Lithium battery danger and safety technology -Lithium - Ion Battery Equipment
1. The dangers of lithium batteries
Lithium battery is a potentially dangerous chemical power source from its own chemical characteristics and system composition.
1 High chemical activity
Lithium is an element of the main group I of the second period of the periodic table and has extremely active chemical properties.
2 High energy density
Lithium battery has extremely high specific energy (≥140Wh/kg), which is several times that of nickel-cadmium, nickel-hydrogen and other secondary batteries. If thermal runaway reaction occurs, it will release high heat and easily lead to unsafe behavior.
3 Using an organic electrolyte system
The organic solvent of the organic electrolyte system is hydrocarbon, which has a low decomposition voltage and is prone to oxidation, and the solvent is flammable; if there is leakage, it will cause the battery to catch fire, even burn and explode.
4 The probability of side reactions is high
During the normal use of the lithium battery, a positive chemical reaction in which electrical energy and chemical energy are converted into each other is carried out. However, under certain conditions, such as overcharging, overdischarging or overcurrent operation, it is easy to cause chemical side reactions inside the battery; when the side reaction is intensified, it will seriously affect the performance and service life of the battery, and A large amount of gas may appear, causing the pressure inside the battery to rapidly increase and then explode and ignite, resulting in safety problems.
5 Structural instability of electrode materials
The overcharge reaction of the lithium battery will change the structure of the positive electrode material and make the material have a strong oxidative use, which will cause strong oxidation of the solvent in the electrolyte; and this use is irreversible, and the heat caused by the reaction will accumulate if it accumulates. There is a danger of thermal runaway.
2. Analysis of the reasons for the safety problems of lithium battery products
After 30 years of industrial development, lithium battery products have made great progress in safety technology, effectively controlling the occurrence of side reactions in the battery and ensuring the safety of the battery. However, with the increasing use of lithium batteries and the increasing energy density, incidents such as explosions and injuries or product recalls due to safety hazards have occurred frequently in recent years. We summarize the main reasons for the safety problems of lithium battery products as follows:(Lithium - Ion Battery Equipment)
1 The problem of cell material
The materials used in the cell include: positive active material, negative active material, separator, electrolyte and shell, etc. The selection of materials and the matching of the composed system determine the safety performance of the cell. When selecting positive and negative active materials and diaphragm materials, manufacturers did not conduct certain assessments on the characteristics and matching of raw materials, resulting in the inherent lack of cell safety.
2 production process problems
The raw materials of the battery cells are not tested strictly and the production environment is poor, which leads to the mixing of impurities in the production, which not only has a great disadvantage on the capacity of the battery, but also has a great impact on the safety of the battery; in addition, if too much is mixed into the electrolyte. Moisture may cause side reactions to increase the internal pressure of the battery and affect safety; due to the limitation of the production technology level, the product cannot achieve good consistency in the production process of the battery, such as poor electrode substrate flatness, The electrode active material falls off, other impurities are mixed in the active material, the electrode is not welded firmly, the welding temperature is unstable, there are burrs on the edge of the pole piece, and no insulating tape is used in the key parts, which may bring about the safety of the cell. negative effect.
3 cell design defects, reduced safety performance
In terms of structural design, many key points that have an impact on safety have not been paid attention to by manufacturers. For example, there is no insulating tape in key parts, there is no margin or insufficient margin in the design of the diaphragm, the design of the capacity ratio of positive and negative electrodes is unreasonable, and the active and negative electrodes are active. The unreasonable design of the material-to-area ratio and the unreasonable design of the length of the tabs may cause hidden dangers to the safety of the battery.
Lithium battery is a potentially dangerous chemical power source from its own chemical characteristics and system composition.
1 High chemical activity
Lithium is an element of the main group I of the second period of the periodic table and has extremely active chemical properties.
2 High energy density
Lithium battery has extremely high specific energy (≥140Wh/kg), which is several times that of nickel-cadmium, nickel-hydrogen and other secondary batteries. If thermal runaway reaction occurs, it will release high heat and easily lead to unsafe behavior.
3 Using an organic electrolyte system
The organic solvent of the organic electrolyte system is hydrocarbon, which has a low decomposition voltage and is prone to oxidation, and the solvent is flammable; if there is leakage, it will cause the battery to catch fire, even burn and explode.
4 The probability of side reactions is high
During the normal use of the lithium battery, a positive chemical reaction in which electrical energy and chemical energy are converted into each other is carried out. However, under certain conditions, such as overcharging, overdischarging or overcurrent operation, it is easy to cause chemical side reactions inside the battery; when the side reaction is intensified, it will seriously affect the performance and service life of the battery, and A large amount of gas may appear, causing the pressure inside the battery to rapidly increase and then explode and ignite, resulting in safety problems.
5 Structural instability of electrode materials
The overcharge reaction of the lithium battery will change the structure of the positive electrode material and make the material have a strong oxidative use, which will cause strong oxidation of the solvent in the electrolyte; and this use is irreversible, and the heat caused by the reaction will accumulate if it accumulates. There is a danger of thermal runaway.
2. Analysis of the reasons for the safety problems of lithium battery products
After 30 years of industrial development, lithium battery products have made great progress in safety technology, effectively controlling the occurrence of side reactions in the battery and ensuring the safety of the battery. However, with the increasing use of lithium batteries and the increasing energy density, incidents such as explosions and injuries or product recalls due to safety hazards have occurred frequently in recent years. We summarize the main reasons for the safety problems of lithium battery products as follows:(Lithium - Ion Battery Equipment)
1 The problem of cell material
The materials used in the cell include: positive active material, negative active material, separator, electrolyte and shell, etc. The selection of materials and the matching of the composed system determine the safety performance of the cell. When selecting positive and negative active materials and diaphragm materials, manufacturers did not conduct certain assessments on the characteristics and matching of raw materials, resulting in the inherent lack of cell safety.
2 production process problems
The raw materials of the battery cells are not tested strictly and the production environment is poor, which leads to the mixing of impurities in the production, which not only has a great disadvantage on the capacity of the battery, but also has a great impact on the safety of the battery; in addition, if too much is mixed into the electrolyte. Moisture may cause side reactions to increase the internal pressure of the battery and affect safety; due to the limitation of the production technology level, the product cannot achieve good consistency in the production process of the battery, such as poor electrode substrate flatness, The electrode active material falls off, other impurities are mixed in the active material, the electrode is not welded firmly, the welding temperature is unstable, there are burrs on the edge of the pole piece, and no insulating tape is used in the key parts, which may bring about the safety of the cell. negative effect.
3 cell design defects, reduced safety performance
In terms of structural design, many key points that have an impact on safety have not been paid attention to by manufacturers. For example, there is no insulating tape in key parts, there is no margin or insufficient margin in the design of the diaphragm, the design of the capacity ratio of positive and negative electrodes is unreasonable, and the active and negative electrodes are active. The unreasonable design of the material-to-area ratio and the unreasonable design of the length of the tabs may cause hidden dangers to the safety of the battery.
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