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Metallic Anodes for Sodium Solid-State Batteries

English title Metallic Anodes for Sodium Solid-State Batteries
Applicant Remhof Arndt
Number 192191
Funding scheme Project funding (Div. I-III)
Research institution Mobilität, Energie und Umwelt Empa
Institution of higher education Swiss Federal Laboratories for Materials Science and Technology - EMPA
Main discipline Condensed Matter Physics
Start/End 01.06.2020 - 31.05.2023
Approved amount 397'768.00
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All Disciplines (2)

Discipline
Condensed Matter Physics
Inorganic Chemistry

Keywords (4)

hydroborates; solid-state conductors; sodium battery; solid-state battery

Lay Summary (German)

Lead
Festkörperbatterien versprechen höhere Energie- und Leistungsdichten sowie eine höhere Betriebssicherheit als heutige Lithium-Ionen-Batterien, die einen brennbaren, flüssigen Elektrolyten verwenden. Wir haben in den letzten Jahren Festkörperelektrolyte auf Hydro-boratbasis mit hoher ionische Leitfähigkeit, hoher thermischer und (elektro-)chemischer Stabilität entwickelt. Die Kombination von hoher Energiedichte (d.h. der Einsatz von Me-tallanoden) und hoher Leistungsdichte (hohe Stromdichten) stellt jedoch eine Herausfor-derung dar. So führen hohe Stromdichten zu Inhomogenität beim Ionentransport, zum Auftreten von Dendriten und schlussendlich zum Versagen der Batterie.
Lay summary

Inhalt und Ziel des Forschungsprojekts

Unser Projekt befasst sich mit den grundlegenden Materialeigenschaften der Hydroborate 
als neuartige, jedoch noch wenig erforschte Klasse von Festkörperelektrolyten im Hinblick
auf eine mögliche Batterieanwendung. Dabei leiten uns folgende Fragen: (i)Welche
Prozesse laufen an der Grenzfläche zwischen Elektrolyt und Anode ab? (ii)Was ist die
mikroskopische Ursache der Kurzschlussbildung und welche Rolle spielt der
Festkörperelektrolyt dabei? (iii) Unter welchen Bedingungen ist ein stabiler Betrieb der
Batterie möglich? Unser Ziel ist es metallische Anoden sicher und stabil in
Festkörperbatterien zu integrieren.
 
Wissenschaftlicher und gesellschaftlicher Kontext des Forschungsprojekts
Die Batterieforschung ist derzeit in Hinblick auf die Energiewende und die 
Elektromobilität von hohem wissenschaftlichem und wirtschaftlichem Interesse.
Festkörperbatterien werden zwar auf Technologie-Roadmaps, z. B. der der "International
Energy Agency" als Zukunftstechnologie genannt, trotzdem sind grundlegende
wissenschaftliche Fragen immer noch nicht gelöst. Unser Projekt hilft diese Lücke zu
schließen und den Innovationsort Schweiz zu stärken.
Direct link to Lay Summary Last update: 14.04.2020

Responsible applicant and co-applicants

Employees

Project partner

Associated projects

Number Title Start Funding scheme
160749 Novel Ionic Conductors 01.12.2015 Sinergia

Abstract

All solid-state batteries promise higher energy and power densities and higher operational safety than state-of-the-art lithium-ion batteries that use a flammable liquid electrolyte. In the resent years, a variety of novel solid-state superionic conductors emerged; among them, the applicants developed a new class of solid-state electrolyte, namely hydroborates, to a point where they compete with state of the art oxide or sulfide based solid-state electrolytes. We real-ized a stable rechargeable 3 V all solid-state sodium battery based on a mixed anion hydroborate solid- state electrolyte, Na4(B12H12)0(B10H10), combining high ionic conductivity of about 1 mS cm-1 (at 30°C), an electrochemical stability window of ~3 V, thermal stability up to 300 °C, and mechanical softness enabling processing by cold pressing. Unlike oxide or sulfide-based elec-trolytes, the hydroborate is stable against sodium and a high capacity metallic sodium anode could be operated with a current density of 0.1 mA cm-1(C/5) at 60 °C. Cycling at higher scan rates or lower temperatures leads to cell failure due to short-circuiting. Generally, the combina-tion of high energy density (metallic anodes) and high power density (high rates) is a common challenge for solid-state batteries. Our proposal addresses basic materials properties of this novel, yet under-explored class of solid electrolytes in view of potential battery application. Specifically the ones concerning the an-ode/electrolyte interface: (i) what is the microscopic origin and a role of solid electrolyte in bat-tery short-circuiting (ii) what are the (electro-chemical) decomposition products of the electrolyte and (iii) are stable interphases towards the electrodes formed as in the case of conventional Li-ion batteries? To answer these questions, we identified the surface/interface stability to be essential. For hy-droborates, detailed studies of their surface properties are missing and this project aims at filling this knowledge gap. In a combined experimental and theoretical approach, we will investigate the chemical and electro-chemical compatibility between the electrolyte and the electrodes, in-cluding the identification of the reaction products at the border of stability limits and the effect of current density/temperature on long term cycling. Thereby, we will combine electrochemical characterization with scanning thermal techniques, microscopy, and operando X-ray diffraction. Theoretical calculations of the structure and the stability of surface and interfaces will comple-ment the experiments,The experimental work will be carried out in the lab Materials for Energy Conversion at Empa, where battery research is the core activity and by the Laboratory of Crystallography at the Uni-versity of Geneva, headed by Prof. Radovan Cerný who joints this proposal as a project partner. The Polish co-proposer, Prof. Zbigniew Lodziana, from the Department of Structural Research IFJ - PAN, Krakow, will provide theoretical expertise and research of thermodynamic, electro-chemical and interfacial properties of hydroborates within density functional theory (DFT) methods. All three partners successfully worked together for more than 10 years, evidenced by numerous joint publications, conference presentations and successfully completed research projects.
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