All-solid-state batteries

Solid-state batteries promise significant gains in energy density and safety by replacing the liquid electrolyte in traditional lithium-ion and sodium-ion batteries with a solid electrolyte. Recent advances in solid electrolyte materials offer hope that high-capacity anodes such as lithium metal and silicon, which are difficult to stabilize in liquid electrolytes due to dendrite formation, parasitic side reactions, and volume changes, may become viable. If these challenges can be mitigated, solid-state batteries could deliver much higher energy densities while improving safety. This makes solid-state batteries particularly promis-ing for applications like electric vehicles and aviation, where long range, low weight, and high operational safety are essential. However, the technology still faces persistent challenges, including limited ionic conductivity, interfacial stability, and high manufacturing costs. 
Our research focuses on advancing solid-state batteries through the development and integration of hydroborate-based solid electrolytes (a) [1-2] and polymerized-ionic-liquid-based solid electrolytes [3-4]. These materials combine high ionic conductivity, compatibility with alkali metal anodes, and soft mechanical properties that promote stable interfacial contact. We investigate their performance in combination with state-of-the-art 4 V-class NMC811 cathodes (b,c) and high-capacity silicon composite anodes at industry-relevant areal capacities. By tailoring electrolyte composition and electrode structure, we achieve high energy density and cycling stability under practical conditions, including room temperature and moderate stack pressures. Our work highlights the unique self-passivating behavior of hydroborates and high stability of polymerized-ion-liquid-based electrolytes and provides insight into their interfacial chemistry and degradation mechanisms, paving the way for a competitive solid-state battery technology.

 

All-solid-state+batteries_Bild_16.10.2025.png

(a) Atomic structure of Li3(CB11H12)2(CB9H10) hydroborate electrolyte. CB11H12- and CB9H10- anions are form-ing a face centered cubic lattice. Hydrogen atoms are not shown here. (b) Scanning electron microscopy im-age of NMC811 cathode particles and vapor-grown carbon fibers embedded in the Li3(CB11H12)2(CB9H10) solid electrolyte (false-colored green). (c) Toward high-voltage, high-capacity all-solid-state-batteries, retracing the evolution of hydroborate solid-state batteries in our lab [5-8].

Selected publications

[1] L. Duchêne, A. Remhof, H. Hagemann, C. Battaglia, Status and prospects of hydroborate electrolytes for solid-state batteries, Energy Storage Materials, 2020, 25, 782, https://doi.org/10.1016/j.ensm.2019.08.032
[2] R. Asakura, A. Remhof, C. Battaglia, Hydroborate-based solid electrolytes for all-solid-state batteries, in Solid State Batteries Volume 1: Emerging Materials and Applications, ACS Symposium Series, 2022, 1413, http://doi.org/10.1021/bk-2022-1413.ch014
[3] C. Fu, G. Homann, R. Grissa, D. Rentsch, W. Zhao, T. Gouveia, A. Falgayrat, R. Lin. S. Fantini, C. Battaglia, A polymerized-ionic-liquid-based polymer electrolyte with high oxidative stability for 4 and 5 V class solid-state lithium metal batteries, Advanced Energy Materials, 2022, 2200412, https://doi.org/10.1002/aenm.202200412
[4] G. Homann, Q. Wang, S. Liu, A. Devincenti, P. Karanth, M. Weijers, F. M. Mulder, M. Piesins, T. Gouveia, A. Ladam, S. Fantini, C. Battaglia, A quasi-solid-state polymer lithium–metal battery with minimal excess lithium, ultrathin separator, and high-mass loading NMC811 cathode, ACS Applied Energy Materials, 2024, 7, 10037, https://doi.org/10.1021/acsaem.4c02099
[5] L. Duchêne, R.-S. Kühnel, E. Stilp, E. Cuervo Reyes, A. Remhof, H. Hagemann, C. Battaglia, A stable 3 V all-solid-state sodium-ion battery based on a closo-borate electrolyte, Energy Environmental Science, 2017, 10, 2609, https://doi.org/10.1039/c7ee02420g
[6] R. Asakura, D. Reber, L. Duchêne, S. Payandeh, A. Remhof, H. Hagemann, C. Battaglia, 4 V room-temperature all-solid-state sodium battery enabled by a passivating cathode/hydroborate solid electro-lyte interface, Energy Environmental Science, 2020, 13, 5048, https://doi.org/10.1039/d0ee01569e
[7] A. Garcia, G. Mueller, R. Cerny, D. Rentsch, R. Asakura, C. Battaglia, A. Remhof, Li4(B10H10)(B12H12) as solid electrolyte for solid-state lithium batteries, Journal of Materials Chemistry A, 2023, 11, 18996, https://doi.org/10.1039/d3ta03914e
[8] H. Braun, R. Asakura, A. Remhof, C. Battaglia, Hydroborate solid-state lithium battery with high-voltage NMC811 cathode, ACS Energy Letters, 2024, 9, 707, https://doi.org/10.1021/acsenergylett.3c02117

Funding

Swiss National Science Foundation, InnoSuisse, Horizon 2020, industry projects.

PD Dr. Arndt Remhof
Group Leader

Group Leader Structure and Dynamics

Phone: +41 58 765 4369

Prof. Dr. Corsin Battaglia

Head of Laboratory

Phone: +41 58 765 4131

Press releases

Towards a sustainable and competitive battery value chain in Europe, novel manufacturing process for high-performance lithium-metal battery
https://www.empa.ch/web/s604/solidify-h2020-lithium-metall-batterie
Energy storage, leveling the path for solid-state batteries,  https://www.empa.ch/web/s604/eq76-solid-state-battery
Strategic partnership between Empa and Fraunhofer-Gesellschaft, solid state batteries for tomorrow's electric cars, https://www.empa.ch/web/s604/icon
"Impact Award" for Empa Project, a liquid approach to solid-state batteries, https://www.empa.ch/web/s604/impact-award
New generation of solid-state batteries, high-performance batteries with improved safety, https://www.empa.ch/web/s604/solid-state-battery
Novel electrolytes for next-generation batteries, sodium and magnesium to replace lithium in batteries, 
https://www.empa.ch/web/s604/sodium-electrolyte

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