Design Of Recycling Processing Equipment For LiFePO₄ Spent Battery And Study On The Modification Of Cathode Scrap

With the rapid development of electric vehicles, the usage of lithium ion power battery increases dramatically, especially LiFePO₄ power batteries. It can be expected that there will be a lot of spent Li-ion power batteries needed to be processed in the near future. If these spent Li-ion power batteries are not handled or mishandled, they will not only lead to a waste of resources, but also pollute the environment.To make full use of spent LiFePO₄ batteries, echelon use is certainly the first choice, but for damaged or echelon used battery, dismantling and recycling disposition is the inevitable choice. Up to now, the reported recycling processes of spent lithium ion battery mainly include chemical precipitation method, extraction method, and electrolysis method. But mineral acid, extraction agent, etc are widely used in those methods, which not only cause high cost, but also bring secondary pollution. They are only applying to Ni, Co and other precious metal elements of the battery, rather than applying to LiFePO₄ batteries.To realize dismantling and recycling spent LiFePO₄ battery with a safe, green and efficient method, this paper proposes a new technology of dismantling and recycling, and designs a series of key equipments to check in practice. To improve added value of the recovery, we repair and modify the reclaimed LiFePO₄ scrap, make it meet standards of the reuse. The main contents as follows:1) Design of dismantling and recycling key equipments of spent LiFePO₄ batteries: The main steps of dismantling and recycling spent LiFePO₄ batteries include discharging, cutting the plastic film, soaking battery cells, separating cathode and anode plates, cutting up and stir ring electrode plates, centrifuging powders, drying and ball-milling powders, sieving powders and purification of waste gas. In order to achieve the above functions, some new devices are designed and some existing equipments are improved. Besides, the computer simulations of some key equipment are conducted. Now, those designed devices has been used and tested on a pilot-scale production line, which demonstrates that those designed devices can successfully disassemble and recycle of spent LiFePO₄ batteries.2) Repair of cathode scrap: The above obtained cathode scrap contains not only carbon black and LiFePO₄, but also impurities?FePO₄, P₂O₅, Fe₂O₃ and Li₃PO₄?. These impurities are attributed to the partial decomposition of the LiFePO₄ after numerous charge-discharge cycles. The LiFePO₄ can be re-synthesized from FePO₄, P₂O₅, Fe₂O₃ and Li₃PO₄ after lowtemperature heat treatment in reducing atmosphere?such as Ar/H₂?, but the poor crystal and low electric conductivity of re-synthesized LiFePO₄ lead to poor electrochemical performance. By contrary, the re-synthesized LiFePO₄ after high-temperature heat treatment has better crystal and higher electrical conductivity, and displays excellent electrochemical performance. The results demonstrate the cathode scrap is effectively repaired.