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Batteries

Batteries. Katy Swancutt ENGR 302I December 2007. What is a battery?. It is something that converts chemical energy into electrical energy. They produce current via redox reactions: Red=reduction (gaining electrons) Ox=oxidation (losing electrons)

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Batteries

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  1. Batteries Katy Swancutt ENGR 302I December 2007

  2. What is a battery? • It is something that converts chemical energy into electrical energy. • They produce current via redox reactions: • Red=reduction (gaining electrons) • Ox=oxidation (losing electrons) • Batteries are essentially Voltaic Cells connected in series.

  3. What is a voltaic cell? Major components: • Metals ZINC COPPER

  4. What is a voltaic cell? Major components: • Metals • Electrolytes ZINC ZnSO4(aq) CuSO4(aq) COPPER

  5. What is a voltaic cell? Major components: • Metals • Electrolytes • “Salt Bridge” • Wire ZINC ZnSO4(aq 1.0 Molar AGAR Battery lifetime depends on the mass of metal in the electrodes. WIRE CuSO4(aq) 1.0 Molar COPPER

  6. ANODE CATHODE What is a voltaic cell? ZINC ZnSO4(aq) AGAR WIRE CuSO4(aq) COPPER

  7. How does it make energy? • The solid zinc anode oxidizes and becomes Zn2+ • Electrons travel through the wire toward the cathode • The aqueous Cu2+ is reduced and adds to the solid copper cathode

  8. How much energy can it make? • You can predict the voltage (direct current) between any two materials based on reduction potentials. • A reduction potential, Eocell, is the difference between the standard reduction potential of the cathode (Eored(cathode)) and the anode (Eored(anode)). Eocell= Eored(cathode)-Eored(anode)

  9. How much energy can it make? Step 1: Write the reaction. Zn(s)+Cu2+(aq)→Zn2+(aq)+Cu(s) Step 2: Look up values. Eored(cathode)= 0.337V Eored(anode)= -0.763V Eocell= 0.337V-(-0.763V) Eocell= 1.10V Actual voltage=1.044V 1.044 Volts

  10. How can you get more energy? • Connect several cells in series (1.044V+1.044V+1.044V…) • Work outside of standard conditions (concentration, temp, etc.) • Use different compounds for the electrodes. The greatest voltages are from a combination of the compound with the most negative potential (anode) and the most positive (cathode). These happen to be Li and F, respectively.

  11. Electrode Combinations Below: Magnesium anode and Zinc cathode Expected Vocell=1.607V Observed Vocell=0.63V Above: Zinc anode and IronIII cathode Expected Vocell=1.534V Observed Vocell=0.70V

  12. Electrode Combinations Below: Magnesium anode and Copper cathode Expected Vocell=2.707V Observed Vocell=1.923V Above: IronIII anode and Copper cathode Expected Vocell=0.434V Observed Vocell=0.432V

  13. Electrode Combinations Above: Magnesium anode and IronIII cathode Expected Vocell=3.141V Observed Vocell=1.373V

  14. Environmental Impacts • Some electrodes are made of hazardous materials • Cadmium in Ni-Cd batteries • Lead in lead-acid batteries (like a car battery) • Mercury-electrode batteries (banned in 1996) • Arsenic and Antimony in lead-acid batteries

  15. Environmental Impacts • When batteries are not recycled, they ultimately end up contaminating soil, air, water, and finally end up in the food chain. • Using secondary (rechargeable) batteries helps to prevent pollution.

  16. THANK YOU!

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