Battery safety is determined by several parameters, primarily the difference in potential between the two electrodes — anode and cathode. The higher the difference, the more dangerous the system is. The second important factor is the presence or absence of organic components in the battery. For example, water electrolytes do not burn, unlike organic ones, and do not withstand the potential above 1.3-1.4 volts. The energy intensity of batteries depends on the potential difference. The higher it is, the more energy is available regarding mass or volume.
The third parameter is the release of combustible gases from the system. Oxygen or hydrogen can form and accumulate in the course of adverse reactions. In this case, the slightest spark will cause the battery to explode. Lead batteries are the most commonly used batteries these days.
They have a low energy density and weigh a lot, so, they are more suitable for energy storage. They are often used in cars to start an internal combustion engine. Lithium-ion batteries are best suited for electric vehicles and mobile devices. Many people believe that these batteries contain lithium metal, but this is not the case. Lithium is in ionized form.In lithium-ion batteries, there is a layer of organic electrolyte between the anodes, and the cathode. The most common electrolyte is a mixture of organic carbonates containing LiPF6, an active and thermally unstable compound.
This is the most dangerous part of the battery. At temperatures above 60 °C, the electrolyte begins to decompose slowly. In this case, the safety of the battery depends on two factors: firstly, the difference in potential between cathode and anode, and secondly, the chemical nature of the cathode material itself.
There are extremely dangerous materials that are chemically unstable and can release oxygen with little heating or change in chemical potential. This type of compounds include lithium cobalt. Most accidents, fires, and explosions occur on this type of battery. An explosion can occur due to an unsuccessful device design. An explosion is also possible when the cathode and anode are connected. Inside the system there is a short circuit - a large amount of heat is released.
This can happen as a result of a production fault. Particles of the electrode peel off and can connect two electrodes to each other. In this case, overheating, evaporation, and decomposition of the electrolyte will occur and the gas will be released and exploded accordingly.
Another possible cause of battery explosion is incorrect charging. If the battery is discharged or not charged very quickly, the lithium will not be fully discharged into the carbon. If the battery is discharged very quickly, dendrites - thin lithium threads that stretch from one electrode to the next - can grow.
The battery can explode due to mechanical influences
If the battery walls are not strong enough, the cathode and anode will close and explode. In all cases of a cathode and anode connection, short circuit, heating and decomposition of the electrolyte will occur. This is followed by evaporation at best. Some systems have special valves that release excess electrolyte so that it does not explode. The most important thing in large systems is the heat sink between the individual cells. If there are a lot of such cells, they stand close to each other and there is no heat sink between them, they are heated up.
The battery should be charged and discharged only in normal mode. In today's large batteries, this is monitored by the electronics and prevents the battery from malfunctioning. There is a one more system which is introduced in powerful accumulators at which electrolyte is in a separator — a porous film.
When the manufacturer releases the battery, it performs two installation cycles. During this time, a thin protective film is formed on the anode. It is this film that prevents lithium germination. If it is not broken and the temperature is not raised, lithium will not germinate. The manufacturer ensures this in the first cycle.!!!!!!!!!!!!!!!!!! Now we are working on the creation of completely safe batteries. Scientists are developing a system in which liquid organic electrolyte will be replaced by glass or ceramic. But so far, this system has not been brought to a device that would demonstrate its characteristics.