Partially carbonised carbon fibres as improved electrodes for structural battery applications

communications materials Article A Nature Portfolio journal https://doi.org/10.1038/s43246-026-01194-x Partially carbonised carbon fibres as improved electrodes for structural battery applications Check for updates 1 1234567890():,; 1234567890():,; Ruben Tavano , James D. Randall Luke C. Henderson 2 & Leif E. Asp 1 2 2 2 , Nguyen Nguyen Le Thao , Claudia Creighton , Johanna Xu 1 , Carbon fibres are promising materials for structural battery anodes because they can simultaneously provide mechanical reinforcement and act as the electrochemically active material. Their performance depends strongly on their internal structure, which is influenced by the temperature used during carbonisation. Here, we show that partially carbonised carbon fibres produced at different maximum carbonisation temperatures (800 °C to 1100 °C) display systematic changes in both mechanical and electrochemical behaviour. Mechanical testing shows that increasing the carbonisation temperature leads to higher stiffness and tensile strength. Electrochemical measurements reveal a similar trend, with higher reversible capacity and improved cycling stability at higher temperatures. Thus, results show that the general antagonistic dependence on carbonisation temperature observed for conventional carbon fibres is not found for partially carbonised fibres. The partially carbonised fibres show up to 40 percent better electrochemical performance than conventional intermediate modulus carbon fibres. These results highlight the potential in the use of partially carbonised carbon fibres for next-generation structural battery composites, allowing for an expanded multifunctional design window. The development of multifunctional materials is transforming energy storage technologies, especially for applications in transportation and portable electronics. Structural battery composites (SBCs) are a promising concept, combining mechanical strength with energy storage capability1–3. By allowing structural components to also store energy, SBCs can reduce overall system weight and improve energy efficiency. This is achieved using materials such as carbon fibres, which provide good mechanical properties while also allowing lithium-ion storage within their microstructure. Typically, SBCs are made from thin-ply carbon fibre tows that act as negative electrodes, stacked with separators and counter electrodes2,4–9. These assemblies are infused with a structural battery electrolyte (SBE), which contributes to both ionic movement and mechanical load transfer between the layers10–15. Although the mechanical behaviour of commercial carbon fibres is well established, due to their longstanding use in composite applications, their electrochemical characteristics remain highly underexplored. The use of carbon fibres as active material in lithium-ion battery negative electrodes was first explored in 199016. This early investigation highlighted the critical relationship between carbon fibre microstructure and electrochemical behaviour. Building on this foundation, Snyder et al. demonstrated that carbon fibres derived from polyacrylonitrile (PAN) precursors exhibit superior lithium-ion intercalation properties compared to their pitch-based counterparts, with more than double the capacity at slow C-rates17. Studies by Jacques et al. and Duan et al. provided early insights into the effects of lithium insertion on the structural and mechanical integrity of these fibres18–21. Furthermore, Kjell et al. systematically evaluated the electrochemical performance of common PAN-based carbon fibres, while Hagberg et al. compared the lithiation behaviour of intermediate modulus (IM) fibres like T800 and IMS65 against high modulus (HM) variants such as M60J using precise coulometry analyses22,23. IM fibres generally delivered higher electrochemical capacities (with reversible capacities up to 140 mAh g−1), although the reasons for this performance difference were not immediately evident. Fredi et al. utilised high-resolution transmission electron microscopy and in-situ Raman spectroscopy to uncover distinct lithiation behaviour among T800, IMS65, and M60J fibres24. Their results revealed that IM fibres displayed behaviour akin to amorphous carbon during lithium insertion, with unique lithiation signatures for each fibre type. In contrast, the HM fibre followed a more graphite-like staging 1 Department of Mechanical Engineering, Chalmers University of Technology, Göteborg, Sweden. 2Institute for Frontier Materials, Deakin University, Waurn Ponds, e-mail: ; VIC, Australia. Communications Materials | (2026)7:135 1 Article https://doi.org/10.1038/s43246-026-01194-x Table 1 | Physical properties for the partially carbonised carbon fibres, and comparison with FC and T800 fibres Fibre type Density [g cm−3] Fibre diameter [μm] BET surface area [m2 g−1] Electrical conductivity [S cm−1] T80059 1.800 5.00 0.52 714.34 FC 1.793 7.50 1.17 675.52 PC800 1.737 8.82 1.10 0.10 PC900 1.758 8.34 1.14 5.65 PC1000 1.765 8.15 1.02 63.09 PC1100 1.780 7.93 1.08 253.40 mechanism that was obstructed by structural defects within its large crystalline domains, ultimately limiting its lithium capacity. Johansen et al. extended this understanding by analysing the impact of nitrogen heteroatoms in the fibre microstructure25. They observed that IMS65 contained a higher proportion of pyridinic and pyrrolic nitrogen (20.5%) compared to T800 (14.2%). Since these nitrogen species tend to localise at defect sites and enhance lithium coordination, their elevated concentration in IMS65 likely contributed to its superior electrochemical performance compared to T800 fibres. More recently, Asp et al. highlighted the potential of IM fibres in multifunctional applications by integrating a T800 fibre tow into a laminated SBC, where it served as the negative electrode26. The resulting prototype combined a specific energy of 24 Wh kg−1 with a tensile stiffness of 25 GPa, demonstrating effective dual functionality. Building on this, Chaudhary et al. developed the first all-fibre-based SBC using lithium iron phosphate-coated carbon fibres as the positive electrode27,28. This advancement enhanced the structural performance, delivering a tensile modulus of 76 GPa, albeit with a slight improvement in energy density, which reached 30 Wh kg−1. Despite these recent developments, several key challenges remain. Commercial carbon fibres have been optimised exclusively for mechanical performance, with no consideration for electrochemical properties. This situation is further complicated by limited transparency around proprietary production features, such as precursor chemistry and processing steps, and the widespread use of sizing agents, whose composition can significantly influence electrochemical performance29,30. To address these limitations, researchers, including Xu et al. and Tavano et al. have investigated customised carbon fibres made from the same PAN-based precursor, each introdu (...truncated)