Alternative binders to simplify the recycling of lithium-ion batteries

Abstract

Binders are a vital component in the structure and function of battery electrodes. They do, however, have implications for the lifetime and recyclability or lithium ion batteries. This project identified several alternative binders that could simplify battery disassembly during end-of-life processing. Primarily anode binders were investigated, and it was found that water-miscible biopolymers, sodium alginate and gelatin, allowed complete delamination of the electrode active material from the current collector using lowpowered ultrasound with water in 5 seconds. Modification of these polymers, with a deep eutectic solvent made from choline chloride and glycerol, also allowed for the enhancement of key properties such as the thermal stability, adhesive strength and, in the case of sodium alginate, the electrochemical stability of the cells at high cycling rates. Other polymer systems were also tested as binders to try and optimise other key characteristics of the anodes, such as the use of polyaniline and sodium alginate to form a polymer blend. Anodes created using these polymer blends found that the conductivity increased with polyaniline content, but other factors such as a poorer adhesive strength was observed. Alternative extracellular adhesives and pack designs were also discussed, where a novel pack structure using a zigzag conformation of the cells joined together with pressure sensitive adhesives such as glue dots. This was shown to significantly reduce disassembly time and create a simplified dismantling procedure that could be easier to automate, increasing the economic viability of battery disassembly versus conventional end-of-life processes like shredding. This study included an environmental impact study comparing battery disassembly steps when alternative adhesives were used in both electrode binders and extracellular adhesives. These were then compared to commercial standards. This showed a 200% reduction in the global warming potential of the overall recycling process highlighting the importance of design for recycle for LIBs benefits, in terms of performance, economic viability of disassembly and environmental impact.</p