Tailoring Sodium Carboxymethylcellulose Binders for High-Voltage LiCoO2 via Thermal Pulse Sintering

Abstract

Polyvinylidene fluoride (PVDF), as the commercial cathode binder for lithium-ion batteries, presents several practical challenges, including insufficient conductivity, weak adhesion to active materials, and the use of toxic N-methylpyrrolidone for slurry preparation. However, while most water-soluble binders can address the aforementioned issues, they fail to meet the requirements of high-voltage cathodes. In this work, we innovatively employed a thermal pulse sintering strategy to modify carboxymethyl cellulose sodium (CMC), enabling their application in 4.6 V LiCoO2 (93% capacity retention after 200 cycles). This strategy facilitates the decomposition of electrochemically active carboxyl groups, leading to ring opening reactions that generate numerous ether linkages (-C-O-C-) without introducing undesirable side effects on LiCoO2. The resulting components form additional charge carrier (i.e., Li+ and e-) pathways on the cathode surface. Additionally, the heating process also promotes uniform coating of the binder on the surface of LiCoO2, creating a protective layer that inhibits interfacial side reactions. Through proposing a scalable and economic manufacturing technology of multifunctional binder, this work enlightens the avenues for practical high-energy-density batteries.