Analysis and Prevention of Explosion of Lithium Battery

First talk about the origin and development of lithium batteries
In March 1976, the United States Exxon oil company engineer Whitingham made the prototype of the ** lithium battery - he used titanium sulfide as the negative electrode, lithium metal as the positive electrode, and lithium ion in the "positive electrode - negative electrode - positive electrode" The movement between the two forms a current and completes the charge-discharge process. Lithium batteries are much better than other rechargeable batteries at the time of energy density and self-discharge degree, which has led to the research and development boom in the scientific and business circles. In the 1980s, people continued to improve lithium batteries. For example, lithium-containing compounds were used as positive electrodes and carbon materials as negative electrodes, which made it smaller, more energy-intensive, more stable, and cheaper. Lithium batteries gradually It has become the mainstream of rechargeable batteries, especially on portable electronic devices, and has even been used as a power source for electric vehicles.



Explosion Analysis of Lithium Battery --- Embedded "Flying Bomb " in Electrolyte
According to a well-known popular science writer Marshall Brian in the lithium battery series article, most of the lithium battery explosion is caused by short circuit, the specific reasons include charging overvoltage / over current, use aging and so on.
In the manufacturing process of lithium batteries, due to the flaws in the manufacturing process itself, it is easy to leave metal dust, copper foil, and aluminum foil fragments between the two poles that should be insulated. These corners are randomly heated in the electrolyte when the battery is hot (more often when used for a long time or when charging), just like the rice grains in boiling water. If there are particles or fragments close to the diaphragm in the middle of the positive and negative stages of the battery, it may cause the diaphragm to be perforated, which may cause a micro short circuit. Since the organic electrolyte in the battery is flammable, micro-short circuit may cause explosion, burning and other accidents. Generally, there are three cases:
1. Producing a spark to ignite the electrolyte, thereby licking the plastic body and the flammable materials in contact with it, causing a fire;
2. Causes the temperature inside the battery to rise sharply, the space inside the battery is very small, and may explode due to increased pressure;
3. The temperature inside the battery rises slowly, and the battery case gradually dissolves, causing the corrosive electrolyte to leak.
The safety hazards of lithium batteries cannot be eliminated at present, because the advanced manufacturing process will inevitably bury "flying bombs" in the electrolyte. It should be pointed out that the formal sector has strict regulations on the production and sales of lithium batteries. In the qualified lithium batteries, the number and size of the fragments are controlled to a small extent, and the probability of breaking through the diaphragm is extremely low; Flame retardant materials are also used, and it is not easy to produce an open flame.
Explosion-proof measures <br> lithium battery safety problems of lithium battery manufacturers certainly know very well, so what they used explosion-proof measures it? Taking the laptop lithium battery as an example, the working principle is: when the lithium battery is nearly full charge and the discharge is nearly dry, the voltage will drop. After the control circuit detects this situation, the protection circuit is notified to cut off the power to prevent overcharging. Or over-discharge to avoid shortening battery life.
The current notebook lithium battery has a relatively complete multi-level protection mechanism, even in the case of abnormal power chargers and laptops, the laptop battery can be automatically protected, and generally does not explode. But once the control circuit and the protection circuit work weakened, the battery is on the verge of "danger." The lithium battery charge and discharge protection mechanism for electronic products such as mobile phones is similar.
No need to "keep away from it"
In recent years, the explosion of lithium-ion electronic products has been reported frequently, causing panic among many consumers. Some people often “keep away from each other” when charging their mobile phones and MP3s. Some people simply leave their laptop batteries for a long time because of fear. Caused retirement. However, from the survey results, most lithium battery explosions are caused by users not paying attention to safety tips, such as unauthorized modification, use of mismatched chargers, and placing the battery in extreme environments.



It should be pointed out that lithium battery technology, as a mature technology that has been successfully commercialized after more than 30 years of research, is guaranteed to be safe. The lithium battery of the regular label will go through numerous test procedures at the factory, and there will be an information feedback mechanism after the sale, so that the problem product can be recalled in time.
The US Transportation Security Administration (TSA) gives the following recommendations for safe use of lithium batteries :
1. Use the original charger: Charging time is the high incidence of lithium battery explosion. The original charger is more secure than a compatible charger.
2. Use a reliable battery: Try to buy the original battery or the well-known brand battery, do not buy "second-hand" or "parallel" to save money, this type of battery may be repaired, not as reliable as the original battery.
3. Do not put the battery in extreme environment: high temperature, collision, etc. are all important causes of battery explosion, try to keep the battery in a stable environment, away from high temperature.
4. Don't try to modify it: Many young people like to give their mobile phones "beauty", and some people are "daring and careful" to transform their mobile phones. But improper modification is extremely easy to cause an accident. A mobile phone is a sophisticated communication device. When designing, the manufacturer will strictly verify its security. After the modification, the battery may be in an environment that has not been considered before, which increases the safety hazard.