BNNT Electrode Coatings for Polysulfide Blocking and Dendrite Control

The patent employs a porous carbon-coated separator that utilizes the porous structure to physically trap polysulfides within its matrix. The porous network provides abundant trapping sites while maintaining ion transport pathways, achieving polysulfide absorption without requiring thick or complex interlayer structures. This resolves the contradiction by using the porous architecture itself as the functional mechanism rather than adding separate absorbing materials.

The carbon-coated separator performs multiple functions simultaneously: it acts as a physical barrier to polysulfide diffusion, provides electrochemical activity for polysulfide conversion, maintains ionic conductivity for Li-ion transport, and provides mechanical support. This multi-functionality eliminates the need for separate interlayer components, reducing overall device complexity while maintaining improved cycling life.

The porous carbon-coated separator achieves effective polysulfide absorption with minimal mass by utilizing its three-dimensional porous network. The high surface area to volume ratio of the porous structure provides abundant polysulfide trapping sites without requiring thick layers or heavy materials, thus improving cycling life while minimizing weight penalty.

The carbon coating is applied locally on the separator surface where polysulfide interaction is most critical. This localized functionalization provides polysulfide absorption capability exactly where needed at the cathode-separator interface, avoiding the need for thick uniform layers throughout the entire separator structure, thereby reducing overall mass while maintaining performance.

The patent introduces a protective interlayer between the metal anode and electrolyte that acts as an intermediary. This interlayer mediates the interaction between metal ions and the anode surface, providing a uniform deposition interface that prevents direct contact between electrolyte and metal anode. This intermediary layer suppresses dendrite formation while allowing high-capacity metal anodes to function, thus maintaining both high specific capacity and improved cycling reliability.

The protective interlayer is pre-formed on the metal anode surface before battery operation begins. This preliminary action creates a stable interface that guides uniform metal ion deposition from the start of cycling, preventing the initial uneven deposition that leads to dendrite formation. The pre-established protective layer ensures reliable cycling capability while maintaining the high capacity benefits of metal anodes.

The porous carbon-coated separator utilizes its porous structure to physically confine polysulfides within its matrix while maintaining pathways for Li-ion transport. The porous network provides abundant trapping sites that prevent polysulfide dissolution into the bulk electrolyte, eliminating the harmful shuttle effect while preserving the high energy density characteristics of lithium-sulfur batteries.

The patent employs a composite structure combining the separator base material with a carbon coating layer. This composite provides both the mechanical support and ionic conductivity of the separator and the polysulfide absorption and electrochemical activity of carbon. The composite structure effectively addresses polysulfide dissolution while maintaining the high specific energy performance of lithium-sulfur batteries.