A few days ago, BYD announced a patent (CN120818239A) related to "polyimide aerogel". 
It is said that after optimizing the process with additives, complete aerogels can be prepared under normal pressure. The structure is less prone to collapse, and it has excellent heat insulation and insulation properties, making it suitable for use as heat insulation material in batteries or electronic control. 
Seeing that domestic technology has made another breakthrough, people naturally gave it a thumbs-up one after another. 
However, many people have raised doubts. After all, aerogel is no longer a rare material. Many car manufacturers use it as an insulating layer for battery packs. In contrast, BYD itself rarely uses it. It is estimated that this time, it has just been developed to gather dust in the patent library again. 
Some people say that aerogel is the airbag for battery safety. Any electric vehicle without aerogel (such as some models of Tesla and BYD) should be completely ruled out and is not worth buying at all. 
Even if aerogel is used, it still depends on how much is used and how it is applied. If the material is not used thoroughly, it is as good as not using it at all. 
However, some people believe that this thing is overhyped. In the face of battery fires, aerogel is completely ineffective. Instead, the problem needs to be solved from the source by improving the battery cells, or by using structural designs such as blade or cylindrical cells to prevent it in advance. 
Some people even think that once ternary lithium is used, nothing can be saved. 
So, regarding the question of whether aerogel is useful or not, there has been continuous online debate. Here, Neck Guy will first help everyone sort it out. 
In fact, aerogel is a genuine aerospace material. It is used as an insulating layer in Mars rovers. 
The reason is that its heat insulation effect is extremely good. 
We should know that the basis of aerogel is actually air. And air itself is a very good insulating material. The thermal conductivity of still air is 0.026 W/(m・K). Buildings, furniture, etc. all use air to achieve insulation effects. For example, the down jackets we wear in winter can keep us warm because they can trap a large amount of air inside. 
However, as a gas, air is a bit too mischievous and hard to control. Once there is a temperature difference, convection is likely to occur, and the insulation effect will be immediately compromised. 
So, people have developed aerogel. Essentially, it is a nano-material with a porous structure. It looks like a jelly in shape but when magnified, it resembles a sponge. 
The network-like material framework itself can reduce heat transfer. Not to mention that the air in the gaps is almost completely still, with no convection, which greatly enhances its heat insulation capacity. 
After all these operations, the room-temperature thermal conductivity of aerogel can reach 0.012 - 0.02 W/(m·K), which is almost twice that of air. In a certain sense, it has approached the physical limit. 
Crucially, it is still the lightest solid in the world, weighing only 1/6 that of air. It does not affect the vehicle's weight at all and is very suitable for lightweight applications. 
So nowadays, many manufacturers have applied this thing to our electric vehicles. 
Take the CTP (Cell to Pack) battery of Ningde Times, the "Qilin Battery", for example. It attaches a 1mm-thick silica aerogel insulation pad to the side of the battery cells. The main purpose is to prevent a short circuit in a single cell from causing thermal runaway and then spreading directly to the entire battery pack. 
And that's not all. Aerogel can also be attached to the water-cooling plate channels, battery pack casings, pressure relief valves, and so on, effectively arming the battery pack from head to toe. Some car manufacturers claim "zero spontaneous combustion", and they do have the confidence to make such a claim. 
But the problem is that the aerogel insulation that car manufacturers have painstakingly developed fails to solve the issue of electric vehicle fires in reality. The vehicles still catch fire when they are supposed to be protected. 
First of all, it should be known that so-called "space materials" are not indestructible. Don't be intimidated by these four words. For instance, the spacesuits worn by astronauts can only insulate against high temperatures in certain environments. If you use them to fight fires, they will definitely be damaged. 
When it comes to aerogels, although the mainstream silica aerogels can withstand temperatures up to 1200℃ for a short period, their fire resistance will drop to 300-600℃ over a longer period of time. 
This value is sufficient for ordinary barbecues, but it definitely cannot solve the thermal runaway of ternary lithium. After all, it can reach 1000-1200℃ in a local area, and the aerogel can only withstand 10-30 minutes at most. Eventually, it will still burn through. 
For instance, if your neighbor's house suddenly catches fire, with aerogel, it's like there's a wall between you two. The fire won't spread to you in a short time, but it doesn't mean that your neighbor's fire will never reach you. 
Its main function is to buy time. But once you see smoke coming out of the window next door or smell smoke, you still need to think of a way to escape as soon as possible. 
So a common situation is that the electric vehicle catches fire, but the people inside are still alive... This is surely thanks to aerogel buying us time, but the key to solving battery thermal runaway still lies in cell technology. 
You can neither regard aerogel as the sole savior nor claim that since fires are inevitable, aerogel is unnecessary. 
In addition, the performance of aerogel is indeed related to its thickness and the materials used. 
For instance, the first-generation Ultium platform, which is more solid in terms of materials, uses Aspen (a NASA supplier)'s aerogel as insulation on a large scale. It contains up to 180+ pieces, with an insulation area of 11.188 square meters. Moreover, it has stronger performance and can withstand a short-term temperature of up to 1400℃, increasing the protection time to 50 minutes. 
However, due to cost considerations, in the later Ultium 2.0, the ternary lithium battery cells were replaced with more stable lithium iron phosphate cells, and the aerogel solution was abandoned. Instead, a composite ceramic material was adopted, which can withstand 1000℃ for two weeks and even reduces costs by 30%. 
This has led more people to doubt whether the path of aerogel is the right one. 
So currently, there are two branches in battery safety. One is the ternary lithium + aerogel for ultimate performance, while the other is the lithium iron phosphate that gives up aerogel for ultimate cost. 
But does that mean that no aerogel is needed when using lithium iron phosphate? Would lithium iron phosphate plus aerogel be even better? All these need further verification and are the key points of the controversy. 
In conclusion, I believe that aerogel remains a promising area worth further exploration. 
On the one hand, with the expansion of production capacity, the average price of ordinary silica aerogel products may drop to 180 yuan per square meter. Whether it is ternary lithium or lithium iron phosphate, it is not a dream for the battery pack to be fully equipped with aerogel. 
On the other hand, domestic enterprises have already accounted for 57% of the global patents on aerogel in the past three years. It is highly likely that they will surpass international giants like Aspen in the future and find safer technical solutions. 
However, for battery safety technology, aerogel is just the tip of the iceberg that we can see. The breakthroughs in the materials of the positive and negative electrodes or the electrolyte behind the scenes are the key sources to solve the problem of battery thermal runaway. 
It is believed that in the future, electric vehicles will definitely become safer and safer. 
Source of information: 
Weibo, Zhihu 
Patent CN120818239A