화학공학소재연구정보센터
Inorganic Chemistry, Vol.59, No.15, 11113-11121, 2020
Revisiting LiCoO2 Using a State-of-the-Art In Operando Technique
Lithium overstoichiometric cobalt oxide, Li(Li delta Co1-delta)O2-delta, still occupies a privileged position as a positive electrode material for lithium-ion batteries. However, despite its widespread applications in commercial lithium-ion batteries, little is known about its reaction mechanisms and the effects of delta on cyclability at deep charge. We herein revisited this material through a recently developed in operando technique, i.e., rapid, alternating measurements of X-ray diffraction and X-ray absorption spectroscopy. The cyclability degraded when the charge cutoff voltage was >4.4 V versus Li+/Li, which corresponds to the Li composition exhibiting a minimum (maximum) lattice parameter along the a(h) (c(h)) axis. Differences in the structural parameters such as lattice parameters and bond distances clearly appeared between the charge and discharge reactions at a capacity below similar to 220 mAh g(-1). These changes occurred because deep charge and/or increasing the amount of delta induced a local distortion in the CoO6 octahedra. We found a critical Li extraction content that satisfied the need for both high capacity and cyclability for Li(Li delta Co1-delta)O2-delta, which can be applied to other layered materials.