Polyethylene Oxide as a Multifunctional Binder for High-Performance Ternary Layered Cathodes.

Jinshan Mo,Lihua Chu,Lehao Liu,Weihao Hu,Dongmei Zhang,Mingzhe Sun,Bing Jiang,Meicheng Li

doi:10.3390/polym13223992

Abstract

Nickel cobalt manganese ternary cathode materials are some of the most promising cathode materials in lithium-ion batteries, due to their high specific capacity, low cost, etc. However, they do have a few disadvantages, such as an unstable cycle performance and a poor rate performance. In this work, polyethylene oxide (PEO) with high ionic conductance and flexibility was utilized as a multifunctional binder to improve the electrochemical performance of LiNi0.6Co0.2Mn0.2O2 cathode materials. Scanning electron microscopy showed that the addition of PEO can greatly improve the adhesion of the electrode components and simultaneously enhance the integrity of the electrode. Thus, the PEO-based electrode (20 wt% PEO in PEO/PVDF) shows a high electronic conductivity of 19.8 S/cm, which is around 15,000 times that of the pristine PVDF-based electrode. Moreover, the PEO-based electrode exhibits better cycling stability and rate performance, i.e., the capacity increases from 131.1 mAh/g to 147.3 mAh/g at 2 C with 20 wt% PEO addition. Electrochemical impedance measurements further indicate that the addition of the PEO binder can reduce the electrode resistance and protect the LiNi0.6Co0.2Mn0.2O2 cathode materials from the liquid electrolyte attack. This work offers a simple yet effective method to improve the cycling performance of the ternary cathode materials by adding an appropriate amount of PEO as a binder in the electrode fabrication process.

Highlights

The utilization of nickel cobalt manganese ternary layered cathode materials can greatly increase the energy density and reduce the cost of lithium-ion batteries; they have several drawbacks, such as a poor rate performance, a quick capacity fading and a low initial Coulombic efficiency [1,2,3]
polyethylene oxide (PEO)-LiTFSI solid electrolyte films were prepared by a solution casting method (Figure 2a) to prove the ionic conductance of PEO and its efficacy in coating the NCM622 particles
It should be noted that when PEO was used as a binder to prepare the electrodes, carbon black nanoparticles, NCM622 particles and other components would function as fillers to reduce the crystallinity of PEO and further increase the ionic conductivity [19]

Summary

Introduction

The utilization of nickel cobalt manganese ternary layered cathode materials can greatly increase the energy density and reduce the cost of lithium-ion batteries; they have several drawbacks, such as a poor rate performance, a quick capacity fading and a low initial Coulombic efficiency [1,2,3]. Li et al [11] synthesized FeF3-coated Li1.2Mn0.54Ni0.13Co0.13O2 cathode materials via a wet chemical process followed by a solidstate reaction, and the Coulombic efficiency, rate capability and cycling stability of the FeF3coating materials were greatly improved (e.g., 95% capacity retention after 100 cycles at 0.5 C). It is worth mentioning that both doping and coating can effectively improve the cycling performance of the ternary cathode materials, but they usually possess a few shortcomings, including complex operation procedures, such as blending and sintering, a high energy consumption and environmental pollution. There is always an urgent need to exploit simple, effective and environmentally friendly modification methods

Methods

Results

Conclusion