lipo battery 3s self-discharge dry goods!

Don't underestimate the impact of self-discharge of lipo battery 3s. Excessive self-discharge will not only affect the user experience, but may also hide some dangerous factors. Next, I will introduce the content of self-discharge of lipo battery 3s in detail. Everyone Take a few minutes to check it out with me.

Lipo battery 3s self-discharge

When the lipo battery 3s is in the open circuit state, the phenomenon that the stored power is spontaneously consumed is called the self-discharge of the battery, also known as the charge retention capacity of the lipo battery 3s, that is, the retention capacity of the battery stored power under certain environmental conditions.

Theoretically, the electrodes of the lipo battery 3s are in a thermodynamically unstable state under the state of charge, and the lipo battery 3s will spontaneously undergo physical or chemical reactions, resulting in the loss of chemical energy of the lipo battery 3s.
Self-discharge of lipo battery 3s is also one of the important parameters to measure battery performance. Different types of batteries have the same self-discharge factor and size. The self-discharge rate of lipo battery 3s is slightly better than that of lead-acid batteries, and significantly better than that of nickel-metal hydride batteries.

Types of lipo battery 3s self-discharge

Self-discharge can be divided into physical self-discharge and chemical self-discharge according to different reaction types.
Generally speaking, the energy loss caused by physical self-discharge is recoverable, while the energy loss caused by chemical self-discharge is basically irreversible.
physical self-discharge

The lipo battery 3s self-discharge caused by physical factors. At this time, part of the charge inside the battery reaches the positive electrode from the negative electrode and undergoes a reduction reaction with the positive electrode material.
The principle is not the same as that of conventional discharge. During normal Lipo battery 3s discharge, the electronic path is an external circuit, and the rate is very fast, while during self-discharge, the electronic path is electrolyte, and the rate is very slow.
Physical self-discharge is less affected by temperature. Continuous physical self-discharge may cause the lipo battery 3s open circuit voltage to be zero, but the energy loss caused by it is generally recoverable.

The cause of physical self-discharge is generally a physical micro-short circuit. When the lipo battery 3s diaphragm is damaged due to some factor, it will cause a physical micro-short circuit. There are mainly the following forms:
1. Burrs on the collector;
2. There is dust with larger particles on the surface of the diaphragm;
3. Metal impurities remaining on the positive/negative electrode sheets.
chemical self-discharge
The voltage drop and capacity decay caused by the spontaneous chemical reaction inside the battery. When chemical self-discharge occurs, no current is formed between the positive and negative electrodes, but a series of complex chemical reactions occur between the positive and negative electrodes of the lipo battery 3s and the electrolyte, resulting in the consumption of the positive electrode and the reduction of battery power.

In addition, the self-discharge process inside the lipo battery 3s is complicated, and two kinds of self-discharge may be carried out at the same time. Chemical reactions are greatly affected by temperature. In addition, chemical self-discharge does not cause charge depletion like physical self-discharge.
In the lipo battery 3s, chemical side reactions consume lithium ions in the electrolyte, resulting in a reduction in the number of intercalated/extracted lithium ions, which in turn leads to a reduction in the capacity of the lipo battery 3s. Both chemical side reactions and electrode consumption are irreversible.

Self-discharge is analyzed from the aspects of positive electrode, negative electrode and electrolyte:
1. Positive electrode: side reactions between the positive electrode/electrolyte interface and the dissolution of transition metal ions in the positive electrode;
2. Negative electrode: side reactions between the negative electrode/electrolyte interface and the formation of electron-ion-electrolyte complexes;
3. Electrolyte: the dissolution of the electrode material in the electrolyte; the corrosion of the negative electrode surface by the electrolyte or impurities; the electrode is covered by the insoluble solid or gas decomposed by the electrolyte to form a passivation layer, etc.

Factors affecting the self-discharge of lipo battery 3s

ambient temperature
The ambient temperature has a greater impact on the self-discharge of the lipo battery 3s. Studies have shown that lithium cobalt oxide batteries (LCOs) have faster capacity decay at higher ambient temperatures.
At high temperature, the aggravation of battery self-discharge can be

summarized as the following reasons:
1. The stability of the SEI layer deteriorates and ruptures, and the regeneration of the SEI consumes more lithium;
2. The high temperature causes the dissolution rate of the positive metal to accelerate;
3. The electrons are more active and easy to participate in the side reactions of the negative electrode/electrolyte;
4. The activity of the electrolyte is enhanced, and the side reaction between the electrolyte and the electrode is intensified.

Environment humidity
Studies have shown that in an environment with high humidity (relative humidity of 90% and above), the self-discharge loss of lipo battery 3s with no moisture-proof tabs is more serious than that of batteries with moisture-proof tabs. The researchers speculate that in a humid environment, the polarity of water molecules causes the electrons in the negative electrode of the lipo battery 3s to move to the tabs. In order to ensure the potential balance, the Li+ in the negative electrode of the lipo battery 3s will move to the negative electrode/electrolyte interface at the same time. Therefore, it is easier to form an electron-ion-electrolyte complex, which accelerates the reversible self-discharge; or it is easier to form an additional SEI layer and cause metal deposition, which increases the irreversible self-discharge loss.

Lipo battery 3s battery state of charge (SOC)
Studies have shown that at the same temperature, the capacity of lipo battery 3s under high SOC conditions decays faster. This is because under high SOC conditions, the anode is in a Li-rich state, which makes it easier to form an electron-ion-electrolyte complex, which intensifies the reversible self-discharge of the battery.

There are also studies that find that the capacity decay rate of 100% SOC batteries is smaller than that of 65% SOC batteries at 60 °C for lithium iron phosphate (LFP) batteries. It is speculated that this is because the negative electrode of LFP is in a two-phase transition state at about 70% SOC. , the decay laws of the high SOC and low SOC parts are inconsistent.
The so-called lipo battery 3s self-discharge is the phenomenon that the stored power of the lipo battery 3s is spontaneously consumed when the lipo battery 3s is in an open circuit state; the self-discharge of the lipo battery 3s mainly includes physical self-discharge and chemical self-discharge; Factors include temperature, humidity and state of charge.

The above is the whole content about the self-discharge of lipo battery 3s brought to you by Die Flash today. I hope it will be helpful to you. More information will be continuously updated. We will see you in the next issue.