Water-assisted delamination of cathode active materials from aluminum foil during electrical pulsed discharge for direct lithium-ion battery recycling

The sustainable recycling of spent lithium-ion batteries (LiBs) requires the selective separation of cathode active materials (CAMs) from aluminum (Al) current collectors without degrading their functional properties. Electrical pulsed discharge (EPD) is a promising pretreatment method; however, delamination can be inconsistent owing to interfacial degradation and non-uniform current flow. We investigated a simple water-assisted approach in which a thin surface coating of water was applied before EPD. Experiments using commercial cathode sheets showed that water coating markedly enhanced CAM delamination, achieving over 90 % at 0.250 J/mg and reaching 94 % at 0.305 J/mg, whereas the uncoated samples failed to delaminate. Importantly, enhanced delamination was achieved without increasing the Al pulverization. High-speed imaging revealed that delamination initiated locally beneath the water-coated regions and propagated outward. Complementary simulations showed that thermal stress alone could not account for this behavior. The rapid vaporization of interfacial water generated transient opening pressures exceeding 100 MPa near the coated interface. These stresses (≈30 MPa) propagated across the CAM layer to the opposing side, contributing to delamination. These results identify water-assisted vapor expansion, rather than thermal stress alone, as the principal driver of coating-enhanced delamination. This facile, chemical-free method offers a robust pathway to improve direct LiB recycling efficiency and reduce environmental impact.