Chemistry Solid State Cells

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  • Topic: Electrochemistry, Lithium, Battery
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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

Outline
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

4

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 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

6

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

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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

LISICON

JES 2001, 148, A742.

Oxide vs. sulfide: larger, more polarizable framework
9

Thio-LISICON
– 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.

Li4GeS4
– Ryoji Kano group

Li+ vacancy Ge4+ + Li+ → P5+

Li4-xGe1-xPxS4

10

Thio-LISICON

JES 2001, 148, A742.

• Partial substitution of Ge4+with P5+ → Li+ vacancy
11

Li2S‐P2S5 Glass Ceramics – M. Tatsumisago

• Glass-ceramic

shows higher ionic conductivity
12
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

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Inorganic Solid Electrolytes
Li10GeP2S12
(R. Kanno)

LLT (La0.5Li0.5TiO3) perovskite

LLZ (Li7La3Zr2O12) garnet

70Li2S-30P2S5 (Li7P3S11)

(M. Tatsumisago & A. Hayashi)

LATP...
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