Is a lithium battery the same as a lithium cell
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2023/10/25 14:54:15
The lithium battery is mainly composed of two large blocks, the battery core and the protection board PCM, the protection board is mainly composed of the protection chip, MOS tube, resistor, capacitor and PCB board; The battery cell is equivalent to the heart of the lithium battery, the management system is equivalent to the brain of the lithium battery, and the battery cell is mainly composed of positive electrode material, negative electrode material, electrolyte, diaphragm and shell. There are some differences between the two.
For those who do not do batteries, most think that lithium batteries and lithium cells are the same, in fact, in general, it is also true. But there is still a difference, so where is the difference between lithium batteries and lithium cells?
battery cell
First of all, let's understand what is lithium cell. The whole of the cell is already a battery, but it is a core unit of the battery pack.
Structure of lithium battery cell:
1. Lithium battery cell positive electrode sheet: the positive electrode material is coated on aluminum foil, and then stamped.
2. Lithium battery cell negative electrode sheet: the negative electrode material is coated on copper foil, and then stamped.
3, lithium battery cell diaphragm: placed between the positive electrode plate and the negative electrode plate, the role of the diaphragm is to separate the positive and negative batteries to prevent direct short circuit between the two poles. The diaphragm itself does not conduct electricity, but electrolyte ions can pass through.
4, lithium battery cell ear: the main role of the ear is to transfer the internal positive and negative electrical energy to the external circuit. Polymer battery pole ear is positive aluminum strip, negative nickel strip, considering the sealing with aluminum-plastic packaging film, so in the sealing of the pole ear with a layer of pole glue. At the same time, because the positive aluminum strip is easy to break, special attention should be paid to protection during processing, transportation, storage, and use.
In order to ensure the sealing effect, the material of the pole ear glue is basically the same as that of the inner layer of the packaging film, mainly PE substances.
5, lithium battery cell packaging film: polymer battery adopts aluminum-plastic composite film packaging, which is divided into at least three layers: the middle layer is the aluminum layer, which plays the role of isolating water; The outer layer is a rubber layer, which protects aluminum from being oxidized by the external environment. The inner layer is a rubber layer, which acts as a seal and prevents the electrolyte from corroding the aluminum layer. The aluminum-plastic film is pressed to form the required shell shape. The pressure resistance of the aluminum-plastic film packaging is much worse than that of the metal shell battery, and the internal short circuit of the battery is easy to cause flatulence, and the severe seal will crack. Because of this, the safety performance of the battery packaged with aluminum-plastic film is better than that of the metal shell battery.
6, lithium battery cell electrolyte: electrolyte in the battery as a carrier of energy transfer. Lithium-ion battery voltage is as high as 3~4.2V, so the electrolyte can only be used with organic solvents, rather than aqueous electrolyte (water decomposition voltage is 1.23V).
Lithium ion batteries commonly used lithium salts are LiPF6, LiBF4, LiClO4, organic solvents PC(Propylene carbonate), EC(vinyl carbonate), BC(butene carbonate), DMC(dimethyl carbonate), DEC(diethyl carbonate), MEC(methyl vinyl carbonate) and so on.
The electrolyte used for lithium-ion batteries should have the following characteristics: high electrical conductivity, high chemical and electrochemical stability, wide temperature range, good safety, and cheap.
Generally, the voltage of a lithium battery cell is as follows:
Lithium battery nominal voltage (operating voltage) : 3.7V
Maximum charging voltage: 4.2V
Discharge cut-off voltage: 2.75V
Optimal storage voltage: 3.8V 0.1V(45%~60% capacity charged state)
Current industry shipping voltage: 3.8V ~3.9V
Overcharge protection voltage: 4.28V or less
This is the voltage data of a single lithium battery cell, so what is the saying of the 12V lithium battery, 36V lithium battery and 48V lithium battery that others often say? In fact, these batteries are actually accurate battery packs, which are assembled by a 3.6V lithium battery cell in series or series parallel. So the cell can be said to be a battery, but the battery can not necessarily be said to be a cell. This is the difference between lithium batteries and lithium cells.
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