3D printing CO₂-activated carbon nanotubes host to promote sulfur loading for high areal capacity lithium-sulfur batteries

Lithium-sulfur batteries (LSBs) have emerged as a promising high energy density system in miniaturized energy storage devices. However, serious issues rooted in large volume change (80%), poor intrinsic conductivity, “shuttle effect” of S cathode, and limited mass loading of traditional electrode still make it a big challenge to achieve high energy density LSBs in a limited footprint. Herein, an innovative carbon dioxide (CO₂) assisted three-dimensional (3D) printing strategy is proposed to fabricate three-dimensional lattice structured CO₂ activated single-walled carbon nanotubes/S composite thick electrode (3DP S@CNTs-CO₂) for high areal capacity LSBs. The 3D lattice structure formed by interwoven CNTs and printed regular macropores can not only act as fast electron transfer networks, ensuring good electronic conductivity of thick electrode, but is beneficial to electrolyte infiltration, effectively boosting ion diffusion kinetics even under a high-mass loading. In addition, the subsequent high-temperature CO₂ in-situ etching can induce abundant nanopores on the wall of CNTs, which significantly promotes the sulfur loading as well as its full utilization as a result of shortened ion diffusion paths. Owing to these merits, the 3DP S@CNTs-CO₂ electrode delivers an impressive mass loading of 10 mg·cm⁻². More importantly, a desired attribute of linearly scale up in areal capacitance with increased layers is observed, up to an outstanding value of 5.74 mAh·cm⁻², outperforming most reported LSBs that adopt strategies that physically inhibit polysulfides. This work provides a thrilling drive that stimulates the application of LSBs in new generation miniaturized electronic devices.