What are the measures to prevent the explosion of 4s lipo battery?

The safety of 4s lipo battery is a complex and comprehensive problem. The biggest hidden danger in the safety of the 4s lipo battery is the random internal short circuit of the 4s lipo battery, resulting in on-site failure and thermal runaway. Therefore, the development and use of materials with high thermal stability is the fundamental way and the direction of efforts to improve the safety performance of 4s lipo battery in the future. Next, professional 4s lipo battery supplier CNHL will introduce you in detail several measures to prevent 4s lipo battery explosion.

1. Improve the thermal stability of 4s lipo battery material

Cathode materials can improve the thermal stability of cathode materials by optimizing synthesis conditions, improving synthesis methods, and synthesizing materials with good thermal stability; or using composite technology (such as doping technology) and surface coating technology (such as coating technology).
The thermal stability of the negative electrode material is related to the type of the negative electrode material, the size of the material particles and the stability of the SEI film formed by the negative electrode. If the particles are made into a negative electrode according to a certain proportion, the purpose of expanding the contact area between the particles, reducing the electrode impedance, increasing the electrode capacity, and reducing the possibility of active metal lithium precipitation can be achieved.

The quality of SEI film formation directly affects the charge and discharge performance and safety of 4s lipo battery. Weak oxidation of the surface of carbon materials, or reduction, doping, surface modification of carbon materials and the use of spherical or fibrous carbon materials help Improvement of SEI film quality.
The stability of the electrolyte is related to the type of lithium salt and solvent. The thermal stability of the 4s lipo battery can be improved by using a lithium salt with good thermal stability and a solvent with a wide potential stability window. Adding some high boiling point, high flash point and non-flammable solvents to the electrolyte can improve the safety of the 4s lipo battery.
The type and quantity of conductive agent and binder also affect the thermal stability of the 4s lipo battery. The binder and lithium react at high temperature to generate a lot of heat. Different binders have different calorific values, and the calorific value of PVDF is almost zero. 2 times of fluorine binder, replacing PVDF with fluorine-free binder can improve the thermal stability of 4s lipo battery.

2. Improve 4s lipo battery overcharge protection capability

In order to prevent the 4s lipo battery from being overcharged, a dedicated charging circuit is usually used to control the charging and discharging process of the 4s lipo battery, or a safety valve is installed on a single 4s lipo battery to provide a greater degree of overcharge protection; secondly, positive temperature can also be used Coefficient resistor (PTC), its mechanism is that when the 4s lipo battery heats up due to overcharging, the internal resistance of the 4s lipo battery is increased, thereby limiting the overcharge current; a special diaphragm can also be used, when the 4s lipo battery is abnormal When the temperature of the diaphragm is too high, the pores of the diaphragm shrink and block, preventing the migration and preventing the overcharge of the 4s lipo battery.

3. Prevent short circuit of 4s lipo battery

For the diaphragm, the porosity is about 40%, and the distribution is uniform. The diaphragm with a pore size of 10nm can prevent the movement of small particles of positive and negative electrodes, thereby improving the safety of 4s lipo battery;
The insulation voltage of the separator is directly related to the contact between the positive and negative electrodes. The insulation voltage of the separator depends on the material and structure of the separator and the assembly conditions of the 4s lipo battery.
The use of composite separators (such as PP/PE/PP) with a large difference between thermal closure temperature and melting temperature can prevent thermal runaway of 4s lipo battery.

The surface of the separator is coated with a ceramic layer to improve the temperature resistance of the separator. Using low melting point PE (125℃) to close the pores at lower temperature, PP (155℃) can maintain the shape and mechanical strength of the diaphragm, prevent the contact between the positive and negative electrodes, and ensure the safety of the 4s lipo battery .
It is well known that the graphite negative electrode is used to replace the metal lithium negative electrode, so that the deposition and dissolution of lithium on the surface of the negative electrode during the charging and discharging process becomes the intercalation and extraction of lithium in the carbon particles, which prevents the formation of lithium dendrites.

But this does not mean that the safety of the 4s lipo battery has been solved. During the charging process of the 4s lipo battery, if the positive electrode capacity is too large, metal lithium will be deposited on the surface of the negative electrode, the negative electrode capacity is too much, and the 4s lipo battery capacity loss is serious.
The coating thickness and its uniformity also affect the intercalation and deintercalation in the active material. For example, the surface density of the negative electrode is thick and non-uniform, so the polarization size is different everywhere during the charging process, and metal lithium may be locally deposited on the negative electrode surface.
In addition, improper use conditions can also cause a short circuit of the 4s lipo battery. Under low temperature conditions, the deposition rate is greater than the insertion rate, which leads to the deposition of metal lithium on the electrode surface and causes a short circuit. Therefore, controlling the ratio of positive and negative materials and enhancing the uniformity of coating are the keys to prevent the formation of lithium dendrites.

In addition, the crystallization of the binder and the formation of copper dendrites can also cause internal short circuits in the 4s lipo battery. In the coating process, all the solvent in the slurry is removed by coating, baking and heating. If the heating temperature is too high, the binder may also crystallize, which will cause the active material to peel off and short-circuit the inside of the 4s lipo battery.
Under over-discharge conditions, when the 4s lipo battery is over-discharged to 1-2V, the copper foil as the negative electrode current collector will begin to dissolve and precipitate on the positive electrode. Internal short circuit of lipo battery.
The above is all the content brought to you today by CNHL lithium 4s lipo battery manufacturers. I hope the above content can help you better understand the measures to prevent the explosion of 4s lipo battery, so that you can use 4s lipo battery safely.
More information about lithium batteries can be found below:
Detailed explanation of 6s lipo battery cathode material
Lipo battery 3s management system and its necessity