| Battery Principle What is battery?
A battery is a source of electrical energy. It is consisted by two substances, and represented by two electrochemically active electrodes of different composition, both of which are immersed in an electrolyte that provides a conductive medium between them. When a battery is connected on an outside load, it provides energy by conveying its internal electrochemical. What is the difference between primary and secondary battery?
A primary battery can discharge once only, while a second battery is rechargeable. When discharge a rechargeable battery, its electrode volume and structure cause a reversible change. Therefore the design of a rechargeable battery must be adequate to adjust these changes. Since a primary battery internal structure is more simple, it doesn't have to accommodate reversible volume changes. The primary battery has bigger quality ratio and volume ratio than rechargeable battery, however it has a far bigger impedance, consequently the load capability is lower. Furthermore self-discharge of a primary battery is far lower than secondary one. What is IEC?
IEC is the abbreviation of International Electrical Commission, which is a worldwide organization of national electrical commission. To promote the standardization in electrician and electron area is its goal. Currently there have been IEC285 for Ni-Cd cell and IEC61436 for Ni-MH. For Li-ion cell doesn't have any IEC standards yet, generally it is based on Sanyo or Panasonic. What is the electrochemistry principle of Ni-Cd battery?
As for Ni-Cd cell, which Ni(OH)2 is used for positive, CdO for negative, KOH for basis electrolyte, when Ni-Cd is charged, its positive reacts as below:
Ni(OH)2 - e + OH- -> NiOOH + H2O
Negative reaction is:
Cd(OH)2 + 2e -> Cd + 2OH-
The whole reaction is described as: 2Ni(OH)2 + Cd(OH)2-> 2NiOOH+ Cd+ 2H2O
When discharged, the reaction is reversible: NiOOH + H2O + e -> Ni(OH)2 + OH-
Cd + 2OH- + 2e -> Cd(OH)2
Ni(OH)2 consistence reduced with NiOOH consistence increasing during charging, and the positive electrical potential gradually raised, while with Cd increasing, Cd(OH)2 is decreased, and the negative electrical potential gradually reduced. When fully charged, the battery's positive and negative electrical potential reached a balance value; and the electrical potential between the two electrodes is battery charge voltage. What is the electrochemistry principle of Ni-MH battery?
Ni-MH has the similar Ni oxide with Ni-Cd as its positive, hydrogen metal as negative, KOH as basis electrolyte. When Ni-MH cell is charged, positive reaction is:
Ni(OH)2 - e + OH- -> NiOOH + H2O
Negative reaction is: MHn + ne -> M + n/2H2
Discharged, positive reaction is:NiOOH + H2O + e -> Ni(OH)2 + OH-
Negative reaction is: M + n/2H2 -> MHn + ne What is the electrochemistry principle of Li-ion battery?
Major element of Li-ion cell positive is LiCoO2,negative is mainly C. When charged,
Positive reaction is: LiCoO2 -> Li1-xCoO2 + xLi+ + xe-
Negative reaction is: C + xLi+ + xe- -> CLix
Total reaction is: LiCoO2 + C -> Li1-xCoO2 + CLix
The reaction is reversible as discharged. What are the main compositions?
The main compositions are: positive plates, negative plates, separators, caps, cases, and insulation layers. How many battery package materials are frequently used?
1)Insulative rings (or paper) e.g. fibre paper, double sides pastern
2) PVC trademarked tubes
3) Connections plates: stainless steel plates, nickel plates, nickel plating steel plates
4) Lead plates: stainless steel plates (easily tin soldered), nickel plates (strong spot welding)
5) Plugs
6) Protectors: thermal switches, polyswitches, current-limited resistances
7) Boxes and cases
8) Plastic shells
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