Detailed explanation of the globally popular all-solid-state AG13 battery technology

　　With the rapid development of electric vehicles in our country, power batteries, as their core components, have always attracted much attention. The improvement of key components directly affects the acceleration of the development of electric vehicles in our country. On January 7, the China Electric Vehicles Association of 100 organized a hot-issue exchange meeting on "Grasping Global Change Trends to Achieve High-Quality Development." Professor Ouyang Minggao conducted a detailed analysis of all-solid-state AG13 battery technology with a professional perspective.

　　On January 7, the China Electric Vehicles Association of 100 organized an exchange meeting on hot issues on "Grasping Global Change Trends to Achieve High-Quality Development"

　　With five major advantages, all-solid-state AG13 battery technology deserves attention

　　The so-called "all-solid-state AG13 battery" is a AG13 battery in which the electrodes and electrolyte materials used are solid within the operating temperature range and do not contain any liquid components. The full name is "all-solid-state electrolyte AG13 battery". Therefore, all-solid-state AG13 battery is already the shortest name that cannot be omitted or changed. To help understand, Professor Ouyang gave an example, just like "all-solid-state" and "solid-state" are different, "AG13 battery" and "lithium-ion battery" are not the same concept. This all-solid-state AG13 battery is divided into all-solid-state lithium primary batteries and all-solid-state lithium secondary batteries. Primary batteries have already been used. All-solid-state lithium secondary batteries are divided into all-solid-state lithium-ion batteries and lithium metal batteries. These are two concepts that need to be distinguished. The so-called all-solid metal AG13 battery means that the negative electrode uses lithium metal, and our current negative electrode uses carbon or silicon carbon or lithium titanate.

　　Professor Ouyang said that the concept of all-solid-state lithium batteries appeared earlier than lithium-ion batteries. As we all know, lithium-ion batteries have only been around for about 25 years and were invented by the Japanese. It has only been 25 years since they were actually used in cars for more than 10 years, so they are very young but making rapid progress. The all-solid-state lithium batteries referred to in the early days all refer to all-solid-state metal lithium batteries with metallic lithium as the negative electrode. Therefore, when talking about all-solid-state, we often talk about this, which means that all-solid-state batteries use lithium metal as the negative electrode. This is the previous term. concept.

　　Regarding all-solid-state lithium batteries, Professor Ouyang summarized the following potential technical advantages. The first is high safety, because all-solid-state lithium batteries do not have organic solvents as electrolytes, so they will not cause electrolyte combustion problems; the second is high energy density. Of course, the density and usage of solid electrolytes are higher than those of liquid electrolytes. When the positive and negative electrode materials are the same, its advantages are not obvious. But with solid electrolytes, there is no problem of electrolyte leakage, so it can be stacked piece by piece, unlike liquid electrolytes that need to be wrapped in soft bags, so the volume specific energy will be higher. Third, all-solid-state lithium batteries have a wide range of cathode material selection, because the negative electrode is lithium metal, and the positive electrode does not contain lithium. Finally, the voltage window of the all-solid-state AG13 battery electrolyte will be wider, the selection range of cathode materials will be wider, and the specific energy can also be improved; in addition, the all-solid-state AG13 battery system has a higher specific energy. Since the electrolyte has no fluidity, it can be easily connected in series to form high-voltage monomers, which is beneficial to improving the efficiency and energy density of the battery system.

　　Four major problems need to be solved, and the development of solid-state lithium-ion batteries is very likely

　　Although it has five major advantages, all-solid-state lithium batteries also have four major problems. The first problem is the low ionic conductivity of solid electrolyte materials. Professor Ouyang said that there are now three types of solid electrolytes, one is polymer, one is oxide, and one is sulfide, polymer electrolyte. Polymer batteries are now used in some cars in France. The problem is that they need to be heated. The battery needs to be heated to 60 degrees before the ionic conductivity rises and the battery can work normally. At present, oxide electrolytes are generally much lower than liquid electrolytes. Only sulfide solid electrolytes are now similar to liquid ones. For example, Toyota uses this sulfide solid electrolyte, so there is a breakthrough in solid electrolytes. The main breakthrough is in sulfide solid electrolytes.

　　The second problem is the poor contact and stability of the solid/solid interface. It is very easy for liquids to combine with solids and penetrate into them. But the contact and stability between solids is not very good, which is a big problem. Although the lithium ion conductivity of sulfide electrolytes has been improved, there are still problems with interface contact and stability. The third problem is the rechargeability of metallic lithium. In solid electrolytes, lithium surfaces also suffer from powdering and dendrite growth problems. Its cyclicity and even safety still need to be studied. In addition, high manufacturing costs are also a major problem in its development.

　　Based on the above problems, especially the solid-state interface contact/stability and the rechargeability of metallic lithium, the true all-solid-state metallic AG13 battery technology is still immature and there are still technical uncertainties. What currently shows or has breakthroughs, performance advantages and industrialization prospects are mainly solid-state lithium-ion batteries.

　　The United States seeks breakthroughs, while China, Japan and South Korea are more conservative, and solid-state lithium batteries are developing differentiatedly in each country.

　　So, what is the difference between solid-state lithium-ion batteries and all-solid-state lithium batteries? Professor Ouyang said that solid-state batteries are not necessarily all solid electrolytes, but also a little liquid. It is a mixture of liquid and solid, depending on the mixing ratio. A true solid-state lithium-ion battery has a solid electrolyte, but there is a small amount of liquid electrolyte in the cell; the so-called semi-solid state means that half of the cell is solid electrolyte and half is liquid electrolyte, or half of the cell is solid and half is. Liquid, so there are also quasi-solids, which are mainly solid and a small amount of liquid.

　　Professor Ouyang conducted a detailed analysis of the development trends of solid-state lithium batteries at home and abroad. He said that solid-state lithium batteries continue to heat up, and the United States, Europe, Japan, South Korea, and China are all investing in it.

　　Although they are all developing the same technology, the mentality of each country is different. For example, the United States is dominated by small and entrepreneurial companies. Professor Ouyang pointed out that there are two good companies in the United States, both startups. One is S-akit3, which has a driving range of 500 kilometers and is still in its infancy. There is also Solid-State, and a company invested by several big companies such as BMW. Therefore, the United States is mainly dominated by small companies and startups, based on disruptive technologies.

　　Looking at Asian countries represented by China, Japan and South Korea, Professor Ouyang commented: "Japan basically uses solid-state lithium-ion batteries. The most famous one is Toyota, which will commercialize it in 2022. But in fact, Toyota does not do all It is a solid-state lithium metal battery, but a solid-state lithium-ion battery. Its negative electrode is graphite, sulfide electrolyte, and high-voltage positive electrode. The single battery capacity is 15 ampere hours and the voltage is more than ten V. It will be commercialized in 2022. This is reliable." So in Japan, there is no subversion. It is still a lithium-ion battery, and the positive and negative electrodes can still be used as before. South Korea's battery development is similar to that of Japan. It is also a graphite negative electrode, not a metallic lithium negative electrode. Professor Ouyang said: "The development situations in China, Japan and South Korea are similar, because we already have a large lithium-ion battery industry chain and do not want to tear it down and start over."

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