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采用脉冲激光沉积(PLD)方法在镀Pt的Si衬底上制备了LiCoO2薄膜, 运用XRD、Raman光谱、SEM和循环伏安等方法对其结构与电化学性能进行表征, 在此基础上着重采用电位间歇滴定技术(PITT)对其Li离子表观扩散进行了分析. 结果表明,600℃制备的LiCoO2薄膜为HT-LiCoO2相, 呈柱状晶结构, 平均晶粒尺寸在100 nm以下, 结晶度高, 并且具有明显的[001]择优取向, 但少量缺Li. 伏安循环曲线表明, 该LiCoO2薄膜具有良好的电化学可逆性, 但只在3.9 V(vs Li)附近出现一对氧化还原峰. PITT测试表明, PLD方法制备的HT-LiCoO2薄膜的Li离子扩散系数在10-8—10-9 cm2/s, 与其它方法(如射频磁控溅射)制备的HT-LiCoO2薄膜相比, 扩散系数高1—2个数量级; 并且PLD方法制备的HT-LiCoO2薄膜中Li离子扩散系数与相变有关, 在两相共存区, 由于相界钉扎的作用, Li离子扩散系数比其它区域小1—2个数量级.

In this work, LiCoO2 films were prepared with the pulsed laser deposition (PLD) method. Their structure was characterized by X-ray diffraction, Raman spectra and Scanning electron microscopy and their electrochemical properties were evaluated with cyclic voltammetry (CV). Results showed that LiCoO2 films prepared with PLD at 600℃ had a well-crystallized columnar HT-LiCoO2 structure with the average grain size less than 100nm and with a strong [001] preferred orientation, while these films contain trace amount of Co3O4. CV tests indicated that PLD-deposited HT-LiCoO2 films had good electrochemical reversibility but only a pair of redox peaks near 3.9V(vs Li) were observed in the cyclic voltammograms. Thereafter, emphasis was laid on the study of apparent diffusion of lithium-ion through LiCoO2 films using the potentiostatic intermittent titration technique (PITT). PITT measurements revealed that the lithium-ion diffusion coefficient of PLD-deposited HT-LiCoO2 films reached 10-8~10-9cm2s-1, 1-2 orders of magnitude faster than those prepared by other methods including R.F. magnetron sputtering and, in the voltage range between 3.85~3.95V(vs Li), the lithium-ion diffusion coefficient of PLD-deposited HT-LiCoO2 films was 1-2 orders of magnitude lower than other voltage ranges. The former should be ascribed to the grain refinement of PLD-deposited HT-LiCoO2 films and existence of many voids, while the later may due to the hindrance arising from phase boundary movement.