Mitigating PTFE decomposition in ultra thick dry-processed anodes for high energy density lithium-ion batteries

Abstract

Dry electrode technology is a next-generation method for manufacturing lithium-ion batteries because it is useful for fabricating thick electrodes without solvents, facilitating high energy densities and cutting down on the battery manufacturing costs. However, the commonly used polytetrafluoroethylene (PTFE) binder in dry electrode technology undergoes severe decomposition in dry-processed anodes during the first lithiation process due to its low lowest unoccupied molecular orbital level. This phenomenon seriously aggravates battery performance, such as in terms of the initial coulombic efficiency and cycle life. Thus, a strategy to suppress this irreversible reaction of PTFE should be established for dry-processed anodes to increase the energy density of LIBs without adverse effects on battery performance. To address this challenge, in this work, fluoroethylene carbonate (FEC) as an electrolyte additive has been introduced to form a preemptive and stable FEC-derived solid electrolyte interface (SEI) to protect a graphite and the PTFE binder. This SEI considerably alleviates the irreversible reaction of PTFE, thereby securing the reversible capacity and maintaining the structure of the electrode through the great binding properties. These results provide guidance for increasing the electrochemical stability in dry-processed anode systems, which gets closer the innovative dry anode technology for cost-effectiveness and high energy density.