Estimation and the Material Design for Functional Oxides by Thermodynamic Measurement

通过热力学测量估算功能氧化物和材料设计

• 批准号: 11650863
• 负责人: IDEMOTO Yasushi
• 金额: $ 1.34万
• 依托单位: Science University of Tokyo
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1999
• 资助国家: 日本
• 起止时间: 1999 至 2000
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-11650863/
• 关键词: Standard enthalpy of formation; Electrode characteristics; Substitution effect; Lithium secondary battery; Positive electrode active material; Crystal structure; Thermodynamic data; Lithium manganese spinel; 溶解熱; カロリーメトリー; 熱力学

LiMn_2O_4 has an advantage of low cost compared with LiCoO_2 and it pays attention as a positive electrode active material for the Lithium secondary battery, which has high charge-discharge potential. The relation between the structure and the electrode characteristics from the viewpoint of thermodynamics was investigated. First, the samples was synthesized of the Li rich spinel, Li_<1.33>Mn_<1.67>O_4, the defect spinel, Li_<0.89>Mn_<1.78>O_4, and substitution spinel to partially replace Mn by Al, LiMn_<2-x>Al_xO_4. It was investigated the relation between property, structure, and ode performance of the samples. Furthermore, the standard enthalpy of formation, Δ_1H^0, and the enthalpy change of reaction, ΔH, were calculated form the heat of dissolution. Thermodynamic stability was examined by these parameters. The Mn valence and lattice parameter a changed with change of structure and metal contents. The crystal structure analysis by neutron diffraction of LiMn_<1.8>Al_<0.2>O_4 and Li_ … More <1.1>Mn_<1.7>Al_<0.2>O_4 was examined. As a result, the bond distance of (Mn, Li, Al)-O decreased and absolute value of the lattice energy (Fourier method) increased with increasing Li and Al. Moreover, the first principle calculation (DV-Xα) method was investigated. From the results, covalent bond of the Mn-O bond was stronger than the Li-O bond. Furthermore, the heats of dissolution of the samples were measured by the solution calorimetry method. When ΔA_fH^0 and ΔH decreased, it brought to a good cycle performance. On the other hand, a change in lattice energy before and after the cell reaction were calculated. From the results, when thermodynamic stability of a positive electrode active material increased and the change of lattice energy decreased, it brought good cycle performance.Accordingly, it is suggested that the stability of the host structure and the existence of Li, which is ionic state in the positive electrode active material, brought to improvement for the cycle performance. Less

与LiCoO_2相比，LiMn_2O_4具有成本低的优点，作为锂二次电池的正极活性材料备受关注，具有较高的充放电电位。从热力学的角度研究了结构与电极特性之间的关系。首先，合成了富锂尖晶石（Li_<1.33>Mn_<1.67>O_4）、缺陷尖晶石（Li_<0.89>Mn_<1.78>O_4）和Al取代尖晶石（LiMn_<2-x>Al_xO_4）。研究了样品的性能、结构和性能之间的关系。通过溶解热计算了标准生成焓Δ_1H^0和反应焓变ΔH。用这些参数考察了热力学稳定性。Mn的价态和晶格参数随结构和金属含量的变化而变化。用中子衍射分析了LiMn_<1.8>Al_<0.2 >o_4和Li_…More <1.1 >mn_ <1.7>Al_<0.2 >o_4的晶体结构。结果表明，随着Li和Al的增加，(Mn, Li, Al)-O的键距减小，晶格能绝对值（傅里叶法）增大。此外，研究了第一性原理计算（DV-Xα）方法。结果表明，Mn-O键的共价键比Li-O键强。用溶液量热法测定了样品的溶解热。当ΔA_fH^0和ΔH减小时，循环性能较好。另一方面，计算了反应前后晶格能的变化。结果表明，正极活性材料的热力学稳定性越大，晶格能变化越小，循环性能越好。因此，认为寄主结构的稳定性和正极活性材料中离子态Li的存在对循环性能的提高起到了促进作用。少

项目成果

Yasushi Idemoto: "Thermodaynamic Stability and Cathode Performance of LiMn_<2-x>Mg_xO_4 as Cathode Active Material for the Lithium Secondary Battery"Electrochemistry. 68(6). 469-473 (2000)

Yasushi Idemoto：“LiMn_<2-x>Mg_xO_4 作为锂二次电池正极活性材料的热力学稳定性和正极性能”电化学。

井手本康: "Li二次電池用正極材料Li_<1+x>Mn_<2-x>O_4の熱力学的安定性と電池特性"日本セラミックス協会誌. 108(9). 848-853 (2000)

Yasushi Idemoto：“Li二次电池正极材料Li_<1+x>Mn_<2-x>O_4的热力学稳定性和电池性能”日本陶瓷学会杂志108(9)848-853(2000)。