Battery technology has always been the key to the next iteration of many consumer products. It directly controls the product's battery life and portability. Any small step forward is a big step forward for consumer products. Of course, it is also extremely critical for cars. In the process of transition to electrification, whether the power batteries of new energy vehicles can be qualitatively improved will directly affect the development pace of cars in the next decade.

　　Previously, Toyota officials have mentioned that among all new forms of battery technology, solid-state batteries are considered to be the products closest to mass production. Their high energy density, high voltage and even bendability are much better than traditional power batteries. Make strides. From that time to today, how far has solid-state battery developed, and how far is it from mass production? In this article we will share some information with you in multiple aspects.

　　● Technical roadmap of solid-state batteries

　　Solid-state batteries currently have many technical systems, including sulfide, oxide, thin film and solid polymer. In the advancement of early solid-state battery technology, thin film and solid-state polymer technology are the main trends. In the past few years, companies such as Bosch and Dyson have continued to increase investment in these two solid-state battery technologies, but this Both companies are pursuing acquisitions to catch up in battery technology.

　　However, thin film and solid polymer technologies have two fatal problems: "high cost" and "low conductivity". For example, thin film technology cannot achieve high conductivity at room temperature (around 25°), so it needs to be continuously heated and maintained at room temperature. 60° can ensure efficient conductivity. Therefore, in many early solid-state battery trial production vehicles, the battery relied on constant heating, causing self-power loss. In fact, it itself was unable to exert other advantages.

　　Toyota has always focused on the development of sulfide solid-state battery technology, but sulfide itself is highly active and will produce hydrogen sulfide once it comes into contact with water during production and use. Hydrogen sulfide is a flammable and hazardous chemical that can form an explosive mixture when mixed with air. It can cause combustion and explosion when exposed to open flames or high heat. Therefore, although the production cost of the sulfide solid-state battery technology route is lower than that of thin film technology, ensuring high enough safety from the manufacturing end to the application end is a higher threshold. In fact, it is also an increase from another perspective. Development costs.

　　The last oxide technology route also has its own shortcomings. The oxide itself is very stable, resulting in high "brittleness", which requires higher production requirements. At the same time, the conductivity does not have advantages, but in a broad sense, compared to For the other three routes, it is easier to overcome production difficulties than to overcome cost and safety. Therefore, in this article, we also interviewed a solid-state battery technology manufacturer that is currently close to marketization to learn about some aspects of ceramic oxide solid-state batteries. Technical advantages and differences from traditional power batteries.

　　At the 2019 CES exhibition, we interviewed Huineng Technology Company (hereinafter referred to as: PLG), which is a supplier specializing in the development of lithium battery technology. Since its establishment in 2006, it has spent 8 years conquering ceramic oxide technology, and solid-state battery technology is currently the company's core R&D project. The full name of this technology is: LCB solid-state lithium ceramic battery. Its technical characteristics are: high energy density and high voltage. For the current development and application of pure electric vehicles, these two Big features are undoubtedly very critical.

　　● Energy density is an inherent advantage, so how to achieve high voltage?

　　Traditional power batteries use liquid electrolyte inside the single cells and may easily decompose or even explode when the carrying voltage exceeds 5V, so they can only be connected in series externally but not internally. But solid-state batteries have such inherent advantages. Solid-state lithium ceramic batteries can first form a series connection inside the battery, so that the rated voltage of a single battery cell can be from 7.4V, and the maximum series connection can be superimposed up to 60V. The single cell voltage is much higher than that of traditional power batteries.

　　After realizing internal series high-voltage support, solid-state batteries can also implement bipolar battery technology, which is also impossible for traditional power batteries. When the single cells are stacked and connected in series, the upper and lower layers of conductive materials are added to realize bidirectional positive and negative connection, and then they are connected in series with another horizontal battery pack again. Up to 4×6 can be achieved to reach 24 single cells with bidirectional positive and negative electrodes. Using pole-to-pole series connection technology, the voltage will be superimposed and increased again to form a complete single battery pack.

　　Finally, 6 pieces of 24 battery packs connected in series are stacked and packaged in an aluminum casing to form a single solid-state battery pack (Cell) with a capacity of more than 20kWh. The energy density of a single solid-state battery pack system can reach 255Wh/kg. This data will increase to 270Wh/kg in 2020. What is the concept of energy density of this system? You can compare China’s new energy vehicle subsidy policy in 2018.

　　"At present, the energy density of domestic electric vehicle power battery systems is still around 140wh/kg"

　　Theoretically, as the density and voltage increase, the BMS electronic control system should be more complex, but in fact the solid-state battery management system has also been simplified, which once again reduces the weight of the final package of the entire battery pack. and volume, which is one of the reasons why the energy density of the system is higher.

　　2. In addition to the advantages of solid-state batteries, what are the disadvantages?

　　● As density and voltage increase, how to solve the problem of heat dissipation?

　　In terms of heat dissipation, solid-state batteries also have inherent advantages. From full charge to the end of discharge, the battery temperature will be maintained within 26°, while the current cylindrical battery will have a temperature above 40° after the entire discharge process. Although solid-state battery technology currently uses water cooling like cylindrical batteries, its discharge temperature can be kept lower, making heat dissipation another major advantage.

　　Based on the low discharge temperature of solid-state batteries, more optimization can be done in the heat dissipation method. For example, heat dissipation glue is added between the battery and the battery pack, and then the heat will be directed to the water flow radiators on both sides of the battery pack through the heat dissipation glue, further reducing the volume and weight of water flow heat dissipation.

　　Solid-state battery technology providers also said that compared with traditional power batteries, the density improvement advantage of this cutting-edge battery technology is a core aspect. On the premise that solid-state batteries themselves have density advantages, other means must be used to continue to optimize the density stack of the entire group. Therefore, for the entire battery pack, the space and weight occupied by other wires or heat dissipation systems should be reduced as much as possible to maximize the overall density of the battery pack.

　　The cooling system and BMS battery control system actually occupy a lot of space in the cylindrical battery pack. Some people have discussed this issue as to whether the prismatic battery pack has a better density advantage than the cylindrical battery pack. The reason is that the prismatic battery pack has a better density advantage than the cylindrical battery pack. The heat dissipation layout takes up less space. Of course, liquid batteries also have the same advantages.

　　●Does solid-state battery have advantages in terms of life and attenuation?

　　With the advantage of leading density, are there also advantages in terms of lifespan and attenuation? Solid-state battery technology vendors also said that compared with traditional power batteries, solid-state batteries do not actually have obvious lifespan advantages. This is also the direction that current technology needs to continue to overcome, because if the lifespan and attenuation capacity cannot be improved, only relying on energy density advantages , the current cost of solid-state batteries still cannot support its large-scale promotion and mass production.

　　Regarding the technical means of optimizing the life of solid-state batteries, it will use smaller voltage detection wires to reduce "detection loss" and improve "detection accuracy". The benefit is to make the battery charge and discharge more efficient. Compared with traditional power batteries, the loss in voltage detection is smaller, and the direction change increases the battery life. Regarding the specific life and attenuation of current solid-state batteries, the technology provider stated that after 1,000 complete charges and discharges, the battery can retain 88% of its original life.

　　●Does the charging efficiency of solid-state batteries have advantages?

　　The charging efficiency of solid-state batteries is not much higher than that of current lithium batteries. Under the same energy density, the charging time of solid-state batteries is about 1 hour, but current lithium batteries also have the same charging efficiency. In addition, in terms of battery life, solid-state batteries can maintain a service life of 84% after 500 complete charges and discharges. The data is also basically consistent with current battery technology. However, the report also mentioned that the electrodes in solid-state batteries absorb ions more efficiently. Although the current charging efficiency is not ideal, there is still room for development.

　　Summarize

　　PLG's ceramic solid-state battery technology is currently in small-scale mass production, and it has stated that it has communicated with European, American, Japanese and Chinese car companies on supply. Based on this battery technology, there are currently four trial production vehicles in Europe, but the official He said it was not convenient to disclose the specific car brand. It is also currently building a solid-state battery Gigafactory, which is expected to be officially put into production in 2020. This is also a signal for the mass production of solid-state batteries. There is another route that is to license "solid-state battery technology IP" to other battery manufacturers or automobile manufacturers, and act as a technology supplier to promote the development of solid-state batteries. The time for this vision will be set in 2022.

　　According to the technical goals in "Made in China 2025", the energy density of lithium battery cells will reach 300Wh/kg by 2020, and the energy density will reach 400Wh/kg by 2025. Therefore, solid-state battery technology is still the most concerned development direction in the world. At present, no specific progress has been seen in the follow-up of solid-state batteries by Chinese car brands. However, following the industry rules of "the closer to mass production, the more confidential it is", what kind of surprises can Chinese car brands bring in the future? Woolen cloth?

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