Small battery: 0.2C charged to 4.1V
Large battery: 0.05C charged to 3.45V; 0.1C charged to 3.95V; 0.2C charged at 3.95V
Just now it is necessary to start charging with a small current as this is the initial formation process of the SEI film. After that, the current can be slightly increased.
What is the reason for the precipitation of copper on the aluminum foil of the positive electrode?
For the lithium-ion secondary battery we manufacture, the current collector of the positive electrode is aluminum foil and the negative electrode is copper foil. During the initial training process, the voltage increases from about 0.5V to about 1.6V in about 15 minutes, which is very fast. No matter how hard I charged it, the tension couldn't build. I removed the battery and took it apart. I found copper on the surface of the positive. electrode. I don't know what it isbecause. Please give me some advice. THANKS !
I really hope that Brother Aubergine will pin it, because this phenomenon is very rare!
I think it's not copper, after all, the power inside is not too big,
And after disassembling the battery, it's there is current, the electrolyte is not yet dry,< /p>
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We will all notice that the negative electrode is made of gold.
But how can we judge the precipitation of copper in the positive electrode?
Are your batteries appearing in batches in the workshop? Or does it appear on individual stacks?
I think your battery polarity was reversed during training, which caused reverse charging during training, and the copper from the negative electrode dissolved and precipitated into the positive electrode. I think you can go back and find out if the battery was reverse charged?
Otherwise, I would also like to know whatis the reason.
If it is a problem with the battery test cabinet, I think the positive and negative poles are connected in reverse. In this way, the potential of the Cu foil must be low, so that the Cu will be oxidized during. charge, and the Cu ions will be dissolved in the electrolyte. They propagate to the other pole and settle, which is why the voltage cannot be charged.
Reverse charging - the positive pole becomes copper-plated<. /p>
I have encountered this problem before and it turns out that the battery is shorted and the battery voltage is still very low. When current flows again, the negative electrode dissolves under low voltage.< /p>
It must be reverse charging! It was placed upside down when put on the shelf. I have also encountered this before.
The battery was clamped upside down and electrolysis occurred.
My own data and experiences show that
No painful precipitation was observed when the positive and negative poles were reversed, but excessive discharge caused copper precipitation.
Overdischarge~
The copper was electrolyzed, transformed into ions, and ran to the positive electrode~~ When the discharge voltage of the lithium-ion battery is below 3.0 V and forced to continue discharging, copper will precipitate at the positive electrode. The principle is this: the negative electrode will lose electrons during discharge, and at that time all the lithium has gone to the positive electrode. Naturally, it cannot provide electrons, so only. carbon or copper can provide electrons, and copper provides electrons. The capacitance of copper is much stronger than that of carbon (you can tell by looking at the standard electrode potential of copper and carbon), so copper donates electrons, et copper which donates electrons. gives electrons which become copper ions. These ions need to be treated as usual.(I don't need to explain the reason), so the copper is deposited on the positive electrode.
This is due to excessive discharge, which is equivalent to reverse charging, which is also equivalent to copper. plating on aluminum.
Reverse charging, overdischarging and short circuiting of the battery will cause copper precipitation in the positive electrode.
gumphong explained it clearly. It's just that it's more difficult to analyze the reason. However, if it is at the beginning of its formation, the voltage range of 0.5V to 1.5V indicates that it can be charged and excessive discharge can be excluded (the initial low voltage cannot be considered excessive discharge). The possibility of reverse charging is relatively high. When the electrodes are connected in reverse, the voltageion continues to increase because there is still ion migration. So it takes 15 minutes to reach 1.5V. Generally speaking, charging to 2.6 V between 1000 and 1200 S (17 to 20 min) is considered normal. We see that the polarization of the poster is important when charging, or that the consumption is too high. We therefore assume that it is most likely a short circuit. When charging and consuming at the same time, a circuit appears inside the battery, so in theory it is as Gummhong says. Of course, the possibility of a counter-accusation cannot be ruled out. You can find a counter to confirm your channel and the problem will be resolved.
Answer: What is the reason for the precipitation of copper on the aluminum foil of the positive electrode?
Do not limit yourself to copper, red ** can be Co, Mn or CU
Given the situation you mentioned, Mn can be caused by a microphone short-circuit. the possibility of a disproportionate reaction is relatively high; the second possibility is that the instantaneous over-emission of CU is caused by a micro-short circuit; the third possibility is that your Li--Co--OO has a decomposition reaction (this possibility is relatively high). rare); the fourth possibility is that caused by instability of the electrolyte system.
What a fool, haha! It is recommended to leave the positive electrode exposed for a few hours and then observe the situation!
Answer: What is the reason for the precipitation of copper on the aluminum foil of the positive electrode?
Our company has specially organized and analyzed this problem. The most important thing is that the qualities of the positive and negative electrodes do not match correctly. For example, when the positive electrodes are much thicker than the negative electrodes. and the negative electrodes aret relatively thin, floor covering will occur. As Comrade Shang said: “When the discharge voltage of a lithium-ion battery is lower than 3.0V and the discharge is forced to continue, copper will precipitate at the positive electrode. The principle is: the negative electrode will lose electrons during discharge, and at that time all the lithium has arrived. When the positive electrode is gone, it naturally cannot supply electrons, so carbon or copper can only supply electrons, and copper has the ability to supply electrons. is much stronger than carbon (you can tell by looking at the standard electrode potentials of copper and carbon), so copper provides electrons, giving copper that has lost its electrons copper ions. These ions naturally serve as a positive electrode (I). no need to explain the reason), so the copper precipitates electricitypositive trode. » This poster analyzed the reason in great depth. This phenomenon is not a unique problem.
1. During reverse charging, the entire positive electrode sheet should be covered with copper
2. Due to a problem with the test cabinet, a small current was used for reverse charging. for a short time;
3, Battery short circuit, it is most likely, especially for small size batteries, if mass produced, the defect rate can reach 30-40%.
Cause. It is recommended to identify the pole piece. Analyze elementary content. What is the reason for the precipitation of copper on the aluminum foil of the positive electrode?
Reverse charging of the battery and short circuit of the battery will cause copper precipitation. In your case this is due to a short circuit. What is the reason for the precipitation of copper on the fpositive aluminum foil?
If the quantity is large, it is a reverse charge. If the quantity is small, it may be an internal short circuit. After identification, the element is made of copper, and it is indeed an internal short circuit. battery cell. It also mainly appears on small batteries (like 501220), and the proportion is not large. --------The possibility of short circuit and insect repellent is very high.