The electrochemical performance of LiCoPO4 (LCP) as a high-voltage positive electrode for lithium-ion batteries is significantly improved by using the aqueous binder sodium carboxymethyl cellulose (CMC). The CMC not only provides a uniform electrode surface as shown by scanning electron microscopy and elemental mapping, but also suppresses the degradation of LiCoPO4 by scavenging HF in the electrolyte solution as demonstrated by FT-IR. In comparison with other water-soluble binders such as sodium alginate (ALG) and polyacrylic acid sodium salt (PAA), the homogeneous distribution of CMC within the electrodes accompanied by high accessibility of carboxylate groups in CMC are shown to be crucial factors to achieve enhanced performance with an excellent capacity retention of 94% after 20 cycles at a rate of C/10.