Alternative binders to simplify the recycling of lithium-ion batteries

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

Alternative binders to simplify the recycling of lithium-ion batteries

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

Improving the Conductivity of Graphite-Based Lithium-Ion Battery Anodes Using Polyaniline–Alginate Blends

This investigation shows the effect of blending sodium alginate (NaAlg) and a conducting polymer, polyaniline (PANI), in lithium-ion battery (LIB) anodes. We demonstrate here that inclusion of the PANI into the binder improves the connectivity of the composite, resulting in better performance. Additionally, the blends are easily formulated without sophisticated methods or additional equipment. When these binders were combined into electrodes, the conductivity rose by between 3- and 5-fold compared with the unmodified NaAlg, depending on the PANI loading. The conducting polymer did not significantly change the thermal stability or cycling of the cells, but it did improve the Coulombic efficiency. During electrochemical testing, it was found that cells containing PANI within the binders exhibited evidence of essential processes, such as SEI formation and lithium intercalation. Evidence of side reactions was observed, predicted to be the lithiation of PANI to create lithium emeraldinate within the polymeric regions, which could increase the Coulombic efficiency of the cells and allow for the decrease in impedance contributions after extensive cycling. Capacities and rate capabilities comparable to anodes prepared using graphite and commercial binders PVDF and CMC/SBR were also observed. Crucially, after cycling, the NaAlg/PANI binder could be fully removed from the active material with mild ultrasonic agitation in water

Iodine speciation in deep eutectic solvents

Iodine has been shown to act as a good electrocatalyst for metal digestion in deep eutectic solvents (DESs) but little is known about its speciation or reactivity in these high chloride containing media. Extended X-ray absorption fine structure (EXAFS) spectroscopy measurements were made at the iodine K-edge in a range of DESs with different glycolic or acidic hydrogen bond donors (HBDs), along with examining the effect of iodine concentration between 0.01 and 0.5 mol dm-3. Three groups of speciation were detected: mixed I2Cl-/I3- (glycol and lactic acid systems), mixed I3-/I2 (oxalic acid and urea systems), and singular I3- (levulinic acid system). UV-vis spectroscopy was used to confirm the speciation. Electrochemistry showed that iodine redox behaviour was unaffected by the changing speciation. Leaching data showed that metal oxidation was related not only to changing iodine speciation, but also the reactivity and coordination ability of the HBD.</p

Tailoring lixiviant properties to optimise selectivity in E-waste recycling

The scale of E-waste production makes the selective recovery of technology metals an important research topic. It has previously been shown that deep eutectic solvents, DESs, can be used to rapidly digest gold and in the current study the effect of varying water and ethylene glycol content on the ability to selectively recover metals in DESs was investigated. It was found that increased water content resulted in an increase in metal etching rates for copper due to the decreasing viscosity of the solution, but etching rates of nickel, silver and gold were decreased due to the competition between chloride and oxide/hydroxide chemistry causing passivating films to form. Iodine was used as a catalyst and speciation was investigated in different solvent compositions. The ratio of the two trihalide species was mostly unaffected by solvent composition, but the presence of molecular iodine was detected with 20 wt% water due to decreased iodine solubility resulting from lower chloride concentration. It was determined that solvent physical properties were most important for metal etching rates at low water content, but at high water content the effect of oxide/hydroxide chemistry was more significant, resulting in the possibility of selective metal etching of copper from PCBs.</p