Chemical Sciences

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Objective: Collection of cathode materials from the dead/ performance degraded lithium ion cells/batteries; Reprocessing of cathode materials; Refurbishing of cathode materials and its performance evaluation

Summary: Lithium ion batteries usually have certain life, normally 1-3 years. Over time, deposits formed over cathode, anode and separator, structural changes during the operation of the cell inhibit ion transport thus leading to the decrease in the cells capacity. Internal resistance increases with both cycling and age, reducing the cell ability to deliver current. Also, rising internal resistance causes the voltage at the terminals to drop under load. Thus, older batteries do not change as much as new ones. It is predictable that lithium ion batteries will become an important part of solid waste which must not be overlooked. Additionally, throwing the batteries away means that fresh metals have to be mined, and mining has a much bigger environmental impact than simple recycling would do. While lithium ion batteries are completely, millions of tons of lithium ion batteries are added to land fill every year, taking up space that could be saved. While 97% lead acid batteries are recycled and over 50 percent of the lead supply comes from recycled batteries, lithium ion batteries are not being recycled widely. The increase of lithium demand is huge, however, analysis of lithium geological resource base shows that there is insufficient lithium available in the Earth crust to sustain electric vehicle manufacture in the volumes required, based solely on li-ion batteries. Refurbishing can dramatically reduce the required lithium amount. In this work, a simple approach which is nondestructive will be adopted to refurbish cathode material from the dead/ performance degraded lithium ion battery. Hydrothermal reaction is widely used in the synthesis of various cathode materials and has the capability of generating particles with high crystallinity and desired stoichiometry. Here, the advantage of this hydrothermal process to pre- does Li into Li deficient cathode particles without being concerned about the the Li/transition metal ratio will be made. Then, as followed in all hydrothermal reactions thermal annealing will be carried out to refurbish cathode with desired microstructure and composition. Compared with the previous approaches, the strategy followed in refurbishing cathode has several major advantages: (i). it does not required tedious chemical analysis to determine the amount of loss and is compatible with batteries under different capacity fading condition; (ii). It does not required long-time energy-consuming sintering treatment since Li is dosed with the correct stoichiometry during the hydrothermal process (iii). Another method which will be studied in this proposal is by solid state synthesis. The solid state method will be carried out by analyzing the Li/transition metal ratio of cathode recovered from the dead cells. The lost Lithium is added step wise to refurbish the cathode material. Therefore, this work will provide promising strategies to refurbish used degraded cathode material of Lithium ion battery.

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