High temperature stabilization of lithium–sulfur cells with carbon nanotube current collector

Abstract

Lithium–sulfur (Li–S) chemistry has been considered for an alternative future generation of rechargeable lithium batteries because of its higher theoretical capacity, safer operation and lower material cost. Here, we report on the impact of temperature on Li–S cell performance. The Li–S coin-cells were prepared by using S infiltrated vertically aligned carbon nanotube arrays (S-CNT) as cathodes and lithium metal foils as anodes. The cells were operated at 25, 50, 70 and 90 °C. Higher temperature operation resulted in higher specific capacity, better rate capability and more stable performance. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and electrochemical impedance spectroscopy (EIS) studies reveal the major impact of temperature on the solid electrolyte interphase (SEI) on Li foil. Thicker SEI with higher content of inorganic phase formed at elevated temperatures greatly reduced both the dendrite formation and the capacity fading resulted from the irreversible losses of S. At 70 °C specific capacities up to ∼700 mAh g−1 were achieved at an ultra-high current density of 3.3 A g−1. At 90 °C and the same current density Li–S cells showed an average capacity of ∼400 mAh g−1 and stable performance for over 150 cycles.