High-voltage anode-free sodium–sulfur batteries
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Article Date: 07 January 2026
Article URL: https://www.nature.com/articles/s41586-025-09867-2
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Summary
This Nature paper presents a high-voltage, anode-free sodium–sulfur (Na–S) battery that uses a reversible high-valent sulfur redox chemistry (S/SCl4) in a chloroaluminate-based electrolyte (notably NaDCA in SOCl2). The authors demonstrate anode-free operation by plating sodium onto an aluminium current collector, verify reversible conversion between S8 and SCl4 using TOF-SIMS and GC-HRMS, and show strong electrochemical performance across multiple formats: pouch cells, scalable dry-coated cathodes and fibre-shaped wearable cells. The work combines experimental electrochemistry, operando characterisation and DFT modelling to explain reaction pathways and interfacial behaviour.
Key Points
- The team reports an anode-free Na–S cell based on a high-voltage S/SCl4 redox couple with a theoretical S capacity up to ~3,350 mAh g−1 (sulfur basis).
- A chloroaluminate electrolyte (8 M AlCl3 with 4.5 M NaDCA in SOCl2) enables reversible S↔SCl4 conversion and stabilises Na plating on Al foil, allowing anode-free operation.
- Surface and bulk analyses (TOF-SIMS, GC-HRMS, operando XRD, Raman, XPS) confirm formation and reversible cycling of high-valent sulfur species and characterise shuttle/intermediate behaviour.
- Demonstrations include pouch cells, scalable dry-coated S cathodes (large-area, high mass loading) and a fibre-shaped wearable Na–S battery that survives bending, cutting and extreme conditions.
- Electrode-level energy density and power density reach practical values (example: 226 Wh kg−1 and 694 W kg−1 for a Bi-COF/S cathode configuration under reported conditions).
- The study also reports anode-free Li–S demonstrations using analogous chemistry and uses DFT to probe reaction pathways and energetics.
Content summary
The authors develop an anode-free Na–S architecture by pairing a sulphur cathode that cycles between elemental S and a chlorinated high-valent species (SCl4) with a highly concentrated chloroaluminate electrolyte containing NaDCA. They show that sodium can be plated and stripped reversibly on Al foil in this electrolyte, eliminating the need for pre-installed sodium metal anodes.
Comprehensive characterisation (operando XRD, TOF-SIMS, GC-HRMS, Raman, XPS) tracks the formation and consumption of SCl4 and related intermediates, while DFT calculations illuminate likely reaction pathways and energetics. The authors address shuttle phenomena, cathode carbon surface effects (Ketjenblack versus acetylene black), and Na deposition morphology. Practical advances include a dry-coating process for large-area S cathodes and fibre-shaped cells for wearable applications. Supplementary materials provide extended figures, tables and videos (pouch-cell behaviour after being cut open and continued LED powering for ~20 minutes are shown).
Context and relevance
Na–S systems have long been attractive because sodium and sulphur are abundant and low cost. Historically, most Na–S work either required high temperatures or struggled with sodium anode issues and polysulphide shuttling. This work is important because it combines a novel high-valent S redox chemistry with an electrolyte that enables stable anode-free operation and scalable cathode processing, addressing several practical bottlenecks at once: energy density, safety (no excess Na metal), and manufacturability.
For researchers and engineers working on post-lithium chemistries, large-scale energy storage or flexible power sources, the demonstrated electrode-level energy metrics, the scalable dry-coating method and the wearable fibre cell all point to clearer routes from lab concept to application. The accompanied mechanistic characterisation helps the field understand how to control shuttle effects and Na deposition in anode-free designs.
Why should I read this?
Short version: it’s a neat trick that could make sodium–sulfur cells actually useful beyond the lab. The team shows chemistry and engineering fixes that let the cell run at higher voltage, ditch the bulky sodium anode and scale up the cathode. If you care about cheaper, safer large-scale batteries or clever wearable power, this paper saves you reading dozens of incremental studies by bundling mechanistic insight with practical demos.
Author style
Punchy: this is a landmark experimental demonstration that stitches together new redox chemistry, electrolytes and cell formats. If you’re tracking next-generation Na-based systems, this is high on the must-read list — it doesn’t just report a subtle improvement, it lays out practical steps (electrolyte formulation, scalable cathode manufacture, wearable cell demos) that materially advance the technology readiness of anode-free Na–S batteries.