A Hydrogen-Bonded Crossing Binder for High-Voltage Applications of the Lithium Cobalt Oxide Cathode

The inferior cycle capacity of the lithium cobalt oxide (LCO) cathode at high potential hinders the further enhancement of its working voltage. In response to this challenge, an innovative water-based binder (SL-GG) was prepared by employing sodium lignosulfonate (SL) and guar gum (GG) as raw materials to achieve high-potential LiCoO₂ (4.6 V) cathodes with cycling stability. Multiple hydrogen bonds are constructed between sulfonic acid functional groups in SL and oxygen-containing functional groups in GG that endow the SL-GG binder with high tensile strength, strong stretchability, and a high oxidation-potential window. In situ X-ray diffraction (XRD) analysis demonstrates that the characteristic peak signal of LiCoO₂ (003) in SL-GG@LCO remains prominent even at 4.6 V, in contrast to PVDF@LCO, demonstrating that the SL-GG binder effectively serves a protective role for the intrinsic structure of LiCoO₂ at high working voltage. After 100 cycles at 4.6 V, the capacity retention rate of SL-GG@LCO is 76.9%, much higher than that of PVDF@LCO (42.8%). In addition, it exhibits a significantly higher specific discharge capacity (143.1 mAh g^-1) at 5 C. Moreover, the LiCoO₂ cathode based on the SL-GG binder even delivers a high potential of 4.6 V with good cycling stability, showing great potential for practical applications.