How Lithium-Ion Batteries Work

Introduction The working principle and mechanism of lithium-ion batteries use carbon materials as the negative electrode and lithium-containing compounds as the positive electrode. There is no metallic lithium, only lithium ions.

How Lithium-Ion Batteries Work

Mechanism of action

Lithium-ion batteries use carbon materials as the negative electrode and lithium-containing compounds as the positive electrode. There is no metallic lithium, only lithium ions. Lithium ion battery. Lithium-ion battery refers to the general term for batteries using lithium-ion intercalation compounds as positive electrode materials. The charging and discharging process of lithium-ion batteries is the process of intercalation and deintercalation of lithium ions. During the process of intercalation and deintercalation of lithium ions, it is also accompanied by the incorporation and deintercalation of electrons equivalent to lithium ions (it is customary to express the positive electrode as insertion or deintercalation, and the negative electrode by insertion or deintercalation). During the charging and discharging process, lithium ions are intercalated/disintegratedrspaced and inserted/deinterspersed between the positive and negative electrodes, which is vividly called "rocking chair battery".

When the battery is charged, lithium ions are generated on the positive electrode of the battery and the generated lithium ions move to the negative electrode via the electrolyte. The carbon used as a negative electrode has a layered structure with numerous micropores. The lithium ions that reach the negative electrode are integrated into the micropores of the carbon layer. The more lithium ions, the higher the charging capacity. Similarly, when the battery is discharged (that is, the process in which we use the battery), the lithium ions embedded in the carbon layer of the negative electrode are released and return to the positive electrode. The more lithium ions returned to the positive electrode, the higher the discharge capacity.

Generally, the charging current of thelithium batteries is set between 0.2 C and 1 C. The higher the current, the faster the charge and the hotter the battery. Additionally, charging with too much current will not fully fill the capacity because the electrochemical reaction inside the battery takes time. Just like pouring beer, if you pour it too quickly it will produce foam and make it unsatisfactory.

Precautions for use (discharge)

For batteries, the normal use is the discharge process. There are several points to note when discharging lithium batteries:

First, the discharge current should not be too large. Excessive current will cause internal heating of the battery and may cause permanent damage. On mobile phones this is no problem and can be ignored.

As the right picture shows, the higher the battery discharge current, the higher the capacity of the battery.e discharge is weaker and the more quickly the voltage drops.

Second, you should not overload! The internal storage of electrical energy in lithium batteries is achieved by a reversible chemical change in electrochemistry. Excessive discharge will cause an irreversible reaction of this chemical change. Therefore, lithium batteries are more afraid of over-discharge once the discharge voltage is lower. exceeds 2.7V, it may cause the battery to be discarded. Fortunately, cell phone batteries have built-in protection circuits. The protection circuit will come into effect and stop discharging before the voltage is low enough to damage the battery.

Lithium battery charging circuit, please help to analyze whether this circuit can work properly

A. The total reaction of thebattery obtained by adding the reactions of the positive and negative electrodes is FePO 4 + Li < td> Discharge
Charge
LiFePO 4, so A is correct ;

B. When K and N are connected, it is the primary battery. When discharging, B is the negative electrode. When the primary battery operates, cations move toward the positive electrode and anions move toward the negative electrode, so B is false; p>

C. When K and M are connected, it is an electrolytic cell, A is the anode, and an oxidation reaction occurs at the anode, so C is correct;

D. At least chemical energy is converted to electrical energy, electrical energy is converted to chemical energy, and electrical energy is converted to light energy, so D is correct.

Then choose B.

Which circuit is this? If there is no image, how can I see it. Can you understand the principle of single cell protection board? p>

1. Overload protection point and overload protection recovery point voltage

When the battery charging voltage reaches the set value VC, 4.125-4.300 V (the specific voltage of the overload protection point Overcharge protection depends on the setting of the chip manufacturer, the manufacturer's application can select the IC chip according to the specific parameters and requirements of the battery core), as shown in the figure above: when VD1 , the Cout pin becomes low, the MOS tube T1 is cut off and charged. stop ; when the battery core voltage drops back to VCR3.6-4.2V (the specific recovery voltage of overload protection depends on the parameter design of the built-in battery cell when conception of the integrated circuit), Cout produces a high level, the MOS tube T1 is on. and the load continues, the VCR must be smaller than VC by a fixed value to avoid frequent jumps.

2. Working principle of over-discharge protection and over-discharge protection recovery

During the battery discharge process, when the cell voltage is discharged and drops to the value set VD (2.1 -2.45V, overdischarge protection point voltage generally cannot be designed and can only be set by different chip manufacturers). When the output voltage VD2 is low, after a short delay, Dout becomes low, T2 is cut off and the discharge stops. When the battery is put into charge, the internal OR gate is reversed, causing T2 to go to again to prepare for the next discharge.

3. Overcurrent protection andShort circuits

When the battery discharges, when the charging circuit current exceeds the set value or is short-circuited, the voltage applied to the MOS tube T2 will increase, the level of the detection resistor R3 will produce a voltage drop after reaching the potential value set by the integrated circuit, cout2 will become a low level, the MOS tube T2 will be turned off, and the power will be cut off. The overcurrent value can be obtained by changing R3 to obtain the desired overcurrent value.

The above is the basic principle of battery protection board management for a single battery. This is very simple since the protection point voltage of different materials is different, as well as the protection point voltage and current of each manufacturer. are also different, so the products on the market There are many lithium battery protection IC chips and major solutions, includingincluding mobile power solutions. As a person engaged in the lithium battery industry, you need to understand the market better. The above chip parameters are used for which battery materials and IC prices are selected according to the different requirements of the process. This is based on accumulated experience.

This article comes from Shenzhen Maifeng Electronic Technology website

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