Cation-Diffusive Carbon Interlayers Stabilize Na Metal and Double the Current in Na-S Redox-Flow Batteries for Grid-Scale Energy Storage

Wu, Wenda [ORNL] (ORCID:000900033307687X); Goswami, Monojoy [ORNL] (ORCID:0000000244734888); Hsieh, Cheng-Tien [Georgia Institute of Technology]; Kim, Chanho [ORNL] (ORCID:0009000888661407); Li, Yuanshun [ORNL]; Liu, Nian [Geogia Institute of Technology]

doi:10.1002/adfm.202531310

DOE OSTI · 3740813

Cation-Diffusive Carbon Interlayers Stabilize Na Metal and Double the Current in Na-S Redox-Flow Batteries for Grid-Scale Energy Storage

Wu, Wenda [ORNL] (ORCID:000900033307687X)·Goswami, Monojoy [ORNL] (ORCID:0000000244734888)·Hsieh, Cheng-Tien [Georgia Institute of Technology]·Kim, Chanho [ORNL] (ORCID:0009000888661407)·Li, Yuanshun [ORNL]·Liu, Nian [Geogia Institute of Technology]

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Abstract

The sodium-sulfur nonaqueous redox-flow batteries (Na-S NARFBs) using earth-abundant elements are highly attractive due to the low material cost and improved energy density for grid-scale energy storage. However, the low current performance, poor Na0/Na+ redox kinetics, and Na dendrite growth pose severe challenges. We introduce cation-diffusive layers (CDLs): thin and Na+ affinitive interlayers at the Na anode that direct Na+ transport and stabilize Na deposition. Benchmarking three archetypal materials—carbon paper (CP), glass microfiber paper (GF), and foam—across Na-Na and Na-Cu, and Na-S cells identifies CP as the optimum. CP reduces symmetric cell overpotential by more than 70%, achieves 98% Na plating-stripping efficiency, and doubles the Na-S cell current density from 0.5 to 1.0 mA cm−2 without sacrificing capacity or efficiency. Ex situ electrochemical and SEM/XPS analysis, combined with molecular dynamics (MD) studies, reveal that electron-rich carbon fibers disperse supporting salt aggregates, enrich near-surface Na+ density, and create ion transport pathways for fast Na0/Na+ exchange while mitigating membrane degradation. Because of the ion-centric mechanism, CDLs can be generalized to other metal-anode designs. Further, this work establishes CDL design rules—cationic affinity and appropriate micro/nanostructure—as a simple, scalable route to high-current, durable metal-anode flow batteries.

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Wu, Wenda [ORNL] (ORCID:000900033307687X), Goswami, Monojoy [ORNL] (ORCID:0000000244734888), Hsieh, Cheng-Tien [Georgia Institute of Technology], Kim, Chanho [ORNL] (ORCID:0009000888661407), Li, Yuanshun [ORNL], Liu, Nian [Geogia Institute of Technology]. 2026-03-01. Cation-Diffusive Carbon Interlayers Stabilize Na Metal and Double the Current in Na-S Redox-Flow Batteries for Grid-Scale Energy Storage. https://doi.org/10.1002/adfm.202531310

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