Charge me to life

Imagine if there is no such thing as a rechargeable battery.
You'll have to always buy new batteries for your cellphone, laptop, camera and many other electrical items (which do need batteries to run).
It'll be a huge waste of money, time and energy having to buy packets and packets of batteries again and again just to power up electrical appliances without wires.
Well fortunately for us, the existence of rechargeable batteries solved our problems pretty much.


All we need to do is to just charge the battery after it has been completely used.
Rechargeable batteries are also known as secondary cells.
The commonly used secondary cells are lead acid, nickel cadmium lead acid, nickel cadmium (NiCd), nickel metal hydride(NiMH), lithium ion (Li-ion), and lithium ion polymer(Li-ion polymer).
The main concept behind secondary cells is the redox reaction.
During charging, the positive active material is oxidized, producing electrons, and the negative material is reduced, consuming electrons. In other words, one half reaction of oxidation and another half reaction of reductions makes a complete redox reaction.

I shall focus on the 3 most commonly used secondary cells in this post.

• Nickel-cadmium (NiCd)

Nickel-cadmium batteries has cadmium anode and nickel(III) oxyhydroxide cathode.
Anode is the positive electrode which undergoes oxidation while cathode is the negative electrode which undergoes reduction.
The electrolyte used in this reaction is potassium hydroxide (KOH).

The chemical reaction in nickel-cadmium battery during discharge is:

at the cadmium electrode, and

at the nickel electrode.

Therefore the net reaction during discharge is

When the battery is recharged, the reaction is reversed.
The flow of electrons from anode the cathode creates the electrical flow able to power up an electrical item.

• Nickel-metal-hydride

The anode of the NiMH battery is nickel hydroxide. The active material for the negative electrode in the NiMH battery is actually hydrogen, the same as it is in a nickel hydrogen battery, except that the hydrogen ions (protons) are stored in the metal hydride structure which also serves as the cathode.
The electrolyte used here is also potassium hydroxide (KOH).
During discharge, the chemical reaction is as follows:

Anode:

Cathode:

The "metal" M in the negative electrode of a NiMH cell is actually an intermetallic compound. Many different compounds have been developed for this application, but those in current use fall into classes as shown in the table below.

AxBy Class (Basis)	Components	Storage Capability (mA/g)	Comments
AB5 (LaNi5)	A: Mischmetal, La, Ce, Ti B: Ni, Co, Mn, Al	300	Most commonly used alloy group for NiMH battery applications
AB2 (TiNi2)	A: V, Ti B: Zr, Ni (+Cr, Co, Fe, Mn)	400	Basis of ‘multi-component alloys’ used in some NiMH battery systems
AB (ZrNi)	A: Zr, Ti B: Ni, Fe, Cr, V		Used in early development of hydrogen storage
A2B (Ti2Ni)	A: Mg, Ti B: Ni

Credits to http://www.cobasys.com/pdf/tutorial/InsideNimhBattery/inside_nimh_battery_technology.html.

• Lithium-ion battery

The electrodes of this secondary cell may differ. However the most commonly used positive electrode is graphite (c) and the cathode is generally one of three materials: a layered oxide, one based on a poly anion, or a spinel.
Electrolytes used in Li-ion batteries consist of lithium salts in an organic solvent.
Li-ion battery mainly works by having the Li ions move from anode to cathode and then from cathode to anode. When a cell is discharging, the lithium is extracted from the anode and inserted into the cathode. When the cell is charging, the reverse process occurs: lithium is extracted from the cathode and inserted into the anode.
The reaction would be:

With x as a variable coefficient based on moles.

Rechargeable batteries may cost more that normal batteries but the number of times we can recharge a battery back to life has already made every sen worth =)
Not forgetting also it does better for the environment compared to the disposable batteries.