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

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.