Solid Electrolyte Batteries
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SOLID ELECTROLYTE BATTERIES John B. Goodenough and Yuhao Lu Texas Materials Institute The University of Texas at Austin Project ID: ES060 DOE Vehicle Technologies Annual Merit Review Meeting May 9-13, 2011 This presentation does not contain any proprietary or confidential information. 1 The University of Texas at Austin Overview Timeline Barriers • Project Start Date-Oct. 2009 • Lithium-ion solid electrolyte. • Project End Date- Sept. 2010 • Choice of redox couples. • Percent complete: 100% complete • Flow-through- cathode cell design Budget Partners • Funding received in FY09-FY10 – $315K • Karim Zaghib of Hydro Quebec • Funding received in FY10-FY11 – $315K 2 The University of Texas at Austin Milestones Develop and test a suitable test cell. (Jan. 10) Completed Optimize components of the cell. (Apr. 10) Completed Develop a lithium/Fe(NO3)3 cell. (July. 10) Completed Design of a new cell (Sept. 10) Completed Test flow-through cell (Jan. 11) Completed 3 The University of Texas at Austin Typical Lithium Ion Battery (LIB) Cell e- e- - Separator + Li+ Anode Li+ Cathode (Reducing Agent) (Oxidizing Agent) Li+ SEI layer Electrolyte Capacity limited by Li solid solution in cathode and loss in SEI layer Voltage limited by Eg of carbonate electrolyte. 4 The University of Texas at Austin Why Oxides? E E Co: 4s0 Co: 4s0 Co(II): t4e2 µLi 4.0 eV Co(IV): t5e0 EFC EFC (pinned) Co(III): t6e0 Co(III): t6e0 O: 2p6 O: 2p6 N(E) N(E) Li CoO (0<x<0.55) LiCoO2 1-x 2 2- + Holes form peroxide (O2) for x> 0.55 or H inserted from electrolyte. 2- 2- At surface, 2(O2) =2O +O2↑ 0 Note: Li1-x(Co0.15Ni0.85)O2 (0<x<0.8) at 3.8 V versus Li . Note: Introduction of Mn(IV) stabilizes top of O: 2p6 bands to above 4.7 V versus Li0. 5 The University of Texas at Austin Carbonate Electrolyte 0.2 eV 0.5 eV 0 µ µLi LiC6 µAlloy 1.5 eV 1.1 3.45 eV LUMO µLTO 4.0 eV 4.75 eV µLFP µLNC 4.3 HOMO µLNM 5.0 Decomposition Li0 - e-=Li+; dentrites on recharge because of SEI layer. - + LiC6 - e = 6C + Li ; SEI layer prevents rapid charge, consumes Li from cathode. Alloy anodes undergo displacement reactions, which give large volume change. Can be buffered by C and have voltages allowing fast charge, but SEI layer if V<1 V. + Need µC matched to HOMO or, with Li -permeable SEI layer, to 6 decomposition voltage. The University of Texas at Austin Existing Insertion Compound Electrodes HOMO Organic electrolyte LUMO . Lithium metal has the highest specific energy of 3860 mAh/g. No cathode materials can match the capacity. Can we use lithium anode and develop a cathode with a capacity to match? 7 The University of Texas at Austin Existing Electrolytes 6 1) High Li+ ion conductivity /Li 5 + 2) Wide electrochemical window 4 3) Retention of electrode/electrolyte interface 3 4) Chemical stability Ionic Liquid Polymer InorganicSolid 2 Organic Liquid 5) Safety (nonflammable) Potential (V) vs. Li Organic Liquid Ionic Liquid + Polymer Ionic Liquid + Polymer + Polymer + OrganicPolymer Liquid 1 Ionic Liquid Organic+ Liquid 0 0.02 0.03 0.18 0.81 1 2 4 7 + -3 8 LiLi-ion ion Conductivity Conductivity ( ×10 S/cm) (mS/cm) The University of Texas at Austin Objectives: Li Batteries Using a Solid Electrolyte Separator Concept Air or S Organic Liquid Inorganic 8 Li Aqueous (Fe3+/Fe2+) flow Or nothing Solid through Present Practice (Visco, PolyPlus Battery Company) 1M LiPF in Li 6 Li Ti Al (PO ) Sea Water EC/DEC 1.3 1.7 0.3 4 3 Li3N Proposed Practice 1M LiPF in Fe(CN) 3-/Fe(CN) 4- flow Li 6 Li Zr R O 6 6 EC/DEC 7 2 3 12 through 3- + 4- Li + Fe(CN)6 (aq) = Li + Fe(CN)6 (aq); E=3.40 V 9 The University of Texas at Austin Solid Electrolytes • All Solid-State Cell • Solid-Electrolyte Separator (+) Would allow a lithium anode (+) All solid-state cell would Would block dendrites from a simplify and lighten packaging lithium anode or a Li/solid- electrolyte interface Would allow alternative cathodes, Sulfides offer large Eg and σLi> 3+ 2+ 10-3 S/cm e.g. air, S8, or Fe /Fe (aq) flow through (-) Insertion compounds change volume on cycling, so cycle life (-) For an aqueous cathode, need an -4 of solid/solid interfaces is oxide separator: σLi(oxide) ≈ 10 problematic S/cm fabricated thin and dense on a support; and not reduced by lithium 10 The University of Texas at Austin Approach: An Alkali-Metal/Aqueous Cathode Cell Organic electrolyte Anode reaction: nA → nA+ + ne-; (A=Li or Na) Cathode Reaction: Mz+(aq) + ne- → M(z-n)+(aq); Overall reaction: nA + Mz+(aq) = nA+ + M(z-n)+(aq); (1≤ n < z). No phase change takes place in the cathode. No catalyst is needed in the cathode. The cell is rechargeable. The cell works at room temperature. The cell works in the voltage range of 2.8 to 4.2 V. 11 The University of Texas at Austin Accomplishments: Selection of Aqueous Cathode with Existing Solid Electrolyte Aqueous electrodes will depend on electrolyte and must have: 1) proper redox potentials; 2) no side reactions; 3) good stability in water; 4) good reversibility; 5) reliable safety; 6) no toxicity and 7) low cost. 12 The University of Texas at Austin Accomplishments: A Lithium|Fe(NO3)3 (aq) Cell 5.5 7.0 First Cycle A B 5.0 6.0 5.0 4.5 Fe(OH)3 pH=4.48 4.0 3+ ∆V= 0.95 V Fe 4.0 ∆V= 1.96 V 3+ 2+ Fe2+ Fe /Fe pH 3.0 3.5 Potential (V) 2.0 FeO(OH) pH=2.0 3.0 Discharge 1.0 Charge 2.5 0.0 0.0 0.2 0.4 0.6 0.8 1.0 0.0 1.0 2.0 3.0 4.0 5.0 Normalized Capacity -1 Concentration (mole L ) The open circuit voltage of the battery is 3.99 V. Its initial discharge voltage is 3.74 V at a current of 0.5 mA. After discharge Its initial charge voltage is 4.73 V at the current of 0.5 mA. Hydrolyzation of Fe(III) results in precipitates of FeO(OH) for pH>2 and Fe(OH)3 for pH>4.8 when pH of the aqueous electrode solution increases with cell discharge. 13 The University of Texas at Austin Accomplishments: 3- Lithium| Fe(CN)6 (aq) Cells 3.8 5.0 110 4.5 B 100 4.0 3.6 90 3.5 80 ∆ 3.0 V=0.35 V 70 3.4 2.5 60 2.0 50 3.2 0.4 40 Potential (V) 0.3 30 3- Capacity (mAh) 0.2 3.0 3- 0.01 M Fe(CN)6 20 0.01 M Fe(CN)6 3- 3- 0.1 10 0.1 M Fe(CN) 0.1 M Fe(CN)6 6 Coulombic efficiency (%) 2.8 0.0 0 0.0 0.2 0.4 0.6 0.8 1.0 1.2 0 5 10 15 20 25 Normalized capacity Cycle number No hydrolyzation of Fe(III) The theoretical voltage of the battery is 3.40 V. Its effective voltage with the commercial solid electrolyte distributes between 3.33 V and 3.68 V. Different concentrations of the redox couple in the aqueous electrode slightly affect the normalized discharge/charge curves. The battery shows a high coulombic efficiency. 14 The University of Texas at Austin Accomplishments: 3- Power Density and Reversibility of Li|Fe(CN)6 (aq) Cells 4.0 14 0.45 120 D 12.53 mW/cm2 3.5 . 12 ) -2 0.40 100 3.0 10 0.35 80 2.5 8 2.0 0.30 60 . 6 1.5 1.77 V 0.25 40 Capacity h) (mA Cycle 3.0 V – 3.75 V Potential (V) 4 1.0 Coulombic Efficiency (%) 0.20 20 0.5 2 Capacity Columbic Efficiency 0.0 0 densityPower cm (mW 0.15 0 0 2 4 6 8 10 12 0 200 400 600 800 1000 Current density (mA cm-2) Cycle number The cell demonstrates a maximum power density of 12.53 mW/cm2, which is competitive with a direct methanol fuel cell of similar active area. Due to no cathode phase change in the charge/discharge, the cell shows a good reversibility. No capacity loss was observed over 1000 cycles. 15 The University of Texas at Austin Accomplishments: 3- Stability of Li|Fe(CN)6 (aq) Cells with Existing Electrolyte -2 Current density (mA cm ) -600 5.0 0.1 0.2 0.5 1.0 1.5 2.0 2.5 3.0 8 A Fresh cell C -500 4.5 7 ) -2 4.0 Rint → RSE after 6 3.5 -400 aging uncycled for 10 h ) 5 2 3.0 2.8 V -300 cm 2.5 4 Ω 2.0 ( Z'' 3 -200 1.5 354.89 Hz Potential (V) 2 1.0 -100 19.95 KHz Potential 1 MHz 2.51 Hz 0.5 1 Power density 0.0 0 density Power cm (mW 0 0 1 2 3 4 5 6 7 8 0 RS 100RF 200 300RSE 400RInt 500 600 2 Time (Hours) Z' (Ω cm ) -800 C After deep discharge A C -700 -600 RS (solution) 42.46 43.79 -500 ) 2 (charge transfer) -400 RF 120.52 115.62 cm Ω Z'' ( Z'' -300 (solid electrolyte) 446.68 Hz RSE 160.24 237.84 -200 22.39 KHz 0.01 Hz 1 MHz -100 RInt(interface) 143.34 346.33 0 0 R 100R 200 300 400R 500 600 700R 800 s F SE2 Int 16 Z' (Ω cm ) The University of Texas at Austin Accomplishments: Rechargeable Lithium|Cathode-Flow Battery (RLCFB) The aqueous cathode in a flow-through mode can be individually stored in a “fuel” tank, which reduces the volume of the battery and increases the design flexibility of the battery structure.