18650 battery

Breakthroughs in key technologies for the cascade utilization of power 18650 battery are imminent

Cascade utilization is another way out for electric vehicle power batteries after retirement, in addition to recycling and disassembly. It is understood that the service life of electric vehicle power batteries is about 5-8 years. In order to ensure driving range and safe operation, the car battery needs to be retired when the remaining capacity is 80%, and enter the cascade utilization or recycling and disassembly stage according to performance. However, the reporter learned that there are still many technical difficulties in the cascade utilization of power batteries, and the high cost also makes it difficult to achieve economic efficiency in cascade utilization.

Cascade utilization has a bright future

It is understood that retired power batteries are currently mainly used in low-speed electric vehicles, energy storage, communication base station backup power supply and other fields, and different application fields have different requirements for batteries. "Battery cascade utilization must find suitable application scenarios and determine suitable use boundary conditions, such as charge and discharge rate, use temperature and charge and discharge depth, etc., to fully utilize the residual value of retired batteries while ensuring safe use." Yang Kai, director of the Energy Storage Battery Body Technology Research Laboratory of the China Electric Power Research Institute, believes.

"The application scenarios of cascade utilization are very wide. The utilization scenarios below the megawatt level include communication base station backup, distributed energy storage systems, tourist sightseeing vehicles, solar street lights, etc. The energy storage system products above the megawatt level are mainly on the new energy power generation side, photovoltaic power stations and wind power plants. You can try to use retired lithium iron phosphate batteries. For example, a single wind power energy storage system can be used for peak and frequency regulation of wind power plants." Gao Yuanbo, general manager of Sander Group Smart Energy Co., Ltd., introduced.

It is understood that the field where retired power batteries are currently widely used is communication base stations. China Tower has been conducting research on the cascade utilization of automotive power batteries since its establishment, and carried out experiments to replace existing lead-acid batteries with retired power batteries in early 2015, verifying the feasibility of cascade utilization batteries in the field of communication base stations.

Key technologies become constraints

The reporter learned that the entry of retired power batteries into cascade utilization is not "taken and used", and there are still technical "hurdles" to overcome. It is generally believed in the industry that the difficulty of cascade utilization of power batteries is battery consistency management and safety control. According to Wang Zidong, director of the National 863 Electric Vehicle Major Project Power Battery Testing Center, when the power batteries of electric vehicles enter the energy storage field for cascade utilization, they face many problems such as inconsistency with the universality of the energy storage system. "The plug-in charging of power batteries and the non-off-grid energy storage method have different standards for battery management." This puts high demands on battery detection and safety monitoring technology.

Yang Kai pointed out that the key technologies for power batteries to enter the cascade utilization link need to be broken through, such as fast and accurate performance evaluation technology, low-cost sorting and reorganization technology, and online safety status warning technology. "In the key steps such as the evaluation of the health status of batteries in cascade utilization, the industry is still relatively superficial." Yang Kai said frankly. There is an essential difference between the safety of batteries in the cascade application link and the safety of the battery itself, but the battery safety in the existing energy storage engineering application link is almost missing. "Once a problem occurs, it is difficult to control. For example, the energy storage system will basically burn out after a fire."

Wang Zidong also admitted that there is currently a lack of better technology to quickly and accurately evaluate the health performance of retired batteries. Yang Kai told reporters that the historical data of power batteries is a very important resource. The testing and monitoring departments can judge the health status, safety hazards, remaining service life, etc. of the battery by analyzing the historical data, which saves a lot of energy compared to directly testing individual batteries. "There is big data for the supervision of the entire process of power battery disassembly, assembly and cascade utilization, but almost no one uses this data to evaluate and diagnose the battery." Wang Zidong said.

"The prospect of cascade utilization of power batteries is broad. In the future, with the rapid growth of the installed capacity of new energy vehicles, the recycling and utilization of retired batteries is imminent." Gao Yuanbo said.

Economic value has not yet been reflected

Industry experts told reporters that not all retired power batteries have cascade utilization value. As for which period of production of batteries can be cascaded, "it is more appropriate for us to draw this line to 2012." Yang Kai said. Gao Yuanbo believes that power batteries after 2014 have the value of cascade utilization. After the early power batteries enter the cascade utilization, the life and safety cannot be guaranteed, and the economy cannot be achieved.

"The economic value of retired batteries can only be realized after the cascade utilization rate reaches a certain level. But why is there no successful business model for cascade utilization? The main reason is that there is no support point in economic efficiency." Wang Zidong analyzed.

Gao Yuanbo believes that reducing the cost of battery cascade utilization is a way to achieve economic efficiency. "After calculation, if the battery is split to the module level in the cascade utilization link, the cost will be very high, even higher than the integration cost of new batteries in the energy storage system, so we advocate the use of the battery pack as a whole."

In addition, Wang Zidong told reporters that there is currently no special agency for cascade utilization-related companies to conduct health performance assessments on power batteries. Although third-party testing agencies can be entrusted, due to the high cost of testing, neither car companies nor battery manufacturers are willing to take responsibility for this, which leads to the lack of safety responsibility.

Industry insiders call for consideration and design of recycling and utilization of power batteries at the beginning of production and manufacturing in order to reduce the technical difficulty of cascade utilization and improve the economic efficiency of utilization. "The level of second-life utilization and the improvement of the level of new batteries complement each other. As the performance of power batteries improves and prices drop, the second-life utilization performance of batteries will definitely get better and better in the future, and prices will continue to fall. Therefore, power batteries still have value for second-life utilization, but in-depth research is needed on the technical aspects of their application." Yang Kai said.

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