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2016 MRS Meeting Presentation Slides

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Three-dimensional Hierarchical Porous Carbon Foam Derived from Chitosan Aerogel for Electrical Double Layer Capacitors (oral presentation, EC2.12.10, 2016 MRS Fall Meeting and Exhibit, Boston, MA, 2016)

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2016 MRS Meeting Presentation Slides

  1. 1. Chitosan-derived Porous Carbon Foams for Supercapacitors Tianyu LIU Li Lab Department of Chemistry and Biochemistry University of California, Santa Cruz 11/2016
  2. 2. UC Santa Cruz
  3. 3. Outline  What Are Supercapacitors?  Current Limitations of Supercapacitors  Design and Fabrication of 3D Porous Carbon Foams  Electrochemical Performance  Summary
  4. 4. Background (Supercapacitors)
  5. 5. Structure of Supercapacitors Charge storage devices Large surface area 5 μm ZnO Nanowires 10 μm Graphene Aerogel
  6. 6. Capacitance Charge storage ability Charge storage mechanisms Electrical Double Layer Capacitance Pseudo- capacitance Activated Carbon, CNT, Graphene etc. Conducting polymers, metal oxides etc. 𝑪𝒂𝒑𝒂𝒄𝒊𝒕𝒂𝒏𝒄𝒆 = 𝐶𝑎𝑝𝑎𝑐𝑖𝑡𝑦 𝑃𝑜𝑡𝑒𝑛𝑡𝑖𝑎𝑙 𝑊𝑖𝑛𝑑𝑜𝑤
  7. 7. Motivation
  8. 8. Conventional Material - Low Capacitance sourcetech411.com Activated Carbon (~100 F g-1)
  9. 9. Conventional Material - Poor Rate Capability ACS Nano 2013, 7, (4), 3589-3597
  10. 10. Capacitance
  11. 11. Capacitance Determining factors 0 r S C d    0 r C S d        Dielectric constant Electric constant (=8.854 pF/m) Surface area (ion-accessible) Separation b/w different chages Capacitance
  12. 12. Enlarge (ion-accessible) surface area 0 r C d S   0 r C d S        Dielectric constant Electric constant (=8.854 pF/m) Surface area (ion-accessible) Separation b/w different chages Capacitance Capacitance
  13. 13. Rate capability
  14. 14. Rate Capability 2D Non-porous Electrode 3D Porous Electrode VS. Electrolyte Reservoir
  15. 15. The Keys (Take-home Message) Capacitance Rate Capability Large Surface Area Porous 3D Structure Excellent Electrical Conductivity
  16. 16. Design and Fabrication of 3D Porous Carbon Foams Liu and Zhang et al. Nano Res., 2016, 9, 2875-2888
  17. 17. Building 3D Structure Chitosan Glutaraldehyde
  18. 18. Building 3D Structure Sample S (m2/g) Vmicro (cm3/g) Vmeso (cm3/g) CF 8.9 0.002 0.030
  19. 19. Creating Porous Structure K2CO3 → K2O + CO2 K2CO3 + 2C → 2K + 3CO K2O + C → 2K + CO Science 2011, 332, 1537-1541 Activation Processes
  20. 20. Creating Porous Structure Sample S (m2/g) Vmicro (cm3/g) Vmeso (cm3/g) PCF 1013.0 0.461 0.154 CF 8.9 0.002 0.030
  21. 21. Surface Area Energ. Environ. Sci. 2011, 4, (9), 3342 Adv. Mater. 2014, 26, (17), 2676-2682 Name Surface Area Carbon Cloth 5.3 m2•g-1 Graphite Powder 6 m2•g-1 Carbon Black ~100 m2•g-1 Porous Carbon Template ~200 m2•g-1 Graphene Aerogel ~500 m2•g-1 PCF 1013 m2•g-1
  22. 22. Electrical Conductivity Potential-Current Plots Slope ∝ (Electrical Conductivity)-1
  23. 23. Capacitances & Rate Capability PCF vs. CF
  24. 24. Capacitances & Rate Capability PCF vs. CF 197.3 F/g (@ 10 A/g) 179.4 F/g (@ 50 A/g) 166.3 F/g (@ 100 A/g) PCF
  25. 25. Electrochemical Performance of PCF Supercapacitor Devices
  26. 26. Device Assembly PVA Powder H2O + → PVA Gel Electrolyte ← Separator + KOH PCF
  27. 27. Excellent Performance Rate Capability Cycling Stability
  28. 28. Ragone Plot Energy Density (Wh•kg-1) How much energy per kg material can store Power Density (W•kg-1) How fast per kg material can charge/discharge
  29. 29. Ragone Plot
  30. 30. Summary
  31. 31. Summary Chitosan Glutaraldehyde K2CO3 3D Carbon Foams 3D Porous Carbon Foams Cross-link Reaction Chemical Activation Outstanding Capacitive Performance
  32. 32. Acknowledgements Prof. Feng Zhang Prof. Yat Li Group, UCSC
  33. 33. Characteristics of Supercapacitors More charges can be stored than conventional capacitors >ca. 100-1000 F/g ca. 1 μF/g Supercapacitors Conventional Capacitors
  34. 34. < ca. seconds ca. hours Li-ion BatteriesSupercapacitors Faster charge and discharge rates than batteries: More charges can be stored than conventional capacitors > Supercapacitors Conventional Capacitors ca. 100-1000 F/g ca. 1 μF/g Characteristics of Supercapacitors
  35. 35. N-doping
  36. 36. Cross-link Reaction
  37. 37. No Cross-linker
  38. 38. Freeze Dry
  39. 39. Thermogravimetric Analysis
  40. 40. BET
  41. 41. Electrical Conductivity Raman Spectroscopy D Band G Band Graphitic regionsDefects Decrease electrical conductivity Increase electrical conductivity IG/ID=0.503 IG/ID=0.345
  42. 42. Sheet Thickness
  43. 43. AFM Average Roughness Ra = 6.6 nm
  44. 44. TEM
  45. 45. Electrochemical Performance of PCF and CF CyclicVoltammetry (CV) Chronopotentiometry (CP)
  46. 46. Electrochemical Performance of PCF
  47. 47. Cycling Stability of PCF
  48. 48. Device Assembly Gel electrolytes Polymer (usually PVA)-based Polyvinyl Alcohol Wikipedia Electrolytes serve as the solute (e.g. LiCl, H2SO4, LiOH)
  49. 49. Electrochemical Performance PCF – nearly ideal capacitive performance
  50. 50. Device Flexibility
  51. 51. Outlook Liu and Zhang et al. Nat. Commun., Under Review

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