Approaching the question of how to
increase battery life from a scientific standpoint, Buchmann recommends
keeping the phone at cold temperatures to minimize unwanted
irreversible side reactions inside
the battery. Chemical reactions tend to
speed up as temperature rises, so keeping a
battery cooler can help it last longer. These
unwanted side reactions interfere with the
reactions at the anode and cathode, decreasing the amount of charge the battery can hold.
Buchmann relates it to the way milk sours if
it is not put back in the fridge. The cold helps
keep the rate of reactions down.
What causes batteries to discharge? Let’s
look inside a battery. Modern batteries come
in different styles, but they all have what
original batteries did—the voltaic pile.
Batteries have three components: an anode
(negative end), a cathode (positive end),
and an electrolyte (the ion transporter).
The anode is an electrical conductor that
easily give up electrons, which chemically
changes it via a process called oxidation. The
cathode is a metal or metallic compound that
does the opposite; it easily accepts electrons
and undergoes reduction. When you put a
battery into a circuit, you create a path for
these electrons to travel. The flow of electrons
from the anode to the cathode creates an
electric current, which can be used to light up
a lightbulb or run a smartphone.
The third component of a battery is the
electrolyte. It is a substance—often a liquid—
made up of positive and negative ions and
is an electrical conductor. As electrons flow
from the anode to the cathode, the anode
compartment becomes positively charged and
the cathode compartment becomes negatively
charged. Sustained electron flow cannot
occur under these conditions. The positive
ion of the electrolyte travels to the cathode
and the negative ion travels to the anode,
keeping the net charge zero and allowing
electrons to flow.
Common single-use alkaline batteries
usually have manganese(IV) oxide (MnO2)
as the cathode and zinc (Zn) as the anode.
“In this type of battery, you have a reaction
in which the zinc is oxidized,” Jim Akridge,
Energizer explained to me. “The zinc metal
goes to Zn2+ and the manganese(IV) oxide
is reduced to manganese(II) oxide (MnO), or
manganese(III) oxide (Mn2O3), depending on
the type of electrolyte. As the reactants are
used up, the amount of power output goes
down. You can’t recharge these batteries, so
once they’re discharged, you discard them.”
Rechargeable batteries differ from single-
use batteries in their chemical makeup and
are driven by reactions that are reversible. For
a lithium-ion battery (Fig.1), a common cath-
ode material is lithium cobalt oxide (LiCoO2),
the anode is graphite (C6, an allotrope of
carbon), and the electrolyte is a combina-
tion of lithium salts, such as LiPF6, LiBF4, or
LiClO4. Unlike a single-use battery, the salt
is dissolved in an organic solvent such as
ethylene carbonate. Water is not a good sol-
vent because it reacts vigorously with alkali
When the battery is discharged, an oxida-
Non-conducting cell separator
Cathode (aluminum foil coated
on one side with LiCoO2)
Membrane permeable to Li+
dissolved in organic solvent
Anode (copper foil coated on
one side with graphite)
When the battery is discharging, Li+
moves through the permeable membrane
from the anode to the cathode and electrons
move through the external circuit from the
anode to the cathode.
Chemical reactions during discharge:
Anode: LiC6→ Li+ + C6(graphite)+ e–
Cathode: Li+ + Co O + e– → LiCoO2
Figure 1. Schematic illustration of a rechargeable lithium-ion battery.
THE STORY OF THE BATTERY STARTS WITH A FROG DISSECTION PERFORMED BY LUIGI GALVANI IN THE LATE 18TH CENTURY.
When he touched his steel knife to the brass hook holding the frog’s leg, he
was surprised, and perhaps a bit horrified, to see the dead appendage twitch.
This led Galvani to theorize how electricity might be contained and used by
animals. This also launched him into a decades-long debate with the established scientist Alessandro Volta. Galvani contended that the electricity was
created and stored in the animal’s muscles, and it conducted through nerves via
some kind of “electrical fluid” when the knife came in contact with the frog’s skin.
Volta, on the other hand, countered that the difference in metals of the knife
and the plate created an electrical potential.
The debate ended in March 1800, when Volta
demonstrated the first battery—a Voltaic pile. He
stacked alternating discs of zinc and copper separated by
wet paper soaked in salt, which served as the electrolyte.
This device created a physical link between two metals
through which electrons could be exchanged to create an
electrochemical potential. When wires connecting the top
and bottom of the pile were brought close together, they
made a spark. No frog necessary! Unfortunately, Volta
could not share the news with his rival, as Galvani passed
away two years before the discovery.
The Origin of Batteries
ChemMatters | DECEMBER 2017/JANUARY 2018 11