"Where do you go to charge?"
Last week, our editorial office came with a National A00 class electric car. The small size coupled with the very direct driving experience makes all colleagues who have experienced the car feel that driving this car has a kind of joy in driving a toy car, even if it only has an endurance of more than 100 kilometers.
After two days of experience testing, the car's range was almost zero. When we were about to charge it, we found out that we were patronizing Happiness and ignoring an important problem: there were fast charging piles everywhere near the office, and slow charging piles were almost extinct, and this car only supported slow charging.
We thought of charging it again with the charger that came with the car. But in a crowded city like Beijing, finding a parking space with a 220V grounding outlet is almost a luxury.
Thus, there is the cry at the beginning of the article.
The embarrassing charging experience made my CTO always very desperate, he was originally a loyal fan of this car, "Why can't it support fast charging?" Mr. Mi said indignantly, "If it can be fast charged in 5 minutes, even if it only has an endurance of more than 100 kilometers, it can actually be accepted, just like the current mobile phone fast charge."
However, the current lithium battery technology, coupled with the cost factor, makes it difficult to do "small capacity battery pack high power fast charging". But a nissan nissan technical workshop on all-solid-state batteries in recent days has seen me some light.
Fast-charging bottleneck for small batteries
Speaking of this, some students may not be convinced, "Now Tesla V3 super charging pile power can reach 250 kW, even if it is a third-party charging brand, 120kW fast charging pile is not a rare thing."
You ignore one of the big premises of the above problem, the "small capacity battery" fast charging technology.
Theoretically, a 120kW fast charging pile takes only 7.5 minutes to charge a 15kWh capacity battery. But in fact, even if you remove factors such as temperature and end trickle charging, it is difficult to achieve this speed - to fill a 15kWh battery in 7.5 minutes, the battery must be an "8C battery".
The "C" mentioned here refers to the charge-discharge rate.
Charge-discharge rate refers to the current value required by the battery to discharge its rated capacity within a specified time. Translating that, if a battery can be fully discharged or charged in 1 hour, we call it a 1C battery; if it can be completed in 0.5 hours, it is a 2C battery, and so on.
At present, the charge and discharge rate of mainstream automotive power batteries is only about 3C, which is the bottleneck of the "small capacity battery fast charging technology" mentioned earlier.
The higher charge and discharge performance is one of the characteristics of Nissan's all-solid-state battery, which is why I call it "dawn".
All solid-state batteries
Whether it is Tesla's 2170 and 4680 batteries or BYD's blade batteries, they are composed of positive and negative electrode materials, electrolytes and separators. Among them, the electrolyte, as the main medium for transmitting the movement of lithium ions, is an important part of lithium batteries.
The all-solid-state battery, as the name suggests, is a rechargeable battery that uses a solid material as an electrolyte.
Switching to a solid electrolyte, the most immediate benefit, is safety.
Lithium batteries generate heat when they are in operation. In extreme cases, a large amount of heat energy will vaporize and expand the liquid electrolyte, break the diaphragm, and short circuit the positive and negative poles of the battery, resulting in safety accidents.
The biggest feature of solid electrolytes is that their physical and chemical properties are more stable. Compared with liquid electrolytes, the changes in the morphology of solid electrolytes in the face of the same temperature are almost negligible, which avoids the occurrence of the above unexpected situations, and the risk of thermal runaway of lithium batteries is greatly reduced. Therefore, solid-state electrolytes are also considered to be one of the solutions to the safety problem of power batteries.
Higher thermal tolerance means that all-solid-state batteries can achieve higher safe operating temperatures. For lithium batteries, higher operating temperatures mean higher lithium-ion activity, fed back to the macro level, that is, we can get faster charging speed. According to information published by Nissan, Nissan's target charging power for all-solid-state batteries is 350 kW.
This is not a vacuum, it is reported that Nissan has completed the 1000Wh/L level of charge and discharge performance measurements, at 25 °C can be charged from 15% of the SOC to 80% in 15 minutes.
The stable nature of solid electrolytes also offers more possibilities for reducing costs. This cost reduction possibility is reflected in the choice of positive and negative electrode materials.
Lithium battery technology has developed to today, considering the relatively active nature of liquid electrolytes, the choice of positive and negative electrode materials is actually not much. This also explains why the recent surge in the price of lithium carbonate raw materials will directly lead to a surge in the price of lithium batteries - because there is no other choice.
The stable nature of the solid electrolyte makes the positive and negative electrode materials have a wider choice, and we can try more readily available, lower cost, and better performance materials, thereby reducing the manufacturing cost of lithium batteries.
Compared to the full voltage of 4.2V for liquid lithium batteries, higher performance positive and negative electrode materials bring more than 5V full voltage to all-solid-state batteries. Higher voltage means higher energy density. At present, Tesla's latest 4680 battery energy density is 300 Wh/kg, which is an absolute leading level in the industry, while the energy density of all-solid-state batteries will exceed 400 Wh/kg.
In a nutshell, all-solid-state batteries will lead to better safety, higher performance, and lower cost. I want to retract the "dawn" mentioned above, which is the new "light" of battery technology.
R&D details
At the meeting, Nissan also talked about several small details in the development process of all-solid-state batteries.
For example, the battery positive and negative electrode material selection.
As mentioned earlier, the stable nature of solid-state electrolytes gives all-solid-state batteries more choices of positive and negative electrode materials. And this "more," to be precise, refers to more than 150,000 materials.
Choose less trouble, choose more as much as there are troubles, which one should be chosen?
One-by-one testing is obviously not the wisest choice. On this issue, Nissan received help from NASA. Through artificial intelligence simulation technology, they used computers to simulate massive materials, so as to find the most suitable combination of positive and negative electrode materials.
In fact, Nissan's help in the exploration of such a new technology comes not only from NASA, but also from other globally renowned institutions. It is also this combination of strength and power that provides more opportunities for the birth of new technologies.
In addition to external assistance, there is also the accumulation of technology from Nissan itself.
Nissan mentioned that the production of all-solid-state batteries is generally a stack of positive electrodes, solid electrolytes, and negative electrodes. Behind the simple word "stacking" means great precision difficulties.
This is because the solid electrolyte material relies on contact with the positive and negative electrode materials to transmit lithium ions. If the direct contact surface of the solid electrolyte and the positive and negative electrode material is not flat enough, or even said to have a bulge, then there will be a gap in the direct contact surface of the dielectric material and the electrode material, so that the transfer efficiency of lithium ions will be greatly reduced, and it will also cause a local heat accumulation. These will hinder the normal operation of all-solid-state batteries.
To solve this problem, high-precision electrode lamination technology is required.
Over the past twelve years, nissan LEAF Leaf has maintained a safety record of zero major battery accidents. It is also through the development and manufacture of the soft-pack lithium-ion battery carried by the Leaf that Nissan has accumulated high-precision electrode lamination technology, and specific to the numbers, this "high precision" refers to 0.0001 m.
Now, Nissan has applied this technology to the production of all-solid-state batteries, which solves the problem of all-solid-state battery production yield.
Based on all-solid-state batteries, Nissan proposed the "Nissan Vision 2030", which is longer range, shorter charging time, and lower battery costs. Isn't that the vision of all EV users?
With the goal in place, the next step is the concrete implementation steps. To paraphrase the popular "OKR", O-Objective naturally refers to "Nissan's Vision 2030", and the most recent KR-Key Result should be the construction of a pilot plant in Yokohama, Japan in 2024. This is a key step in the large-scale mass production of Nissan's all-solid-state batteries.
If all goes well, in 2028, we will be able to see Nissan's electric model equipped with Nissan's all-solid-state battery.
All colleagues in our company sincerely wish Nissan all the best and do not skip the ticket.
Because, the howl of the general is really too hard to hear.
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