Using electric double layer capacitors to prevent fires in pure electric vehicles

The industry's expectations for large-capacity capacitors are increasing day by day. At present, there are many companies that develop lithium-ion rechargeable batteries as power storage devices. However, due to different uses, there are limits to output characteristics and charge-discharge cycle life, and some people are concerned about safety.

Among capacitors, the development history is the electric double layer capacitor (EDLC).

Reasons for the attention of large-capacity EDLC

The main reason is that various rechargeable battery fire accidents have occurred frequently in recent years. For example, since 2011, I have heard many news of the fire of a pure electric vehicle (EV) equipped with a Chinese-made lithium-ion rechargeable battery-the lithium-ion rechargeable battery equipped with passenger cars and buses suddenly caught fire and burned on the road .

Although these fire accidents are indispensable for the design and manufacturing errors of lithium-ion rechargeable batteries, I think there are other factors. For example, BMS (Battery Management System) has a great relationship with ensuring safety.

By using EDLC in combination with BMS that controls rechargeable lithium-ion batteries, the risk of battery fire can be reduced. Needless to say, pure electric vehicles (EV) and hybrid electric vehicles (HEV) require large currents. If a lithium ion rechargeable battery is used to cope with such a sudden load fluctuation, the battery output will fluctuate greatly, resulting in a reduction in battery capacity or deterioration in charge-discharge cycle characteristics. The use of EDLC can absorb rapid load fluctuations and can suppress the deterioration of lithium ion rechargeable batteries. This can prevent the lithium ion rechargeable battery from catching fire.

In automotive-oriented applications, there are also inquiries regarding the use of large-capacity capacitors when supporting fast charging and wireless power supply. And in this case, it can happen that the capacitor has faster charging and discharging speed and longer charge and discharge cycle life than the lithium ion rechargeable battery.

Has EDLC made progress in technology?

As for the important technology of EDLC, it has been improved in several areas, specifically: (1) high pressure resistance and low resistance technology; (2) low dew point drying chamber / cabin technology; (3) high-speed liquid injection technology; (4) Automatic reset type safety valve, etc.

For example, in terms of low-resistance technology, I proposed an improved electrode structure. Specifically, a mutual diffusion layer is provided between the conductive layer and the active material layer on the collector electrode. Therefore, compared with the original structure EDLC, the electrode resistance can be reduced to 1/2 to 1/10.

In the field of capacitors, Japanese manufacturers are one step ahead in terms of technology, but they are not far behind some manufacturers such as South Korea and China. While the competition in technology development is becoming increasingly fierce, with the improvement of performance, the application range of EDLC will be further expanded in the future.