Solid-state batteries on the journey to "obtain scriptures and conquer demons"

Recently, solid-state batteries have once again become a hot topic in the market.

On September 1, Zeng Yuqun, chairman of CATL, mentioned the recently hot topic of solid-state batteries at the World Power Battery Conference.

Zeng Yuqun said that CATL has invested 7 to 8 years in research on all-solid-state batteries. If we use numbers from 1 to 9 to represent the technical and manufacturing maturity of solid-state batteries, 1 means just beginning to get involved in this field, and 9 means the technology is mature and can be put into large-scale production, then the current highest level in the industry is only around 4.

Most companies have only made some device samples for experimental verification, and there are still many boundary conditions for their use, such as achieving high low-temperature performance under 6000 atmospheres of pressure.

This means that these released products cannot yet be put into market application.

CATL’s current research progress is also around 4%, but compared with the situation around the world, it should be considered “a big step ahead”.

In fact, just recently, two companies released solid-state battery products within one day.

On August 21, Penghui Energy announced that the company had achieved a major breakthrough in solid-state batteries. A related press conference was held on August 28, and actual products were displayed.

As soon as the news came out, it attracted much attention from the market. Penghui Energy’s stock price hit the daily limit on the same day and the next day, recording an increase of more than 60% within 4 trading days.

However, judging from the press conference on August 28, the progress of Penghui Energy's solid-state batteries was not so optimistic.

On the one hand, solid-state batteries were rarely mentioned at the press conference, taking up only more than ten minutes of explanation. And judging from the R&D roadmap, its mass production time is not much different from that of other power battery companies. It is expected to carry out pilot R&D and small-scale production in 2025, establish a production line and start mass production in 2026, and only after three years is it expected to be truly mass-produced on a large scale. It is not a major breakthrough.

On the other hand, the energy density of the products released so far is only 280Wh/kg, which is close to the energy density limit of ternary lithium batteries of 250~300Wh/kg, but it is far behind the energy density of solid-state batteries, which can reach up to 500Wh/kg. Even compared with the semi-solid-state batteries released by Zhiji and NIO (with energy densities of 300Wh/kg and 360Wh/kg respectively), this data is far inferior.

In addition to Penghui Energy, another company, China Innovation Aviation, announced the progress of its all-solid-state batteries on the same day.

The "Boundless" all-solid-state battery released by China New Energy Aviation has an energy density of 430Wh/kg and a capacity of 50Ah. It is planned to achieve small-scale vehicle installation verification of this all-solid-state battery in 2027.

Compared with Penghui Energy, China New Energy is much more famous, and its market share in 2023 ranked among the top five in the world.

In terms of energy density, China New Energy's solid-state batteries are more reliable, but small-scale installations will have to wait until 2027, and large-scale applications will probably be even later.

Faced with competitors who have announced their progress in solid-state batteries one after another, CATL seems to be a little restless.

As early as March this year, Zeng Yuqun stated at the 2023 annual report performance interpretation meeting that solid-state batteries are still far from becoming a commodity.

In an interview at the end of March, he also said that the current technical effects of solid-state batteries are "still not good enough" and there are safety issues, and it is still several years away from commercialization.

But in April of the same year, CATL's chief scientist Wu Kai changed his tone and said that CATL had the opportunity to produce solid-state batteries in small batches in 2027.

Then at the World Power Battery Conference, Zeng Yuqun boldly stated CATL's leading position in solid-state batteries. It is not difficult to see that with such an epoch-making product as solid-state batteries, under the industry's overwhelming marketing methods, Ning Wang also felt a little anxious.

Zeng Yuqun also explained that the key to the current development of all-solid-state batteries lies in the research on materials and chemical systems, and the biggest difficulty lies in the "solid-solid interface" problem.

The "solid-solid interface" problem is difficult to solve because it involves complex interactions in multiple aspects such as physics, chemistry and electrochemistry.

Solid electrolytes lack fluidity and cannot fully wet the electrode materials through capillary action like traditional liquid electrolytes. Therefore, the contact area between them and the electrodes is small, resulting in increased interfacial impedance.

In addition, during the charge and discharge process, the volume change of the electrode material may lead to poor contact and further increase the interfacial impedance.

(a) Reaction at the Li/LAGP interface; (b) Reaction at the Li/LZPO interface; (c) Reaction at the Li/LLZO interface (Source: Gong Yue et al. Structural evolution and material transport at the interface in all-solid-state batteries)

In terms of chemical stability, chemical reactions may occur at the interface between the electrode and the electrolyte, forming an interface layer that is not conducive to ion transport. These interface layers may also increase the internal resistance of the battery and affect the charge and discharge performance.

Moreover, during the electrochemical cycle, the potential change at the interface between the electrode and the electrolyte may lead to the instability of the interface structure, affecting the long-term cycle performance of the battery. At the same time, the growth of lithium dendrites on the contact surface between the negative electrode and the electrolyte may penetrate the battery's diaphragm, causing the battery to short-circuit, which not only affects the performance of the battery, but may also cause safety problems.

The "solid-solid interface" problem has become an unavoidable problem in the research and development of solid-state batteries.

In addition, problems such as low conductivity of solid-state electrolytes, difficult cost control, and the development of positive and negative electrode materials also plague solid-state battery researchers.

However, despite this, given that solid-state batteries can effectively solve current problems such as insufficient battery life of new energy vehicles and the risk of spontaneous combustion of lithium batteries, major manufacturers have invested in research and are competing to release mass production plans.

At present, according to incomplete statistics, there are more than 10 companies in China that have released solid-state battery products or mass production plans.

In addition to CATL, Penghui Energy and Sinotruk mentioned above, Guoxuan High-tech has also launched an all-solid-state battery - Jinshi Battery, which is planned to be put into small-scale vehicle experiments in 2027 and mass production in 2030; Yiwei Lithium Energy expects to achieve a breakthrough in production technology in 2026 and launch a high-energy-density all-solid-state battery in 2028; Xinwangda's first-generation all-solid-state battery product with an energy density of 400Wh/kg has achieved small-scale trials and plans to have mass production capabilities in 2026; Honeycomb Energy already has the ability to prepare 20Ah all-solid-state batteries, and it is expected to be installed on vehicles after 2030, etc.

In addition, foreign companies such as Toyota, Honda, Panasonic, and LG Energy Solution are also promoting the research and development and mass production plans of solid-state batteries.

On the one hand, facing the situation where CATL and Fudi share more than 70% of the market share, solid-state batteries are likely to become an opportunity for other power battery manufacturers to overtake and catch up. After all, solid-state batteries rely on many new technologies, and the advantages are not entirely in the hands of giants.

It is hard for second- and third-tier power battery suppliers not to be tempted by the possibility of changes in the market competition landscape, and it is hard for giants like CATL not to feel anxious and in crisis.

On the other hand, for car companies, assembling "solid-state batteries" can be used as a good marketing point for outsiders who do not know the truth; for power battery suppliers, they also need to demonstrate their leading advantages in new technologies to reassure investors and partners.

As a result, solid-state batteries seem to be getting hotter and hotter in the entire industry. In such an atmosphere, companies that originally planned not to go into mass production so quickly may have to rush into it in order to avoid being seen as lagging behind the industry.

However, as Zeng Yuqun said earlier, there are still many problems to be solved in the mass production of solid-state batteries, and the industry is far from reaching technological maturity.

What is needed for current solid-state batteries is to solve problems at the technical level, rather than simply being viewed as a marketing gimmick or even a means of reaping profits from shareholders.

In an era when pure electric vehicles are slowing down and power battery competition is serious, marketing may bring temporary benefits, which is understandable, but real research and development is the key to success.