A high energy density Li2S@C nanocomposite cathode with a nitrogen-doped carbon nanotube top current collector

Abstract

Lithium sulfide (Li₂S), with a high theoretical capacity of 1166 mA h g⁻¹, is considered as one of the most promising cathode materials for the next-generation lithium-ion batteries. In this work, a novel cell configuration with a top current collector was designed for Li₂S based batteries. The nitrogen-doped carbon nanotube (N-CNT) film was applied on top of the cathode, which serves not only as a top current collector but also as a barrier layer to effectively impede the polysulfide diffusion and enhance the utilization of active materials. A sheet-like Li₂S@C nanocomposite was synthesized from low-cost and environmentally friendly raw materials of lithium sulfate (Li₂SO₄) and activated graphite. The as-prepared Li₂S@C composites were directly used as cathode materials without adding any binder or carbon additive, which enabled a high Li₂S loading up to 68% in the total cathode weight. The cells exhibited superior electrochemical performance. The specific energy at 0.5C was 804 W h kg⁻¹ based on the total electrode weight including the N-CNT top current collector, which is among the highest values demonstrated so far for sulfur and Li₂S cathodes.