In the production process of lithium battery packs, after the production of
the electrode plates is completed, the positive and negative electrode plates
and separators are assembled and manufactured by winding or lamination to form
the basic battery core. Subsequently, the battery core is generally hot-pressed
and shaped. The following is a brief introduction to the process and process
control points of the hot press shaping process. Keep your eyes open and
watch.
1. Lithium battery pack production process
In order to make the lithium-ion battery cells straight and avoid shrinkage
and recovery after shaping. The battery hot pressing shaping process is as
follows: Place the wound or laminated battery core on the template, set the
pressure of the booster cylinder and the temperature of the template, and then
the upper and lower templates shape the battery core under a certain pressure
and temperature to achieve The consistent thickness of the battery core reduces
the elasticity of the battery core, reduces the core installation qualification
rate and ensures the consistency of the thickness of the finished battery
core.
For square batteries, the hot pressing shaping device is shown in Figure 1.
The upper and lower templates are flat plates, and the flat plates are clamped
under pressure to flatten the cells.
For cylindrical batteries, the hot pressing shaping device is shown in
Figure 2. It consists of two cylinders fixed on the base to produce relative
motion. There are two semi-circular molds with cylindrical grooves at the ends
of the piston rods of the two cylinders. The two semi-circular molds have
cylindrical grooves. The radius is equal to and equal to or smaller than the
preset core radius. Use a manipulator or clamp to clamp the winding core and
place it at the center of the two semi-circular dies. Control the two cylinders
to drive the two semi-circular dies to move toward each other, causing the two
semi-circular dies to squeeze the winding core, thereby shaping the winding to
Preset dimensions to fit into matching housing.
Generally, during the hot pressing and shaping of the battery core, the
insulation withstand voltage test of the battery core is performed at the same
time to detect whether there is a micro short circuit inside the battery core.
If there are tiny metal foreign matter particles inside the battery core, the
battery core diaphragm will be pierced when the battery core is pressed down,
and it is easy to detect micro-short-circuit defective products.
2. Key points of lithium battery pack production process
The main process parameters for hot pressing and shaping of battery cores
include pressurization pressure, pressurization time and template temperature.
Under appropriate process parameters, there is almost no air inside the thick
battery core, the separator and the pole piece are tightly bonded together, and
the loose battery core can become a hard block. In the process determination
test, the test items include the air permeability and thickness changes of the
separator; whether the thickness of the battery core meets the requirements for
shell insertion; whether the pole piece is broken, etc.
As the core component of the lithium battery pack, the battery separator
plays a key role in isolating electron conduction between the positive and
negative electrodes and allowing lithium ions to pass back and forth between the
two poles. The microporous structure on the separator is how these ions travel
to and from the positive and negative electrodes. An important channel, its
breathability will directly affect the performance of the battery. The
breathability of the separator refers to the amount of gas that can pass through
the separator under a certain time pressure. If the separator has poor air
permeability, it will affect the transfer of lithium ions between the positive
and negative electrodes, thereby affecting the charging and discharging of
lithium batteries.
The test process is: fix the battery separator, apply air pressure on one
side of the separator, measure the air pressure drop and the time used, and
detect the air permeability of the separator. The shorter the time used, the
better the air permeability. During the hot pressing process, the separator may
be severely compressed, and the thickness of the separator changes greatly,
causing the micropores to be blocked, and the separator will become transparent
when viewed with the naked eye. This situation indicates that the hot pressing
shaping effect on the battery core exceeds the limit and will affect lithium
ions. transmission. The wound battery core is shown in the figure.
If the pole pieces are relatively brittle, the bent areas of the battery
cells are prone to powder loss or even breakage during hot pressing and shaping,
which will result in limited electron transmission and increase the internal
resistance of the battery. Therefore, hot pressing and shaping of the battery
core must also avoid this situation. These two aspects require that the hot
press shaping pressure should be as small as possible and the time as short as
possible.
3. Safety issues to pay attention to during the production process of
lithium batteries
⑴Insufficient understanding of the toxicity of battery fluid. Many
companies do not know that battery fluid is toxic.
⑵ Optimization of the composition of the electrolyte. The requirement for
the electrolyte in the lithium battery production process is to maintain
capacity and extend battery life:
⑶The high bonding strength of the electrode coating is conducive to
reducing the cycle capacity decline rate. It is the most technical process in
the lithium battery production process, so attention should be paid to this.
⑷Insufficient understanding of the fire and explosion hazards of lithium
battery packs.
Okay, the above is a detailed explanation of the lithium battery pack
production process and the safety issues that should be paid attention to when
producing lithium battery packs. Do you remember it? Do you understand it? If
not, then quickly save this article and keep it for future research.
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