Improvement in the cycling stability and rate capability of LiNi0.5Co0.2Mn0.3O2 cathode material via the use of a Ta2O5 coating

The electrochemical properties of the layered structure LiNi0.5Co0.2Mn0.3O2 (NCM523) material decrease at an elevated cut-off voltage. The Ta2O5 coating method effectively enhances the surface stability of NCM523. The present study used Ta2O5 as a hydrofluoric acid (HF) barrier material to effectively resist HF attacks on NCM523. The electrochemical properties of Ta2O5-coated NCM523 were enhanced at a normal cut-off voltage of 4.3 V and an elevated cut-off voltage of 4.5 V. With the optimal amount of Ta2O5 coating (1.0 wt%), the capacity retention increased from 91.36% to 97.6% at 3–4.3 V after 210 cycles and from 88% to 92.45% after 210 cycles at 3–4.5 V. The Ta2O5 (1.0 wt%)-coated sample also exhibited a higher rate capability and maintained discharge capacities of 107 mAh g-1 and 125 mAh g-1 over the voltage ranges of 3–4.3 V and 3–4.5 V, respectively, at a current of 5C. The improvement in the electrochemical cycling performance is attributed to the effects of the Ta2O5 coating layer, which mitigates the Mn and Ni dissolution and side reactions caused by HF. The coating layer prevents the active material and the electrolyte from being in direct contact and promotes Li+ transmission. These effects produced a better cycling performance for Ta2O5-coated than the pristine NCM523.