Working Principle and Assembly Process of Lithium Battery

Lithium-ion batteries use carbon materials as negative poles, lithium-containing compounds as positive poles, and no metallic lithium exists, only lithium ions. Lithium-ion batteries refer to the general term for lithium ion embedded compounds as positive material batteries. The process of charge and discharge of lithium-ion batteries is the process of embedding and de-embedding lithium-ion batteries. In the process of embedding and de-embedding of lithium ions, it is accompanied by the embedding and de-embedding of equivalent electrons with lithium ions(traditionally the positive pole is represented by embedding or de-embedding, and the negative pole is represented by insertion or de-embedding). In the process of charging and discharging, lithium ions are embedded/de-embedded and inserted/de-inserted between positive and negative poles, and are vividly referred to as "rocking chair batteries."

Lithium-ion batteries have high energy density and high average output voltage. Self-discharge is small, less than 10 % per month. No memory effects. The operating temperature range is -20 °C to 60 °C. High cycle performance, fast charging and discharging, charging efficiency up to 100 %, and output power. Long service life. There is no environmental pollution and it is called a green battery.

Mechanism of action

Lithium-ion batteries use carbon materials as negative poles, lithium-containing compounds as positive poles, and no metallic lithium exists, only lithium ions, which are lithium-ion batteries. Lithium-ion batteries refer to the general term for lithium ion embedded compounds as positive material batteries. The process of charge and discharge of lithium-ion batteries is the process of embedding and de-embedding lithium-ion batteries. In the process of embedding and de-embedding of lithium ions, it is accompanied by the embedding and de-embedding of equivalent electrons with lithium ions(traditionally the positive pole is represented by embedding or de-embedding, and the negative pole is represented by insertion or de-embedding). In the process of charging and discharging, lithium ions are embedded/de-embedded and inserted/de-inserted between positive and negative poles, and are vividly referred to as "rocking chair batteries."

When the battery is charged, lithium ions are generated on the positive electrode of the battery, and the resulting lithium ions move through the electrolyte to the negative electrode. The carbon as a negative electrode has a layered structure. It has many micro-pores. Lithium ions that reach the negative electrode are embedded in the micro-pores of the carbon layer. The more lithium ions embedded, the higher the charging capacity. Similarly, when the battery is discharged(that is, when we use the battery), the lithium ions embedded in the negative carbon layer are removed and moved back to the positive pole. The more lithium ions that return to the positive pole, the higher the discharge capacity.

In general, the charging current of a lithium battery is set between 0.2 C and 1C. The greater the current, the faster the charge, and the greater the battery heat. Moreover, excessive current charging is not full enough because the electrochemical reaction inside the battery takes time. Just like pouring beer, if you pour too fast, you will produce foam, but you are dissatisfied.

Use(discharge) precautions

For batteries, normal use is the process of discharge. Lithium battery discharge needs to pay attention to several points:

First, the discharge current must not be too large. Excessive current causes heat inside the battery and may cause permanent damage. On the phone, there's nothing wrong with that.

The larger the discharge current of the battery, the smaller the discharge capacity and the faster the voltage drop.

Second, absolutely not over discharge! The internal storage of electrical energy in a lithium battery is achieved by a reversible chemical change in electrochemistry. Excessive discharge will lead to an irreversible reaction of this chemical change. Therefore, the lithium battery is most afraid of over discharge. Once the discharge voltage is lower than 2.7 V, it may cause the battery to scrap. Fortunately, the protective circuit has been installed inside the cell phone battery. The voltage is not yet low enough to damage the battery. The protective circuit will work and stop the discharge.

The working principle of lithium-ion batteries refers to its charging and discharging principle. When the battery is charged, lithium ions are generated on the positive electrode of the battery, and the resulting lithium ions move through the electrolyte to the negative electrode. The carbon as a negative electrode has a layered structure. It has many micro-pores. Lithium ions that reach the negative pole are embedded in the micro-pores of the carbon layer. The more lithium ions embedded, the higher the charging capacity.

Similarly, when the battery is discharged(that is, when we use the battery), the lithium ions embedded in the negative carbon layer are removed and moved back to the positive pole. The more lithium ions that return to the positive pole, the higher the discharge capacity. What we usually refer to as battery capacity refers to discharge capacity.

It is not difficult to see that in the process of charging and discharging of lithium ion batteries, lithium ions are in a state of motion from positive to negative to positive. If we compare the lithium-ion battery image to a rocking chair, the two ends of the rocking chair are the two poles of the battery, and the lithium ion is like a good athlete, running back and forth between the two ends of the rocking chair. So experts gave lithium-ion batteries a cute name for a rocking chair battery.

1 Pulp:

Using special solvents and adhesives, they were mixed with powder positive and negative active substances. After high speed stirring, the positive and negative polar substances were formed.

Working Principle and Assembly Process of Lithium Battery

2 coating:

The resulting slurry is evenly coated on the surface of the metal foil, dried, and made into positive and negative polar plates.

Working Principle and Assembly Process of Lithium Battery

3 Assembly:

According to the positive electrode-diaphragm-negative electrode-diaphragm arranged in a top-down order, winding into a battery core, and then injected into the electrolyte, seal and other process, that is, complete the battery assembly process, Made a finished battery.

4 into:

The battery of finished product is tested with special battery charging and discharging equipment, each battery is tested, and qualified finished battery is screened and ready to go out of the factory.

END

matters needing attention

The technology of lithium-ion battery is very strict and complicated. Here is a brief introduction!

(1) The electrode is divided into positive and negative materials by its polarity. Common negative material is graphite; There are many types of positive materials.

(2) Electrolytes can be divided into two categories: one is an aqueous solution of acid, alkali, and salt; The other is organic electrolyte solution. The electrolyte is a carrier of lithium ions transmitted by positive and negative electrodes, so it determines the battery's capacity, cycle efficiency, doubling, high and low temperature discharge, high temperature storage, life, and safety[ 23, 24] and  Organic electrolytes generally consist of the following substances: solvents, electrolytes, lithium salts, and additives. Commonly used organic solvents are ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate, different solvents have a great influence on the performance of the battery. For example, a solvent with a large dielectric constant can reduce the gravitational pull between lithium ions and fully liberalize lithium ions; Solvent flash point determines the working temperature of lithium ions[ 25, 26] and Lithium-ion salt is a material that provides lithium ions. It mainly has two series of inorganic salts and organic salts. Additives are substances that can significantly improve the performance of lithium ions. For example, membrane additives can prevent the destruction of the electrode by the solvent, and increase the capacity and circulation life of the electrode's imbedded lithium and de-lithium. In addition, there are anti-overcharge additives, conductive additives, flame retardant additives and so on.

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