Investigation on xanthan gum as novel water soluble binder for LiFePO4 cathode in lithium-ion batteries

Abstract

Xanthan Gum (XG) is systematically investigated and employed as water soluble binder for LiFePO4 (LFP) cathode in Li-ion batteries. XG binder exhibits good thermal stability and processes abundant functional groups such as carboxyl and hydroxyl, displaying a better adhesion strength of 0.085 N cm−1 than sodium carboxymethyl cellulose (CMC, 0.050 N cm−1), but inferior to polyvinylidene difluoride (PVDF, 0.170 N cm−1). The Rheology test reveals that the viscosity of LFP slurry prepared with XG binder is higher than that of PVDF, resulting in a better dispersion of LFP and carbon black particles. The electrochemical performances of LFP-XG electrode are investigated and compared with those of aqueous CMC and conventional PVDF binder. LFP-XG displays better cycle stability and rate performance than PVDF, comparable to CMC, which retains 55.3% capacity of C/5 at 5 C as compared to PVDF (34.8%) and CMC (57.8%). Cyclic voltammetry (CV) shows that LFP-XG has smaller redox polarization and faster lithium diffusion rate than PVDF while electrochemical impedance spectroscopy (EIS) measurement at specified intervals reveals its more favorable electrochemical kinetics than that with PVDF, similar to CMC, thus better rate capability. Scanning electron microscopy (SEM) displays that LFP-XG has a more homogenous distribution of LFP and conductive carbon black particles with XG before cycling and better maintains its structure integrity after 100 cycles than that of PVDF. Furthermore, LFP-XG is observed to process a high ionic conductivity supported by dQ/dV profiles.