Center for Energy Convergence, Korea Institute of Science and Technology (KIST) , Seoul 02792, Republic of Korea.
Carbon Composite Materials Research Centre, Institute of Advanced Composite Materials, KIST , Wanju-gun 55324, Republic of Korea.
ACS Appl Mater Interfaces. 2017 Jun 7;9(22):18883-18888. doi: 10.1021/acsami.7b04478. Epub 2017 May 24.
Here, we take advantage of in situ transmission electron microscopy (TEM) to investigate the thermal stability of P2-type NaCoO cathode materials for sodium ion batteries, which are promising candidates for next-generation lithium ion batteries. A double-tilt TEM heating holder was used to directly characterize the changes in the morphology and the crystallographic and electronic structures of the materials with increase in temperature. The electron diffraction patterns and the electron energy loss spectra demonstrated the presence of cobalt oxides (CoO, CoO) and even metallic cobalt (Co) at higher temperatures as a result of reduction of Co ions and loss of oxygen. The bright-field TEM images revealed that the surface of NaCoO becomes porous at high temperatures. Higher cutoff voltages result in degrading thermal stability of NaCoO. The observations herein provide a valuable insight that thermal stability is one of the important factors to be considered in addition to the electrochemical properties when developing new electrode materials for novel battery systems.
在这里，我们利用原位透射电子显微镜（TEM）研究了 P2 型钠离子电池正极材料 NaCoO 的热稳定性，该材料是下一代锂离子电池的有前途的候选材料。我们使用双倾 TEM 加热支架直接表征了材料在升温过程中形貌以及晶体和电子结构的变化。电子衍射图案和电子能量损失谱表明，由于 Co 离子的还原和氧的损失，在较高温度下存在钴氧化物（CoO、CoO），甚至金属钴（Co）。明场 TEM 图像显示，NaCoO 的表面在高温下变得多孔。较高的截止电压导致 NaCoO 的热稳定性降低。这些观察结果提供了一个有价值的见解，即在为新型电池系统开发新的电极材料时，除了电化学性能外，热稳定性也是需要考虑的重要因素之一。
