Chemistry Solid State Cells

Topics: Electrochemistry, Lithium, Battery Pages: 8 (1246 words) Published: May 15, 2013
Solid State Cell Chemistries and Designs

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

History Basic theory (solid state electrolytes) SOA solid state batteries All-solid-state lithium secondary batteries Solid Power, Inc. 2

Why solid state battery?

Advantages No flammable liquid electrolyte  Ultimate safety  No thermal runaway High energy density No safety devices required Excellent cycling stability Excellent shelf life 3

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


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 5

Conduction Mechanisms
Vacancy conduction Interstitial conduction

Schottky defect
(a cation & anion vacancy pair)

T ↑ → defect ↑ → conductivity ↑ ∴shows Arrhenius relationship

Ea σT = Aexp(− ) RT
Derived from Random walk theory

Frenkel defect


Basic Theory – the concept of material design
High mobile ion concentration High number of empty/vacant sites for ions hoping Small activation energy for conduction High number of conduction channel High polarizability of framwork ions In general, Amorphous > Crystalline


Solid Electrolyte
Dry polymer electrolyte – Low ionic conductivity (10‐5‐10‐4 S/cm @ RT) Gel polymer electrolyte – still flammable, poor mechanical property, reasonable conductivity (~10‐3 S/cm) Inorganic or ceramic solid electrolyte Conventional thin-film micro-battery

JPS 2000, 135, 33

LIPON (lithium phosphorous oxynitride) (~10‐6 S cm‐1)

Low cell capacity limits applications (only for special devices) 8


JES 2001, 148, A742.

Oxide vs. sulfide: larger, more polarizable framework

– Large ionic radius & more polarizability

– R. Kanno

– Amorphous Li2S-SiS2-LiI and Li2S-SiS2-Li3PO4 (10‐4‐10‐3 S/cm) – Crystalline Rb4Cu16I7Cl13,RbAg4I5 have higher ionic conductivity than any copper and silver conducting glasses. This is not true for crystalline lithium ion conductors.

– Ryoji Kano group

Li+ vacancy Ge4+ + Li+ → P5+




JES 2001, 148, A742.

• Partial substitution of Ge4+with P5+ → Li+ vacancy

Li2S‐P2S5 Glass Ceramics – M. Tatsumisago

• Glass-ceramic

shows higher ionic conductivity
J. Solid State Electrochem. 2010, 14, 1761. Adv. Mater. 2005, 17, 918

Li10GeP2S12 – R. Kanno
• 12 mS/cm @ 27oC

Agree with the computation results by G. Ceder group (9 mS/cm). Proposed 3D channel rather than 1D. Nat. Mater. 2011, 10, 682. Chem. Mater. doi: 10.1021/cm203303y


Inorganic Solid Electrolytes
(R. Kanno)

LLT (La0.5Li0.5TiO3) perovskite

LLZ (Li7La3Zr2O12) garnet

70Li2S-30P2S5 (Li7P3S11)

(M. Tatsumisago & A. Hayashi)

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