Some notes about polymer lithium batteries

Some notes about polymer lithium batteries

During production of polymer lithium-ion batteries, the following factors must note. The produced polymer lithium-ion battery is packaged and then chemicalized. The formation conditions are more critical because it involves formation of an SEI film to prevent negative electrode from spontaneously reacting with electrolyte; at the same time, it can also bring good contact between the active material and the electrolyte. Normally, each manufacturer has its own formation conditions.

Polymer lithium-iron battery / raw material

1 For the negative electrode, in addition to using a polymer dissolved in an organic solvent as a binder, a polymer dissolved in an aqueous solution may be used as a binder. A schematic diagram of the structure of a water-soluble binder poly (acrylamide-co-diallyldimethylammonium chloride) (AMAC). Compared with polyvinylidene fluoride, it has certain advantages, which is beneficial to form a more conductive SEI film on the surface of the negative electrode, and the permeability of the organic electrolyte is better.

2 Although the dispersion of the conductive agent is not an important aspect, it cannot ignored. The influence of the dispersion of the conductive agent on the negative electrode material has described above, and the same effect exerted on the positive electrode material, which affects the function of the positive electrode capacity and the rate performance of the battery. For example, for LiMn2O4, the new process can ensure uniform dispersion of the conductive agent, low polarization, high capacity and good rate performance compared with the conventional process. The relationship between the capacity and discharge rate of LiMn2O4 positive electrode sheets prepared by different processes.

3 The ratio of the positive electrode to the negative electrode is also different for different raw materials. For example, for natural graphite // LiFePO4, the capacity of the latter should be equal to the sum of the capacity of natural graphite and the charge required for SEI film formation. In addition, the thickness of the electrode is different depending on the material.

4. At present, the polymer lithium-ion battery used in the commodity uses the carbonate solution of LiFP6 as a plasticizer, and decomposes at a higher temperature (80-100 ° C) under the action of a trace amount of water or alcohol, which produces some toxic alkyl fluoride phosphates. This thermal decomposition is inhibited by the action of a Lewis acid or a composite oxide of lithium and a metal.

5 In the formation and circulation of polymer lithium-ion batteries, swelling and other phenomena may also occur. In the case where lithium cobalt oxide is used as the positive electrode, the phenomenon of inflation mainly occurs below 4 V, which is caused by the reduction of the electrolyte. Of course, when in the state of charge, the positive electrode is in a high valence state, and gas generated. The swelling phenomenon of lithium cobalt oxide is significantly lower than that of LiNi0.8Mn0.1Co0.1O2. The latter began to swell above 32V. Therefore, for a specific user, the occurrence of inflation must avoided. This is a major indicator when selecting materials.

Precautions

During the formation process, the composition of the electrolyte has a significant effect on the gassing of the battery. For example, in a lithium-ion battery assembled with different PVDF cathode materials in a state of storage at 90 ° C for 4 h under different charging conditions, an EC/PC electrolyte solution of 1 mol/L LiClO 4 is used, and about 60% of the electrode surface exists. The gas phase causes separation and structural destruction between the negative active particles; and 1 mol/L of LiBF4 EC. Therefore, the shelf life after the formation related to the composition of the electrolyte. Some specific instructions about the formation. After the formation, the short-circuited battery picked out, then stored for a period, and then measured. If the voltage decays quickly, the battery itself is also short-circuited, and must treated as waste to prevent leakage into the market and create safety problems. After these steps, the buyer carries out the inspection and then boxes the factory.

Battery maintenance knowledge:

A memory phenomenon is common on nickel-metal hydride rechargeable batteries. The specific performance is if you start using the battery when you not fully charged for a long time, the battery's power will drop significantly, even if you want to be full in the future. Therefore, an important way to maintain NiMH batteries is that the electricity must use up before it can start charging. If it is fully charged, it can put into use. The memory effect of commonly used lithium batteries can be negligible.

2. Fully charged, fully discharged for lithium batteries.

Complete discharge refers to the process of adjusting the power consumption smart device, such as a mobile phone, to the lowest power state until the mobile phone automatically shuts down.

Fully charging refers to the process of fully discharging a powered smart device, such as a mobile phone, to the charger until the phone says "full".

3. Over-discharge is for lithium batteries.

A small amount of electricity left inside the lithium battery after complete discharge, but this part of the power is critical to the activity and life of the lithium battery.

Over-discharge: After full discharge, if you continue to use other methods, Such as forcibly turning on the mobile phone again, the battery connected to the small light bulb to consume residual power; this called over-discharge, which will cause irreversible damage to the lithium battery.

4. Protection chip Lithium battery has extremely strict requirements on the current and voltage of the battery when charging and discharging. In order to protect the battery from damaged due to abnormal external environmental environment, a chip for managing the battery state is set inside the battery body. This chip also has the function of recording battery capacity and correcting battery capacity. Now, even if it is a cottage mobile phone battery, it will not save this key protection chip, otherwise the cottage mobile phone battery cannot used for a long time.

5. Over-punching and over-discharging protection circuit the intelligent chip built into the battery and circuit for managing the battery.

For example, on a mobile phone, there is such a circuit, and the functions are as follows:

6. When charging, provide the most suitable voltage and current to the battery. Stop charging at the right time.

7. When charging, always check the residual battery power, and order the phone to shut down at an appropriate time to prevent excessive discharge.

8 When booting, check if the battery has completely discharged. If it has completely discharged, prompt the user to charge and then turn off the battery.

9 Avoid battery or charging line power abnormality, disconnect the circuit when abnormality is found, and protect the mobile phone.

10. Overcharge: It is for lithium batteries.

Under normal circumstances, when the lithium battery is charged to a certain voltage (that is, full), the charging current is cut off by the upper circuit, but the voltage and current parameters of the over-current protection circuit of some devices are different (such as mobile phone battery charger). This has caused the phenomenon that it is already full but has not stopped charging. Overcharging can also cause battery performance damage.

11. Activate the lithium battery for a long time (more than three months) without using, the electrode material will passivated, the battery performance will be degraded, and three times of full charge and complete discharge can be used to de-purify and exert the highest performance of the battery.

Second, common mistakes:

1 First use must fully discharged, and then fully charged, repeated three times in order to activate the battery. Otherwise the battery will never work!

Answer: If you are free to do nothing, you can do this, but it is not necessary, because the activation operation does not have to done on the first use. If it used continuously, the electrode passivation can be slowly disappeared without deliberate activation.

2 Do not use mobile phone during charging, it is harmful to battery. and it will cause excessive radiation damage to the human body.

Answer: Whether the use of the phone during charging is harmful to the battery depends on the situation (described later in this article), but one thing is certain: using the phone during charging will not produce more radiation than usual.

Lithium batteries can only charged and discharged XXX times in the life cycle, so use automatic shutdown every time you use them, and charge them to full power every time you charge.

The first clause is correct and the latter is wrong.

Each of these times refers to a complete one, such as charging from 20% to 30%, which is only 1/10 times, from 80% to 60%, only 1/5 times.

The first three charges must be 12 hours; otherwise, it will affect the battery performance.

If it is to activate the battery, it only needs to be fully charged. The general mobile phone will fully charged within 5 hours. If the charger continues after the completion, the overshoot protection circuit will cut off the charging current of the mobile phone. After that, the battery is in a non-state, and the effect of discharging the charging line immediately after it is full is the same.

The first three charges must be 12 hours for the nickel-metal hydride rechargeable battery. The result habitually and ignorantly written by many manufacturers in the lithium-battery user manual. No culture is terrible. International companies such as Dell, Lenovo, Asus, and Apple's products will never have the words "12 hours." Moreover, for lithium batteries, this is a commonality and part of the principle. It is impossible for some manufacturers to produce 12 hours, and some manufacturers do not.

It should noted that if the charger is used, since most of the chargers do not reach the maximum current of the official line charge, the charging time may exceed 6 hours, but if the battery is fully charged, the charger will automatically power off and use the line. The charge is the same.

When fully charged, it is best to remove the charging cable immediately to prevent overcharging.

Overshoot and over discharge protection, circuit is not vegetarian, OK! If overcharge occurs, most of it is due to over-punching and circuit damage of over-discharge protection, but in terms of current electronic product process and pressure resistance, this probability is low, no need to worry.

Once the mobile phone prompts the user to charge, it must charge immediately, or shut down immediately to avoid over-discharge. Overshoot and over discharge protection, circuit is not vegetarian, OK! This circuit will force a shutdown when necessary (that is, before over-discharge) without damaging the battery. The prompt of the mobile phone is to let the user know in advance to deal with or prepare in advance.

It should noted that if the mobile phone has been automatically shut down, it must not be forced to boot for a call, because it is likely to cause over-discharge, and due to the existence of protection, most of the over-discharge protection circuit will be over before the boot is completed. Forcibly power off.

Third, use correctly

1. New factory battery: no need for any treatment, such as activation, can put into normal use.

2. Batteries that are not in use for a long time (within three months): No, need for any treatment (such as activation), can be put into normal use.

3. set the battery for a long time (more than three months): can activated to make the battery activity the highest, or not, so that it will naturally return to the highest activity with normal use.

4. Sub-product evaluation personnel, in order to ensure the correct statistics of battery life, it is necessary to activate before the test.

5. Lithium battery normal charging method:

Charge at any time, and stop charging at any time, do not worry about it. This is an important advantage of lithium batteries - no memory effect, please face up to this advantage, and let your lithium battery to show its important advantages.

Fourth, what is the most afraid of lithium batteries at work?

1. High temperature above 100 °C will seriously affect the battery life and storage capacity, and may cause the battery to melt, or explode. Therefore, please keep the lithium battery away from fire and other heat sources.

2.35 ° C to 100 ° C high temperature Yes, you are not mistaken, starting from 35 ° C (body temperature is generally 36.2 ° C -37.2 ° C) battery life begins to be significantly affected by temperature, the higher the temperature, the greater the impact.

The design life of a lithium battery is at least 400 times full charge and discharge. According to the average charge of the mobile phone every three days, a battery should use for at least three and a half years. However, most of the batteries have not been able to live for so long; a large part of the reason is because the battery affected by human body temperature, and partly because of the heat generated by other chips on the phone.

Why does the battery of the laptop always feel that there is no durability of the mobile phone? That is because first, the notebook computer heats more than the mobile phone, and the heat of the computer chip easily transmitted to the battery, which is lighter than 40°C. Second, for faster charging, the notebook charging current is generally higher, the battery capacity is large, and the charging and discharging battery it hot. Third, the battery is generally located at the lower panel, which is less likely to dissipate heat.

Then, if your device is in use, it will generate more heat, such as a long phone call, a large game on a mobile phone, a game on a laptop, and this heat will transmitted to the battery, plus the heat of the battery itself during charging. Although it does not pose a security risk, it will also affect the battery.

So, if you find that the device in charge is very hot (such as playing the 3D game while the iPhone is charging), you can consider waiting for the full charge, then connect to the charging cable.

3.-40 °C below the low temperature will reach the freezing point and completely freeze.

4.10 ° C to -40 °C low temperature will reduce the battery life, but will not cause permanent damage to the battery, if the temperature returns to room temperature, the power will automatically recover back.

5. What the most afraid of lithium batteries in idle:

1.35 ° C above the high temperature, and the same lithium battery.

2. Idle after full power, the battery ages faster than usual.

3. After the discharge is idle, the battery will self-discharge during the idle process, and the battery will self-discharge after full discharge.

4.-40°C below the low temperature will reach the freezing point and completely freeze.

5. Lithium battery ideal state:

The idle environment temperature of lithium battery is suitable at around 20 ° C (almost the indoor temperature), at which time the battery discharge charging performance can maximized. If you want to idle the battery for a long time (more than three months), please be sure to charge it to about 40% and then idle (for a short time, the key is trouble). Because of this, when the battery is shipped, the battery factory charged to 40% and then shipped.

The lower temperature of idle battery, the slower aging is, but should no below -40°C.

The page contains the contents of the machine translation.