Battery Revolution: How far are solid-state batteries from mass production?

Latest update time：2022-01-22

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The development of batteries has gone through nearly two hundred years of history. Today, lithium-ion batteries are the most outstanding secondary energy storage batteries. With many advantages such as high operating voltage, fast charge and discharge characteristics, long cycle life, and no memory effect, it has become the first choice for large-scale applications in today's digital products and electric vehicles.

Although lithium-ion batteries have excellent performance, their development also has its own challenges and obstacles that are difficult to overcome: the structural characteristics of the battery limit the performance of the battery. The existing battery structure is the root cause of battery aging and safety hazards.

The principle of battery power generation is that two electrode materials exchange ions with each other in the electrolyte. However, because this structure also makes its reaction interface always exist, the battery is in a state of always working, causing it to age easily and also posing safety risks.

For example, electric cars break down in winter because the batteries fail to perform at low temperatures. Material scientists and battery engineers have proposed many solutions for battery materials. For example, adding a large amount of organic solvents to the electrolyte to reduce the solidification temperature of the electrolyte. However, this makes the electrolyte more flammable, sacrificing battery safety.

Some scientists have tried to replace the electrode materials, but although the battery's energy has increased, it cannot resist thermal runaway; fast charging will cause the battery interface to be too flammable and cannot guarantee its safety. Solving the problem from the perspective of optimizing battery management systems has led to a decrease in energy density and an increase in unit cost.

There is no solution to the contradiction between the need for high activity at low temperatures and high stability at high temperatures. It seems that batteries also have obstacles that they cannot have both. Energy density, safety, fast charging and other factors cannot be perfectly integrated in the battery. If these problems are solved, the large-scale development of new energy vehicles will revolutionize and reshape the century-old automobile industry.

Therefore, the ultimate development goal of power batteries is to move towards the advantages of safety, high energy density, good cycle performance, and fast charging speed.

As the new terminator of lithium batteries, solid-state batteries are becoming the killer weapon for new energy vehicles to kill fuel vehicles.

The value of power batteries is advancing

When will new energy vehicles replace fuel vehicles? In the field of power batteries, the market generally agrees that the energy density of the battery system of existing electric vehicles will double from the common 160wh/kg to 400wh/kg. The solution to the problem of battery energy density must be the innovation of power batteries.

We know that the mainstream power batteries in the electric vehicle market are ternary lithium batteries and lithium iron sulfate batteries. If classified according to the physical state of the electrolyte, these two batteries are typical liquid batteries. If we want to eliminate mileage anxiety and innovate the new energy vehicle market, solid-state battery performance characterization is the goal of power battery development. Solid-state batteries are also known as the new direction of future lithium battery development.

Ternary lithium and lithium iron sulfate, which are popular choices in the field of power batteries, are not perfect choices. Ternary lithium batteries have high energy density but poor high temperature resistance. Lithium iron phosphate batteries have high safety but low energy density limit. Liquid lithium-ion batteries generally have safety hazards such as electrolyte oxidation, electrode expansion, and high-temperature runaway, and can only sacrifice energy density in exchange for stability. Solid-state batteries can be compatible with the shortcomings of both: they can meet the needs of energy density and take safety into consideration.

Solid-state batteries use solid materials as electrolytes, so there is no continuous reaction interface and byproducts will not dissolve in the interface, so they have better stability and cycle characteristics. At the same time, the drying and leakage problems faced by liquid electrolytes will not exist. This makes solid-state batteries have advantages over ternary lithium batteries and lithium iron phosphate in terms of safety and life cycle.

In addition, solid-state batteries are also resistant to high temperatures, non-corrosive, small in size, and have high energy density, avoiding the main weaknesses of traditional liquid lithium batteries. It is reported that a solid-state car can have a range of up to 1,000 kilometers, and it only takes 10 minutes to charge. Over time, solid-state batteries will also deteriorate less.

All-solid-state batteries use solid electrolytes, which are relatively safer and have better performance, while traditional liquid lithium-ion batteries are gradually unable to meet the standards of advanced technology: they can both increase driving range and be safer. Therefore, all-solid-state batteries have become a new trend in the development of power batteries.

A large number of them come: occupying the market opportunity

In November 2020, the General Office of the State Council issued the "New Energy Vehicle Industry Development Plan (2021-2035)", which explicitly requires accelerating the research and development and industrialization of solid-state power battery technology. It is predicted that by 2030, the global solid-state battery market will exceed US$6 billion (approximately RMB 38.3 billion), and the Chinese market will account for more than 50%.

The good performance indicators of solid-state batteries in the laboratory mean rich commercial value, which has also become the driving force for companies to accelerate their layout and seize the technological commanding heights. Domestic and foreign companies and institutions have put the research and development and mass production of power batteries on the agenda.

Toyota also started its layout in power batteries early. Toyota's automotive-grade solid-state batteries have more than 1,000 patents, ranking among the top in the world, and most of them are invention patents with high gold content. At CES 2022, Gill Pratt, Toyota's chief scientist and director of the Toyota Research Institute, reiterated that the first Toyota car using solid-state battery technology will arrive around 2025.

Thomas Schmall, chief technology officer of Volkswagen Group Components, said in an interview last year that Volkswagen has high hopes for the development of a new generation of solid-state batteries. The company hopes to form a complete solid-state battery sales model by 2025 and supply solid-state batteries to the market. It also plans to build six large-scale battery factories in Europe by 2030, with a total annual production capacity of 240GWh.

The BMW Group has released a plan, saying it plans to achieve mass production by 2030; LG Energy is also developing all-solid-state batteries, which are expected to be mass-produced in 2026.

The development of solid-state batteries in China is also in full swing, and the technical route is a mixture of all-solid and semi-solid. CATL, a big player in the battery industry, has previously disclosed two patents related to solid-state batteries, and announced in May last year that it has been able to make samples of solid-state batteries, but there is still a long way to go before commercialization, and it is expected to be launched on the market in 2030. SAIC Group announced in June last year that it will launch high-safety, high-energy-density, commercially applicable solid-state lithium batteries in 2025.

Players who have chosen to focus on semi-solid research and development include Weilan New Energy, Qingtao Development, Guoxuan High-tech, Ganfeng Lithium Battery, etc. Although they also have all-solid-state battery production lines, the mass-produced all-solid-state batteries are mainly used in consumer electronics, special power supplies and other fields. The semi-solid-state batteries that have been put into use in new energy vehicles are currently in the verification and testing stage.

NIO previously advertised that it would be equipped with a solid-state battery, which made the industry excited. After it was launched, this so-called solid-state battery also showed its true face. It was not the fully solid-state battery that the industry had been waiting for. NIO’s Li Bin used a commercial packaging term, and the battery pack equipped with the ET7 sedan was actually a semi-solid-state battery. However, the attention and discussion caused by the gimmick also made NIO’s new car stand out. The battery with a range of more than 1,000 km made people see the potential of solid-state batteries.

Whether it is the timetable set by car companies or the mass production time given by industry researchers and experts, they all point to 2025 and 2030, but there is no sign of advancement at present. According to the results of actual car company tests, there is a trend of further postponement to 2030. We can see that it will take some time for the process from leaving the laboratory to large-scale implementation, and the actual implementation of large-scale mass production is a long and arduous journey.

Mass production is slow to a crawl

Compared with other lithium-ion power batteries, solid-state batteries have superior technical indicators, but these data are also greenhouse indicators in the laboratory. In the actual mass production process, there are still many bottlenecks that have not been overcome.

1. The technical indicators of solid-state batteries still need to be improved. Solid-state electrolytes have low ionic conductivity, slow charging, poor solid/solid interface contact and stability, and electrolytes are sensitive to air.

2. The manufacturing process is complex and the production process is immature. For example, the oxide and sulfide electrolytes used to make solid-state batteries are porous ceramic materials. The characteristic of this type of material is that it is brittle and it is difficult to process it into a very thin electrolyte. If you are not careful, it will break.

3. High manufacturing cost. The preparation process of all-solid-state batteries is complicated, and the solid electrolyte is expensive. At present, the cost of all-solid-state electrolyte lithium power batteries is relatively high.

4. The industry chain is not yet complete, making it difficult to mass produce. At this stage, solid-state batteries are mostly greenhouse products in the laboratory. There are only a handful of batteries that have been tested in practice. With the current process level and equipment capabilities, the yield of the finished product cannot be guaranteed, let alone large-scale mass production and listing.

Solving these practical bottlenecks is not so easy. Fisker, an American automaker that has been deeply engaged in the research and development of solid-state batteries for many years, announced at the beginning of last year that it would give up the development of all-solid-state batteries. This decision also means that years of efforts to research solid-state batteries have gone to waste. Massachusetts Solid Energy (SES), a lithium battery unicorn company, has also given up the development of all-solid-state battery technology and chosen the solid-liquid mixed semi-solid battery route. In the final stage of the tough battle, these veteran players in solid-state batteries chose to give up, which to a certain extent also shows that the final research and development sprint stage of solid-state batteries is more difficult and dangerous than the 90% of the mileage that has been completed.

In short, for solid-state batteries, no matter whether it is energy density, cycle life, safety, cost or other technical indicators, the lack of any one of them will be a stumbling block on the road to large-scale commercialization.

Whether companies still insist on the all-solid-state battery route or compromise and choose the semi-solid-state route, there is uncertainty in the technical route of solid-state batteries. The mainstream view in the industry is that semi-solid-state batteries may be able to achieve large-scale mass production around 2025, but it will take at least 10 years for all-solid-state batteries to be fully commercialized. After a decade of development, no one can be 100% sure whether solid-state batteries will eventually be the ultimate route for power batteries.

Industrial products cannot be developed without a decade of preparation from R&D to verification and implementation. Solid-state batteries are still in the process of exploration from materials to structure to manufacturing technology. As an emerging power battery option, it also takes time to settle and brew. Only in this way can we ensure the long-term endurance of new energy vehicles, subvert and innovate the century-old automobile industry, and contribute to the ecological construction of green travel.

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