Sehee Lee Department of Mechanical Engineering University of Colorado at Boulder
Crash‐Safe Energy Storage Systems For Electric Vehicles Workshop Denver, CO November 12 & 13, 2012 1
Outline
History Basic theory (solid state electrolytes) SOA solid state batteries All-solid-state lithium secondary batteries Solid Power, Inc.
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Why solid state battery?
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Advantages No flammable liquid electrolyte Ultimate safety No thermal runaway High energy density No safety devices required Excellent cycling stability Excellent shelf life
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Disadvantages Slower kinetics due to • Low ionic conductivity • High interfacial resistance • Poor interfacial contact
General Solid State Battery Construction
Two electrodes are separated by solid state electrolyte layer – Electrolyte has high ionic conductivity and is electronically insulating Composite electrodes – Incorporate solid electrolyte into composite for fast ion transport – Incorporate conductive additive into composite for fast electron transport
Solid Electrolyte Lithium Metal Anode Cathode Li anode SSE Cathode Conductive Additive Active Material
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History
1839 (Michael Faraday) The first solid state electrolyte, PbF2 at high temperature
1884 (Warburg) Demonstrated Na+ conduction in glass 1888 (Warburg & Tegetmeier) The first measurement of transference number ~ 1900 (Walther Nernst) Discovery of “ Nernst glower” – a ceramic rod was heated to incandescence → SOFC (solid oxide fuel cell), oxygen gas sensor
1914 1966
(Tubandt & Lorenz) High Ag+ conductivity of AgI at 150oC (Ag/AgI/Ag) (Kummer & Webber @ Ford Motor) Developed Na/S battery by using Na+ conductor “sodium beta alumina (β-Al2O3)”. 1973 (P. V. Wright) 1978 (M. B. Armand, J. M. Chabagno, M. Duclot) First polymer electrolyte
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Conduction Mechanisms
Vacancy conduction Interstitial conduction
Schottky defect
(a cation & anion vacancy pair)
T ↑ → defect ↑ → conductivity