The synergistic effect of sodium carboxymethyl cellulose and polytetrafluoroethylene for highly stable graphite anodes

In order to reduce the preparation cost of lithium-ion batteries (LIBs), dry eletrode technology has been proposed. However, the polytetrafluoroethylene (PTFE) binder mainly used in the dry eletrode technology accepts electrons and becomes reduced in the anode, causing instability. To solve these issues, this study proposes a composite binder system of PTFE and sodium carboxymethyl cellulose (CMC). This design is based on the theory of electronic structure matching, while also considering practical factors such as dynamic stability and system synergy. Materials with energy levels close to PTFE were screened to achieve this goal, this binder system is designed to reduce the contact between PTFE and lithium in the active material, and improve the long-term stability of graphite anode materials. The performance of the anodes prepared with the composite binder system was evaluated in terms of electrochemical performance and microstructure in graphite and lithium half-cells. The results show that incorporating CMC as a component in the PTFE composite binder leads to a significant performance improvement, in the graphite and lithium half-cells, the initial Coulombic efficiency (ICE) has increased from 62 % to 73 %, the capacity retention after 430 cycles was significantly improved, rising from 17 % for the SF PTFE anode to over 50 % for the SF CMC anode, the charge transfer impedance and ion diffusion impedance have decreased, and the ion diffusion coefficient has been significantly enhanced. These findings demonstrate the potential of this composite binder system for enabling high-performance, low-cost graphite anodes, offering a promising technical path towards the development of advanced LIBs.