Chemistry Solid State Cells free essay sample

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 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 â€Å" 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 â€Å"sodium beta alumina (? -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 ? T = 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 gt; 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 LISICON JES 2001, 148, A742. Oxide vs. sulfide: larger, more polarizable framework 9 Thio-LISICON – Large ionic radius more polarizability – R. Kanno ALD for Solid State Li Batteries Energizer Primary Lithium Cells www. energizer. com, 6 February 2012 Overall Reaction FeS2 + 4Li+ + 4e? 2Li2S + Fe0 894 mAh g? 1 vs. Li1/2CoO2 + ? Li+ + ? e? LiCoO2 140 mAh g? 1 A four electron reaction, but it’s only a one time use battery! Yang Shao-Horn et al. , Journal of the Electrochemical Society, 2002 Why is the FeS2 four electron redox reaction so troublesome? Dissolution of soluble polysulfides, Sn2- Agglomeration of elemental iron nanoparticles, Fe0 Initial Discharge (1) FeS2 + 2Li+ + 2e? Li2FeS2 (2) Li2FeS2 +2Li+ + 2e? Subsequent Charge and Discharges (3) Fe0 + Li2S Li2FeS2 + 2Li+ + 2e? (4) Li2FeS2 Li2? xFeS2 + xLi+ + xe? (0. 5 lt; x lt; 0. 8) (5) Li2? xFeS? 2 FeSy + (2? y)S + (2? x)Li+ + (2? x)e? A model system: Solvothermally synthesized FeS2 ? We study this ideal system in order to gain a better understanding of the FeS2 redox chemistry. (Solid state enabled four electron storage. Submitted to AEM; under review) A rechargeable FeS2/Li battery ? First demonstration of a reversible FeS2/Li battery at the moderate temperature of 30-60 C. Previously, the only reversible FeS2/Li batteries were thermal batteries with a molten salt electrolyte and an operating temperature in excess of 400 C (Henriksen et al. Handbook of Batteries, 2002). A rechargeable FeS2/Li battery Coulometric Titration and dQ/dv of FeS2 23 Focus Ion Beam (FIB) sample preparation of charged FeS2 electrode for TEM analysis Transmission Emission Microscopy (TEM) Analysis of charged FeS2 electrode Nanoparticles of orthorhombic FeS2 explain better reaction kinetics of subsequent cycles. We can now revise eqn. 5 to the following: (6) Li2? xFeS? 2 0. 9ortho? FeS2 + 0. 1FeS8/7 + 0. 085S + (2? x)Li+ + (2? x)e? How did we revise the FeS2 redox chemistry at ambient to moderate temperature? Coulometric titration dQ/dV analysis TEM and fast Fourier analysis DFT simulation Initial Discharge (1) FeS2 + 2Li+ + 2e- Li2FeS2 (2) Li2FeS2 +2Li+ + 2e- 2Li2S + Fe0 Subsequent Charge and Discharges (3) Fe0 + Li2S Li2FeS2 + 2Li+ + 2e(4) Li2FeS2 Li2-xFeS2 + xLi+ + xe- (0. 5 lt; x lt; 0. 8) (5) Li2-xFeS-2 FeSy + (2-y)S + (2-x)Li+ + (2-x)e(6) Li2-xFeS-2 0. 9ortho-FeS2 + 0. 1FeS8/7 + 0. 085S + (2-x)Li+ + (2-x)eAdvanced Energy Materials (in press) FeS2/Li Battery 1. Threefold improvement over the specific energy density of the state of the art LiNi1/3Mn1/3Co1/3O2/graphite cells High Energy Density (1340 Wh/kg vs. 500 Wh/kg) 2. Excellent cycling stability enabled by solid state electrolyte which successfully confines electro-active species 3. FeS2: inexpensive, environmentally benign and energy dense 27 Solid Power, Inc. Doug Campbell, COO [emailprotected] com (720) 300-8167 †¢ Spin? Out of Univ. of Colorado at Boulder – Research under Profs. Conrad Stoldt and SeHee Lee – 3 year, $1. 7M funding from DARPA DSO to establish feasibility Need: Ultra? high energy, rechargeable and safe batteries †¢ Problem: Lithium metal anode can potentially meet this need; however, limited cathode capacity and cell stability have thus far stalled further development †¢ Solution: Solid Power’s solid? state battery configuration has shown feasibility in addressing these issues †¢ Benefits: – High specific energy (600 Wh/kg vs. ~200 Wh/kg SOTA Li? ion) – Eliminates most safety concerns associated w/ Li? ion technology †¢ IP: 3 patents covering cathode and anode chemistry †¢ IP Rights: Exclusive Option from CU? Boulder Tech? Transfer Thank you for your attention! 30 31 Strategies For Increasing Conductivity †¢ Open framework †¢ Doping – Sodium beta alumina, NASICON, Li3N, etc Rep. Prog. Phys. 2004, 67, 1233. †¢ Composites – LiI/Al2O3: high ionic conductivity along the grainboundary of LiI and Al2O3 32 Sodium beta alumina †¢ ? -alumina: M2O ·nX2O3 (n = 5? 11, M = monovalent cation – alkali+, Cu+, Ag+, Ga+, In+, Tl+, NH4+, H3O+, X = trivalent cation – Al3+, Ga3+, Fe3+) †¢ Sodium beta alumina: Na2O ·Al2O3 partially occupied layer ? fast Na+ conduction NASICON: Na superionic conductor Li3N Na1+xZr2(P1? xSixO4.