Solid State Batteries Are Here, But Not Again

Original link: https://www.latepost.com/news/dj_detail?id=1249

The Oak Ridge National Laboratory in the United States created a solid-state battery in 1990, which can be charged and discharged tens of thousands of times without failure. It only takes a few minutes to fully charge, and the energy density exceeds 700Wh/kg, which is 2.5 times that of the current liquid lithium battery. However, in the following 30 years, solid-state batteries that can be mass-produced have not appeared.

Toyota, which has developed solid-state batteries for more than 30 years, gives a mass production timeline of 2025. Chinese start-up companies generally choose a compromise solution on this extremely difficult technical route-making semi-solid batteries.

In early 2021, Weilai announced that it will be equipped with a 150kWh semi-solid battery in its new car ET7 to achieve a cruising range of 1,000 kilometers. “Late Auto” learned that Weilai is expected to receive small batches of semi-solid batteries from suppliers in September this year, and mass-produce this car in the fourth quarter.

The semi-solid battery is provided by “Beijing Weilan” with the background of the Institute of Physics of the Chinese Academy of Sciences, which was established in 2016. In the early days, this company was not widely favored by capital, and its investors were mostly state-owned energy companies. But after cooperating with Weilai, its valuation has grown all the way to 16 billion yuan. Xiaomi, Geely Auto and Huawei Hubble also came in in a funding round in March this year. A person close to Beijing Weilan revealed that more than 40 institutions sent out invitations for this round of financing, but in the end only 10 institutions successfully invested.

In addition to Beijing Weilan, dozens of start-up solid-state battery companies such as Qingtao Energy, Tailan New Energy, High Energy Times, and Enli Power have also received financing. Most of these companies only have mass production plans, no products, and no customers. orders, but the valuation can exceed 2 billion.

The choice of car companies has stirred up the power battery industry dominated by giants. Investors are eager to invest in the next Ningde era, and entrepreneurs also dream of becoming the next Ningde era. In their mouths, the Ningde era is called a “traditional lithium battery company”, an old force that needs to be subverted.

A technical route will not emerge out of thin air and become mainstream, it requires continuous support from capital and the market. In addition to Weilai Automobile, power battery company Guoxuan Hi-Tech, Funeng Technology and lithium battery material supplier Ganfeng Lithium have all announced that they will realize semi-solid battery installation in 2022.

Some people have always believed that semi-solid batteries are the transition route. It does not have the safety of all-solid-state batteries, but also faces cost and performance competition with liquid batteries. In recent years, the structural innovation of liquid batteries cannot be ignored. The Weilai ET7 equipped with a 150kWh battery pack can achieve a cruising range of 1,000 kilometers, while the Kirin battery, which was just released by CATL last month, also plans to achieve 1,000 kilometers.

Up to now, battery giants such as CATL, BYD, and Panasonic have not released semi-solid battery plans. For these liquid battery giants, adopting a transitional solution will not only subvert the existing basic disk, but also cannot meet the needs of long-term development.

But the lineup for the technical route has already begun.

Liquid batteries are reaching their limit

In the past few years, the improvement of energy density by car companies and power battery manufacturers has mainly been achieved by improving the battery structure.

For example, Tesla’s cylindrical battery, the single cylindrical battery is getting bigger and bigger, the diameter is expanded from 18 mm to 46 mm, and the height is increased from 65 mm to 80 mm. Correspondingly, the number of cells required in a battery is reduced from 7000 to 1000. By improving group efficiency, space waste is reduced, and the cruising range of the vehicle is increased by 16%.

The evolution path of BYD’s blade battery and Ningde era’s CTP (Cell To Pack) battery is similar. They all remove the module and integrate the higher-capacity cells directly into the battery pack. Through structural improvement, the energy density is increased from 160Wh/kg to 200Wh/kg.

The Kirin battery released by CATL last month is the latest achievement of this line. Wu Kai, chief scientist of CATL, said that the Kirin battery increases the volume utilization rate of the battery pack from about 56% to 72%, and the new energy vehicle equipped with the Kirin battery can have a cruising range of more than 1,000 kilometers.

The next-generation form of battery structure improvement is to integrate the battery directly into the chassis of the electric vehicle. Tesla and Ningde call it CTC technology (Cell To Chassis, the battery is integrated into the chassis), and BYD calls it CTB (Cell to Chassis). Body).

Tesla Model Y is the first model in the world to use CTC technology. Its new Model Y integrates more than 1,000 4680 batteries into the chassis and has a cruising range of 600 kilometers. BYD’s third-generation electric vehicle platform (e 3.0 platform) also uses similar technology, integrating the blade battery into the upper cover of the chassis.

CATL announced as early as 2019 that it would make CTC batteries, and it went one step further than Tesla and BYD, integrating motors, batteries, electronic control and other systems into the chassis. In April this year, Cai Jianyong, general manager of Huawei’s smart car solution BU smart car control field, resigned to join CATL as the person in charge of this project.

Compared with structural innovations, improvements in battery materials are relatively slow.

The last step-by-step replacement of the battery material system was the emergence of lithium batteries and the replacement of lead-acid batteries. It is also because of the application of lithium batteries that we can say goodbye to “big brother” and use smaller mobile phones.

Tesla moved Panasonic’s 18650 batteries from laptops to cars in 2008, and BYD also put lithium iron phosphate batteries into cars at the same time. This has laid the mainstream material technology route for electric vehicles today, and subsequent material improvements have been incremental.

Before 2020, battery companies such as CATL and LG New Energy were used to increasing the proportion of active materials in ternary lithium cathodes to increase energy density. CATL increased the nickel content in the ternary lithium cathode from 33% to 80% in 2019, and created NCM 811 (the ratio of nickel, cobalt, and manganese is 8:1:1) battery, which has a higher energy density than NCM111 battery. 17% increase.

However, adding high active materials will sacrifice battery safety to a certain extent. For high-nickel batteries, when the nickel content of the positive electrode exceeds 90%, the thermal stability and capacity retention rate of the battery will drop rapidly, making it more prone to thermal runaway and decay.

In the second half of 2020, GAC Aeon S models equipped with CATL’s 811 batteries spontaneously ignited many times. Another company, LG Chem, which chose the high-nickel ternary lithium route, recalled nearly 70,000 vehicles in 2021 due to a spontaneous combustion incident, and was sued by General Motors for $1 billion.

The aforementioned engineer told Auto Late that most of the high-nickel batteries on the market currently cannot pass the acupuncture test (simulating the scenario of a car crashing into a damaged battery pack), and the high-nickel ternary battery is a safety problem. After the exposure, most new energy car companies began to return to conservative, and switched to the use of nickel 523 and 622 batteries.

The route of improving the cathode material by adjusting the ratio has almost come to an end. The upper limit of the theoretical specific capacity of the ternary lithium battery is 275 mA h/g, and the specific capacity of the NCM 90.0.5 (the ratio of nickel, cobalt, and manganese is 9:0.5:0.5) in the current laboratory environment is 230 mA·h/g. As early as 2018, the specific capacity of lithium iron phosphate materials has reached 150 mA h/g, which is close to the theoretical limit of 170 mA h/g.

In July 2022, Ningde Times released a lithium iron manganese phosphate battery. Manganese material was added to the lithium iron phosphate positive electrode, and the specific capacity reached 165mA h/g, which almost pushed the performance of lithium iron phosphate batteries to the limit. There are only theoretical Optimize space.

Solid-state batteries have not been mass-produced for 30 years

The battery industry has always known what a better material is — lithium metal. However, unlike lithium compounds in liquid batteries, lithium is extremely active when it exists in the form of metal, and it is easy to chemically react with lithium salts in the electrolyte, causing thermal runaway.

In the early days of solid-state battery development, the academic community believed that this was the ultimate solution for batteries. It is non-flammable and has an energy density of 700Wh/kg, which is 2.5 times that of current lithium-ion batteries.

In 1970, Panasonic created a lithium metal primary battery, but it couldn’t be cycled. In 1988, Moli Energy in Canada mass-produced lithium metal rechargeable batteries, three years before the mass production of lithium-ion batteries. However, Moli Energy’s batteries suffered multiple fires and explosions after mass production, and had to be recalled on a large scale. At that time, the Japanese battery giants Sony, Sanyo and Panasonic successively decided to terminate the development of lithium metal solid-state batteries, and Mitsui Group decided to give up the lithium metal solid-state battery route forever.

In the more than a decade since then, with the exception of Toyota, only university laboratories are still developing solid-state batteries. The explosion of the electric vehicle market has also promoted the development of the battery industry. Chinese companies started developing solid-state batteries six or seven years ago. Scientists from the Chinese Academy of Sciences went to sea to start businesses, and Chinese scientists who studied abroad returned to China to join leading companies.

Nan Cewen of Tsinghua University founded Qingtao Energy in 2014. In 2015, Liang Chengdu, who had been studying at Oak Ridge National Laboratory for more than ten years, joined CATL. In the same year, Ganfeng Lithium began to enter the power battery business, taking solid-state batteries as its core goal, and two years later hired Xu Xiaoxiong, a researcher at the Ningbo Institute of Materials, Chinese Academy of Sciences. Beijing Weilan was established in 2016 by researcher Li Hong and academician Chen Liquan of the Institute of Physics, Chinese Academy of Sciences.

The research and development of solid-state batteries is a matter of solving preparation and manufacturing problems based on known formulas, and technical barriers rely on continuous trial and error accumulation.

Japan’s Toyota, Hitachi Shipbuilding and other companies have tried tens of thousands of electrolyte formulations in the past 30 years, and selected dozens of materials for use in batteries. What other companies have solved is how to better apply these dozens of materials in batteries. middle.

According to the material system, the current solid-state battery can be divided into three technical routes. Japan and South Korea are betting on the sulfide system, Europe is mainly the polymer route, and China is mainly oxide.

These three technical routes all have corresponding basic shortcomings. The polymer electrolyte needs to be heated to 60 ℃ to obtain sufficient conductivity; the conductivity of lithium ions in oxide electrolytes is much lower than that of liquid state; the conductivity of lithium ions in sulfide electrolytes is similar to that of liquid state, but it is easy to oxidize and produce toxic gases.

Bollore in France put polymer batteries into city buses in 2012. Because the polymer needs to be heated to 60 degrees Celsius to function properly, Bollore has also incorporated a unique heating element into the battery pack.

Due to the high cost and energy density comparable to that of liquid batteries (the energy density of polymer batteries is 150Wh/kg, and the energy density of lithium iron phosphate batteries at that time was about 140Wh/kg), Bollore’s solution was not eventually promoted on a large scale.

Before Toyota released sulfide solid-state batteries in 2012, companies all over the world were making oxide and polymer solid-state batteries. At that time, the main problem that plagued the industry was that the conductivity of polymer and oxide route batteries was much lower than that of liquid batteries. Toyota’s sulfide electrolyte makes solid-state batteries more conductive than liquid batteries for the first time.

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Toyota’s solid-state battery concept car

In national projects such as Alca Spring, Rising2, Solid EV, etc., Japan has united 38 R&D institutions, including Toyota, Nissan, Honda and other automobile companies, and universities to develop all-solid-state batteries with sulfide systems.

Sulfide is the highest and most difficult solid-state battery technology route. Even Toyota, which owns nearly one-third of the world’s sulfide battery patents, has skipped a ticket on loading the car.

Back in December 2017, Toyota said it would start producing solid-state batteries in early 2020. “In 2018, Toyota’s solid-state battery samples could only be charged and discharged 50 times. At that time, the charge and discharge life of liquid batteries was about 2,000 times.” express.

Due to the inability to solve the ionic conductivity of oxide batteries and other issues, solid-state battery company SES abandoned the all-solid-state battery route in 2015 and began to develop semi-solid-state batteries. “People who do scientific research will not be too absolute, but it is difficult to make all-solid-state batteries. The problems we encounter are basic chemical problems, and such problems cannot be solved by time.” Hu Qichao, founder of SES, told ” Late Auto” said.

To be sure, there will be no mass production of solid-state batteries in the world in the next five years. “If a new battery needs to be mass-produced within 5 years, it must have a formed product formula now, have a thousand-ton battery material production capacity within 2 years, and then have a 1GWh production line, and finally expand to an annual production capacity of more than 10GWh, At present, even Toyota has not yet determined the formula of battery materials.” A researcher from a solid-state battery company told Auto Delay.

There are also doubts whether solid-state batteries will really be used in cars on a large scale in the future. In the past, the industry generally believed that the cruising range of electric vehicles reached 1,000 kilometers, and solid-state batteries must be switched. Today, the Kirin battery of CATL has reached 1,000 kilometers, which is more than most fuel vehicles (800 kilometers).

The value of all-solid-state batteries in the future may be mainly reflected in light weight and safety. However, the promotion of this technology requires a subversive transformation of the existing battery industry, and the cost is extremely high. This makes it difficult for solid-state batteries to compete with the cost advantages of liquid batteries even if they overcome the difficulties in research and development and technology, and car companies may not be willing to pay a lot of money for lightweight and improved safety.

Semi-solid, scientific research compromises with industry

The research and development of batteries is different from other products, using an exhaustive method, not as sure as writing code. Scientists cannot create something out of nothing, and need to select the most suitable elements and compounds for batteries from the existing physical world and put them into batteries.

Success is a probabilistic event. Companies such as CATL choose to deploy a variety of routes and use a larger base to increase the possibility.

Startups in the battery field cannot bet on multiple routes like the CATL era, and investors do not allow them to take risks on basic chemical problems. Most of these companies choose an easier commercialization route – semi-solid batteries, which caters to car companies. The pursuit of battery safety is also easier to mass produce.

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QuantumScape’s battery samples

In terms of materials, the current semi-solid batteries are mainly divided into three routes – graphite anode, silicon-based anode and lithium metal anode. Among them, the lithium metal anode has the highest energy density, but it is also the most difficult to mass-produce.

The four leading solid-state battery companies in China—Beijing Weilan, Jiangsu Qingtao, Ningbo Fengli, and Huineng Technology, all use high-nickel ternary as the positive electrode material, oxide semi-solid electrolyte, and silicon-based negative electrode for their mass-produced products. of semi-solid batteries.

Among them, Beijing Weilan and Ningbo Feng Lithium (an affiliated company of Ganfeng Lithium) both announced that they will mass-produce semi-solid batteries in 2022; Qingtao Energy, invested by SAIC, has not yet disclosed the time line; Hui Neng Technology, which has received orders from Mercedes-Benz, plans to produce semi-solid batteries in 2023. Annual mass production.

When NIO announced in early 2021 that it would be equipped with a 150-degree semi-solid battery on the NIO ET7, the industry’s perception of semi-solid graphite/silicon-based batteries changed. The ultimate problem for battery companies is whether car companies are willing to buy it or not, and the rest is not important.

In terms of performance, the silicon-based anode semi-solid batteries selected by Beijing Weilan and other companies are not significantly improved compared to the existing liquid batteries. The energy density of the silicon-based anode semi-solid battery is 360Wh/kg, and the energy density of the existing liquid battery is 300Wh/kg. Compared with liquid batteries, the safety improvement of semi-solid batteries is limited. After the use of semi-solid electrolytes, the internal resistance of batteries increases, which will lead to battery polarization problems, which will ultimately affect battery cycle life and safety.

In terms of cost, semi-solid batteries also have many challenges. “According to the calculation of loading 100,000 vehicles a year, the cost of graphite semi-solid batteries is 3-4 times that of existing liquid batteries, and the cost of silicon-based negative electrodes is higher.” The chairman of a start-up battery company said to “Late Auto”, according to the current The cost of a single vehicle for a liquid lithium battery of 100,000 yuan is calculated, and a car with a price of more than 1 million yuan can absorb the cost of a semi-solid-state battery.

High cost comes from more difficult manufacturing process and material cost. There is a coating process in the battery production process. The coating speed of a mature liquid battery production line is 70-80 meters per minute, while the coating efficiency of semi-solid batteries is about 60 cm per minute.

The yield problem brought about by complex processes has further pushed up the cost of mass production of semi-solid batteries. A person familiar with the matter said that the yield rate of Beijing Weilan semi-solid battery production lines is less than 50%. In addition, the lithium lanthanum zirconium oxide materials required for semi-solid oxides have not yet been mass-produced by suppliers.

In this regard, people close to Weilan told “Lady Auto” that the battery materials required by Weilan have mass-produced suppliers, and the efficiency of the pre-lithiation coating process “has room for improvement.”

Hu Qichao believes that semi-solid batteries with graphite anodes and silicon-based anodes are only transitional technologies, and lithium metal anode semi-solid batteries are the long-term stable solutions.

To improve the energy density of batteries, the key is to replace the graphite anode with a lithium metal anode, rather than the material of the electrolyte. When the semi-solid battery adopts lithium metal negative electrode, the energy density of the battery can exceed 450Wh/kg, and the corresponding loading range can exceed 1500 kilometers. Currently South Korea’s LG New Energy, SK and SES are exploring this route.

The current difficulty of this route is that a battery using a lithium metal negative electrode will generate lithium crystals, that is, “lithium dendrites”, in the battery during charging and discharging. When the crystal grows to a certain extent, it will pierce the battery and cause safety problems.

In addition, lithium metal batteries also face high costs. Due to its high activity, lithium metal materials easily react with moisture in the air, so they need to be manufactured in vacuum or inert gas, and the cost is extremely high. The current market price of lithium metal materials is 3 million yuan / ton, which is about 7 times that of lithium carbonate.

At present, the four solid-state battery companies in China have all chosen to make semi-solid-state batteries with silicon-based anodes. The raw material cost rise is limited, and the manufacturing process is also close to the existing liquid batteries. The aforementioned sources close to Weilai revealed that the price of semi-solid batteries purchased by Weilai Automobile from Weilan did not increase significantly compared with the existing liquid batteries.

Others believe that semi-solid-state batteries can neither achieve the energy density and safety of all-solid-state batteries, nor have the cost advantage of lithium-ion batteries, and are speculative products jointly spawned by capital and electric vehicle arms race.

A person close to the Ningde era told “Lady Auto” that the Ningde era pays attention to all technical routes except for semi-solid batteries, “The effect of semi-solid batteries that other companies have been tossing for several years, Ningde era thinks that they will change the liquid state. The battery structure or electronic control can also be achieved.” He said that NIO used a 150-degree semi-solid battery for 1,000 kilometers of battery life, and the Kirin battery of the Ningde era can also be used.

What is next-generation battery technology

There are 6 elements in the performance assessment of power batteries in CATL: energy density, safety, cost, charging speed, temperature resistance and yield. These six elements determine whether a battery can be recognized by the market.

“Whether the battery is solid and what electrolyte is used is not critical to car companies. They only look at the performance data of the battery.” The aforementioned Yutong bus person said.

The difficulty of solving automobile manufacturing problems is no less than that in the aerospace field. The aerospace field can be developed regardless of cost, but the car needs a controllable cost, and the battery needs to be used in the car for 8 years without exhaustion.

3C products such as mobile phones require about 600 times of battery charge and discharge life, and 200 times for drones. Without considering the cost, the existing solid-state battery samples can meet the performance requirements. But in the automotive field, the national standard requires more than 1,000 times the life of the power battery. And solid-state batteries that only meet the national standard cannot compete with lithium batteries with a charge-discharge life of more than 3,000 times.

Although several companies have officially announced the mass production and loading timelines of solid-state/semi-solid-state batteries, these routes still have shortcomings or technical difficulties compared with liquid batteries.

Whether to choose a more risky plan is a problem that car companies need to face today. Also in order to achieve 1,000 kilometers of battery life, Weilai Automobile chose and supported Beijing Weilan to take the semi-solid battery route, while Li Auto, Nezha Auto and other car companies chose to use the Kirin batteries of the Ningde era.

The cruising range is no longer the primary consideration for car companies to choose batteries. Tesla, Xiaopeng and Ideal are all vigorously developing ultra-fast charging technology, using an 800V high-voltage platform with 4C batteries, and the goal is to charge 80% in 10 minutes.

The key to 4C batteries is positive and negative electrode materials and processes. At present, both liquid and solid hybrid batteries can be made into the 4C standard.

A senior scientific researcher of a battery company believes that the most competitive batteries on the market in the next five years are: 600 km battery life, 800V high voltage platform batteries, and 1000 km liquid/mixed solid-liquid batteries.

In the choice of batteries, both car companies and battery factories will bear the corresponding risks. The mass production and loading of power batteries needs to go through the ABC sample stage. The A sample is the test of a single cell, the B sample is the battery pack test after the battery is grouped, and the C sample is the loading test. Each stage takes about a year. .

Car companies will bear the cost of battery testing, each of which exceeds 100 million yuan. More ambitious car companies will also choose to build factories in joint ventures with battery companies. The construction cost of a semi-solid battery production line with an annual production capacity of 1GWh is 400-500 million yuan. If you choose the wrong technical route, it means that all these investments are in vain.

For battery factories, the cost is even greater. Because car companies will only choose the most cost-effective batteries for mass production in order to increase the competitiveness of their products, regardless of the liquid, solid and semi-solid technical routes. If semi-solid batteries cannot surpass the performance and cost advantages of liquid batteries, it will be difficult to popularize them on a large scale.

If semi-solid state is truly the next-generation technology for liquid batteries, then the giants of the battery industry today are not turning a blind eye. There is no first-mover advantage in this race. A semi-solid battery practitioner said, “If CATL fully invests in the direction of semi-solid batteries, it will catch up with us in 3 years.”

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