Lithium batteries are a result of some bizarre chemistries, which
are not necessarily taught in freshman chemistry. It may seem
undaunting for a new chemist, but with a good basic knowledge of
atomic and molecular theory you can start to understand things
quickly. Consider the phenomena of Li intercalation of graphite at
the anode of a Lithium Ion battery, something you should have run
across in your review. Intercalation of lithium metal in between the
layers of graphite forms a thermodynamically stable compound whose
formula is LiC6. At the cathode of a lithium ion battery
is another bizarre chemical, typically lithium cobalt oxide (LiCoO2).
The two half cell reactions can be expressed as follows:
+ e- + C6 --> LiC6 Eo = -2.84 V
+ e- + CoO2 --> LiCoO2 Eo = +0.25 V
a. Which of
the two reactions will undergo reduction and which one will undergo
oxidation when the battery discharges (spontaneous reaction)?
b. What is
the theoretical voltage that can be produced by this cell at
standard conditions? Show your work.
c. Use the
above information to write the complete spontaneous redox reaction
that combines the half cell reactions.
d. Calculate the standard Gibb’s free energy, Go
for this reaction. Calculate the equilibrium constant for this
reaction at 25oC.
how your typical LiCO2/LiC6 cell could
possibly have a higher voltage (3.6 V) than the voltage you
calculated above for a cell at standard conditions?