Polyimide Encapsulated Lithium-Rich Cathode Material for High Voltage Lithium-Ion Battery

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• 作者：Jie Zhang ; Qingwen Lu ; Jianhua Fang ; Jiulin Wang ; Jun Yang ; Yanna NuLi
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2014
• 出版时间：October 22, 2014
• 年：2014
• 卷：6
• 期：20
• 页码：17965-17973
• 全文大小：650K
• ISSN：1944-8252

文摘

Lithium-rich materials represented by xLi₂MnO₃路(1 鈥?x)LiMO₂ (M = Mn, Co, Ni) are attractive cathode materials for lithium-ion battery due to their high specific energy and low cost. However, some drawbacks of these materials such as poor cycle and rate capability remain to be addressed before applications. In this study, a thin polyimide (PI) layer is coated on the surface of Li_1.2Ni_0.13Mn_0.54Co_0.13O₂ (LNMCO) by a polyamic acid (PAA) precursor with subsequently thermal imidization process. X-ray diffraction (XRD), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HR-TEM) results confirm the successful formation of a PI layer (鈭? nm) on the surface of LNMCO without destruction of its main structure. X-ray photoelectron spectroscopy (XPS) spectra show a slight shift of the Mn valence state from Mn(IV) to Mn(III) in the PI-LNMCO treated at 450 掳C, elucidating that charge transfer takes place between the PI layer and LNMCO surface. Electrochemical performances of LNMCO including cyclic stability and rate capability are evidently improved by coating a PI nanolayer, which effectively separates the cathode material from the electrolyte and stabilizes their interface at high voltage.

Keywords:

lithium-rich material; surface coating; polyimide; interfacial reaction; lithium-ion battery