The Experimental Study Of Remanufacturing Technology Of Lithium-ion Batteries

Li-ion battery has many special properties, such as light weight, large specific capacity, high discharge power, quick charge performance, long life and so on, which makes it widely used in field of electric vehicles, electric tools, energy storage devices, aeronautics and astronautics, electronic products. Especially, with increasing environmental awareness, and rapid development of electric vehicles generating a mass of wasted Lithium-ion batteries, caused severely secondary pollution and largely amount of resources and energy wastes. In recent years, the rise of remanufacturing technology can provide an innovative approach to solve these problems. Therefore, a new remanufacturing technology for Li-ion battery has considerable potential values in fundamental research and industrial application.Till now, there are many methods to remanufacture Lithium-ion batteries, however, most of them are difficult to control battery’s quality, environmental contamination, operation safety and high cost. In order to solve these problems, two issues are proposed. Firstly, the remanufacturing time indicator named battery internal impedance is defined through theoretical research and experiments; secondly, a new remanufacturing approach for Li-ion battery is put forward using the pulsed laser cleaning technology.The growth model between Lithium-ion consumption and solid electrolyte interface (SEI) was created. Three working stage of Lithium-ion battery and the main reasons of battery capacity attenuation in these working stage were analyzed. All of which provide theoretical foundation for the remanufacturing timing selection. Then, in order to identify the relationship between battery capacity, battery internal impedance and cycle numbers, the battery charging and discharging platform is established. In the end, the battery remanufacturing time is determined where the battery internal impedance is 3.5-4 times of the original level.Theoretical models of ablation effect, thermo-dynamics effect and photochemistry effect were established according to the physical and chemical phenomena exist in interaction process between pulsed laser and SEI on the surface of electrodes. The three mechanisms between pulsed laser and SEI were validated and the optimum pulsed laser energy density of remanufacturing electrode is 0.142J/mm2 in our experiments. The optimum process parameter are 13.4%< γ1≤ 20%,25%< γ2 ≤ 30%, through theoretical and experimental analysis overlap rate of pulsed laser spots and the overlap rate of pulsed laser roads can influence the surface cleaning cleanness.In addition, the granularity and clearance of lithium iron phosphate particle was analyzed before and after remanufacturing. Electrochemical performance of Li-ion battery after remanufacturing was established by measuring the internal impedance of experimental monolayer battery after remanufacturing. In the end, the recovery rate of battery capacity of remanufactured battery was predicted theoretically based on SEM analysis of electrode sections. The experiment shows that battery capacity can recover 95.28% of the original after using pulsed laser technology, which is 5% higher than traditional chemical remanufacturing process.