Safety Analysis of Lithium-ion Battery Mobile Power

Safety analysis of lithium ion battery mobile power supply (1) Internal factors affecting the safety of lithium ion battery 1. Materials. (1) The thermal stability of the positive electrode material and its reactivity with the electrolyte. Most cathode materials have good thermal stability in the discharged state and thermal instability in the charged state. Without contact with the electrolyte, the reason for the heat generation of the charged positive electrode material is mainly due to the change in the shape of the crystal. After the charged positive electrode contacts the organic electrolyte, it reacts with the electrolyte to oxidize the electrolyte and release a large amount of heat. (2) The safety of anode materials. The anode material should be chemically stable, able to form SEI with the electrolyte, and not react with the electrolyte, otherwise the large amount of heat generated by the reaction will cause the battery to explode. (3) Electrolyte composition. The role of the electrolyte for charge transfer is between the positive and negative electrodes of the battery. High conductivity and the chemical properties of the electrolyte must be stable to minimize the electrochemical reaction rate and the storage of interfacial active materials between the electrolyte, so the battery The self-discharge capacity loss is very small. At present, the electrolyte of lithium-ion batteries contains a certain amount of acid HF, and the positive electrode material is easily dissolved and corroded. The dissolved positive electrode material will increase the internal resistance of the battery, and poor thermal stability may cause safety hazards. (4) The choice of diaphragm. When the internal temperature of the battery approaches the melting point of the polymer film, the polymer matrix ions will melt the polymer film, clogging the pores and becoming a non-porous insulating layer. The internal resistance of the battery rises rapidly, and the current through the battery is limited. When the temperature continues to rise above the melting point of the polymer film, the polymer film further melts, causing direct contact between the positive electrode and the negative electrode, resulting in an internal short circuit, and ultimately causing the battery to explode. Therefore, the melting point, thickness and porosity of the diaphragm should be considered when selecting the diaphragm. 2. Reasonable battery structure design. Lithium-ion battery protection is usually achieved by setting safety valves, thermistors, and designing protection circuits. The protection circuit is a PCB circuit composed of a variety of electronic components, which controls the charging and discharging process of the battery and prevents the overcharge and overdischarge of the battery. Each component has the possibility of failure. Once the protection circuit fails, the probability of battery accidents will be greatly increased. 3. Manufacturing process. There are many noteworthy details in the production process, which are likely to cause safety hazards, such as: pole burrs, pole powder falling off will pierce the diaphragm and cause a short circuit; caused by too long electrode ears and contact with electrode plates or electrode shells Short circuit; the tabs compress the coil core, resulting in a short circuit between the positive and negative electrodes, causing the battery to heat up, and in severe cases, it will cause an explosion; in the production process, the positive and negative materials are not used properly, which will cause the lithium to be unsustainable and easy to pass through. The diaphragm causes an internal short circuit. At the same time, prevent the use of secondary batteries to prevent short-circuit and other safety accidents. (2) External factors that affect the safety of lithium-ion batteries. One is overcharging and overdischarging. Overcharge or overdischarge can easily cause the positive electrode material or electrolyte of the lithium-ion battery to release gas and heat, which will cause the battery to expand and the internal pressure to rise sharply. In severe cases, the battery may even explode due to smoke and fire. The second is an external short circuit. External short circuit The positive and negative short circuit of the protection circuit board caused by improper operation or failure. When the short circuit occurs, the battery discharge current is large, so the electric core is heated, and the high temperature will shrink or completely destroy the diaphragm in the cell, causing an internal short circuit in the battery, resulting in Explosion; third, the temperature is too high. Excessive external temperature can cause deformation of battery metal casing, melting of battery inner membrane, decomposition of anode and cathode materials or electrolyte, which can easily lead to battery short circuit statement: Some pictures and contents of articles published on this site are from the Internet. Please contact us if there is any infringement. Delete the previous article: How do consumers use and buy lithium-ion batteries correctly?