Geometry-matched chelation enhances Li⁺ diffusion on electrodes binded by modified carboxymethyl cellulose

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Chemistry

Background:

• Carboxymethyl cellulose (CMC) is a sustainable binder for flexible lithium-ion batteries.
• Its dense hydrogen-bond network and limited oxygen functionalities hinder chain mobility and Li+ coordination.

Purpose of the Study:

• To molecularly engineer CMC to improve Li+ coordination and transport.
• To enhance binder compatibility and reduce viscosity for better battery performance.

Main Methods:

• Grafting CMC with polyisoprene chains and oxidizing to form cis-glycol units.
• Utilizing density-functional theory and molecular-dynamics simulations.
• Conducting galvanostatic intermittent titration and electrochemical impedance spectroscopy.

Main Results:

• Engineered CMC exhibits geometry-matched cis-glycol chelation for Li+, enhancing Li+ correlation and interfacial diffusion.
• Grafted chains improve compatibility with carbons, reduce viscosity by 42%, and increase chain mobility.
• Demonstrated a 2.4-fold increase in interfacial Li+ diffusivity and 69% capacity retention after 500 cycles.

Conclusions:

• Geometry-matched chelation is an effective strategy for enhancing Li+ transport in electrode surfaces.
• The modified CMC binder leads to a more stable solid electrolyte interphase (SEI), suppressing dendrite formation.
• Provides molecular-level guidance for developing next-generation carbohydrate-based battery binders.