Production process and attention issues of polymer lithium battery

　　In the production process of polymer lithium ion batteries, the following factors must be paid attention to. The produced polymer lithium-ion battery is packaged and then formed. The conditions of formation are critical, because it involves the formation of SEI film to prevent the negative electrode from spontaneously reacting with the electrolyte; at the same time, it can also make good contact between the active material and the electrolyte. Generally speaking, each manufacturer has its own formation conditions

　　Abstract: In the production process of polymer lithium-ion batteries, the following factors must be paid attention to. The produced polymer lithium-ion battery is packaged and then formed. The conditions of formation are critical, because it involves the formation of SEI film to prevent the negative electrode from spontaneously reacting with the electrolyte; at the same time, it can also make good contact between the active material and the electrolyte. Generally speaking, each manufacturer has its own formation conditions

　　In the production process of polymer lithium ion batteries, the following factors must be paid attention to. The produced polymer lithium-ion battery is packaged and then formed. The conditions of formation are critical, because it involves the formation of SEI film to prevent the negative electrode from spontaneously reacting with the electrolyte; at the same time, it can also make good contact between the active material and the electrolyte. Generally speaking, each manufacturer has its own formation conditions.

　　polymer lithium ion battery/raw materials

　　1 For the negative electrode, in addition to using a polymer soluble in an organic solvent as a binder, a polymer soluble in an aqueous solution can also 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 conducive to the formation of 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 be ignored. The influence of the dispersion of the conductive agent on the negative electrode material has been described above, and it also plays the same role for the positive electrode material, affecting the performance of the positive electrode capacity and the rate performance of the battery. For example, for LiMn2O4, the use of a new type of process can ensure uniform dispersion of the conductive agent, low polarization, high capacity, and good rate performance than the traditional process. The relationship between the capacity and discharge rate of LiMn2O4 positive pole pieces prepared by different processes.

　　3 The ratio of positive electrode and 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 the formation of the SEI film. In addition, the thickness of the electrode has different requirements according to different materials.

　　4Currently commercial polymer lithium-ion batteries basically still use LiFP6 carbonate solution as a plasticizer. At higher temperatures (80~100℃), they will decompose under the triggering of trace moisture or alcohol, and produce Some toxic alkyl fluorinated phosphates. This thermal decomposition is suppressed by the action of the Lewis acid or the composite oxide of lithium and metal.

　　5 During the formation and cycling of polymer lithium-ion batteries, swelling and other phenomena may also occur. In the case of lithium cobalt oxide as the positive electrode, the phenomenon of swelling mainly occurs below 4V, which is caused by the reduction of the electrolyte. Of course, when it is in a charged state, the positive electrode is in a high valence state and gas is also generated. The swelling phenomenon of lithium cobalt oxide is significantly lower than that of LiNi0.8Mn0.1Co0.1O2. The latter begins to bloat above 32V. Therefore, for certain users, it is necessary to avoid bloating. This is a major indicator when selecting materials.

　　Precautions

　　During the formation process, the composition of the electrolyte has a significant effect on the swelling of the battery. For example, in the swelling based gel electrolyte of lithium-ion batteries assembled with different cathode materials of PVDF at 90°C for 4 hours under different charging conditions, using 1mol/LLiClO4 EC/PC electrolyte, about 60% of the electrode surface is present. The gas phase leads to the separation between the active particles of the negative electrode and the destruction of the structure; while the EC of 1 mol/LLiBF4 is 3%. Therefore, the shelf time after chemical conversion is related to the composition of the electrolyte. Some specific instructions about the formation. After formation, pick out the short-circuited battery, store it for a period of time, and then measure it. If the voltage decays quickly, the battery itself is also short-circuited and must be treated as a waste product to prevent it from entering the market and causing safety problems. After these steps, the buyer inspects the goods and then packs them out of the factory.

　　Battery maintenance common sense:

　　1 A common phenomenon on Ni-MH rechargeable batteries with memory effect. The specific performance is: if you start using the battery without being fully charged for a long time, the battery's power will drop significantly, even if you want to fully charge in the future, you will be dissatisfied. Therefore, the important way to maintain Ni-MH batteries is: the battery must be used up before charging can be started, and the battery can be put into use only when it is fully charged. The memory effect of commonly used lithium batteries can be negligibly small.

　　2 Fully charged and fully discharged is for lithium batteries.

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

　　Full charge refers to the process of connecting a fully discharged smart device, such as a mobile phone, to the charger until the phone prompts "full".

　　3 Overdischarge is for lithium batteries.

　　There will be a small amount of power inside the lithium battery after it is completely discharged, but this part of the power is very important to the activity and life of the lithium battery.

　　Over-discharge: After a complete discharge, if you continue to use other methods, such as: forcibly turning on the phone again, and connecting the battery to a small light bulb to consume residual power, this is called over-discharge, which will cause irreversible damage to the lithium battery.

　　4 Protection chip Lithium batteries have very strict requirements on the current and voltage that are connected during charging and discharging. In order to protect the battery from damage due to abnormal external electrical environments, a chip that manages the battery status is installed inside the battery body. This chip also has the function of recording battery capacity and correcting battery capacity. Now, even if it is a counterfeit mobile phone battery, this key protection chip will not be saved, otherwise the counterfeit mobile phone battery cannot be used for a long time.

　　5 Overshoot and overdischarge protection circuit The integrated battery management chip and circuit built in smart devices.

　　For example, there is such a circuit on a mobile phone, and its 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 remaining battery power and order the phone to shut down at an appropriate time to prevent over-discharge.

　　8 When starting up, check whether the battery has been completely discharged, if it has been completely discharged, prompt the user to charge, and then shut down.

　　9 Avoid abnormal battery or charging line power, disconnect the circuit when an abnormality is found to protect the phone.

　　10 Overcharge: It is for lithium batteries.

　　Under normal circumstances, when a lithium battery is charged to a certain voltage (that is, fully charged), the charging current will be cut off by the upper-level circuit, but because the voltage and current parameters of the built-in overshoot and overdischarge protection circuit in some devices are different (such as mobile phone battery holder charging), This leads to the phenomenon that although it is fully charged, the charging has not stopped. Overcharging can also cause damage to battery performance.

　　11 Activated lithium battery is not used for a long time (more than three months), it will produce passivation of the electrode material, and the battery performance will decline. You can use three full charge and full discharge to remove the purification, and give play to the highest performance of the battery.

　　2. Common misconceptions:

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

　　Answer: If you have nothing to do in your spare time, you can do so, but it is not necessary, because the activation operation does not have to be done the first time you use it. As long as it is continuously used, electrode passivation can slowly disappear without deliberate activation.

　　2 Do not use the mobile phone when charging, it is harmful to the battery, and it will also produce a large amount of radiation to harm the human body.

　　Answer: Whether using a mobile phone while charging is harmful to the battery depends on the situation (explained later in this article), but one thing is certain is that using a mobile phone during charging will never produce more radiation than usual.

　　Lithium battery can only be charged and discharged XXX times during its life cycle, so try to use automatic shutdown every time you use it, and try to fully charge it every time you charge it.

　　The first clause is correct, and the following is wrong.

　　Each of these times refers to a complete one. For example, charging from 20% to 30% stopping charging is only 1/10 times, and discharging from 80% to 60% can only be regarded as 1/5 times.

　　The first three charging must reach 12 hours, otherwise it will affect the battery performance.

　　If it is to activate the battery, it is enough to prompt the phone to be fully charged. Generally, the mobile phone will prompt to be fully charged within 5 hours. If you continue to connect the charger after completion, the overshoot and overdischarge protection circuit will cut off the charging current of the phone. After that, the battery is in an inactive state, and the effect is the same as removing the charging cable immediately after being fully charged.

　　The first three charging must reach 12 hours is for Ni-MH rechargeable batteries. As a result, many manufacturers habitually and ignorantly write in the lithium battery user manual. It is terrible to have no culture. International manufacturers such as Dell, Lenovo, Asus, and Apple will never have the words "12 hours" appear on their products. And for lithium batteries, this is a commonality and part of the principle. It is impossible for some manufacturers to produce it in 12 hours, and some manufacturers do not need it.

　　It should be noted that if you use a cradle charger, since most of the cradle chargers do not reach the highest current of the official line charger, the charging time may exceed 6 hours, but as long as it is fully charged, the seat charger will automatically cut off the power and use the line Charging is the same.

　　It is best to disconnect the charging cable immediately after it is fully charged to prevent overcharging.

　　The overshoot and overdischarge protection circuit is not vegetarian, OK! ! ! If overcharge occurs, it is mostly due to damage to the overshoot and overdischarge protection circuit, but in terms of current electronic product technology and pressure resistance, this probability is too low, so you don’t have to worry about it.

　　Once the mobile phone starts to prompt the user to charge, it must be charged immediately or turned off immediately to avoid over-discharge. The overshoot and overdischarge protection circuit is not vegetarian, OK! ! ! This circuit will be forced to shut down when necessary (that is, before over-discharge) without damaging the battery. The reminder of the mobile phone is to let the user know in advance, so as to deal with it or prepare psychologically in advance.

　　It should be noted that if the mobile phone has been automatically turned off, it must not be forced to turn on for the purpose of making a call, because it is likely to cause overdischarge, and due to the existence of protection, it will probably be overcharged before the power on is completed. The overdischarge protection circuit Power off forcibly.

　　Three, use correctly

　　1 Newly manufactured batteries: without any treatment, such as activation, etc., they can be directly put into normal use.

　　2 Batteries that have not been idle for a long time (within three months): Without any treatment (such as activation, etc.), they can be directly put into normal use.

　　3 batteries for a long time (more than three months): can be activated to maximize the battery activity, 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 processing before testing.

　　5 Normal charging method of lithium battery:

　　Charge at any time and stop charging at any time, don’t hesitate. This is an important advantage of lithium batteries-no memory effect. Please face up to this advantage and let your lithium battery exhibit this important advantage as much as possible.

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

　　High temperatures above 1.100°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℃ to 100℃ high temperature Yes, you read it right, starting from 35℃ (human body temperature is generally 36.2℃-37.2℃) battery life will be obviously affected by temperature. The higher the temperature, the greater the impact.

　　The design life of a lithium battery is at least 400 full charge and discharge cycles. If the mobile phone is charged once every three days, a battery should last at least three and a half years. But most batteries do not last that long. A large part of the reason is that the battery is affected by human body temperature, and the other part is because it is affected by the heat generated by other chips in the mobile phone.

　　Why do laptop batteries always feel less durable than mobile phones? That’s because: First, laptop computers generate more heat than mobile phones, and the heat from computer chips can easily be transferred to the battery when it exceeds 40°C. Second, in order to charge faster, the notebook charging current is generally high, the battery capacity is large, and the charging and discharging battery itself will also generate heat. Third, the battery is generally located on the lower panel, and it is not easy to dissipate heat.

　　Furthermore, if your device generates more heat during use, such as long-term phone calls, mobile phone playing large-scale games, notebook computer playing games, and this heat will be conducted to the battery, plus the battery's own heat during charging , Although there is no safety risk, it will also affect the battery.

　　So if you find that the charging device is heating up significantly (such as an iPhone while charging and playing 3D games), you can consider waiting for it to be fully charged before playing with the charging cable.

　　3. The temperature below -40℃ will reach the freezing point and freeze completely.

　　4.10℃ to -40℃ low temperature will reduce the battery life, but will not cause permanent damage to the battery, as long as the temperature returns to room temperature, the power will automatically recover.

　　5. What is the most afraid of the idle lithium battery:

　　High temperature above 1.35℃, same as medium lithium battery.

　　2. Idle after fully charged, the battery will age faster than usual.

　　3. Idle after discharging, the battery will self-discharge during the idle process, and self-discharge of the battery after full discharge will cause over-discharge.

　　4. When the temperature is below -40℃, it will freeze to the freezing point completely.

　　5. Ideal state of lithium battery:

　　The ambient temperature of the idle lithium battery is around 20°C (almost indoor temperature). At this time, the battery discharge and charge performance can be maximized. If you want to idle the battery for a long time (more than three months), please charge it to about 40% before leaving it idle (for a short time, the key is trouble). Because of this, when the battery leaves the factory, the battery factory basically charges it to 40% before leaving the factory.

　　The lower the temperature of the idle battery, the slower the aging, but it should not be lower than -40°C.