What is the internal factors influencing the lithium ion battery safety?

Source: 2020 - 04 - 11 19:04 hits: once the safety factor of the large capacity mobile power supply with the continuous development of mobile devices, mobile power supply is becoming one of the indispensable equipment in the people's life. However, with the widening its application scope and single battery capacity increasing, the security of mobile power supply more and more get people's attention. Factors affecting the safety of mobile power supply mainly has three aspects: the rationality of the design of PCB is 2. 2. Mobile power supply unit within the selection and use of; 3. The correctness of the manual operation. PCB should be reasonably according to the needs of choice of battery and charge and discharge design, and set the voltage and current control and protection circuits, such as can realize PCB protection Settings, under normal circumstances security incidents will not occur. Therefore, this article mainly summarized on security of mobile power supply. Common on the market of mobile power battery has two kinds, one is the lithium ion battery, the other is a polymer lithium ion batteries. The following is a brief overview of two battery safety affect: mobile power lithium ion batteries ( 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 effect of electrolyte on transfer charge between the positive and negative electrode in battery, need high electrical conductivity, and chemical properties of the electrolyte must be stable, in order to reduce the electrochemical reaction rate between electrolyte and active substances during the storage interface, therefore the self-discharge of the battery capacity loss is small. At present, lithium battery electrolyte will contain a certain amount of HF acid, positive electrode material is likely to be 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 is a lot to pay attention to the details of the production process, the details are easy to cause potential safety hazard, such as: pole burr, pole falls off powder can Pierce the diaphragm and cause internal short circuit; 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.