Low-Cost Carbon Surface Passivation for Achieving Exceptionally Long Battery Life

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1 Low-Cost Carbon Surface Passivation for Achieving Exceptionally Long Battery Life NEXT-GENERATION ENERGY STORAGE 2016 Track 3: Banking on Batteries, Tuesday April 19 Dr. Alexander Bistrika President, echemion Inc.

2 Wind Power Deficit Compensation/ Backup Generation Excess Mitigation/Storage ~110 [MWh] Wind Power Capacity / GW NW Wind (Actual) NW Wind (Model) Council Prediction 2005 BPA Testimony 2012 ~90 [MWh] Year 2

3 Power Management There is a wide range of power management needs; the greatest need is depicted as Renewable Energy Management Some commercially available storage technologies? It should be noted that the combined spectrum does not cover the entire power needs spectrum Redox Flow Batteries (RFBs) Figures courtesy ESA 3

4 Redox Flow Battery catholyte carbon felt electrode current collector membrane anolyte pump pump ENERGY POWER 4

5 Advantages, Drawbacks, and Hurdles Zinc Bromide Advantages: A major advantage of this chemistry is the inherently high power density Relatively inexpensive electrolyte and abundant active species All-Vanadium Advantages: A major advantage of this chemistry is (and arguably a major engineering and design hurdle) that there is only one active species True RFB Disadvantages: Hybrid RFB Corrosive free bromine and tribromide species Complex system of reactions Disadvantages: Expensive/specialty exchange membranes Corrosive high oxidation state vanadium species Slow reaction kinetics A major drawback for both chemistries is performance loss and degradation of carbon electrodes during operation 5

6 The Problem? Solution! 100% Reactor cell stack 2X - Performance 50% M M M 2+ X 2 2X - M 2+ X 2 0% Years Performance Degradation 6

7 Degradation Chemistry Using the all-vanadium chemistry as an example system: DESIRED REACTIONS: H + V 4+ H O H V 3+ + e - V 2+ V 4+ V 5+ + e - VV V 4+ O 2- H + O 2- H + V 5+ O V 5+ H + C O V 5+ O O O 2- H + VO H + H + H + UNDESIRED REACTIONS: H 2 O 2H + + O 2-2H + + 2e - H 2 (gas) O 2- O 2 (gas) + 2e - C x + 2xO 2- xco 2 (gas) + 4xe - (fast once the oxygen radical is generated) 7

8 Cyclic Voltammetry V 2+ V 3+ + e - UNDESIRED REACTIONS: H 2 O 2H + + O 2-2H + + 2e - H 2 (gas) O 2- O 2 (gas) + 2e - V 4+ V 5+ + e - Current, I [A] V 5+ + e - V 4+ untreated V 3+ + e - V 2+ treated Potential, E [V] v. Ag/AgCl in 1M KCl 8

9 N Technology O H O H O H H O Selectivity/ Catalysis High reaction activity F F F Impervious/ High surface area Patent Pending Chemical resistance 9

10 Performance of Graphite Activity loss (degradation) can be measured by various analytical methods Tafel perameter evolution Potentiostatic/galvanotatic cycling i / ma cm t Treated Untreated t2 t3 C / Ah cm -2 Surface analysis (by SEM/EDX) shows a modified surface and progression of the elemental composition at the surface with aging Elemental Composition % 100% 95% 90% 85% Br F O C 80% ug-t0 ug-t1 tg-t0 tg-t1 tg-t2 tg-t3 10

11 Industry Relevant Testing 11

12 Test Reactor Assembly OUTLET INLET OUTLET INLET Aluminum Plate Viton Rubber Gasket Polypropylene Housing Silicone Rubber Gasket Graphite Composite Plate Collector Material Electrode Material Polypropylene Felt Stainless Steel Contact Polypropylene Gasket Membrane Flow Direction 12

13 Cell Resistance 30 Resistance [Ω] COMP FOIL ufelt tfelt 13

14 Electrochemical Performance 20 New Midway Aged 15 i / ma cm Untreated SGL GFD 4.6 Treated SGL GFD

15 Aging of Commercial Felt Activity for commercial felt electrodes is likewise measured and compared between treated and untreated materials The performance loss attributed to both chemical and mechanical degradation can be visually observed at the macro and micro scale i / A g Treated Untreated Treated Untreated C / Ah cm -2 SEM image of damaged felt fiber provided courtesy LI Xiao-gang et al

16 Making Today s Batteries Better, and Tomorrow s Possible Saving the world one electrode at a time Innovative wet chemistry pretreatment to prevent performance loss Virtually no degradation is observed in our accelerated aging experiments over typical service life Changing the way we view and understand batteries Maximizing the power density of an RFB s by stabilization of graphitized carbon Both incremental increases by exfoliation as well as immediate preservation of activity that would otherwise be lost Ensuring that a sustainable energy future is also affordable Reducing the Levelized Cost of Energy (LCoE) With prolonged service life (ca. 20 years) RFBs become very cost competitive 16

17 Acknowledgements: Collaborations & Partners Advantage Accelerator & Venture Development Fund 17

18 Thank You!