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Development Of Non Aqueous Asymmetric Hybrid Supercapacitors Part Ii

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Development Of Non Aqueous Asymmetric Hybrid Supercapacitors Part Ii

  1. 1. DEVELOPMENT OF NON-AQUEOUS ASYMMETRIC HYBRID SUPERCAPACITORS BASED ON Li-ION INTERCALATED COMPOUNDSGUIDEDr.D.KALPANA, SCIENTIST, BYEEC DIVISION, NAKKIRAN.A,CECRI,KARAIKUDI.
  2. 2. An overview of previous presentation• Introduction• Hybrid supercapacitors• Synthesis of LiMn2O4 and the same multidoped with Ni, Co and Cu• Physical characterization - XRD, SEM, FTIR• Cell Fabrication
  3. 3. ElectrochemicalCharacterization techniques
  4. 4. • Cyclic voltammetry• Galvanostatic charge-discharge• Electrochemical impedance spectroscopy
  5. 5. Cyclic Voltammetry Before cycles: LiMn2O4 LiCo0.25Ni0.25Cu0.25Mn1.25O40.0010 1mV/s 0.0010 1mV/s 2mV/s0.0005 2mV/s 5mV/s 5mV/s 0.00050.0000 current(A) 0.0000-0.0005 -0.0005-0.0010 -0.0010-0.0015 2000 1000 0 -1000 -2000 2000 1000 0 -1000 -2000 Voltage (mV) voltage(mV)
  6. 6. Cyclic Voltammetry After 5000 cycles: LiMn2O4 LiCo0.25Ni0.25Cu0.25Mn1.25O4 0.0010 0.0010 1mV/s 1mV/s 2mV/s 2mV/s 5mV/s 5mV/s 0.0005 0.0005 current(A)current(A) 0.0000 0.0000 -0.0005 -0.0005 -0.0010 -0.0010 2000 1000 0 -1000 -2000 2000 1000 0 -1000 -2000 voltage(mV) voltage(mV)
  7. 7. Cyclic Voltammetry Scan rate = 5mV/s LiMn2O4 LiCo0.25Ni0.25Cu0.25Mn1.25O4 0.0010 before cycles 0.0010 before cycles after 5000 cycles after 5000 cycles 0.0005 0.0005current(A) 0.0000 current(A) 0.0000 -0.0005 -0.0005 -0.0010 -0.0010 -0.0015 -0.0015 2000 1000 0 -1000 -2000 2000 1000 0 -1000 -2000 voltage(mV) voltage(mV)
  8. 8. Cyclic Voltammetry Scan rate = 5mV/s Before cycles: After 5000 cycles: LiMn O 2 4 0.0010 0.0010 LiMn2O4 Li(CoNiCu)0.25Mn1.25O4 Li(CoNiCu)0.25Mn1.25O4 0.0005 0.0005 current(A)current(A) 0.0000 0.0000 -0.0005 -0.0005 -0.0010 -0.0015 -0.0010 2000 1000 0 -1000 -2000 2000 1000 0 -1000 -2000 voltage(mV) voltage(mV)
  9. 9. Formula used Average currentSpecific capacitance = Scan rate x Weight
  10. 10. Cyclic Voltammetry Results Specific capacitance of Specific capacitance of LiMn2O4 LiMn1.25Co0.25Ni0.25Cu0.25O4 (F/g)Condition ( F/g) 1mV/s 2mV/s 5mV/s 1mV/s 2mV/s 5mV/s Before 34 31 29 22 20 19 cyclesAfter 5000 27 22 18 18 16 15 cycles
  11. 11. Charge-Discharge Profiles of LiMn2O4 Current density = 500µA/cm2 2.4 2.4 cycle no.2 2.2 2.0 after 5000 cycles 2.0 1.8 1.6 1.6Voltage(V) voltage in V 1.4 1.2 1.2 0.8 1.0 0.8 0.4 0.6 0.4 0.0 0.2 0.0 900 1000 1100 1200 1300 1400 1500 1600 700 750 800 850 900 950 1000 1050 1100 1150 Time (sec) Time in s
  12. 12. Charge-Discharge Profiles of LiCo0.25Ni0.25Cu0.25Mn1.25O4 Current density = 500µA/cm2 2.0 2.0 cycle no.3 after 1.8 1.8 5000 cycles 1.6 1.6 1.4 1.4Voltage(V) 1.2 1.2 voltage in V 1.0 1.0 0.8 0.8 0.6 0.6 0.4 0.4 0.2 0.2 0.0 6300 6350 6400 6450 6500 6550 6600 6650 450 500 550 600 650 700 750 Time(sec) Time in s
  13. 13. Formulae usedSpecific Capacitance = Current x Discharge time Voltage x weight Current x VoltageSpecific Power = weight Current x Voltage x Discharge timeSpecific Energy = weight
  14. 14. Charge-Discharge results LiMn2O4 LiMn1.25Co0.25Ni0.25Cu0.25O4Condition Specific Specific Specific Specific Specific Specific capacitance power energy capacitance power energy F/g kW/kg kWh/kg F/g kW/kg kWh/kg Before 14.55 200 21.98 5.36 110 5.8 cyclesAfter 5000 7.85 200 11.83 4.17 110 4.58 cycles
  15. 15. Columbic efficiency Vs CyclesCoulombic efficiency = discharge time/charging time 100 LiMn2O4 Li(CoNiCu)0.25Mn1.25O4 Coulombic efficiency (%) 90 80 70 0 1000 2000 3000 4000 5000
  16. 16. Internal resistance Vs Cycles IR = ∆V/ ∆I 800 LiMn2O4 Li(CoNiCu)0.25Mn1.25O4Internal resistance(ohm) 700 600 500 400 300 0 1000 2000 3000 4000 5000 No of cycles
  17. 17. Specific capacitance Vs Cycles 20Specific Capacitance (F/g) 16 LiMn2O4 Li(CoNiCu)0.25Mn1.25O 4 12 8 4 0 0 1000 2000 3000 4000 5000 No of cycles
  18. 18. Electrochemical Impedance spectroscopy Before cycles: After 5000 cycles: -800 LiMn2O4 -8 LiMn2O4 -700 Li(CoNiCu)0.25Mn1.25O4 Li(CoNiCu)0.25Mn1.25O4 -600 -6 -500 Zim(ohm)Zim(ohm) -400 -4 -300 -200 -2 -100 0 0 -200 0 200 400 600 800 4 6 8 10 12 14 Zre(ohm) Zre(ohm)
  19. 19. Impedance results LiMn2O4 LiMn1.25Co0.25Ni0.25Cu0.25O4Condition Rs Rct Cdl Rs Rct Cdl ohm ohm mF/g ofm ohm mF/g Before 5.128 0.2917 2.98 5.043 0.2394 3.14 cyclesAfter 5000 7.829 278 0.195 6.573 122.4 0.59 cycles
  20. 20. Structure Vs capacity fading• The structural stability of a host electrode to the repeated insertion and extraction of lithium is undoubtedly one of the key properties for ensuring that a lithium ion cell operates with good electrochemical efficiency• In transition metal oxides, both stability of the oxygen ion array and minimum displacements of the transition metal cations in the host are required to ensure good reversibility.
  21. 21. Structure of cubic SPINEL
  22. 22. Structural Change• the cubic symmetry of Li[Mn2]O4(space group Fd3m), in which the lithium ions occupy tetrahedral sites and Mn occupy the Octahedral sites• On cycling the lithium ions occupy octahedral sites of Mn ion ,So the cubic symmetry of LiMn2O4 is reduced to tetragonal Li2[Mn2]O4 (space group F41/ddm)
  23. 23. Cubic to tetragonal transitionLiMn2O4 Li2Mn2O4 CUBIC TETRAGONAL [a=b=c] [a=b=c]
  24. 24. • This crystallographic distortion, which results in a 16% increase in the c/a ratio of the unit cell parameters• Average Oxidation state of cubic spinel is 3.5• Average Oxidation state of tetragonal spinel is 3
  25. 25. Jahn Teller distortionWhen the ratio of Mn3+ increases ,it follows a disproportionate reaction 2Mn3+ Mn4+ + Mn2+ Where Mn2+ is an acid-soluble species .It dissolute into solution. And distrust its structural integrity during cycling.
  26. 26. Remedy• This multi-doped system maintains the average oxidation state of Mn ion between 3.5 to 4.• So JT distortion is reduced to the greater extend
  27. 27. Conclusions• The faster rate of capacity fading in pure substance than doped one may be attributed to the onset of Jahn-Teller distortion• The above point may be confirmed without any doubts soon after the arrival of XRD results for the sample after 5000 cycles.
  28. 28. Conclusions• The low IR in the case of doped substance is also a strong reason for its better performance• The impedance profiles too explain clearly that doped substance is a better candidate for supercapacitors than the pure one
  29. 29. Conclusions• With LiMn2O4 we were able to reach a high voltage of 2.4v, while the highest voltage that has ever been reported for this system is 1.8v• This high voltage may be attributed to the use of organic electrolyte – 1M LiClO4 in EC-PC
  30. 30. Lithium Cobaltate(LiCoO2)• Commercially successful• The layered structure of LiCoO2enables easy diffusion of Li- ions in and out of the structure
  31. 31. Synthesis Of Cathode Material• Two cathode materials were synthesized, i) Pure LiCoO2 ii) LiCoO2 doped with Al - LiCo1-xAlxO2 ( x = 0.2, 0.4,…..0.8 )• The cathode material was synthesized by soft combustion method• Compositions were taken on a stoichometric ratio based on following equations,• LiNO3 + Co(NO3)2.6H2O LiCoO2 (for pure substance)• LiNO3 + 0.8Co(NO3)2.6H2O + 0.2Al(NO3)2.9H2O LiCo0.8Al0.2O2 (for doped substance)
  32. 32. Composition For Pure SubstanceBasis : 0.1 moles(9.8g) of product Chemical Weight LiNO3 6.9 g Co(NO3)2.6H2O 29.1 g Glycine ( C2H5NO2) 15 g Distilled Water 100 ml
  33. 33. Composition For Doped SubstanceBasis : 0.2 moles of product Chemical Weight LiNO3 13.8 g Al(NO3)2.9H2O 15 g Co(NO3)2.6H2O 46.56 g Glycine ( C2H5NO2) 30 g Distilled Water 100 ml
  34. 34. The Soft Combustion Process Weighing of required chemicals Dissolve in 100ml distilled water Stir well at 600C Heat the mixture at 1000C for 8 hoursProduct is formed following a soft combustion
  35. 35. Thermal Analysis
  36. 36. Future Work• Physical characterization of LiCoO2• Cell fabrication• Electrochemical characterization• Comparison of LiMn2O4 and LiCoO2 using the available data
  37. 37. Thank you
  38. 38. Queries?

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