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Samsung has made breakthrough progress on the road to mass production of all-solid-state batteries!
A few days ago, Samsung Advanced Institute and Samsung Research Center Japan published an article in the magazine "Nature Energy" titled "Achieving High Energy Density and Long Battery Life All-Solid-State Through Silver-Carbon Anode" The paper "Lithium Battery" demonstrates Samsung's solution to the problems of lithium dendrites and charge and discharge efficiency that plague the mass production of all-solid-state batteries.
▲Samsung published a paper in the magazine "Nature-Energy"
It is understood that this solution will help Samsung's all-solid-state battery achieve 900Wh/L (different from Wh/kg unit of measurement (the two cannot be converted due to different densities of different materials), more than 1,000 charge and discharge cycles and a Coulombic efficiency of 99.8 (also known as charge and discharge efficiency). Although my country's currently more advanced solid-state battery technology can also achieve more than 1,000 charge and discharge cycles, its Coulomb efficiency is currently not close to 100.
According to the paper, Samsung has processed the negative electrode, electrolyte and positive electrode of solid-state batteries by introducing silver-carbon composite negative electrodes, stainless steel (SUS) current collectors, pyroxene-type sulfide electrolytes and special material coatings. , effectively solved the three core problems faced by mass production of solid-state batteries, namely lithium dendrite growth, low Coulombic efficiency and interface side reactions, and pushed solid-state battery technology one step closer to industrialization.
Breakthroughs in key technologies mean the start of a competition in the solid-state battery market. Players including Panasonic, CATL, Toyota, and BMW are sharpening their skills. It is foreseeable that in the next five years, solid-state battery technology will become the key to the technological competition and industrial layout of these companies.
Samsung will have a considerable lead in this competition because it was the first to achieve a technological breakthrough.
1. The world is competing for a new outlet for solid-state batteries? Samsung is the first to achieve a technological breakthrough
Solid-state batteries were once considered the most suitable battery technology for electric vehicles, but what exactly is this? What about the technology?
Literally understood, all-solid-state batteries mean completely replacing the liquid electrolyte in the existing battery system with a solid electrolyte. But in the definition of the battery industry, solid-state batteries have three major technical characteristics-solid electrolytes, high-energy compatible positive and negative electrodes, and lightweight battery systems.
Solid electrolytes are easy to understand. Different from liquid electrolytes such as ethylene carbonate, propylene carbonate, and diethyl carbonate used in traditional lithium batteries, solid electrolytes are a new type of positive and negative electrolytes used in batteries. The materials for the ion movement channel between the poles are currently mainly divided into three categories - polymer materials, inorganic oxide materials, and inorganic sulfide materials.
Compared with liquid electrolytes, solid electrolytes have physical and chemical properties that are stable at high temperatures and non-flammable. At the same time, their mechanical structure can also inhibit the growth of lithium dendrites and prevent them from piercing the separator and causing battery short circuits.
At the same time, the characteristics of conventional liquid electrolytes that are easily oxidized under high pressure no longer exist for solid electrolytes. Therefore, solid-state batteries can use positive and negative batteries with higher energy density, higher discharge windows, and larger potential differences. Extreme solution.
Since the solid-state battery cells do not contain liquid inside, they can be assembled first in series and then in parallel, reducing the weight of the battery PACK; the stable nature of solid-state batteries can also eliminate the need for internal components of the power battery. Temperature control components further reduce the weight of power batteries.
The above three characteristics correspond to the technical advantages of solid-state batteries compared with traditional lithium batteries. Simply put, it means higher energy density, greater discharge rate, longer cycle life and lighter battery system design.
These technical advantages determine that solid-state batteries will be the most suitable power batteries for electric vehicles in the next ten years. Based on the internal research and development of solid-state battery production progress in the power battery industry, after 2025, solid-state batteries will Gradually becoming a mainstream product in the field of power batteries.
It can be said that whoever seizes solid-state batteries will seize the opportunity to develop the new energy industry in the next ten years.
Under the guidance of this idea, international first-tier car companies such as Toyota, BMW, and Volkswagen, power battery companies such as Panasonic, Samsung, and CATL, and even Dyson, NGK|NTK, etc. have crossed over. Giant players have poured into the field of solid-state batteries one after another, trying to complete their position before the industrialization of solid-state batteries has been achieved through investment and mergers and acquisitions, technical cooperation, independent research and development, etc.
▲Volkswagen launched the Audi PB18?e-tron equipped with solid-state batteries
But when these players actually laid out their plans, the technical difficulty of solid-state batteries was far beyond their imagination. At present, solid-state battery technology still needs to solve many difficulties before mass production. Studies have shown that problems such as the formation of lithium dendrites, low Coulombic efficiency caused by interface impedance, and side reactions between solid electrolytes and positive and negative electrodes are particularly obvious in solid-state battery experiments. .
Samsung recently published a paper in the journal "Nature-Energy" that formally proposed solutions to these problems.
▲Samsung published a paper in the journal "Nature-Energy"
First of all, Samsung reduced excessive and uneven deposition of lithium ions in the negative electrode through silver-carbon composite materials and stainless steel (SUS) current collectors , and uses a sulfide solid electrolyte with a higher lithium ion migration number (generally, the lithium ion migration number of liquid electrolytes is 0.5, and the lithium ion migration number of sulfide solid electrolytes is 1), which reduces the deposition of lithium ions in the electrolyte, between the negative electrode and the electrolyte The possibility of lithium dendrite formation is reduced in both regions.
Secondly, Samsung applied LZO coating to the NCM positive electrode layer, using 0.5nm LZO coating to separate the positive electrode material from the sulfide solid electrolyte, and the LZO coating itself is good The conductivity reduces the impedance to improve the Coulombic efficiency of the battery system.
At the same time, the existence of the LZO coating and the silver-carbon composite material layer also blocks the possibility of side reactions between the sulfide solid electrolyte and the positive and negative electrodes, ensuring the maximum stability of the solid-state battery during its working process. normal performance and recyclability.
Through this solution, Samsung’s all-solid-state battery has achieved an energy density of 900Wh/L, more than 1,000 charge and discharge cycles, and a Coulomb efficiency of 99.8.
As for the Toyota and Panasonic teams that are also researching solid-state batteries, although the current solid-state battery technology can achieve a higher level of cycle times, its energy density is only 700Wh/L, and its Coulomb efficiency is also 90 about. CATL's solid-state lithium batteries can theoretically achieve an energy density of more than 1,000Wh/L, but they are also weaker than Samsung in terms of Coulomb efficiency.
Samsung’s solution effectively overcomes the technical difficulties of solid-state battery industrialization. If Samsung’s position among many competitors is evaluated based on the idea of ????a positional competition, then Samsung’s key technologies for solid-state batteries The breakthrough undoubtedly gave it an advantage in the starting stage.
2. Three ways for Samsung to solve the problem of lithium dendrite growth
The first problem Samsung encountered in the research process of all-solid-state batteries was the problem of lithium dendrites. The formation of crystals is a problem that all lithium batteries have to face.
The generation principle is the uneven deposition of lithium ions in the negative electrode and electrolyte, forming tree-like lithium ion crystals. These crystals are formed when the discharge rate exceeds the battery design upper limit and during long-term charge and discharge cycles. may appear in any of them.
Once lithium dendrites appear, it means that the lithium ions inside the battery are irreversibly reduced. At the same time, lithium dendrites will continue to absorb free lithium ions to grow, and may eventually pierce the separator, causing Direct contact between the positive and negative terminals of the battery causes a short circuit.
There has been a view that the mechanical properties of solid electrolytes can inhibit the growth of lithium dendrites and prevent them from damaging the separator, but in fact, such an idea has not been realized.
Research has shown that the position of lithium ions passing through the solid electrolyte ion channel when they arrive at the negative electrode is more uneven. There is also a gap between the solid electrolyte and the negative electrode interface, so it is easy to cause irregular deposition of lithium ions, thus Formation of lithium dendrites. And in this case, the voltage that causes lithium dendrites to appear is even lower than in conventional lithium batteries.
Faced with this problem, Samsung proposed a three-in-one solution:
1. Silver carbon composite material layer
Samsung’s sulfide A layer of silver-carbon composite material is added between the solid electrolyte and the negative electrode material.
The working principle of the charging process is that during the final deposition of lithium ions through the electrolyte to the negative electrode, the lithium ions are combined with the silver ions in the middle of the silver carbon material layer, reducing the nucleation energy of the lithium ions. (can be simply understood as the ability to gather together), thereby allowing lithium ions to be evenly deposited on the anode material.
▲Schematic diagram of the silver-carbon composite layer (red line part) in the battery structure
During the discharge process, in the silver-lithium metal coating originally deposited on the negative electrode material, lithium ions Completely disappears and returns to the positive electrode. The silver ions will be distributed between the negative electrode material and the silver-carbon composite material layer, waiting for the arrival of lithium ions during the next charging process.
The Samsung team conducted controlled experiments to determine whether the silver-carbon composite layer had an effect during the lithium ion deposition process.
First, the team studied the case where the negative electrode was in direct contact with the sulfide solid electrolyte without a silver carbon composite layer.
When the charge rate (SOC) is 50 and the charge rate is 0.05C (0.34mAh/cm2), although the deposition of lithium ions on the negative electrode is not dense, the deposits are thick and randomly shaped. Possibility of generating lithium dendrites.
▲The deposition of lithium ions on the negative electrode without the silver carbon layer
And, after 10 complete charge and discharge cycles, the battery capacity dropped significantly compared with the initial capacity. After about 25 charge and discharge cycles, the battery's capacity has dropped to about 20 of its initial capacity.
▲The power attenuation of silver-free carbon layer batteries
According to the analysis of the Samsung research team, this situation is likely to be caused by the generation of lithium dendrites inside the battery, resulting in a large number of active lithium ions. Reduced, thereby reducing the battery's discharge capacity.
In the presence of a silver-carbon composite layer, during the first charging process (0.1C, 0.68mAh/cm2), after lithium ions pass through the silver-carbon layer, a dense and uniform deposit is formed on the negative electrode. .
According to Samsung's research team, the silver in the silver carbon layer combines with lithium ions when lithium ions pass by to form a silver-lithium alloy, which reduces the nucleation energy of lithium ions and reaches the negative electrode during the process. A solid solution is formed in the lithium ions, allowing lithium ions to be evenly deposited on the negative electrode material.
▲Distribution of silver ions after multiple cycles
During the subsequent discharge process, images under an electron microscope showed that lithium ions 100 returned to the cathode material and did not There are residues in the negative electrode material, which means that during this charge and discharge process, there is almost no loss of lithium ions, and no deposits remain to avoid the formation of lithium dendrites.
2. SUS current collector negative electrode
The silver-carbon composite material layer largely solves the problem of uneven deposition of lithium ions, but in order to reduce the formation of lithium dendrites as much as possible, "Excess" lithium in batteries also needs to be reduced.
The reason for this statement is that Samsung found that metallic lithium, which is widely rumored to be suitable as an anode material with high energy density (3,860?mAh?g?1), is not suitable for solid-state batteries.
Excess lithium is likely to spontaneously aggregate under the action of high voltage to form lithium dendrites.
Therefore, Samsung uses lithium-free stainless steel (SUS) current collector as the negative electrode in its all-solid-state battery solution. As a deposition carrier of lithium ions and the structure of the battery, the SUS material The mechanical strength is very reliable.
And because the negative electrode material does not contain lithium, it can also inhibit the formation of lithium dendrites.
3. Pyroxene-type sulfide solid electrolyte
Another place where lithium dendrites are formed is the electrolyte. Since the lithium ion migration number of traditional electrolytes is usually 0.5, it is caused by excessive discharge. The migration of a large amount of lithium ions will cause lithium ions to be deposited in the ion channels, which may form lithium dendrites in long-term cycles.
The electrolyte used by Samsung in its all-solid-state battery solution is a pyroxene-type sulfide solid electrolyte with a lithium ion migration number of 1. Its lithium ion migration number is larger than that of ordinary electrolytes, making it difficult for lithium to Ions are deposited therein, thus also inhibiting the formation of lithium dendrites.
Through the above three methods, Samsung’s all-solid-state battery solution effectively avoids the formation of lithium dendrites. In its thousands of cycle tests, the solid-state battery using this solution did not form lithium dendrites. crystal.
3. Special coating solves the impedance problem? The charge and discharge efficiency is as high as 99.8
Two other difficulties in the development of all-solid-state batteries are the Coulombic efficiency problem caused by high interface impedance and the solid electrolyte Samsung has also provided a solution to the problem of side reactions with the positive and negative electrodes.
In solid-state batteries, a solid-solid interface is formed between the solid-state electrode and the solid electrolyte. Unlike the solid-liquid interface of traditional batteries, which has good contact, direct contact between solid and solid is difficult. Make it seamless. That is to say, the contact area of ??the solid-solid interface is smaller than the contact area of ??the solid-liquid interface of the same specifications.
According to the principle that the contact area affects the ionic conductivity, the smaller the contact area, the lower the ionic conductivity between the interfaces and the greater the impedance.
Under the same voltage, the greater the impedance, the smaller the current, and the lower the Coulombic efficiency of the battery.
Not only that, the solid electrolyte will also produce interface side reactions during the contact with the active cathode material.
According to the research results of the University of California, San Diego, the oxygen generated during the deintercalation process of the positive electrode lithium ions will have a strong electrostatic interaction with the lithium in the sulfide solid electrolyte, and the cationic interaction between the electrolyte and the positive electrode material will Interdiffusion will form an SEI film (a passivation layer covering the electrode surface), which will thicken and hinder ion transport during repeated cycles.
This phenomenon will also cause the Coulombic efficiency of the battery to decrease.
In order to deal with the above two problems, Samsung has dealt with both the positive and negative electrodes.
In terms of the cathode, Samsung coats the cathode NCM material with a 5nm thick LZO (Li2O–ZrO2) coating to improve the impedance performance of the solid-solid interface between the cathode and the electrolyte.
▲The LZO coating coated on the NCM cathode material
At the same time, the applied LZO coating blocks the side reaction between the cathode material and the sulfide solid electrolyte , which prevents the SEI film from appearing between the two, improves the Coulombic efficiency, and greatly slows down the attenuation of the discharge capacity.
As for the negative electrode, the sulfide solid electrolyte is in indirect contact with the negative electrode through the silver carbon layer, and the interface impedance is also improved. Silver ions can also help lithium ions complete uniform deposition on the negative electrode, further reducing the impedance.
Another reason why Samsung uses SUS current collectors as negative electrode materials is because SUS current collectors hardly react with sulfides, which means that the possibility of side reactions between the negative electrode and the sulfide solid electrolyte is also eliminated. cut off.
In addition, the pyroxene-type sulfide solid electrolyte selected by Samsung has the same ionic conductivity (1-25ms/cm) as that of general liquid electrolytes. Therefore, the conductivity of the electrolyte itself is It is very strong and helps to improve Coulomb efficiency.
In 1,000 charge and discharge cycles performed by the Samsung research team, the average Coulombic efficiency of this battery solution was greater than 99.8.
In July last year, in the solid-state battery solution published by the Institute of Physics of the Chinese Academy of Sciences, the Coulombic efficiency of the battery was approximately 93.8.
4. Samsung is one step ahead? Other players still have a five-year window period
Samsung’s all-solid-state battery solution has, to a certain extent, solved the three major problems in the current solid-state battery industrialization. Technical difficulties. The key technology has been conquered, which means that solid-state batteries are one step closer to industrialization, and the day when solid-state batteries can be used in electric vehicles is getting closer.
Samsung’s research team bluntly stated in the paper: “The all-solid-state battery we developed has an energy density of more than 900Wh/L and a charge-discharge cycle life of more than 1,000 times. The excellent performance makes this solution a solid-state solution. A key breakthrough in the battery field is likely to help all-solid-state batteries become the high-energy-density and high-safety battery choice for future electric vehicles.”
But it should be noted that when a company announces that it has completed its forward-looking process. Breaking through the key technical difficulties also means that the company's technical barriers are being established, and the opportunities for other companies are shrinking accordingly. Especially in industries such as batteries where technological advantages are overwhelming, the difficulty of breaking through technical barriers is self-evident.
Previously, Japanese lithium battery material manufacturer Hitachi Chemical completed the research and development of carbon-based anode technology and blocked Chinese materials companies for 30 years.
Samsung, LG Chem, SKI and other companies have already laid out the separators, electrolytes, electrodes and other fields upstream of batteries. While cultivating their own supplier systems, they have also acquired a large number of patents, forming a The trend of blocking other battery companies.
This time Samsung takes the lead in breaking through the technical difficulties of solid-state batteries, and will inevitably impose patent blockades on other battery companies. Power battery companies such as China, Japan and South Korea have one less technical path to break through the difficulties of solid-state batteries.
This is the result of Samsung’s first-mover advantage in the solid-state battery competition.
But for Samsung, first-mover advantage does not mean victory is guaranteed. There are still many difficulties for Samsung in the mass production of solid-state batteries.
First of all, sulfide solid electrolytes have extremely high requirements on the production process. They are prone to oxidation when exposed to the air, and can easily produce H2S and other harmful gases when exposed to water. The production process needs to be isolated from moisture and oxygen.
Secondly, the large-scale production of silver carbon layers requires the purchase of precious metal silver on a large scale, which is quite costly.
For Samsung’s battery business, which has been in poor profitability in recent years, the input-output ratio between the cost of purchasing precious metals for new production lines and the market after mass production of solid-state batteries is worth measuring.
Therefore, before the popularity of solid-state batteries has yet to come (the industry believes that small-scale mass production will be in 2025), other power battery companies still have a market and technology window period, and the first solid-state battery The top spot is still vacant.
In Japan, Panasonic has formed an alliance with Toyota and came up with a solid-state battery solution with an energy density of 700Wh/L two years ago.
The recently announced patent of CATL in China shows that the energy density of its all-solid-state lithium metal battery can theoretically exceed 1000Wh/L. The Institute of Physics of the Chinese Academy of Sciences has also completed a project that can increase the coulombic efficiency of solid-state batteries to more than 93 material research and development.
Solid Power, an American power battery start-up company, has received investment from Hyundai, BMW, Ford and other car companies, and announced that it will mass-produce solid-state batteries for electric vehicles in 2026.
It is foreseeable that in the next five years, the power battery industry will start a secret war around the key technology of solid-state batteries. Power battery companies from China, Japan, the United States, and South Korea have all entered the market, preparing to compete for the leading position in this field when the solid-state battery trend arrives.
Conclusion: The difficulty of solid-state batteries has been overcome by Samsung
In previous solid-state battery research and development, lithium dendrite problems, Coulombic efficiency problems and interface side reaction problems have stumped many people in the battery field. R&D team.
However, this time Samsung effectively solved the problem of lithium dendrite formation through silver-carbon composite materials and SUS current collector negative electrodes. The LZO coating covering the positive electrode also made the Coulombic efficiency of the battery system reach 99.8 .
It can be considered that the key difficulties in solid-state battery technology have been overcome by Samsung, and solid-state battery products are one step closer to mass production.
This phenomenon means that in the next five years, car companies, power battery suppliers and cross-border players deploying in the field of solid-state batteries will all conduct research along this line of thinking to promote the field of solid-state batteries. Achieve breakthroughs from R&D to mass production.
Based on the three factors of player volume, capital boost, and demand from the electric vehicle industry, the solid-state power battery industry may soon come to the forefront.
This article comes from the author of Autohome Chejiahao and does not represent the views and positions of Autohome.