As a future-oriented technology, solid-state batteries do not have the prerequisites for mass production, but every time there is a rumor, it can always easily tug at the heartstrings of the public, such a magical existence.
According to Bloomberg, Toyota, the world's largest car company, is looking to set up a wholly-owned plant in Shanghai to manufacture high-end electric models for the Lexus brand.
Toyota's appeal is to enjoy the same treatment as Tesla, including tax breaks, policy support, land subsidies and other subsidies.
If the rumors come true, this will be one of the manifestations that Toyota believes in and increases the weight of new energy vehicles and the Chinese market, if combined with GAC Toyota's recent electric plan: the launch of all-solid-state batteries in 2027. I can't help but wonder: will the Shanghai factory be an important position for the mass production of Toyota's solid-state batteries?
As early as this year's Beijing Auto Show, solid-state batteries have once again been hotly discussed by the industry. Hiroki Nakajima, vice president and chief technology officer of Toyota Motor Corporation, said during the Beijing Motor Show that the development of solid-state batteries is progressing smoothly as planned, and the advantages of long life and short charging and discharging time remain unchanged.
On April 28, Wu Kai, chief scientist of global power battery giant CATL, also disclosed at the China International Battery Technology Exchange Conference that CATL has the opportunity to produce solid-state batteries in small batches in 2027.
SAIC Motor is even more aggressive, and after launching the Zhiji L6, a model equipped with a semi-solid-state battery, it further announced that it plans to mass-produce all-solid-state batteries in 2026 and launch a model equipped with a solid-state battery in 2027. Its solid-state batteries come from Qingtao Energy, of which SAIC is one of the investors.
Subsequently, a rumor of a national-level support plan for solid-state battery research and development has pushed the popularity of solid-state batteries to a new high: China may invest about 6 billion yuan in all-solid-state battery research and development, including CATL, BYD, FAW, SAIC, Weilan New Energy and Geely, a total of six companies or receive basic research and development support from the government.
Multinational auto giants also have their own solid-state battery technology reserves.
For example, in addition to Toyota, Volkswagen and BMW have continued to increase their investment in star startups Quantum Space and Solid Power, and the most attractive technologies of these two companies are focused on solid-state batteries.
But the mass production schedule for solid-state batteries has been repeatedly postponed, three years later, and three years later..."mass production in three years" has been shouted for almost a decade.
Repeatedly bounced, but it can still attract people's hearts, what is the charm of solid-state batteries? First of all, it comes from the significant increase in energy density of solid-state batteries.
In the early days, new energy vehicles had many power battery routes, such as lead-acid batteries, which were favored by Toyota, Nissan, General Motors and other car companies because of their low cost, safety and stability, but lithium-ion batteries still lagged behind by virtue of their energy density advantages.
The lithium-ion battery is composed of a lithium metal oxide cathode, a graphite anode, an electrolyte and a separator, and the combination of lithium metal oxide cathode and graphite anode is that the strong lithium-ion holding capacity makes the volume energy density of the single battery reach 300-650Wh/L, and the weight energy density can reach 200-260Wh/kg.
The excellent performance in terms of both volumetric energy density and mass energy density enables electric vehicles with lithium-ion batteries to carry more power and thus have a higher range.
再结合硅基石墨负极的化学材料层面创新，以及CTP（Cell to Pack）、CTC（Cell to Chassis）等物理结构上的革新，即使磷酸铁锂电池，成包后的能量密度仍能达到200Wh/kg。
As for the Kirin battery, which uses ternary lithium cathode with higher energy density and a volume utilization rate of more than 72%, its energy density can reach 255Wh/kg.
Solid-state batteries can easily push the energy density of the battery to a higher level, to 400-900Wh/kg.
For example, the vehicle-grade solid-state battery launched by Tailan New Energy, which has just received hundreds of millions of yuan in Pre-B round financing, has a single energy density of 720Wh/kg, which means that the mileage of electric vehicles will exceed that of fuel vehicles.
The reason for the high energy density of solid-state batteries is that they replace the electrolyte with a solid-state electrolyte, and the separator is no longer required, which greatly improves chemical safety, so that it can be used to use positive and negative electrode materials with higher energy density, such as the graphite anode in lithium-ion batteries with a lithium metal anode with a higher lithium holding capacity.
According to Samsung's paper on the basics of solid-state batteries, it is feasible to develop a super-high-capacity solid-state battery that has significantly improved energy density compared to the best lithium-ion batteries available.
After the energy density of the power battery is improved, it can not only bring higher endurance performance, but also effectively improve the structural layout of pure electric vehicles, especially pure electric cars.
The high chassis caused by the excessive thickness of the battery pack is still a major problem of the current pure electric car, so we have to make some trade-offs:
Xiaomi SU7, with a dynamic appearance, the posture is close enough to the ground, but the space is awkward
NIO ET5 has a dynamic appearance and is compatible with battery swap structures, but the space is more touching
Zhijie S7, plenty of space, strong passability, but the appearance is not pleasing
Moreover, the overweight battery pack also seriously affects the vehicle's dynamic response. When high-energy-density solid-state batteries are installed in vehicles, smaller and lighter weight battery packs will inevitably bring about the optimization of vehicle structure and bring back the elegance of pure electric cars.
Another promising advantage of solid-state batteries is safety, as the solid-state electrolyte keeps the lithium metal electrodes flat at all times, which is very important.
Spontaneous combustion of new energy vehicles is an unavoidable problem, and one of the reasons behind it is the cycle stability and life of lithium-ion batteries.
As we have introduced, lithium-ion batteries require a liquid electrolyte as the medium for internal chemical reactions, and thus a separator to separate the positive and negative reaction zones.
In the process of charging and discharging, the void structure of the graphite anode can ensure that the electrolyte inside it can efficiently "absorb" lithium ions, but when the charging is carried out to a certain extent, the lithium in the graphite void becomes more and the space becomes smaller.
If the charge continues, the electrolyte in the graphite anode will tend to be saturated, and the electrons will be difficult to enter, and they will no longer combine with lithium ions in the graphite, but will consume the electrolyte and form a reaction layer on the surface of the graphite anode.
We call this reactive layer SEI (solid electrolyte interphase), thanks to which the lithium-ion battery can continue to work and cycle.
However, with the increase of the number of charge-discharge cycles, the free lithium ions will gradually accumulate on the surface of the SEI layer, forming lithium metal dendrites to precipitate and no longer participate in the charge-discharge cycle of the battery, which is one of the reasons for the battery power attenuation.
As this process continues, the lithium metal dendrites formed on the surface of the SEI continue to accumulate, which will eventually puncture the separator, causing a short circuit inside the lithium-ion battery, and the electrolyte happens to be a flammable organic solvent, which will also cause spontaneous combustion.
This phenomenon is exacerbated by inappropriate fast charging operations, and the excessive pursuit of batteries with higher integration and higher energy density can also weaken the stability of the battery.
For example, one speculation about the cause of the explosion of the Samsung Galaxy Note 7 battery is that in order to further increase the energy density of the battery and use thinner batteries to drive a more high-definition screen, the thickness of the Note 7 battery separator was reduced to 4 μm, compared to the industry limit of 8 μm at the time.
The introduction of solid-state electrolytes cleverly solves these problems. While greatly increasing energy density, the solid-state electrolyte also keeps the surface of the lithium metal electrodes of solid-state batteries flat after thousands of charge-discharge cycles.
This means a revolutionary upgrade of the cycle safety and energy density of the power battery. Wu Kai said that the core value of solid-state batteries to attract the participation of all countries is that they can greatly improve the energy density of batteries under the premise of ensuring safety.
At the same time, solid-state batteries also have a broad imagination space in terms of fast charging. However, although the prospect is bright, the feet of solid-state batteries are a thorn, and the landing of "commercialization" is not clear.
Similar to the divergence of the early power battery route, neither the academic community nor the industry has found a clear solid-state electrolyte technology route, because in order to mass produce and load vehicles, the solid-state electrolyte must be a polygon warrior that takes into account the characteristics of total conductivity, lithium stability, air stability, fracture toughness, elastic modulus, and machinability.
For example, Japan's TDK (Tokyo Denkikagaku Kogyo K.K) recently developed a new solid-state battery called "CeraCharge", which uses an oxide-based solid-state electrolyte and a lithium metal anode to increase the energy density of the battery to 1000Wh/L.
However, in order to ensure efficiency and stability, CeraCharge uses a large number of ceramic materials, which makes the fracture toughness of the battery questionable, so it is more likely to be used as a power supply for 3C electronic products such as mobile phones and watches, rather than a vehicle-grade power battery.
At present, in the battle for solid-state electrolyte materials, the sulfide route is slightly ahead and has the most hope for mass production, while Toyota's R&D direction is precisely sulfide solid-state electrolyte.
However, lithium metal, as the anode, is actually more likely to produce lithium metal dendrites than the graphite anode, so it puts forward higher requirements for the stability of the solid-state electrolyte. The sulfide electrolyte is not stable enough in the air and is easy to react with water molecules in the air to form toxic gases.
At the same time, the cost of sulfide electrolytes is very high, and the special process for preparing these raw materials also increases the cost. So for now, the technology route for solid-state electrolytes is still "a hundred flowers": Toyota and Nissan are betting on sulfides, Samsung is preferring another sulfur-silver-germanium ore, and QuantumScape is fond of oxides.
When it comes to the cost of landing, the cost of solid-state batteries is still comparable to gold. Tesla CEO Elon Musk, whose mission is to "accelerate the world's transition to sustainable energy", is also not optimistic about solid-state batteries, citing the lack of "commercial advantages".
And when the cost remains high, is the performance boost brought by solid-state batteries still so attractive?
For example, according to GAC Toyota's electric plan: an all-solid-state battery is expected to be launched in 2027-2028, with a range of 1,000km and a fast charging time of less than 10 minutes.
The high-performance lithium-ion battery, which will also be launched in 2027-2028, can also have a range of more than 1,000km, and the fast charging time can be controlled within 20 minutes, and the key thing is that its cost will be reduced by 10%.
"More competitive price" vs. Slightly faster charging time + possible safety improvement", if you are a consumer with real money, under the same battery life conditions, how will you choose at that time?
It should also be taken into account that the landing of solid-state batteries is also facing the risk of bouncing.
Toyota is undoubtedly the leader in the field of solid-state batteries, and the number of related patents is far ahead, but as early as the last decade, the outside world has released the rumors that Toyota is expected to promote solid-state batteries, and so far Toyota has not yet had an exact batch of vehicle test plans.
In this case, we should also be cautiously optimistic about whether Toyota, which has always been stable, will be able to mass-produce solid-state batteries in 2027 or 2028 as in the latest schedule.
As Dr. Wu Kai said, the R&D and mass production of solid-state batteries is not a gradual innovation, but an original innovation, which is a very difficult task. Therefore, our current attitude towards solid-state batteries should be: with expectation and enthusiasm, but also calm and scrutiny.
The author of this article is Sun Xiaoshu, a kicking car gang