Lithium-ion batteries, mobile power supply safety analysis

Source: 2020 - 04 - 12 consecutive hits: lithium-ion batteries, mobile power supply security analysis ( 1) The internal factors influencing the lithium ion battery safety 1. Materials. ( 1) Thermal stability of the positive electrode materials and its reactivity with electrolyte. Most of the cathode material in the condition of discharge has good thermal stability, has the thermal instability under the charging status. In the case of no contact with the electrolyte, the cause of the heat charging battery anode materials is mainly due to the change of crystal shape. After charging the positive contact with the organic electrolyte, react with the electrolyte, the electrolytic liquid oxygen, and release a lot of heat. ( 2) The safety of the anode material. Anode material should chemical stability, can with electrolyte SEI formation, does not react with the electrolyte, etc. , or reaction produces a large amount of heat will cause the battery explosion. ( 3) Composition of the electrolyte. The role of the electrolyte on the charge transfer between the positive and negative electrode in battery, need high electrical conductivity, and chemical properties of the electrolyte must be stable, to minimize the electrochemical reaction rate and the interface between the electrolyte storage of active material, so the self-discharge of the battery capacity loss is very small. At present, lithium battery electrolyte will contain a certain amount of HF acid, positive electrode material is easy to dissolve erosion, dissolved positive electrode material, will increase the battery internal resistance, thermal stability is easy to cause potential safety hazard. ( 4) The choice of the diaphragm. When the battery internal temperature near the melting point of polymer membrane, the polymer substrate ion polymer membrane fusion, make pore blockage, become a nonporous insulating layer. Rapid rise of battery internal resistance, through the battery's current is limited. When the temperature continues to rise more than the melting point of polymer membrane, polymer membrane further melting, lead to the positive and negative direct contact, lead to internal short circuit, eventually lead to the battery explosion. Therefore, should be considered when choosing the diaphragm melting point and thickness and porosity of the diaphragm. 2. Battery structure design is reasonable. Lithium ion battery protection usually by setting the relief valve, thermal resistance and protection circuit is designed to realize. Protection circuit is a kind of PCB circuit composed of a variety of electronic components, control of battery charge and discharge process, prevent the battery overcharge and over discharge, each element has the possibility of failure. Once the failure protection circuit, battery accident probability will greatly increase. 3. Manufacturing process. There are many worthy of attention in the process of production details, these details easy to cause potential safety hazard, such as: pole burr, pole falls off powder can cause short-circuit pierced diaphragm; Due to the electrode ear is too long and contact with the plate electrode or electrode shell caused by short circuit; Ear compression core coil, lead to negative short circuit, cause the battery heating, serious will cause explosion; In the process of production, the material of the positive and negative usage not appropriate, will cause the lithium discontinuity, and to cause internal short circuit by puncture of the diaphragm. At the same time, should avoid to use secondary battery, avoid the short circuit, etc. Safety accidents. ( 2) The external factors influencing the lithium ion battery safety. One is the overcharge, over discharge. Overcharge or overdischarge could easily lead to lithium ion battery anode materials and electrolyte release gas and heat, causing cell expansion, internal pressure rising sharply. In serious cases, batteries may even because of the smoke and fire explosion. The second is external short circuit. External short circuit caused by improper operation or malfunction protection circuit of positive and negative short circuit, short circuit, battery discharge current is very big, so the core electric heating, high temperature can make the cells of the diaphragm shrinkage or completely destroyed, causing the battery internal short circuit, leading to explosion; Three is the temperature too high. High outside temperature will cause the battery metal shell deformation, cell membrane fusion, anode and cathode materials or electrolyte decomposition, easy to cause the battery to short circuit