Enhancement of Thermal Stability and Cycling Performance of Lithium-Ion Battery at High Temperature by Nano-ppy/OMMT-Coated Separator

Shuo Yang,Huijun Li,Huiya Qin,Xuan Li,Pei Yao

doi:10.1155/2017/6948183

Abstract

Nanopolypyrrole/organic montmorillonite- (nano-ppy/OMMT-) coated separator is prepared by coating nano-ppy/OMMT on the surface of polyethylene (PE). Nano-ppy/OMMT-coated separator with three-dimensional and multilayered network structure is beneficial to absorb more organic electrolyte, enhancing the ionic conductivity (reach 4.31 mS·cm-1). Meanwhile, the composite separator exhibits excellent thermal stability and mechanical properties. The strong covalent bonds (Si-F) are formed by the nucleophilic substitution reaction between F−from the thermal decomposition and hydrolysis of LiPF6and the covalent bonds (Si-O) of nano-ppy/OMMT. The Si-F can effectively prevent the formation of HF, POF3, and LiF, resulting in the inhibition of the disproportionation of Mn3+in LiNi1/3Co1/3Mn1/3O2material as well as reducing the internal resistance of the cell. Therefore, the nano-ppy/OMMT-coated separator exhibits outstanding capacity retention and cycling performance at 80°C.

Highlights

With the extensive application of lithium-ion battery (LIB) to electric vehicles and energy storage, the security of LIB at high temperature should be given more attention
LiF, HF, and POF3 from the thermal decomposition and hydrolysis of LiPF6 at high temperature may be formed on the surface of the electrodes [5]
The diffraction peak becomes much smoother, meaning that the nano-ppy/organic montmorillonite (OMMT) is in amorphous state, which makes it much easier to enhance the ionic conductivity of polymer electrolytes [28, 29]

Summary

Introduction

With the extensive application of lithium-ion battery (LIB) to electric vehicles and energy storage, the security of LIB at high temperature should be given more attention. The electrochemical property and stability of LIB at high temperature depend on the thermal stability of organic electrolyte and separator. To handle these problems, inorganic materials, such as TiO2, Al2O3, and SiO2, are coated on the surface of separator [9,10,11,12]. To ensure the safety of LIB and achieve its excellent performance at high temperature, it is essential to select proper inorganic coatings to enhance the thermal, mechanical, and electrochemical performances of the separator. OMMT coated with high specific surface area can improve the absorbing ability of organic electrolyte, enhancing the ion conductive ability of electrolyte membrane [17]. C and of the cell assembled with PE separator under the same conditions

Experimental

Results and Discussion

Conclusions