Crystallographically Oriented Thin-Film Nanocrystalline Cathode Layers Prepared Without Exceeding 300°C
Crystallographically Oriented Thin-Film Nanocrystalline Cathode Layers Prepared Without Exceeding 300°C
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DOI：
10.1149/1.1400119
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发表时间：
2001-10
影响因子：
3.9
通讯作者：
J. Whitacre;W. West;E. Brandon;B. Ratnakumar
中科院分区：
文献类型：
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作者：
J. Whitacre;W. West;E. Brandon;B. Ratnakumar
研究发现，用于薄膜固态电池的最高容量射频溅射阴极层需要温度超过 700°C 的退火步骤。由于这种高温工艺步骤与硅器件技术和柔性聚合物基板不兼容，因此开发了低工艺温度（小于或等于300°C）阴极层。使用平面磁控管射频溅射沉积由LiCoO 2 组成的薄膜阴极层，随后将其并入由LiPON电解质和锂金属阳极组成的薄膜固态电池中。使用卢瑟福背散射光谱法和电感耦合等离子体质谱法检查薄膜成分，同时通过斯坦福同步辐射实验室进行的 X 射线衍射实验研究相含量和晶体结构。使用透射和扫描电子显微镜检查微观结构和形态。发现LiCoO 2 可以在室温下以具有限定的(104)面外织构和高度晶格畸变的纳米晶态沉积。通过将这些层加热至 300°C，平均晶粒尺寸增大，同时晶格畸变最小化。电化学循环数据表明，低温退火步骤将电池容量提高到接近理论值，同时显着提高倍率性能和放电电压。对测试电池的阻抗分析表明，加热到300°C后电池的电阻降低。
The highest capacity rf sputtered cathode layers created for use in thin-film solid-state batteries have been found to require an annealing step with temperatures in excess of 700°C. Since this high-temperature process step is incompatible with silicon device technology and flexible polymer substrates, the development of a low-process temperature (less than or equal to 300°C) cathode layer has been undertaken. Thin-film cathode layers consisting of LiCoO 2 were deposited using planar magnetron rf sputtering and subsequently incorporated into thin-film solid-state cells comprised of a LiPON electrolyte and lithium metal anode. Film composition was examined using Rutherford backscattering spectrometry and inductively coupled plasma mass spectroscopy, while phase content and crystal structure were studied through X-ray diffraction experiments conducted at the Stanford Synchrotron Radiation Laboratory. Microstructure and morphology were examined using transmission and scanning electron microscopy. It was found that LiCoO 2 could be deposited at room temperature in a nanocrystalline state with a defined (104) out of plane texture and a high degree of lattice distortion. By heating these layers to 300°C, the average grain size was increased while lattice distortion was minimized. Electrochemical cycling data revealed that the low temperature annealing step increases cell capacity to near theoretical values while significantly improving both the rate capability and discharge voltage. Impedance analysis on test cells showed that the electronic resistance of the cells is decreased after heating to 300°C.