What is inside a lithium battery?

According to the U.S. department of energy: “A battery is made up of an anode, cathode, separator, electrolyte, and two current collectors (positive and negative). The anode and cathode store the lithium. The electrolyte carries positively charged lithium ions from the anode to the cathode and vice versa through the separator. The movement of the lithium ions creates free electrons in the anode which creates a charge at the positive current collector. The electrical current then flows from the current collector through a device being powered (cell phone, computer, etc.) to the negative current collector. The separator blocks the flow of electrons inside the battery.”

Recently, many electric vehicle fires and explosions have once again pushed the safety of power batteries to the forefront. Peng Yumin, director of the Industrial Technology Research Institute, pointed out that the safety problems of lithium batteries mainly come from the increase in the internal temperature of the battery, including improper heating of the battery, overcharging, and short circuits caused by contact between the positive and negative materials, which will all cause the internal temperature of the lithium battery to rise.

What devices use lithium batteries?

Including mobile phones, mobile power supplies, etc. are using lithium batteries. Owing to the mobile products to be brought with yourself, if you use a normal battery, you must change it very often and feel inconvenient. Therefore, the light and long-lasting "lithium battery" is the best choice. Besides that, the lithium batteries are used as energy storage devices for ESS energy cabinets & systems.

What causes lithium batteries to catch fire?

Lithium battery has been developed for decades since published. Most mobile phones currently on the market also have built-in lithium batteries. Despite decades of development, lithium batteries still can not guarantee 100% safety, and even explode in some specific environments. Lithium Ion batteries are subject to Thermal Runaway, and this occurs when the separator blocking the flow of electrons in the battery fails. According to the statistics of the Fire Department of the Ministry of the interior in Taiwan, there have been 32 lithium battery fires throughout the country from January to May in 2020. The main reason for the lithium battery fire is that the heat is out of control. From energy storage power system to mobile power supply, the main cause of battery fire is thermal runaway.
The fire and explosion of lithium battery has the following characteristics:

  1. The negative electrode capacity of lithium battery is insufficient
    When the capacity of the negative part of the positive part of the lithium battery is insufficient, the lithium atoms generated during charging can not be inserted into the interlayer structure of the negative graphite, and will precipitate on the surface of the negative electrode to form crystals. Long term crystallization in lithium battery will lead to short circuit, when the cell discharges rapidly, a lot of heat will be generated and the diaphragm will be burned. High temperature will decompose the electrolyte into gas. When the pressure is too high, the cell will explode.
  2. High moisture content
    When charging, the water can react with lithium to produce lithium oxide, which will cause the capacity loss of the cell. It is easy to overcharge the cell and generate gas. The decomposition voltage of water is low, so it is easy to decompose and generate gas when charging. When this series of generated gas will increase the internal pressure of the cell, and when the shell of the cell cannot bear it, the cell will explode.
  3. Internal short circuit
    The short circuit of the internal cell will cause large current discharge, generate a lot of heat, burn the diaphragm, and cause greater short circuit phenomenon, which will decompose the electrolyte into gas. If the internal pressure is too high, the cell will explode.
  4. Overcharge of lithium battery
    When the cell is overcharged, the excessive discharge of lithium in the positive electrode will change the structure of the positive electrode, and the excessive discharge of lithium is easy to be unable to be inserted into the negative electrode, and also easy to cause lithium evolution on the surface of the negative electrode. Moreover, when the voltage reaches more than 4.5V, the electrolyte will decompose and produce a large amount of gas. All of which could cause an explosion of lithium batteries.
  5. External short circuit
    The external short circuit may be caused by the wrong connection of the positive and negative electrodes. Due to the external short circuit, the discharge current of the battery is very high, which will make the cell heat up. The high temperature will shrink or completely damage the diaphragm inside the cell, causing the internal short circuit and explosion.

The safety problems of lithium batteries do exist. In addition to the manufacturers must recognize and prevent the possible safety risks caused by the use of lithium batteries, the general consumers also have the responsibility. They must face up to the danger of lithium batteries and understand the combustion characteristics of lithium batteries in order to avoid accidents.