Written by | Little devil
As a rookie in the field of batteries, all-solid-state batteries have attracted great interest in all corners of the energy industry.
With no flammable liquid electrolyte (hence the name "solid state"), this type of battery skips many of the safety concerns of traditional lithium-ion batteries without sacrificing power.
It is precisely because of the advantages of all-solid-state batteries that in the electric vehicle industry, most car companies and battery technology companies regard it as the optimal solution for power batteries. In order to strive for leading chips in the fierce battle of electric vehicles in the next decade, some car companies have even taken the initiative to enter the field for exploration and research and development.
As a member of the car companies that are actively exploring all-solid-state battery technology, Nissan recently revealed their latest progress.
Nissan has set up three important time nodes for its own solid-state battery mass production road, the first is to establish a laboratory-level feasibility study of all-solid-state batteries this year; then it will set up a solid-state battery production line in Yokohama in 2024; and officially realize the installation of all-solid-state batteries in 2028.
Compared with traditional lithium batteries, all-solid-state batteries have many benefits such as high energy density, high charge and discharge rate, long cycle life, and not susceptible to temperature, so why didn't car companies, including Nissan, choose this development direction at the beginning?
First of all, let's briefly introduce the two important factors that affect the basic performance of lithium batteries.
First, the positive and negative electrodes of the battery as a repository of lithium ions, its ability to store lithium ions will directly affect the level of battery energy storage; second, the electrolyte between the positive and negative electrodes (used to ensure the stability of the anode and cathode) determines the speed of lithium ion movement, which will affect the charging power and charging time of the entire battery.
In order to have a high ion movement speed, the ternary lithium (NCM) and lithium iron phosphate (LFP) batteries used in electric vehicles and hybrid vehicles on the market currently use liquid electrolytes, and the main component of this electrolyte is vinyl carbonate.
However, vinyl carbonate itself is flammable, and researchers found that the more ethylene carbonate is added to the electrolyte, the more dendrites grow in the negative electrode during the charging and discharging process of the battery, which will not only reduce the energy storage capacity of the battery, but also the growing dendrites will pierce the separator between the positive and negative electrodes to cause a short circuit, which will cause a battery fire and produce toxic gases.
In addition, lithium batteries with a liquid electrolyte are also sensitive to the outside temperature. At too low a temperature, the electrolyte will become viscous, causing the ion movement speed to become slower, reducing the discharge capacity of the battery, which is reflected in the electric vehicle is that the winter endurance is reduced, and the charging efficiency is reduced.
If the temperature is too high, the electrolyte will become more active at this time, and the chemical reaction balance between the positive and negative electrodes and the electrolyte will be destroyed, accelerating the side reactions in the battery and damaging the cycle life of the battery.
If you use solid electrolytes instead, you can greatly improve the above problems. But in earlier studies, it was found that solid electrolytes, whether using polymers or oxides, were not ideal.
The former lithium ion movement speed is too slow, must be heated to 60 ° C or 85 ° C above to improve, if used in the car means that the vehicle needs to often remain in a state of charging and high temperature; the latter ion movement speed is higher than the polymer, but it is easy to produce brittle cracks, for the manufacture of batteries For processing is too difficult, and it is not easy to make large-capacity batteries, so the all-solid-state battery technology in the early stage can not see the prospect of achieving commercial value.
In fact, it wasn't until 2011 that researchers discovered that sulfide solid electrolytes have high conductivity to ions that solid-state batteries have the real possibility of achieving commercial value.
After determining that sulfide is the most suitable solid-state electrolyte, solid-state batteries that can go commercial show more advantages.
In addition to achieving higher energy density and better safety, because the electrolyte itself is more stable than the liquid, the battery is affected by the external temperature and the capacity of the sudden decrease will be smaller, that is to say, the electric vehicle in the winter endurance shrinkage or high temperature overheating caused by the decline in battery performance can be improved to a certain extent.
And because sulfide acts as a solid electrolyte to reduce the side reactions between materials, the selection of positive and negative electrode materials for batteries has also been expanded.
Nissan uses AI technology to select a wide range of materials, with the goal of selecting a cathode material that minimizes cost. At the same time, it also uses some technical means to reduce the thickness of the lithium-ion storage spacer and increase the lithium-ion storage capacity of the negative electrode material to improve the energy density of the battery.
Nissan is currently working to reduce material costs and increase energy density at the same time, and has established a small-scale all-solid-state battery laboratory that can produce about 50 four-layer soft pack batteries per month.
If the all-solid-state battery can be successfully installed in 2028, Nissan believes that the endurance of its electric vehicle can be increased to 2 times, the charging time can be reduced to 1/3 of the original, and the battery cost can be reduced to 75 US dollars / kWh (according to Bloomberg New Energy Finance statistics, the price of the battery pack for pure electric passenger cars in 2021 is 118 US dollars / kWh).
Through continuous innovation, the cost of batteries will be further reduced to $65/kWh in the future to achieve cost parity for electric vehicles and fuel vehicles.
As for which cars will the all-solid-state battery appear first? Considering the advantages of its high energy density, Nissan will give priority to installing this battery in large electric vehicles to improve the problem of reducing the mileage of large electric vehicles due to the increase in battery weight, and then promote it to small cars as the cost gradually decreases.
As we mentioned earlier, in addition to Nissan, almost all mainstream car companies have laid out in the field of all-solid-state batteries.
Among them, Nissan chose to cooperate with NASA to develop this technology, and announced that it will be installed in 2028;
Volkswagen has invested in solid-state battery startup QuantumScape to collaborate on the development of its own all-solid-state battery, which has set the commercialization of solid-state batteries in 2025;
Toyota chose to cooperate with Panasonic, and its mass production plan is also set for around 2025;
BMW and Ford have both invested in Solid Power, and the landing time given by BMW is also 2025;
Both Honda and GM have reached cooperation intentions with SES, a U.S. electric vehicle battery research and development company, but they have not yet given a specific time-to-market plan.
In China, although it started late, car companies such as BYD and Beiqi Blue Valley have also made some progress in the field of all-solid-state batteries.
In view of the fact that there are still many technical problems to be overcome before the solid-state battery really goes to mass production, mass production and loading also need a certain amount of time, and some car companies have also chosen the "semi-solid state" route as a transition. Electrolyte is still used in the electrolyte of semi-solid batteries, but its content is basically controlled at about 5-10%.
Although the defects of liquid electrolyte lithium batteries cannot be completely overcome, semi-solid-state technology can improve the energy density and charging speed of the battery to a certain extent, and the technical difficulty is much lower than that of all-solid-state batteries, and mass production is easier.
For example, WEILAI ET7 has taken the lead in equipping a semi-solid-state battery provided by Fu Neng Technology, which supports the endurance of NEDC of more than 1,000 kilometers, and its performance is obviously better than that of the same class using traditional liquid lithium batteries. In addition, according to Fu Neng Technology, Mercedes-Benz EQS equipped with its semi-solid-state batteries has also begun to accept orders in the European market.
Although the all-solid-state battery is the consensus reached by most car companies and battery manufacturers on the next-generation power battery technology, it will take at least 5 years to truly enter the commercialization from the current time node given by car companies and battery companies.
In fact, for users, they may not care much about what kind of battery technology their electric vehicles will have, but they will certainly care about when the electric vehicles that cost more expensive prices than fuel vehicles can really get rid of endurance and charging anxiety, and they do not have to worry about safety and stability.
The war between electric vehicles and power batteries has not yet been determined, whether it is semi-solid-state, all-solid-state or even other battery technology, as long as which car company uses the means to achieve the user's above demands as soon as possible, then its products will be sought after by the market is inevitable, and may even change the rules of the game in the electric vehicle industry, depending on who can preemptively reach this new highland of battery technology. 【iDailycar】