The effect of using alternative binders and second life graphite materials on the electrochemical performance of lithium-ion battery electrodes

Abstract

Lithium-ion battery anodes were produced and tested using gelatin and sodium alginate (NaAlg) biopolymers, modified with a deep eutectic solvent (DES). Anodes created with these alternative binder systems showed comparable capacities and Coulombic efficiencies to cells assembled using commercial PVDF and CMC/SBR binders. Rate tests of these cells found that DES-NaAlg possessed a higher rate capability than PVDF, showing a greater capacity (∼70 mAh.g−1 higher) when cycled at 1C. Anodes using gelatin materials exhibited lower rate stability, showing significant capacity fade at cycling rates <0.5C. EIS measurements showed that NaAlg anodes were similar to the cells using conventional binders, but gelatin possessed an extra impedance contribution relating to a polymeric coating of the graphite active materials. NaAlg binders were incorporated into graphite anodes reclaimed from a commercial pouch cell using an ultrasound delamination technique. These cells showed reduced rate performance, brought about by ultrasonic fracturing and particle agglomeration. The capacities at low cycling rates were, however, comparable to pristine materials and evidence of key processes such as SEI formation were observed.