Nanostructured S@VACNTs Cathode with Lithium Sulfate Barrier Layer for Exceptionally Stable Cycling in Lithium-Sulfur Batteries

TL;DR

This paper introduces a novel sulfur cathode with a lithium sulfate barrier layer on vertically aligned carbon nanotubes, significantly enhancing cycle life and stability in lithium-sulfur batteries through improved conductivity and polysulfide suppression.

Contribution

It presents a simple modification to sulfur cathodes using VACNTs decorated with sulfur and Li2SO4, achieving high capacity and long cycle life, which is a notable advancement over traditional designs.

Findings

Stable capacity of 0.9 mAh/cm² after 1600 cycles at 1 C

Capacity retention of 80% after 1200 cycles

Demonstrated good performance in full Si-Li-S cells for 100 cycles

Abstract

Lithium-sulfur technology garners significant interest due to sulfur's higher specific capacity, cost-effectiveness, and environmentally friendly aspects. However, sulfur's insulating nature and poor cycle life hinder practical application. To address this, a simple modification to the traditional sulfur electrode configuration is implemented, aiming to achieve high capacity, long cycle life, and rapid charge rates. Binder-free sulfur cathode materials are developed using vertically aligned carbon nanotubes (CNTs) decorated with sulfur and a lithium sulfate barrier layer. The aligned CNT framework provides high conductivity for electron transportation and short lithium-ion pathways. Simultaneously, the sulfate barrier layer significantly suppresses the shuttle of polysulfides. The S@VACNTs with Li 2 SO 4 coating exhibit an extremely stable reversible areal capacity of 0.9 mAh cm --2 after 1600 cycles at 1 C with a capacity retention of 80% after 1200 cycles, over three times higher than lithium iron phosphate cathodes cycled at the same rate. Considering safety concerns related to the formation of lithium dendrite, a full cell Si-Li-S is assembled, displaying good electrochemical performances for up to 100 cycles. The combination of advanced electrode architecture using 1D conductive scaffold with high-specific-capacity active material and the implementation of a novel strategy to suppress polysulfides drastically improves the stability and the performance of Li-S batteries.