“What is a battery?” A battery is a device that creates electric energy through the
conversion of chemical energy. “How?” Through oxidation-reduction reactions,
that’s how! “What’s that?” An oxidation-reduction reaction (also known as a redox
reaction) is a reaction in which electrons are passed from one object to
1 Although we commonly refer to these power-packs as batteries, the more scientifically
appropriate terms for these electrochemical units would be the
cell. 3 “Why?” In the
chemistry world, a cell is defined as the most generic unit of electrochemistry
that takes chemical energy and transforms it into electrical energy. Sounds a
lot like a battery, doesn’t it? Batteries are typically comprised of at least
one or more electrochemical cells that are electrically linked and assorted in
a parallel fashion in order to supply the necessary functional voltage and
Every battery is
composed of 3 major parts: The anode (negative electrode), the cathode
(positive electrode) and the electrolyte.
2 An electrode is a type of
conductor, through which electricity will enter or leave an object.
Electricity travels or flows through a circuit. The anode relinquishes its
electrons to the external circuit, making it the reducing agent.
is the one that gets oxidized during the electrochemical reaction. The cathode accepts
the electrons from the external circuit, making it the oxidizing agent.
It gets reduced during the electrochemical reaction. The electrolyte (usually a
liquid) serves as the medium in which electrical charge flows between the
cathode and anode.
electrochemical cells are distinguished as either primary cells or secondary
cells. Primary cells are batteries that do not readily or efficiently recharge.
In primary cells, the electrochemical
reaction that takes places in them is an irreversible process, meaning that the
active material cannot be restored to its original state.
of their inability to recharge, these batteries are good for only one time use
and are disposed of thereafter.
3 Primary cells are thus deemed as
handy and low-cost batteries. An example of an everyday primary cell is an Alkaline
Battery (there are also rechargeable alkaline batteries, but we will only
discuss the non-rechargeable ones!).
are batteries that have the ability to recharge to its original state after
being used. Just as in primary cells, secondary cells produce current (the rate
at which electrical charge passes through a circuit) in a similar fashion.
They undergo an electrochemical reaction via an anode, cathode, and electrolyte.
The difference, however, is that in a secondary cell, this process is
3 The cells are able to reverse the discharge flow of
electrons from the anode to the cathode when electrical energy is introduced,
thus replenishing the cell’s charge.
1 Lithium-ion batteries are one
of the most popular rechargeable batteries.
are a great example of primary cells. These batteries come in a variety of
forms, such as AA, AAA, D or C .
3 In this type of battery, zinc
powder is used to create the anode. This allows for more surface area which in
turn increases the current.
1 The cathode is constructed of manganese
dioxide. Aqueous potassium hydroxide is the electrolyte. Ions will flow from
the zinc powder to the manganese dioxide, which will also cause electrons to be
released from the electrode. These electrons will then gather inside the anode,
resulting in a difference of charges between the two electrodes. The half
a lithium ion battery, the lithium ions migrate back and forth from the anode
to the cathode.
2 These batteries are extremely popular in consumer
electronics. They contain one of the finest energy densities and experience a minor
loss of charge while not in use.
2 These batteries are becoming more
desired in electric vehicles, aerospace, and military uses. A carbonaceous sort
of material (typically graphite) is what makes up the anode.
carbonaceous material contains small regions in which lithium atoms and lithium
1 When the intercalation method begins, the lithium
migrates into the electrode.
2 Lithium moves out of the electrode
during the extraction process. When a battery is expending energy, the lithium
is removed from the anode and injected in the cathode.
2 A transition
metal oxide, CoO
2, which is what the cathode is composed of, can
also hold lithium ions. This metal has a high reactivity and therefore, a
non-aqueous electrolyte must be used.
1 When the battery is set to
recharge, the reverse reaction takes place. During the discharge of the
battery, half reactions are:
Anode (oxidation):Li(s) --> Li+(aq) + e-
Cathode (reduction):Li+(aq) + CoO2(s)
+ e- --> LiCoO2(s)
+ CoO2(s) -->