Enhanced Cyclability of Li/Polysulfide Batteries by a Polymer-Modified Carbon Paper Current Collector

Abstract

Lithium-sulfur (Li-S) batteries are considered to be the next-generation rechargeable systems due to their high energy densities and low cost. However, significant capacity decay over cycling is a major impediment for their practical applications. Polysulfides Li2Sx (3<x≤8) formed in the cycling are soluble in liquid electrolyte, which is the main reason for capacity loss and cycling instability. Functional polymers can tune the structure and property of sulfur electrodes, hold polysulfides, and improve cycle life. Herein, we examine a polyvinylpyrrolidone-modified carbon paper (CP-PVP) current collector in Li/polysulfide cells. PVP is soluble in the electrolyte solvent, but shows strong affinity with lithium polysulfides. The retention of polysulfides in the CP-PVP current collector is improved by ∼50%, which is measured by a linear sweep voltammetry method. Without LiNO3 additive in the electrolyte, the CP-PVP current collector with 50 μg of PVP can significantly improve cycling stability with a capacity retention of >90% over 50 cycles at C/10 rate. With LiNO3 additive in the electrolyte, the cell shows a reversible capacity of >1000 mAh g(-1) and a capacity retention of >80% over 100 cycles at C/5 rate.