility of electrode materials and their integration in the cell are also needed.
Our group recently reported a novel class of nano-composite electrolytes (nano-SCEs) for which ion conductivity values are obtained higher than those seen in conventional liquid electrolytes. These nano-SCEs constitute a nano-porous SiO2 monolith that encloses an adsorbed ionic liquid electrolyte. Different from to so-called ionogel electrolytes – which follow a similar approach in that they confine an ILE in a porous oxide matrix [3] – our electrolytes feature the unique property that the ionic conductivity of the composite ( ) is higher than to that of the ionic liquid electrolyte ( ) [4]. The high ion conductivity and enhancement factor were established by engineering the surface chemistry in the nano-SCE.
In this presentation, novel solid-state nano-composite electrolytes are reported having the unique feature of enhanced ion conductivity. Along the pore walls of the oxide matrix, the ionic liquid electrolyte is organizing itself such that “highway” conduction paths are created for fast Li-ion transport. The exact nature of these highway conduction paths strongly depends on the chemistry of the ionic liquid electrolyte.

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[1] Z. Zhang, Y. Shao, B. V. Losch, Y. Hu, H. Li, J. Janek, C. Nan, L. Nazar, J. Maier, M. Armand, L. Chen, Energy Environ. Sci. 2018, DOI: 10.1039/C8EE01053F
[2] M. Keller, A. Verzi, S. Passerini, DOI: 10.1016.j.powsour.2018.04.0999
[3] N. Chen, H. Zhang, L. Li, R. Chen and S. Guo, Advanced Energy Materials, vol. 8, p. 1702675, 2018.
[4] X. Chen, B. Put, A. Sagara, K. B. Gandrud, M. Murata, J. Steele, H. Yabe, T. Hantschel, M. Roeffaers, M. Tomiyama, Y. Kaneko, M. Shimada, M. J. Mees, P. M. Vereecken, Sci
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Adv
. 2020; 6: eaav3400