Synthesis, Characterization, and Thermal Stability of LiNi_(1/3)Mn_(1/3)Co_(1/3-z)Mg_zO2, LiNi_(1/3-z)Mn_(1/3)Co_(1/3)Mg_zO2, and LiNi_(1/3)Mn_(1/3-z)Co_(1/3)Mg_zO_2

摘要

LiNi_(1/3)Mn_(1/3)Co_(1/3-z)Mg_zO2, LiNi_(1/3-z)Mn_(1/3)Co_(1/3)Mg_zO2, and LiNi_(1/3)Mn_(1/3-z)Co_(1/3)Mg_zO2(0 ≤ z ≤ 1/3) were prepared from hydroxide precursors. The hydroxide precursors were heated with Li2CO3 at 900 °C to prepare the oxides. Rietveld refinements of XRD data show that Mg substitution for Co, Ni and Mn results in different degrees of cation mixing in the Li layer with very little cation mixing in LiNi_(1/3)Mn_(1/3-z)Co_(1/3)Mg_zO2 and the most cation mixing in LiNi_(1/3)Mn_(1/3)Co_(1/3-z)Mg_zO2. Electrochemical studies of the LiNi_(1/3)Mn_(1/3)Co_(1/3-z)Mg_zO2, LiNi_(1/3-z)Mn_(1/3)Co_(1/3)Mg_zO2, and LiNi_(1/3)Mn_(1/3-z)Co_(1/3)Mg_zO2 (0 ≤ z ≤ 1/3) samples were used to measure the rate of capacity reduction with Mg content, found to be about -389 (mAh/g)/(z = 1) independent of which cation was substituted by Mg. The impact of Mg substitution on the thermal stability of NMC samples was studied via accelerating rate calorimetry and compared with Al-substituted NMC samples. The substitution of Mg did not improve the thermal stability of the samples, independent of which cation was substituted and independent of the amount of Mg added, in contrast to the effect of Al, which dramatically improves thermal stability.