脉冲激光沉积制备的HT-LiCoO_2薄膜中Li离子表观扩散的研究  

INVESTIGATION OF APPARENT DIFFUSION OF Li ION IN HT-LiCoO_2 FILMS FABRICATED BY PULSED LASER DEPOSITION METHOD

作　　者：张耀[1] 钟志源[2] 朱敏[1] 

机构地区：[1]华南理工大学机械工程学院,广州510641 [2]香港城市大学物理与材料科学系

出　　处：《金属学报》2007年第8期818-822,共5页Acta Metallurgica Sinica

基　　金：教育部长江学者与创新团队发展计划项目IRT0551;广东省自然科学基金团队项目资助

摘　　要：采用脉冲激光沉积(PLD)方法在镀Pt的Si衬底上制备了LiCoO_2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LiCoO_2薄膜为HT-LiCoO_2相,呈柱状晶结构,平均晶粒尺寸在100nm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LiCoO_2薄膜具有良好的电化学可逆性.但只在3.9V(vs Li/Li^+)附近出现一对氧化还原峰.PITT测试表明,PLD方法制备的HT-LiCoO_2薄膜的Li离子扩散系数在10^(-8)—10^(-9)cm^2/s,与其它方法(如射频磁控溅射)制备的HT-LiCoO_2薄膜相比,扩散系数高1—2个数量级;并且PLD方法制备的HT-LiCoO_2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.The structure of LiCoO2 films prepared with the pulsed laser deposition （PLD） method was characterized by XRD, Raman spectroscopy and SEM, and their electrochemical properties were evaluated with cyclic voltammetry （CV）. Results showed that the LiCoO2 films deposited at 600 ℃ have a well-crystallized columnar HT-LiCoO2 structure with the average grain size less than 100 nm and a strong [001] preferred orientation, while these films contain trace amount of Co304. CV tests indicated that the HT-LiCoO2 films have good electrochemical reversibility but only a pair of redox peaks near 3.9 V （vs Li） were observed in the cyclic voltammograms. Potentiostatic intermittent titration technique （PITT） measurements revealed that the lithium ion diffusion coefficient of the HT- LiCoO2 films can reach 10^-8--10^-9 cm^2/s, 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--3.95 V （vs Li） the diffusion coefficient 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 be due to the hindrance arising from phase boundary movement.

关 键 词：LICOO2 脉冲激光沉积 薄膜电池 Li离子扩散 

分 类 号：O484.4[理学—固体物理]