In today‘s life, mobile phones are more than just communication tools. They are used in work, social life or leisure, and they play an increasingly important role. In the process of using mobile phones, what makes people most anxious is when the mobile phone appears low battery reminder.

In recent years, a survey showed that 90% of people showed panic and anxiety when the battery level of their mobile phone was less than 20%. Although major manufacturers are working hard to expand the capacity of mobile phone batteries, as people use mobile phones more and more frequently in daily life, many people are gradually changing from one charge per day to N times a day, even many People will also bring power banks when they are away, in case they need it from time to time.

Living with the above phenomena, what should we do to extend the service life of the mobile phone battery as much as possible when we use mobile phones every day?

1. The working principle of lithium battery

At present, most of the batteries used in mobile phones on the market are lithium-ion batteries. Compared with traditional batteries such as nickel-metal hydride, zinc-manganese, and lead storage, lithium-ion batteries have the advantages of large capacity, small size, high voltage platform, and long cycle life. It is precisely because of these advantages that mobile phones can achieve a compact appearance and longer battery life.

Lithium-ion battery anodes in mobile phones usually use LiCoO2, NCM, NCA materials; cathode materials in mobile phones mainly include artificial graphite, natural graphite, MCMB/SiO, etc. In the process of charging, lithium is extracted from the positive electrode in the form of lithium ions, and finally embedded in the negative electrode through the movement of the electrolyte, while the discharge process is just the opposite. Therefore, the process of charging and discharging is the cycle of continuous insertion/deintercalation and insertion/deintercalation of lithium ions between the positive and negative electrodes, which is vividly called the "rocking chair battery".

2. the reasons for the decline in the life of lithium-ion batteries

The battery life of the newly purchased mobile phone is still very good at the beginning, but after a period of use, it will become less and less durable. For example, after a new mobile phone is fully charged, it can last for 36 to 48 hours, but after an interval of more than half a year, the same full battery may only last for 24 hours or even less.

(1). Overcharge and overdischarge

Lithium-ion batteries rely on lithium ions to move between the positive and negative electrodes to work. Therefore, the number of lithium ions that the positive and negative electrodes of a lithium-ion battery can hold is directly related to its capacity. When the lithium-ion battery is deeply charged and discharged, the structure of the positive and negative materials may be damaged, and the space that can accommodate lithium ions becomes less, and its capacity is also reduced, which is what we often call a reduction in battery life. .

Battery life is usually evaluated by cycle life, that is, the lithium-ion battery is deeply charged and discharged, and its capacity can be maintained at more than 80% of the number of charge and discharge cycles.

The national standard GB/T18287 requires that the cycle life of lithium-ion batteries in mobile phones is not less than 300 times. Does this mean that our mobile phone batteries will become less durable after being charged and discharged 300 times? the answer is negative.

First, in the measurement of cycle life, the attenuation of battery capacity is a gradual process, not a cliff or step;

Second, the lithium-ion battery is deeply charged and discharged. During daily use, the battery management system has a protection mechanism for the battery. It will automatically power off when it is fully charged, and it will automatically shut down when the power is insufficient. To avoid deep charging and discharging, therefore, the actual life of the mobile phone battery is higher than 300 times.

However, we cannot completely rely on an excellent battery management system. Leaving the mobile phone in low or full power for a long time may damage the battery and reduce its capacity. Therefore, the best way to charge a mobile phone is to charge and discharge shallowly. When the mobile phone is not used for a long time, maintaining half of its power can effectively extend its service life.

(2). Charging under too cold or too hot conditions

Lithium-ion batteries also have higher requirements for temperature, and their normal working (charging) temperature ranges from 10°C to 45°C. Under low temperature conditions, the electrolyte ionic conductivity decreases, the charge transfer resistance increases, and the performance of lithium-ion batteries will deteriorate. The intuitive experience is the decrease in capacity. But this kind of capacity decay is reversible. After the temperature returns to room temperature, the performance of the lithium-ion battery will return to normal.

However, if the battery is charged under low temperature conditions, the polarization of the negative electrode may cause its potential to reach the reduction potential of lithium metal, which will lead to the deposition of lithium metal on the surface of the negative electrode. This will lead to a decrease in battery capacity. On the other hand, there is lithium. The possibility of dendrite formation can cause a short circuit of the battery and cause danger.

Charging a lithium-ion battery under high temperature conditions will also change the structure of the lithium-ion positive and negative electrodes, resulting in an irreversible decline in battery capacity. Therefore, try to avoid charging the mobile phone under too cold or too hot conditions, which can effectively extend its service life.

3. Regarding charging, are these statements reasonable?

Q1. Will charging overnight have any effect on the battery life of the mobile phone?

Overcharge and overdischarge will affect the life of the battery, but charging overnight does not mean overcharging. On the one hand, the mobile phone will automatically power off after it is fully charged; on the other hand, many mobile phones currently use a fast charging method of first charging the battery to 80% capacity, and then switching to a slower trickle charge.

Q2. The summer weather is very hot, and the mobile phone will experience high temperature when charging. Is this normal, or does it mean that there is a problem with the battery of the mobile phone?

Battery charging is accompanied by complex processes such as chemical reactions and charge transfer. These processes are often accompanied by the generation of heat. Therefore, it is normal for the mobile phone to generate heat when charging. The high temperature and hot phenomenon of mobile phones is generally caused by poor heat dissipation and other reasons, rather than the problem of the battery itself. Remove the protective cover during charging to allow the mobile phone to better dissipate heat and effectively extend the service life of the mobile phone. .

Q3. Will the battery life of the mobile phone be affected by the power bank and car charger charging the mobile phone?

No, no matter whether you use a power bank or a car charger, as long as you use a charging device that meets the national standards to charge the phone, it will not affect the service life of the phone battery.

Q4. Plug the charging cable into the computer to charge the mobile phone. Is the charging efficiency the same as the charging plug plugged into the power socket connected to the charging cable to charge the mobile phone?

Whether it is charged with a power bank, car charger, computer or directly plugged into the power supply, the charging rate is only related to the charging power supported by the charger and mobile phone.

Q5. Can the mobile phone be used while charging? What caused the previous case of "Electric death while calling while charging"?

The mobile phone can be used when it is charged. When charging a mobile phone, the charger converts 220V high-voltage AC power through a transformer into a low-voltage (such as a common 5V) DC to power the battery. Only the low-voltage part is connected to the mobile phone. In general, the safe voltage of the human body is 36V. That is to say, under normal charging, even if the phone case leaks, the low output voltage will not cause harm to the human body.

As for the relevant news on the Internet about "calling and being electrocuted while charging", it can be found that the content is basically reprinted. The original source of the information is difficult to verify, and there is no report from any authority such as the police, so it is difficult to judge the truth of the relevant news. sex. However, in terms of using qualified charging equipment that meets national standards to charge mobile phones, "the phone was electrocuted while charging" is alarmist, but it also reminds the masses of people to use official manufacturers when charging mobile phones. A charger that meets the relevant national standards.

In addition, do not disassemble the battery autonomously during the use of the mobile phone. When the battery is abnormal such as bulging, stop using it in time and replace it with the mobile phone manufacturer to avoid safety accidents caused by improper use of the battery as much as possible.

The above article comes from scientific rumors, the author Cao Bowei