Mass production is imminent, a brief overview of the current status of aa alkaline battery technology development

Battery technology has always been the key to the next iteration of many consumer products. It directly grasps the pulse of product endurance and portability. Any small step forward is a big step forward for consumer products. Of course, it is also extremely critical for automobiles. In the process of transitioning to electrification, whether the power battery of new energy vehicles can be qualitatively improved will directly affect the development rhythm of automobiles in the next decade. Previously, Toyota officials 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 bendable characteristics have achieved a leap forward compared to traditional power batteries. From then to today, what has the development of solid-state batteries reached, and how far is it from mass production? In this article, we will share some information with you in multiple aspects. Technical route of solid-state batteries Solid-state batteries currently have many technical systems, including sulfides, oxides, thin films and solid polymers. In the early advancement of aa alkaline battery technology, thin film and solid polymer technology are the main trends. In the past few years, companies such as Bosch and Dyson have been increasing their investment in these two aa alkaline battery technologies, but the two companies have achieved catch-up in battery technology through acquisitions. 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 (about 25°), so it needs to be continuously heated and maintained at 60° to ensure efficient conductivity. Therefore, in many early aa alkaline battery trial production vehicles, the battery relies on continuous heating, causing self-power loss, and in fact, it cannot play other advantages. Toyota has always focused on the development of sulfide aa alkaline battery technology, but sulfide itself is very active. Once it comes into contact with water during production and use, it will produce hydrogen sulfide. Hydrogen sulfide is a flammable hazardous chemical. It can form an explosive mixture when mixed with air, and it can cause combustion and explosion when exposed to open flames and high heat. Therefore, although the sulfide aa alkaline battery technology route has lower production costs than thin-film technology, if the safety from the manufacturing end to the application end is guaranteed to be high enough, it actually increases the development cost from another perspective. The last oxide technology route also has its own shortcomings. The oxide itself is very stable, which leads to high "brittleness", and the production requirements are higher. At the same time, the conductivity does not have an advantage. But in a broad sense, compared with the other three routes, it is easier to overcome the production difficulties than to overcome the costs and safety. Therefore, in this article, we also interviewed a aa alkaline battery technology company that is currently close to marketization to understand some of the technical advantages of ceramic oxide solid-state batteries and the differences from traditional power batteries. At the 2019CES, we visited Prologix Technologies (hereinafter referred to as PLG), a supplier specializing in the development of lithium battery technology. Since its establishment in 2006, it has taken 8 years to overcome ceramic oxide technology. At the same time, aa alkaline battery technology is also the company's core research and development project. The full name of the technology is: LCB solid-state lithium ceramic battery. Its technical characteristics are: high energy density and high voltage. These two characteristics are undoubtedly very critical for the development and application of pure electric vehicles. Energy density is an innate advantage, so how to achieve high voltage? Traditional power batteries use liquid electrolytes inside single cells, and may be easy to decompose or even explode after the carrying voltage exceeds 5V, so they can only be connected in series externally but not in series internally. But solid-state batteries have such an innate advantage. 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, which is much higher than the voltage of a single cell. After achieving high voltage support for internal series connection, solid-state batteries can also achieve bipolar battery technology, which is also impossible for traditional power batteries. When the single battery is stacked in series, two layers of conductive materials are added to achieve bidirectional positive and negative connection, and then connected in series with another battery pack in the horizontal direction, the maximum 4×6 can achieve bidirectional positive and negative connection of 24 single batteries. The voltage will be superimposed and increased again to form a complete single battery pack. Finally, after the 6 pieces of 24 battery packs in series are stacked, they are packed in an aluminum shell to form a single aa alkaline battery pack (Cell). The capacity can reach more than 20kWh, and the energy density of its single aa alkaline battery pack system can reach 255Wh/kg, and this data will increase to 270Wh/kg in 2020. What is the concept of this system energy density? You can compare it with China's new energy vehicle subsidy policy in 2018. In theory, with the increase in density and voltage, the BMS electronic control system should be more complex, but in fact, the aa alkaline battery has also been simplified in the management system, which once again reduces the weight and volume of the battery for the final package, which is one of the reasons for the higher system energy density. How to solve the heat dissipation problem when the density and voltage are both increased? In terms of heat dissipation, solid-state batteries also have inherent advantages. The battery temperature of the entire battery pack will be maintained within 26° from full charge to the end of discharge, while the temperature of the current cylindrical battery will be above 40° after the entire discharge process. Although aa alkaline battery technology currently uses water cooling like cylindrical batteries, because the discharge temperature itself can be kept lower, heat dissipation has become another major advantage. Based on the low discharge temperature characteristics of solid-state batteries themselves, more optimization can be made 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 radiator on both sides of the battery pack through the heat dissipation glue, further reducing the volume and weight of water flow heat dissipation. aa alkaline battery technology providers also stated that this cutting-edge battery technology has a core advantage in density improvement compared to traditional power batteries. On the premise that solid-state batteries themselves have density advantages, other means must still be used to continue to optimize the density stacking 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 whether the square battery pack has a better density advantage than the cylindrical battery pack. The reason is that the heat dissipation layout of the square battery pack takes up less space. Of course, liquid batteries have the same advantage. Does the life and attenuation of solid-state batteries have advantages? With the advantage of leading density, are there also advantages in life and attenuation? aa alkaline battery technology vendors also said that compared with traditional power batteries, solid-state batteries do not actually have obvious life advantages. This is also the direction that current technology needs to continue to overcome, because if the life and attenuation capabilities cannot be improved, relying only on the energy density advantage, 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 reduce the "detection loss" and improve the "detection accuracy" through finer voltage detection wires. The benefit is to make the battery charge and discharge more efficient, and the loss in voltage detection is smaller than that of traditional power batteries, which in turn increases the battery life. Regarding the specific life and attenuation of solid-state batteries, technology vendors said that after 1,000 full charge and discharge cycles, the battery can still retain 88% of its original life. Does solid-state batteries have an advantage in charging efficiency? The charging efficiency of solid-state batteries is not much higher than that of current lithium batteries. At the same energy density, the charging time of solid-state batteries is also about 1 hour, but current lithium batteries also have the same charging efficiency. In addition, in terms of battery life, solid-state batteries can still maintain 84% of their service life after 500 full charge and discharge cycles, and the data is basically consistent with current battery technology. However, the report also mentioned that in solid-state batteries, the efficiency of electrode absorption of ions is higher. Although the current charging efficiency is not ideal, there is still room for development. In summary, PLG's ceramic aa alkaline battery technology is currently in a small-scale mass production state, and it has stated that it has communicated with European, American, Japanese and Chinese automakers on supply. Based on this battery technology, Europe currently has four trial production vehicles, but officials said it is inconvenient to disclose specific car brands. It is also currently building a aa alkaline battery Gigafactory, which is expected to be officially put into production in 2020, which is also a signal for the mass production of solid-state batteries. Another route is to license "aa alkaline battery technology IP" to other battery manufacturers or car manufacturers, and to promote the development of solid-state batteries as a technology supplier, and the time point for this vision will be set in 2022. According to the technical goals of "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, so aa alkaline battery technology is still the most concerned development direction in the world. At present, there has been no specific progress in the follow-up of Chinese auto brands on solid-state batteries, but following the industry rule of "the closer to mass production, the more confidentiality", what kind of surprises can Chinese auto brands bring in the future?

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