College of Chemistry and Bioengineering, Guilin University of Technology, Guilin 541004, P. R. China.
Phys Chem Chem Phys. 2014 Feb 21;16(7):2882-91. doi: 10.1039/c3cp54399d.
In this work, carbon-free and carbon-coated spinel LiCrTiO4 oxides were synthesized by a conventional solid state reaction. The lithium-ion diffusion coefficient and electronic conductivity of prepared electrode materials were systematically investigated using the galvanostatic intermittent titration technique (GITT), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The rate performances of the prepared materials were evaluated by galvanostatic charge-discharge. Carefully comparing the charge-discharge polarization potential of both materials, we unexpectedly discovered that the pristine LiCrTiO4 electrode demonstrated asymmetric polarization during the charging-discharging process, which is possibly attributed to the nonuniform electron conductivity between the endmember of a two-phase reaction, whereas carbon coating could level this phenomenon. Additionally, using an asymmetric core-shell model from the microscopic point of view can easily explain this common phenomenon. Meanwhile, this new research perspective can be extended to other active materials in lithium ion batteries.
在这项工作中，通过传统的固相反应合成了无碳和碳包覆尖晶石 LiCrTiO4 氧化物。使用恒电流间歇滴定技术（GITT）、循环伏安法（CV）和电化学阻抗谱（EIS）系统研究了制备电极材料的锂离子扩散系数和电子电导率。通过恒电流充放电评估了制备材料的倍率性能。仔细比较两种材料的充放电极化电位，我们意外地发现，在充放电过程中，原始 LiCrTiO4 电极表现出不对称的极化，这可能归因于两相反应端元之间的非均匀电子电导率，而碳包覆可以消除这种现象。此外，从微观角度来看，使用非对称核壳模型可以很容易地解释这种常见现象。同时，这种新的研究视角可以扩展到锂离子电池中的其他活性材料。
