Battery technology has always been the key to the next iteration of many consumer products. It directly pinches the pulse of the product in terms of battery life 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 transforming to electrification, whether the power battery of new energy vehicles can be improved qualitatively will directly affect the pace of automobile development in the next decade.
Previously, Toyota officials mentioned that among all new forms of battery technology, solid-state batteries are considered to be the closest to mass production. Its high energy density, high voltage and even bendable characteristics are far superior to traditional power batteries. Achieve strides. From then to now, how far has the solid-state battery developed, and how far is it from the state of 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 advancement of early solid-state battery technology, thin-film and solid-state polymer technologies 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 The approach of both companies is to catch up in battery technology through acquisitions.
However, thin film and solid polymer technologies have two fatal problems of "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 high conductivity. Therefore, in many early solid-state battery trial production vehicles, the battery itself was unable to exert other advantages because it relied on continuous heating, causing self-power loss.
Toyota has been focusing on the development of sulfide solid-state battery technology, but sulfide itself is very active, and once it comes into contact with water during production and use, hydrogen sulfide will be produced. Hydrogen sulfide is a flammable and hazardous chemical, which can form an explosive mixture when mixed with air, and can cause combustion and explosion when exposed to open flames and high heat. Therefore, although the production cost of the sulfide solid-state battery technology route is lower than that of the thin-film technology, if the safety from the manufacturing end to the application end is guaranteed to be high enough, the threshold is higher. In fact, it is also added 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 has higher requirements for production. 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 the difficulty of production than to overcome the cost and safety. Therefore, in this article, we also interviewed a solid-state battery technology supplier that is currently close to marketization to understand some of the ceramic oxide solid-state batteries. Technical advantages and differences from traditional power batteries.
At the 2019CES exhibition, we interviewed ProLogium Technology Co., Ltd. (hereinafter referred to as: PLG), which is a supplier specializing in the research and development of lithium battery technology. Since its establishment in 2006, it took 8 years to overcome ceramic oxide technology. At the same time, solid-state battery technology is also the core research and development project of the company. 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 Characteristics are undoubtedly very critical.Also read:lithium ion battery pack manufacturers
Energy density is an inherent advantage, so how to achieve high voltage?
Because the traditional power battery uses liquid electrolyte inside the single battery, and the carrying voltage exceeds 5V, it may easily decompose or even explode, so it can only be connected externally but not internally. But solid-state batteries have such inherent advantages. Solid-state lithium ceramic batteries can be connected in series first inside the battery, so that the rated voltage of a single battery cell can be from 7.4V, and the maximum series stack can be as high as 60V. The voltage of a single battery is much higher than that of traditional power batteries.
After realizing the internal high-voltage support in series, solid-state batteries can also realize 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 the connection of the two-way positive and negative poles, and then connected in series with another battery pack in the horizontal direction again, up to 4×6 up to 24 single cells with two-way positive and negative electrodes can be realized With the series technology of pole butt connection, the voltage will be superimposed and increased again to form a complete single battery pack.
Finally, after stacking 6 pieces of 24 series-connected battery packs, they are added to the aluminum casing to form a single solid-state battery pack (Cell), with a capacity of more than 20kWh and a single solid-state battery pack system with an energy density of 255Wh/kg. In 2020, this data will increase to 270Wh/kg. What is the concept of energy density of this system? You can compare it with China's new energy vehicle subsidy policy in 2018.
"At present, the energy density of domestic electric vehicle power battery systems is still maintained at around 140wh/kg."
Theoretically, the BMS electronic control system should be more complex while the density and voltage increase, but in fact, the management system of solid-state batteries has also been simplified, which once again reduces the weight of the final pack of batteries And volume, which is one of the reasons for the higher energy density of the system.
Density and voltage both increase, how to solve heat dissipation?
In terms of heat dissipation, solid-state batteries also have inherent advantages. The temperature of the entire battery pack will remain within 26° from full charge to discharge, while the temperature of the current cylindrical battery will be above 40° after the entire discharge process. Although the solid-state battery technology is currently the same as the cylindrical battery, it also uses water cooling, but because the discharge temperature itself can be kept lower, heat dissipation is another major advantage.
Based on the low discharge temperature of the solid-state battery itself, more optimizations 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 radiators on both sides of the battery pack through the heat dissipation glue, further reducing the volume and weight of water heat dissipation.
The provider of solid-state battery technology also stated that compared with traditional power batteries, this cutting-edge battery technology has the advantage of increasing density as a core aspect. On the premise that the solid-state battery itself has a density advantage, it is still necessary to continue to optimize the density superposition of the entire group through other means. Therefore, for the entire battery pack, the space and weight occupied by other wires or cooling systems should be reduced as much as possible, so that the battery pack can have a maximum overall density increase.
In fact, the cooling system and BMS battery control system currently occupy a lot of space in the cylindrical battery pack. Some people have discussed whether the prismatic battery pack has a better density advantage than the cylindrical battery pack. The reason is that the prismatic battery pack The heat dissipation layout occupies less space, and of course the liquid battery also has the same advantages.
Is there an advantage in the life and attenuation of solid-state batteries?
With the advantage of leading density, does it also have 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, which is why the current technology needs to continue to overcome Because if the lifespan and attenuation ability cannot be improved, the cost of solid-state batteries still cannot support mass production by relying solely on the advantages of energy density.
Regarding the technical means of optimizing the life of solid-state batteries, it will reduce the "detection loss" and improve the "detection accuracy" through smaller voltage detection wires. The benefit is to make the battery charge and discharge more efficient. Compared with the traditional power battery, the loss in voltage detection is smaller, and the direction change improves the battery life. Regarding the specific life and attenuation of the current solid-state battery, the technologist said that after 1,000 full charge and discharge cycles, the battery can still retain 88% of its original life.
Is there an advantage in the charging efficiency of solid-state batteries?
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, the solid-state battery can maintain 84% of its service life after 500 full charge and discharge cycles, and 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
At present, PLG's ceramic solid-state battery technology is in a small-scale mass production state, and said that it has communicated with European, American, Japanese and Chinese car companies on the supply side. Based on this battery technology, there are currently four trial production vehicles in Europe, but the official It is not convenient to disclose the specific car brand. At present, it is also building a solid-state battery Gigafactory, which is expected to be officially put into production in 2020, which is also a signal for mass production of solid-state batteries. Another route is to authorize "solid-state battery technology IP" to other battery manufacturers or automakers, as a technology supplier to promote the development of solid-state batteries, and the time point for this vision will be set in 2022.
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