Effects of Mechanical Stirring and Ultrasound Treatment on the Separation of Graphite Electrode Materials from Copper Foils of Spent LIBs: A Comparative Study

Abstract

In this paper, mechanical stirring and ultrasonic treatment are used to separate graphite electrode materials from copper foils in recycling spent lithium-ion batteries (LIBs). Firstly, the effects of ultrasonic power (60–180 W), ultrasonic time (1–8 min), stirring speed (420–2000 rpm), and stirring time (1–8 min) on the abscission rate of active material on copper foil were studied. It was found that the peeling-off ratio of electrode material under ultrasonic treatment was 91.34% compared with stirring treatment (84.22%). The removal of electrode material from copper foil during stirring was mainly through mechanical scrubbing. As a comparison, the generation of the microjets induced by ultrasound, the local high-temperature and high-pressure environment, and the free radicals during ultrasonic treatment are the key factors to further improve electrode material removal efficiency. An integrated ultrasound-mechanical stirrer technique can achieve a high-efficient separation performance (approximately 100% peeling-off ratio) of anode electrode materials from copper foils. The effects of mechanical stirring speed, temperature, and treatment time on the peeling-off ratios of the ultrasound-mechanical stirrer-assisted system were investigated. Finally, the results of XRF (X-ray fluorescence spectrometer), XRD (X-ray diffraction), and SEM-EDS (scanning electron microscopy coupled with energy dispersive X-ray spectroscopy) showed that the as-separated graphite electrode material had high purity and contained almost no copper foil impurities. Numerical simulation analyses briefly showed that the difference between pressure and ultrasonic temperature changes in the boundary between different anode layers (graphite on copper foil in aqueous solution) was the main effective factor in the considerable separation of graphite from copper anode foil under ultrasonic-assisted delamination.

Enhancement Mechanism of the Difference of Hydrophobicity between Anode and Cathode Active Materials from Spent Lithium-Ion Battery Using Plasma Modification

“…The electrode sheets with a side length of 1 cm × 1 cm were cut and stripped in acetic acid with a concentration of 1 mol/L and under ultrasonic power of 300 W (ultrasonic equipment: Changzhou Gaode Instrument Manufacturing Co., Changzhou, China). 46 The stripped electrode materials were washed several times and then wet sieved, and samples with a particle size of smaller than 74 μm obtained after filtering and drying were used for the plasma treatment experiments. The anode and cathode materials before and after plasma treatment were sampled and pressed using the contact angle measuring instrument (Model JC2000D1), then the contact angle tests were carried out, the contact angle values were measured three times via the angle measurement method, and the arithmetic mean value was taken.…”

Review of Ultrasound-Assisted Recycling and Utilization of Cathode Materials from Spent Lithium-Ion Batteries: State-of-the-Art and Outlook

“…When the bubble rapidly collapses, the gas or vapor inside the bubble is compressed, and in the extremely short time of the bubble's collapse, it can generate enormous energy locally (10 18 kW/ m 3 ). 36,37 Shock waves and microjets are the physical effects of powerful ultrasonic waves. After reaching their maximum radius, cavitation bubbles collapse and form shock waves under positive pressure (Figure 2a).…”

“…Schematical diagrams of (a) the isotropic bubble collapse and shock wave propagation and (b) the microjet generated by cavitation bubble collapse. Reproduced with permission from ref . Copyright 2023 MDPI.…”

“…The acoustic chemical reaction refers to the reaction between oxidants generated during the cavitation process of bubbles in an ultrasound field and solutes. ,− The sharp increase in the temperature inside bubbles leads to the decomposition of water vapor and oxygen into various oxidants, such as hydroxyl radicals (OH·), H 2 O 2 , oxygen atoms, and O 3 . As oxygen atoms easily react with water to produce limited amounts of H 2 O 2 and O 3 , oxidants generated by ultrasonic cavitation mainly exist in the form of OH·.…”

“…Power ultrasonic waves have a high power density, and the cavitation phenomenon is mainly transient cavitation. , Bubbles continue to grow during the negative pressure phase, and when the positive sound pressure arrives, bubbles continue to grow due to inertia until they reach their maximum radius and then rapidly contact until they collapse and close. When the bubble rapidly collapses, the gas or vapor inside the bubble is compressed, and in the extremely short time of the bubble’s collapse, it can generate enormous energy locally (10 18 kW/m 3 ). , Shock waves and microjets are the physical effects of powerful ultrasonic waves. After reaching their maximum radius, cavitation bubbles collapse and form shock waves under positive pressure (Figure a).…”