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Batteries

This document provides a comprehensive overview of batteries, detailing how they convert chemical energy into electrical energy through redox reactions. It explains the essence of voltaic cells, major components including metals, electrolytes, and the role of wires and salt bridges. Additionally, the document explores energy production, voltage prediction based on reduction potentials, and strategies to enhance energy output. It also highlights the environmental impacts of battery materials and the importance of recycling to mitigate pollution.

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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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