Ding yonghua of Penghui: What are the potential risk solutions for power cell safety?

Power battery fire explosion news has become a common occurrence. What are the hidden dangers involved in its safety risk?

On November 17th, the 2016(second) Guangzhou International Electric Vehicle Industry Summit with the theme of "Intelligent Control of the Electric Future" was held at the Pazhou Convention and Exhibition Center. The conference was jointly hosted by China International Trade Promotion Committee Automobile Industry Branch and High-tech Electric Vehicle Network, attracting thousands of new energy car industry personnel.

Guests at the summit include leaders of automotive companies such as Guangzhou Automobile, Chang 'an, Chirui, Future, Tesla, and leaders of electric core companies such as CATL, Guoxuan, Zhongtian, Chuangming and Penghui. KDS, Dajun, Jiangte, Sheng Hao, power generation and other electric drives, electric control and other corporate leaders.

In the power battery link, Chengpenghui, general manager of the energy storage division of the vice president of the Guangzhou Penghui Energy Group(Xia Dingyonghua Energy) Research Institute, delivered a keynote speech on "Power Cell Module and System Safety Potential Risk Analysis" from the power cell module. Safety and system safety have conducted a wonderful analysis from two perspectives.

Penghui Energy's main business is polymer lithium ion, lithium iron phosphate, nickel hydrogen and other secondary rechargeable batteries. The products are widely used in mobile power sources, new energy automotive power batteries, automotive start-up power sources, communication base station backup power sources, scenery energy storage and home energy storage. Battery system solution, And take the lead in achieving large-scale production.

Dingyonghua pointed out that the DC resistance of a single battery itself is at the mΩ level, and the farther to the battery module current collection point, the greater the conduction resistance, and the disguised increase in the conduction resistance of the battery. The operating current of the core in the same module has a certain difference. For a long period of accumulation, the performance produces a differential increase. In the initial design, the shape of the battery module, the width of the bus, and the internal resistance of the conductive connection have a great relationship.

Differentiation of power cell modules also leads to circulation phenomena, low capacity & amp; High-resistance batteries will be in different states in the charging and discharging platform voltage, such as discharge platform voltage is always lower than other core, external discharge cycle, parallel internal charging cycle, core performance decline faster, internal short-circuit risk increased.

So how do we solve this problem? The method proposed by Dingyonghua is to optimize the battery health evaluation strategy and improve the diagnostic sensitivity of abnormal cells in time to detect abnormal cells.

In terms of the safety of the power battery system, shell protection, battery module connection, heat management, and fire protection devices will also pose potential risks to the battery.

Take the example of Tesla ModelS hitting a tow rod that was scattered on the road. The huge impact caused the tow rod to pierce the chassis armor of the battery pack and eventually the battery was damaged and caught fire. This also exposed the problem of power cell shell protection.

In fact, as one of the core components of new energy vehicles, the power battery system has its own protection management specifications. For example, the physical protection of the shell should be guaranteed by the body bracket protection and battery box protection. Stainless steel or rust-proof fasteners will be used inside the power battery system.

However, there are many kinds of metal materials used for fasteners inside the battery. With the change of ambient temperature and different thermal expansion factors during use, continuous vibration and self-heating will cause loosening and poor contact.

In view of the above problems, Dingwenhua put forward the solution from two aspects of battery material and heat management system. On the battery material, improving the stability of the cathode material, SEI membrane, and electrolyte reduces the heat generation and heat production rate. At the same time, the decomposition of SEI membrane is the key to control internal thermal runaway and reduce the probability of thermal runaway chain reaction.

In the thermal management system, the power battery management should meet the IP67 protection level standard stipulated by the battery safety, including the influence of the temperature protection layer to reduce the external ambient temperature on the battery system; Secondly, it is also a big way to strengthen the temperature of the management battery system that can be controlled in unit time by convection, radiation, heat conduction and other heat dissipation methods.

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