Perspectives of electric vehicles in terms of safety
Today, there is an increased interest in reducing environmental pollution. In addition to renewable power sources, as a substitute for traditional energy, various options for replacing internal combustion engines in cars as a source of local pollution are considered.
The topic of electric cars has already been discussed here:
Modern electric cars - a story from the beginnings to the horizons
Use of batteries after the end of their life
Tesla's battery production
The immediate future of batteries
But is this a good idea from the point of view of safety?
Today, in the automotive industry, one of the three battery technologies is most often used: lead-acid batteries, lithium-ion batteries, and supercapacitors.
It is obvious that at the moment in terms of energy / mass ratio are precisely lithium-ion batteries.
The theoretical voltage limit of a modern unit in the 18650 format is 4.2 V, but not a single battery allows it to be used. The problem is that when lowering below a safe level, the so-called Lithium plating (lithium metallization) occurs - the formation of conductive sites from lithium, which leads to an internal short circuit and, as a result, to thermal acceleration of the battery (thermal runaway). A similar situation can also occur with a strong decrease in temperature. When the voltage is exceeded, temperature instability of the cell occurs, which also leads to its destruction.
Thus, there is a need to limit stresses from above and below, including because during production there is some variation in characteristics.
To date, the safest in this regard are batteries with a voltage of 2.1 V cells with electrodes LTO and LiFePO 4 , but you have to pay for safety by reducing the voltage, and hence the available energy, by half.
The second main problem is the durability of batteries in collisions, since there have always been, are and will be accidents. The problem with all such batteries is that when they are destroyed, a fire occurs that can be extinguished exclusively using special equipment.
As a rule, when nailing lithium-ion batteries with the form factor 18650 up to 80% of cases, spontaneous combustion occurs. This is the problem of the Tesla car - more than 6,000 such batteries are used to power it.
The third problem, which has no solution at the moment, is the quality of battery production. Problems with it can arise regardless of operation, simply by the ingress of foreign bodies into the battery itself.
The most striking examples that have shown the problems of lithium-ion batteries are problems with the Boeing 787 and Dell. In the second case, they were simply replaced by similar ones.
The first is a more striking example. Boeing pioneered the use of lithium-ion batteries in aircraft. The battery used was not standard, larger. Due to thermal acceleration, an explosion occurred, all planes lost access to flights in January 2013. After a statement about the solution to the problem, the planes were again allowed to fly in April 2013. In January 2014, the battery ignited. In general, the “solution” of the Boeing was to install the battery in the fortified compartment, so when the problem is with the battery, the rest of the plane does not touch. The problem has not been resolved, since it is physically impossible at this stage in the development of technology.
To date, there have been three fires in the Tesla car caused by problems in the production of batteries.
Battery reliability is currently insufficient for mass use of batteries. In the near future they will remain an expensive alternative, but over time the cost of production will increase their number. And according to a pessimistic scenario, the safety issue of using this vehicle will lie on the shoulders of the owner.
In general, battery safety is a very important factor that should not be forgotten by those who use them in laptops and mobile phones. It is very likely that without the development of the automotive industry and their introduction into transport, these issues would not be so acute.
1. Course "Battery Storage Systems", RWTH Aachen, Prof. Dr. rer. nat. Dirk Uwe Sauer
2. About quenching of lithium
3. Problems with Boeing 787 batteries
4. Review of batteries by Dell
The topic of electric cars has already been discussed here:
Modern electric cars - a story from the beginnings to the horizons
Use of batteries after the end of their life
Tesla's battery production
The immediate future of batteries
But is this a good idea from the point of view of safety?
Existing problems
Today, in the automotive industry, one of the three battery technologies is most often used: lead-acid batteries, lithium-ion batteries, and supercapacitors.
It is obvious that at the moment in terms of energy / mass ratio are precisely lithium-ion batteries.
Stability
The theoretical voltage limit of a modern unit in the 18650 format is 4.2 V, but not a single battery allows it to be used. The problem is that when lowering below a safe level, the so-called Lithium plating (lithium metallization) occurs - the formation of conductive sites from lithium, which leads to an internal short circuit and, as a result, to thermal acceleration of the battery (thermal runaway). A similar situation can also occur with a strong decrease in temperature. When the voltage is exceeded, temperature instability of the cell occurs, which also leads to its destruction.
Thus, there is a need to limit stresses from above and below, including because during production there is some variation in characteristics.
To date, the safest in this regard are batteries with a voltage of 2.1 V cells with electrodes LTO and LiFePO 4 , but you have to pay for safety by reducing the voltage, and hence the available energy, by half.
Impact resistance
The second main problem is the durability of batteries in collisions, since there have always been, are and will be accidents. The problem with all such batteries is that when they are destroyed, a fire occurs that can be extinguished exclusively using special equipment.
As a rule, when nailing lithium-ion batteries with the form factor 18650 up to 80% of cases, spontaneous combustion occurs. This is the problem of the Tesla car - more than 6,000 such batteries are used to power it.
Production
The third problem, which has no solution at the moment, is the quality of battery production. Problems with it can arise regardless of operation, simply by the ingress of foreign bodies into the battery itself.
The most striking examples that have shown the problems of lithium-ion batteries are problems with the Boeing 787 and Dell. In the second case, they were simply replaced by similar ones.
The first is a more striking example. Boeing pioneered the use of lithium-ion batteries in aircraft. The battery used was not standard, larger. Due to thermal acceleration, an explosion occurred, all planes lost access to flights in January 2013. After a statement about the solution to the problem, the planes were again allowed to fly in April 2013. In January 2014, the battery ignited. In general, the “solution” of the Boeing was to install the battery in the fortified compartment, so when the problem is with the battery, the rest of the plane does not touch. The problem has not been resolved, since it is physically impossible at this stage in the development of technology.
To date, there have been three fires in the Tesla car caused by problems in the production of batteries.
conclusions
Battery reliability is currently insufficient for mass use of batteries. In the near future they will remain an expensive alternative, but over time the cost of production will increase their number. And according to a pessimistic scenario, the safety issue of using this vehicle will lie on the shoulders of the owner.
In general, battery safety is a very important factor that should not be forgotten by those who use them in laptops and mobile phones. It is very likely that without the development of the automotive industry and their introduction into transport, these issues would not be so acute.
Sources
1. Course "Battery Storage Systems", RWTH Aachen, Prof. Dr. rer. nat. Dirk Uwe Sauer
2. About quenching of lithium
3. Problems with Boeing 787 batteries
4. Review of batteries by Dell