Lithium ion battery products after 30 years of industrialization development, security technology has achieved great progress, effectively control the occurrence of adverse events within the battery, ensure the safety of the battery. However, with the use of lithium ion battery is more and more widely, the energy density is higher and higher, or have exploded in recent years hurt or product recalls due to safety concerns. We summarize the cause of lithium ion battery product safety problems mainly include the following:
1.The problem of cell material
The materials used by the cell include: positive active substance, negative active substance, diaphragm, electrolyte and shell, etc., the selection of materials and the matching of the system determines the safety performance of the cell. In the selection of positive and negative anode active materials and diaphragm materials, manufacturers do not have a certain assessment of the characteristics and matching of raw materials, resulting in the innate deficiency of cell safety.
2. Production process problems
The cell raw material detection is lax, the production environment is poor, leading to the production of mixed impurities, not only the capacity of the battery has a greater disadvantage, the safety of the battery also has a great impact; In addition, if too much water is mixed into the electrolyte, side reaction may occur and increase the internal pressure of the battery, which will affect the safety; Due to the limitation of production technology level, in the process of production of batteries, the product can not meet the good consistency, such as the electrode substrate flatness, electrode active material appear fall off, active material to mix other impurities, very ear welding, welding temperature is not stable, plate edge burr and key parts use the insulating tape, may for the safety of batteries To have an adverse effect.
3. Defects in cell design and reduced safety performance
On structure design, a lot of impact on the safety of key points are not manufacturers, such as key parts without insulating tape, diaphragm design did not leave allowance or absence, is negative than design capacity is not reasonable, is the cathode active material area than design is unreasonable, ear length design is not reasonable, these could set a dangerous precedent for the safety of the battery. In addition, in the process of cell production, some cell manufacturers in order to save costs and improve performance, as far as possible to save and compress raw materials, such as reducing the diaphragm area, thinning copper foil, aluminum foil and do not use pressure relief valve, do not use insulating tape, etc., these will reduce the safety of the battery.
4. Energy density is too high
At present, the market is in the pursuit of higher capacity battery products, manufacturers in order to increase the competitiveness of the product, constantly improve the volume of lithium-ion battery energy, which to a large extent increases the risk of the battery.