Karki Khim, Huang Yiqing, Hwang Sooyeon, Gamalski Andrew D, Whittingham M Stanley, Zhou Guangwen, Stach Eric A
NECCES, Binghamton University , Binghamton, New York 13902, United States.
Center for Functional Nanomaterials, Brookhaven National Laboratory , Upton, New York 11973, United States.
ACS Appl Mater Interfaces. 2016 Oct 19;8(41):27762-27771. doi: 10.1021/acsami.6b09585. Epub 2016 Oct 6.
Layered transition metal oxides such as LiNiCo AlO (NCA) are highly desirable battery electrodes. However, these materials suffer from thermal runaway caused by deleterious oxygen loss and surface phase transitions when in highly overcharged and overheated conditions, prompting serious safety concerns. Using in situ environmental transmission electron microscopy techniques, we demonstrate that surface oxygen loss and structural changes in the highly overcharged NCA particles are suppressed by exposing them to an oxygen-rich environment. The onset temperature for the loss of oxygen from the electrode particle is delayed to 350 °C at oxygen gas overpressure of 400 mTorr. Similar heating of the particles in a reducing hydrogen gas demonstrated a quick onset of oxygen loss at 150 °C and rapid surface degradation of the particles. The results reported here illustrate the fundamental mechanism governing the failure processes of electrode particles and highlight possible strategies to circumvent such issues.
层状过渡金属氧化物，如LiNiCoAlO（NCA），是非常理想的电池电极材料。然而，这些材料在高度过充电和过热条件下会因有害的氧损失和表面相变而发生热失控，引发严重的安全问题。利用原位环境透射电子显微镜技术，我们证明，通过将高度过充电的NCA颗粒暴露在富氧环境中，可以抑制其表面氧损失和结构变化。在400 mTorr的氧气超压下，电极颗粒的氧损失起始温度延迟到350°C。在还原性氢气中对颗粒进行类似加热时，在150°C时氧损失迅速开始，颗粒表面迅速降解。本文报道的结果阐明了电极颗粒失效过程的基本机制，并突出了规避此类问题的可能策略。
