Green biomass-derived hierarchically porous non-activated carbon from carob waste for high-performance lithium-sulfur batteries

Abstract

To expedite the development of lithium-sulfur (Li–S) battery technology, it is necessary to address the inherent technological hurdles surrounding sulfur-based cathodes, including mitigating the shuttle effect and enhancing the electrical conductivity of sulfur. The use of biomass-derived carbonaceous materials offers a promising avenue to alleviate these challenges and help reduce the carbon footprint associated with battery technologies. Herein, we report the green synthesis of carob-derived carbonaceous material without additional physical/chemical activation steps, making the process sustainable, affordable, and eco-friendly. The obtained carob-derived carbon (CC) offers a hierarchical micro/meso/macroporous structure with a high surface area of 633 m² g⁻¹. The electrochemical performance with a sulfur content of 70% (CC@S70) in the composite and a sulfur mass loading of 1 mg cm⁻² delivers an initial discharge capacity of 1405 mAh g⁻¹, reducing to 798 mAh g⁻¹ after 260 cycles. Increasing the sulfur content to 90% in the cathode (CC@S90) yields a high capacity in Li–S cells, reaching a discharge capacity of 937 mAh g⁻¹ with a sulfur loading of 2 mg cm⁻² at 0.3C (1C = 1675 mA g⁻¹) after 100 cycles. The improved performance can be attributed to the well-preserved interconnected pores within the carbon material, serving as an efficient framework to accommodate high sulfur content.