Breakthrough in cell resistance technology, Toyota intends to start commercialization of all-solid-state batteries

by:CTECHi     2021-07-26

Lithium Grid News: Toyota plans to commercialize all solid-state batteries in the first half of the 2020s. The research of Nikkei x TECH / Nikkei Automotive found that its basic core technology is to realize the technology of reducing the internal resistance of the all-solid battery cell.

According to Nikkei reports, through this technology, Toyota opened the road to commercialization of all-solid-state batteries. Originally, due to the low output density, the use of all-solid-state batteries for electric vehicles (EV) was difficult. (Note: If the power density is low, the energy density associated with the cell design cannot be increased, which makes it difficult to achieve mass production.)

Through this basic technology, Toyota will use this basic technology to convert all-solid-state batteries. The volumetric power density is increased to about 2.5 kW/L. At the same time, the volumetric energy density has been successfully increased to as high as about 400Wh/L, which is equivalent to about twice the level of lithium ion batteries (LIB) around 2010.

Although this level of performance is currently unable to reach the same level as the most advanced LIB battery, according to Mr. Iwase, the director of Toyota’s power battery production technology development department, at this stage Toyota is surpassing LIB. The company will continue to advance development with the goal of commercialization and mass production in advance. The company will first use the above-mentioned internal resistance reduction technology as a basis to achieve a certain range of practical applications of all-solid-state batteries in the first half of 2020, and then establish mass production technology The goal.

Figure 1: Toyota's commercial application of all-solid-state battery basic technology and corresponding effects

Toyota adopted the four technologies shown in the countermeasures in the figure, The volumetric power density of its all-solid-state battery is increased to about 2.5kw/L, and the volumetric energy density is increased to about 400wh/L. According to the company, these technologies will be the basic technology for Toyota to achieve its goal of commercializing all-solid-state batteries in the first half of the 2020s.

Toyota aims to commercialize the all-solid-state battery in the first half of 2020. It uses a sulfide-based solid electrolyte with high ion conductivity, and the current mainstream LIB is used as the anode and cathode materials. Active materials, specifically, the positive electrode considers layered oxides [lithium cobalt oxide (LCO), nickel-manganese-lithium cobaltate (NMC), lithium nickel cobalt aluminate (NCA), etc.] materials, while the negative electrode considers carbon Department and other candidate materials.

Solve the existing EV cruising range and charging time issues

Toyota has invested a lot of resources in the commercial application of all-solid-state batteries. Another point is Research and development to achieve the volumetric energy density of the EV battery pack at least 2 times that of the existing LIB (described by Mr. Iwase), and to significantly reduce the fast charging time (currently, it takes more than 30 minutes to reduce the fast charging time to less than 1/3) .

Existing EV vehicles are expensive compared with fuel vehicles, and at the same time, the range of a single charge is short, and the charging time is long, and other factors have greatly hindered the popularization of electric vehicles. The all-solid-state battery, in view of the above problems, at least has the possibility of improving the short cruising range and long charging time to a large extent.

No cooling is required, and the pack size is greatly reduced

According to Mr. Iwase, the reason why the all-solid-state battery can greatly increase the volumetric energy density of the battery pack One big reason is that the solid electrolyte has high flame retardancy and heat resistance.

Existing LIBs usually use flammable organic electrolytes as electrolytes. This kind of electrolyte solution generally decomposes to produce gas at a temperature above 80 degrees, and may even cause explosions or fires. The solid electrolyte used in all solid-state batteries has flame retardancy that cannot burn even at 200 degrees, and heat resistance that can withstand high temperatures of 80-150 degrees. The risk of fire and explosion is reduced, and the indispensable exhaust and cooling system in the existing LIB battery pack can also be directly omitted. Therefore, even if the volumetric energy density of an all-solid-state battery is equivalent to LIB, it is possible to achieve at least 2 times the volumetric energy density of the battery pack.

According to the research data of NEDO in Japan, the volume ratio of the cells in the existing LIB battery pack is about 20~50% (Figure 2), while the all-solid-state battery is used, the battery pack does not need to be cooled The volume of the system can be reduced to about half the size of the existing LIB air-cooled battery pack on the EV.

Figure 2: In the existing LIB battery pack, the volume ratio of the cells is low

Data a~g are the existing LIB battery packs Part of the model data. At present, the volume ratio of the battery cells in the Pack is less than 50% at the highest, because the relevant space for the exhaust and cooling system is required.

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