Subramani Tamilarasan, Navrotsky Alexandra
Peter A. Rock Thermochemistry Laboratory, NEAT ORU, University of California Davis CA 95616 USA.
School of Molecular Sciences, Center for Materials of the Universe, Arizona State University Tempe AZ 85287 USA
RSC Adv. 2020 Feb 12;10(11):6540-6546. doi: 10.1039/c9ra09759g. eCollection 2020 Feb 7.
High temperature oxide melt solution calorimetry studies on (M' = Nb, M'' = Mn and Fe and = 0.20, 0.30 and 0.40) oxides and a new family of Ta containing Li excess disordered cathode materials, (M' = Ta, M'' = Fe and = 0.20, 0.30 and 0.40), synthesized by a rapid quenching method, are reported in this study. The enthalpies of formation determined from high temperature calorimetry studies reveal that the stability of compounds increases with the increasing Li content per formula unit. The reaction between more basic LiO and acidic transition metal oxides results in the more negative enthalpies of formation for these compounds. The work reveals that the formation enthalpy term plays a more important role in the stabilization of such disordered Li ion materials at room temperature whereas configurational entropy along with lattice entropy (vibrational and magnetic) contributes to the stabilization at high temperature from which the samples are quenched.
本研究报道了对（M' = Nb，M'' = Mn和Fe且x = 0.20、0.30和0.40）的氧化物以及通过快速淬火法合成的含锂过量的新型无序Ta基正极材料家族（M' = Ta，M'' = Fe且x = 0.20、0.30和0.40）进行的高温氧化物熔体溶液量热法研究。高温量热法研究确定的生成焓表明，化合物的稳定性随每个化学式单元中Li含量的增加而增加。碱性更强的LiO与酸性过渡金属氧化物之间的反应导致这些化合物的生成焓更负。该研究表明，生成焓项在室温下此类无序锂离子材料的稳定化中起更重要的作用，而构型熵以及晶格熵（振动和磁熵）则有助于在样品淬火的高温下实现稳定化。
