Li ion battery safety – risk factors and using tips
Table of Contents
Li ion batteries are an essential energy source that provide power for many of the tools and electronic devices we use in daily life, and are also one of the environmentally friendly energy products advocated today. Li ion batteries have the advantages such as high energy density, long service life and maintenance free, but there are also many points to pay attention to in the use and preservation of batteries. This article will introduce you the knowledge of li ion battery safety.
What is li ion battery
A li ion battery is a rechargeable battery that works primarily by moving lithium ions between the cathode and anode. Li ion battery materials include cathode, anode, electrolyte, diaphragm and shell. The cathode materials of the li ion battery uses lithium compounds LiXCoO2, LiXNiO2, LiXMnO2 or LiFePO4, and the anode uses lithium-carbon interlayer compound LiXC6. Li ion battery electrolyte is dissolved lithium salts LiPF6, LiAsF6 and other organic solute.
During the charge and discharge process, Li+ is inserted and uninserted between the two electrodes. When the battery is getting charged, Li+ is removed from the cathode and embedded into the anode through the electrolyte, and the anode is in a lithium-rich state. The opposite is true when it’s discharged.
Classification of li ion batteries
Li ion batteries are divided into cylindrical batteries, square batteries, pouch batteries according to their appearance. According to the material, it can be divided into ternary batteries, lithium iron phosphate batteries, lithium manganese oxide batteries, lithium titanate batteries, etc. According to the application, it is divided into power battery, energy storage battery, consumer battery,etc.
Risk factors of li ion battery safety
There are a few factors affecting li ion battery safety as below.
Electrolyte solvent
The electrolyte (electrolyte salt LiPF6) solvent is mainly composed of alkyl carbonates, such as dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), etc., which are flammable liquids with very low boiling points, making it easy to burn in case of fire. Electrolyte solvent greatly affects the li ion battery safety.
In many cases, the electrolyte of a lithium battery will generate gas. For example, the electrolyte may decompose and release gas when it continuously interacts with the electrodes during the cycle of charging and discharging. If there are impurities such as moisture in the electrolyte, the moisture or acid will also be decomposed to generate gas during charging.
LiPF6, on the other hand, is corrosive and nonflammable, and produces harmful hydrogen fluoride (corrosive) when heated and reacted with acids. The reaction between hydrogen fluoride and metal will produce explosive gas and sparks to ignite the electrolyte, which will damage the plastic body and the flammable materials in contact with it, causing a fire.
When the temperature inside the battery rises sharply, due to the small space inside the battery, it may explode due to the increase in pressure. When the temperature inside the battery rises slowly, the battery shell will gradually melt, resulting in the leakage of corrosive electrolyte.
Anode The charged anode stores a large amount of strong reducing substance lithium carbide (intercalation compound), the potential of LiC6 is close to -3.0V, and the reducing agent is similar to metal lithium, and it can burn when it meets water.
Dendrite
In some poorly designed or manufactured lithium batteries, long-term cycling will form dendrites, and lithium metal will be deposited to form a powdery element (usually gray-black powder at the edge of the electrode), which can burn when it encounters air, which affects lithium battery safety.
Internal short circuit
When the lithium battery separator between the cathode and anode of the battery is accidentally punctured (such as dendrite growth, external force) and the cathode and anode are directly connected, it will cause an internal short circuit, and a large amount of energy is released inside the battery, which is easy to burn or explode.
Shell damage
Li ion batteries are usually packaged in a steel or aluminum shell. In some cases, if the charging equipment or protection circuit fails to cause overcharging, the internal diaphragm of the battery is pierced and causes an internal short circuit. So the internal temperature of the battery will rise rapidly, and the pressure will also increase sharply. At this situation, the li ion battery safety valve may fail or be too late, move and a destructive explosion may happen.
For batteries packaged in aluminum-plastic composite film, if the packaging film is punctured or cut, electrolyte leakage may occur, seriously damage the safety of lithium battery safety.
Overcharge Under certain conditions in li ion batteries, such as external circuit failure or when protection is not used, gas may be generated for various reasons:
1) The cathode is over-discharged to release O2, and at the same time the electrode material turns into a form that cannot be recharged, and the capacity will drop significantly.
2) The electrolyte is decomposed. This is the main cause of gas generation. The gases that may be produced are carbon dioxide, carbon monoxide, methane, ethane, ethylene, etc.
3) Other reasons. For example, when the temperature is high, the electrolyte vaporizes its own steam, and the side reactions produced by additives, etc.
The properties of the electrolyte
The most commonly used electrolyte salt in li ion batteries is lithium hexafluorophosphate LiPF6, which has good conductivity, high solubility in organic solvents and good oxidation resistance, and is currently the most important electrolyte salt for lithium-ion electrolyte. However, when it reacts with water, it will produce hydrofluoric acid, which is very harmful to the environment and human health.
Other accidents
● The injection of liquid ventilation may cause poisoning, leakage may cause explosion.
● Formation, aging may cause explosion.
● Using ethanol and acetone to scrub the container, causing explosion.
● In the production and storage process, there may be li ion battery safety risks.
● The imprecise operation in the production process of lithium batteries leaves li ion battery safety risks.
Li ion battery safety rules
For li ion battery safety, there are some rules that must be followed.
Storage
● Storage area of the li ion batteries should be cool and dry and not affected by weather. The normal battery storage temperature is between 0-25℃, and the maximum temperature should not exceed 45℃, and the long-term storage temperature requirements are more stringent. The relative humidity should be kept between 30% and 70%.
● Battery components cannot be stored near heat sources such as heaters, water heaters, etc.
Mixed use
Under ideal storage conditions (such as the temperature and humidity specified by the original factory), the battery can be stored for one year, but after half a year, these early production batteries can not be mixed with the newly produced batteries. All batteries assembled into the same battery combination must be the same batch number of the same grade of products, different batches of different grades of batteries are prohibited from mixing.
Internal short circuit
Li ion batteries are charged to about 30% when shipped from the original factory, and must comply with the following li ion battery safety requirements:
● Do not use metal to short-circuit the battery poles;
● Do not cut the battery with blade;
● Do not put more than two batteries or other metals in the same plastic bag to prevent accidental short circuits;
● Do not heat the battery, do not touch the battery body with chromium iron, or use the hot air gun directly to blow the battery;
● Do not place the battery in a place that may generate high temperatures;
● Do not forcefully strike the battery assembly;
● Be careful when take and place the battery to avoid falling;
● Do not hit the battery or damage the battery for other reasons;
● Do not wipe the battery with water or other liquor;
● Do not violate the rules of operation, do not squeeze, crush or use any sharp tools to damage the battery insulation and lead to short circuit;
● Do not disassemble the battery without permission;
● Do not grab the cathode and anode poles of the battery with bare hands;
● Do not grab more than two batteries at once.
Battery disposal
● Once the battery has short circuit, dent, leakage, etc., it should be disposed of according to the scrapping process;
● If the battery itself smells or discolors, the battery must be removed and must not be exposed to heat sources;
● Immediately disassemble components such as PCM and CELL, and confirm that the battery has been kept away from heat sources to lower the temperature of the battery; the battery generates a lot of heat due to a short circuit, and the heating will stop after the component that caused the short circuit is removed;
● When the battery fluid leaks, the battery should be isolated immediately; if the skin touches the battery fluid, wash it with soap and water immediately; if the battery fluid gets in your eyes, wash it with clean water immediately, and then see a doctor.
● If a single battery is hot, immediately put it in a ventilated and fire-proof area or an airtight container to cool it down. This may be an internal short circuit, which will produce smoke. When the internal energy release is over, the temperature will stop rising.
Scrap
● All batteries found to be short-circuited, leaky, rusty and dented during assembly must be scrapped;
● The scrapping process should be careful, do not let the battery case cause a short circuit of another battery;
● Never disassemble the battery, except in a well-controlled environment, and do not destroy the battery in fire.
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Li ion battery safety – risk factors and using tips
Li ion batteries are an essential energy source that provide power for many of the tools and electronic devices we use in daily life, and are also one of the environmentally friendly energy products advocated today. Li ion batteries have the advantages such as high energy density, long service life and maintenance free, but there are also many points to pay attention to in the use and preservation of batteries. This article will introduce you the knowledge of li ion battery safety.
What is li ion battery
A li ion battery is a rechargeable battery that works primarily by moving lithium ions between the cathode and anode. Li ion battery materials include cathode, anode, electrolyte, diaphragm and shell. The cathode materials of the li ion battery uses lithium compounds LiXCoO2, LiXNiO2, LiXMnO2 or LiFePO4, and the anode uses lithium-carbon interlayer compound LiXC6. Li ion battery electrolyte is dissolved lithium salts LiPF6, LiAsF6 and other organic solute.
During the charge and discharge process, Li+ is inserted and uninserted between the two electrodes. When the battery is getting charged, Li+ is removed from the cathode and embedded into the anode through the electrolyte, and the anode is in a lithium-rich state. The opposite is true when it’s discharged.
Classification of li ion batteries
Li ion batteries are divided into cylindrical batteries, square batteries, pouch batteries according to their appearance. According to the material, it can be divided into ternary batteries, lithium iron phosphate batteries, lithium manganese oxide batteries, lithium titanate batteries, etc. According to the application, it is divided into power battery, energy storage battery, consumer battery,etc.
Risk factors of li ion battery safety
There are a few factors affecting li ion battery safety as below.
Electrolyte solvent
The electrolyte (electrolyte salt LiPF6) solvent is mainly composed of alkyl carbonates, such as dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), etc., which are flammable liquids with very low boiling points, making it easy to burn in case of fire. Electrolyte solvent greatly affects the li ion battery safety.
In many cases, the electrolyte of a lithium battery will generate gas. For example, the electrolyte may decompose and release gas when it continuously interacts with the electrodes during the cycle of charging and discharging. If there are impurities such as moisture in the electrolyte, the moisture or acid will also be decomposed to generate gas during charging.
LiPF6, on the other hand, is corrosive and nonflammable, and produces harmful hydrogen fluoride (corrosive) when heated and reacted with acids. The reaction between hydrogen fluoride and metal will produce explosive gas and sparks to ignite the electrolyte, which will damage the plastic body and the flammable materials in contact with it, causing a fire.
When the temperature inside the battery rises sharply, due to the small space inside the battery, it may explode due to the increase in pressure. When the temperature inside the battery rises slowly, the battery shell will gradually melt, resulting in the leakage of corrosive electrolyte.
Anode
The charged anode stores a large amount of strong reducing substance lithium carbide (intercalation compound), the potential of LiC6 is close to -3.0V, and the reducing agent is similar to metal lithium, and it can burn when it meets water.
Dendrite
In some poorly designed or manufactured lithium batteries, long-term cycling will form dendrites, and lithium metal will be deposited to form a powdery element (usually gray-black powder at the edge of the electrode), which can burn when it encounters air, which affects lithium battery safety.
Internal short circuit
When the lithium battery separator between the cathode and anode of the battery is accidentally punctured (such as dendrite growth, external force) and the cathode and anode are directly connected, it will cause an internal short circuit, and a large amount of energy is released inside the battery, which is easy to burn or explode.
Shell damage
Li ion batteries are usually packaged in a steel or aluminum shell. In some cases, if the charging equipment or protection circuit fails to cause overcharging, the internal diaphragm of the battery is pierced and causes an internal short circuit. So the internal temperature of the battery will rise rapidly, and the pressure will also increase sharply. At this situation, the li ion battery safety valve may fail or be too late, move and a destructive explosion may happen.
For batteries packaged in aluminum-plastic composite film, if the packaging film is punctured or cut, electrolyte leakage may occur, seriously damage the safety of lithium battery safety.
Overcharge
Under certain conditions in li ion batteries, such as external circuit failure or when protection is not used, gas may be generated for various reasons:
1) The cathode is over-discharged to release O2, and at the same time the electrode material turns into a form that cannot be recharged, and the capacity will drop significantly.
2) The electrolyte is decomposed. This is the main cause of gas generation. The gases that may be produced are carbon dioxide, carbon monoxide, methane, ethane, ethylene, etc.
3) Other reasons. For example, when the temperature is high, the electrolyte vaporizes its own steam, and the side reactions produced by additives, etc.
The properties of the electrolyte
The most commonly used electrolyte salt in li ion batteries is lithium hexafluorophosphate LiPF6, which has good conductivity, high solubility in organic solvents and good oxidation resistance, and is currently the most important electrolyte salt for lithium-ion electrolyte. However, when it reacts with water, it will produce hydrofluoric acid, which is very harmful to the environment and human health.
Other accidents
● The injection of liquid ventilation may cause poisoning, leakage may cause explosion.
● Formation, aging may cause explosion.
● Using ethanol and acetone to scrub the container, causing explosion.
● In the production and storage process, there may be li ion battery safety risks.
● The imprecise operation in the production process of lithium batteries leaves li ion battery safety risks.
Li ion battery safety rules
For li ion battery safety, there are some rules that must be followed.
Storage
● Storage area of the li ion batteries should be cool and dry and not affected by weather. The normal battery storage temperature is between 0-25℃, and the maximum temperature should not exceed 45℃, and the long-term storage temperature requirements are more stringent. The relative humidity should be kept between 30% and 70%.
● Battery components cannot be stored near heat sources such as heaters, water heaters, etc.
Mixed use
Under ideal storage conditions (such as the temperature and humidity specified by the original factory), the battery can be stored for one year, but after half a year, these early production batteries can not be mixed with the newly produced batteries. All batteries assembled into the same battery combination must be the same batch number of the same grade of products, different batches of different grades of batteries are prohibited from mixing.
Internal short circuit
Li ion batteries are charged to about 30% when shipped from the original factory, and must comply with the following li ion battery safety requirements:
● Do not use metal to short-circuit the battery poles;
● Do not cut the battery with blade;
● Do not put more than two batteries or other metals in the same plastic bag to prevent accidental short circuits;
● Do not heat the battery, do not touch the battery body with chromium iron, or use the hot air gun directly to blow the battery;
● Do not place the battery in a place that may generate high temperatures;
● Do not forcefully strike the battery assembly;
● Be careful when take and place the battery to avoid falling;
● Do not hit the battery or damage the battery for other reasons;
● Do not wipe the battery with water or other liquor;
● Do not violate the rules of operation, do not squeeze, crush or use any sharp tools to damage the battery insulation and lead to short circuit;
● Do not disassemble the battery without permission;
● Do not grab the cathode and anode poles of the battery with bare hands;
● Do not grab more than two batteries at once.
Battery disposal
● Once the battery has short circuit, dent, leakage, etc., it should be disposed of according to the scrapping process;
● If the battery itself smells or discolors, the battery must be removed and must not be exposed to heat sources;
● Immediately disassemble components such as PCM and CELL, and confirm that the battery has been kept away from heat sources to lower the temperature of the battery; the battery generates a lot of heat due to a short circuit, and the heating will stop after the component that caused the short circuit is removed;
● When the battery fluid leaks, the battery should be isolated immediately; if the skin touches the battery fluid, wash it with soap and water immediately; if the battery fluid gets in your eyes, wash it with clean water immediately, and then see a doctor.
● If a single battery is hot, immediately put it in a ventilated and fire-proof area or an airtight container to cool it down. This may be an internal short circuit, which will produce smoke. When the internal energy release is over, the temperature will stop rising.
Scrap
● All batteries found to be short-circuited, leaky, rusty and dented during assembly must be scrapped;
● The scrapping process should be careful, do not let the battery case cause a short circuit of another battery;
● Never disassemble the battery, except in a well-controlled environment, and do not destroy the battery in fire.