Chapter 4: 4.4 Batteries Flashcards
Define:
Battery
A device that converts the chemical energy stored in its active materials into electrical energy
How are batteries classified?
- Primary
- Secondary
What are characteristics of primary batteries?
- Can only be used once
- Cannot be recharged, once it dies it is dead
What are some characteristics of secondary batteries?
- Rechargeable
What are the reasons that a battery dies?
- ΔG = 0
- Limiting reagent used up
What was the world’s first recheargeable battery? Describe it
Lead-Acid Battery
* A spiral roll of two sheets of pure lead
* Separated by a linen cloth
* Immersed in a sulfuric acid solution
Later made into a 9-cell version
What are key characteristics of a Lead-Acid Battery?
- Cheap, available components
- Low energy density
- High currents generated in short periods of time
How is a lead-acid battery recharged? What can this reaction be classified as?
Recharged by the current provided by the alternator (in a car)
A disproportionation reaction
What are the key characteristics of a Nickel-Cadmium (NiCd) Battery?
- Rechargeable
- Inexpensive
- Memory-effect
- Toxic
- Heavy
State:
The reactions for the cathode and anode of a lead-acid battery
- Anode: Pb to PbSO4
- Cathode: PbO2 to PbSO4
State:
The reactions for the cathode and anode of a nickel-cadmium battery
- Anode: Cd to CdO
- Cathode: NiO2 to NiO
Define:
Memory effect
(in NiCd batteries)
Gradually lose their maximum energy capacity after repeated recharging when they are not fully discharged (remembers the smaller capacity and only charges tot that level)
In a NiCd battery, what is memory effect caused by?
Due to crystal buildup; can be reversed by deep discharge and recharge
What are key characteristics to Nickel-Metal Hydride (NiMH) batteries?
- “Improved” NiCd batteries
- No toxicity
- Much less memory effect
- Better energy-to-weight ratio
State:
The reactions of the anode and cathode of a NiMH battery
- Anode: MH to M (MH stands for metal alloy)
- Cathode: NiO(OH) to Ni(OH)2
What are key characteristics of Lithium ion (Li-ion) batteries?
- Lightweight
- High energy density/energy-to-weight ratio
- Expensive
True or False:
Li+ ions are oxidized/reduced in a Li-ion battery
False, they undergo intercalation
What happens in a Li-ion battery? Describe the reactions at the anode and cathode of the battery
- Electrons flow to maintain charge neutrality as Li+ move
- Co is reduced during discharge
- Anode (graphite): LiC6 to Li+
- Cathode (CoO2): CoO2 to LiCoO2
True or False:
Various cathode materials can be used in an Li-ion battery
True
What are the downsides of Li-ion batteries?
- Can rupture, ignite, and/or explode when sujected to high temperature or overcharging
- Short circuits and electrolyte breakdown, causing fires
- Cannot deliver high currents
What is a Lithium-Polymer (Li-Pol) Battery?
A variation in lithium battery technology
* Uses a polymer (solid phase) electrolyte between the two electrodes
* As a result, a cyclindrical container is usually used to hold the max amount of reagents
What is an advantage of using a polymer electrolyte as opposed to using a liquid electrolyte?
Allows materials to be stacked with little chance of two electrodes coming into contact (means that these batteries can be made into virtually any shape)
