All-solid-state batteries, a big gamble

All-solid-state batteries are ushering in a big "all in" gamble. Various players have "come to the table" one after another.

Let's first look at the four most recent patent information, which are from Huawei and CATL. Huawei's patent is called "doped sulfide materials and preparation methods thereof, lithium-ion batteries", and just passed the preliminary review of the State Intellectual Property Office on November 5.

The three solid-state battery patents of CATL announced by the State Intellectual Property Office are "Modified solid-state electrolyte and its preparation method, solid-state battery and electrical device", "Solid-state electrolyte membrane and its preparation method, solid-state battery, electrical device" and "Solid-state battery monomer and its manufacturing method".

The patent of CATL is needless to say, and the news of Huawei's patent is more of a signal than a practical significance, and of course no one will take it lightly. In addition, another battery giant BYD applied for a patent for the invention of all-solid-state batteries as early as August 7.

Not only patents, but also the battery leader CATL has made some new moves recently. According to media reports, CATL has also brought in thousands of people and huge resources to gamble on all-solid-state batteries. Suddenly, there is a sense of change.

Betting on the future

At the Power Battery Conference in September, Zeng Yuqun, chairman of CATL, revealed that the industry's R&D level for all-solid-state batteries is still not high, and CATL's own R&D is at TRL (Technology Maturity Level) 4, which is the stage of technology finalization. It is planned to upgrade to TRL 7~8 by 2027, and small-scale production may be achieved.

Zeng Yuqun also said that compared with its competitors, CATL's research is "a big step ahead" and "second to none". We don't know whether it is true or not, but the industry's competitors have high hopes and enthusiasm for solid-state batteries. Now, Huawei has also entered the market.

This time, the doped sulfide material invented by Huawei's patent has better stability to metallic lithium (as the negative electrode) and can be used as a sulfide solid electrolyte in lithium-ion batteries, giving lithium-ion batteries a longer service life.

The background of this invention patent is that the electrochemical stability window between the materials used in the sulfide solid electrolyte and the metallic lithium negative electrode is relatively narrow, and the side reactions at the "solid-solid interface" during the charging and discharging process are serious.

Although sulfide solid electrolytes are the most promising of several solid electrolytes and have higher room temperature ionic conductivity, the serious side reactions at the solid-solid interface cannot be solved. This is also a difficult problem in the industry, and there is no good solution at present.

Huawei has proposed a solution that seems to be good. There is no information on whether it works or not. However, it means that Huawei has taken action.

Of course, the leader CATL is also focusing on the sulfide route. According to media reports, CATL has recently entered the 20Ah sample trial production stage, in other words, it has entered the production technology exploration stage. In terms of team, CATL has expanded its all-solid-state battery R&D team to over 1,000 people.

From following to making a big bet, CATL's planning timeline for solid-state batteries is similar to that of Toyota, LG Energy Solution, Samsung SDI, etc., and slightly faster than BYD. Now it has clearly accelerated.

In the middle of last year, Wu Kai, chief scientist of CATL, said, "If Toyota says that it can mass-produce all-solid-state batteries today, I am skeptical. Currently, no one in the industry has the ability to mass-produce all-solid-state batteries. As for whether it can be mass-produced in 2027, as a technician, it is difficult for me to say accurately."

But in March this year, Wu Kai shared CATL's progress in all-solid-state battery research and development at a forum. Half a year later, Zeng Yuqun disclosed the timetable for "small-scale mass production of all-solid-state batteries in 2027."

In April, Wu Kai reiterated at the International Battery Technology Exchange Conference that CATL has built a 10Ah all-solid-state battery performance verification platform, and has made technological progress in the positive and negative electrode materials, processes and manufacturing equipment of all-solid-state batteries.

While most solid-state battery companies cannot even build a laboratory worth hundreds of millions of dollars, CATL is willing to invest billions of resources and personnel to gamble on solid-state batteries, which shows unprecedented confidence.

I have also said in many previous articles that the problem of solid-state batteries will not be solved so quickly, and it may be resolved once semi-solid-state batteries reach a balance between technology and cost.

In fact, in my opinion, only high-end long-range models, eVTOL (electric vertical take-off and landing vehicles) and other directions have a clear demand for solid-state batteries.

Because eVTOL has higher requirements for battery energy density, power, rate, safety, fast charging and long life, and the energy density of mass-produced batteries cannot be achieved at present. Therefore, all-solid-state batteries are a better source of power, and eVTOL is relatively insensitive to cost. CITIC Securities also mentioned that eVTOL has become an important landing scenario for solid-state batteries.

According to data released by the China Automotive Power Battery Industry Innovation Alliance, the installed capacity of semi-solid-state batteries reached 2.2GWh in the first half of this year, which is considered to be a beginning in scale.

But why do people still gamble now?

On the one hand, the existing lithium batteries are imperfect and have safety loopholes. On the other hand, they are relatively large in size and weight, while the solid-state battery solution seems perfect in all aspects. That's it. The question is, can we achieve the goal of "the other side of victory"?

Find a way

Toyota was the first to develop solid-state batteries. Toyota claimed early on that it would mass-produce solid-state batteries in 2027. In 2024, although the latest battery dynamics were released, with a full charge in 10 minutes and a range of 1,200 kilometers, and news of mass production starting in 2026, according to an article in the Toyota Times, the actual mass production plan is "2030 and beyond." In other words, the time for mass production has been reversed again and again.

The situation in China is even more bizarre. From time to time, there are news and announcements about solid-state batteries being installed in cars. However, after a little research, they are all semi-solid-state batteries in a transitional state, and those with the word "full" are just substitutions of concepts. In a word, it's all marketing tricks.

However, since this year, the release of solid-state batteries has become more official. For example, when Chery released the Kunpeng battery not long ago, it clearly stated that it would be installed in cars in 2026, and even demonstrated a solid-state battery VCR that could still be used normally after cutting a corner.

Since CATL is very clear about the battery segmentation, its timetable for solid-state batteries will be more reliable and practical.

At present, there are three main technical routes for solid-state batteries: sulfide, oxide and polymer. As mentioned earlier, CATL has chosen a sulfide route similar to Toyota. Wu Kai also said at a previous technical forum that the sulfide route has the highest performance ceiling and the fastest mass production progress.

In addition, there are new technical routes such as halides. For example, BYD is focusing on the research and development of halide solid-state batteries.

The reason why CATL and Toyota chose sulfide electrolytes is that the conductivity of lithium ions is similar to that of liquid, and the material is not "stuck". Of course, sulfides are still very difficult to prepare and expensive, and the price is also very high. Currently, one kilogram of sulfide material costs more than $500. In addition, sulfide electrolytes are easily oxidized to produce toxic gases.

To be frank, these technical routes all have corresponding basic shortcomings, including the "solid-solid interface" problem mentioned above and the "lithium dendrite" problem.

In addition, the production and manufacturing process of all-solid-state batteries is incompatible with the existing battery production process and requires the reinvention of multiple processes, which naturally increases the manufacturing cost.

However, judging from Wu Kai's speech on "Research and Industrial Development of All-Solid-State Batteries for Automotive Use", CATL has found ideas and solutions to solve these problems at the 10Ah sample stage.

Simply put, CATL's solution for all-solid-state batteries is to change the high-nickel ternary positive electrode particles from polycrystalline to single crystal materials, and to perform double-layer coating. The first layer is an inorganic oxide coating to inhibit interface reactions, and the second layer is a solid electrolyte coating to enhance interface ion diffusion.

This is to improve structural stability. The contact interface between the positive and negative electrodes and the solid electrolyte relies on a self-developed multifunctional composite binder to build a stable and efficient electrode conductive network, that is, to improve conductivity.

Lithium metal or alloy is used for the negative electrode, which is coated with a hydrophobic layer of a sulfide solid electrolyte. The hydrophobic layer is removed before the battery cell is sealed to improve air stability.