Pyrolysis temperature dependence of sodium storage mechanism in non-graphitizing carbons

• Published in: Carbon (New York) Vol. 208; pp. 216 - 226
• Main Authors: Tonnoir, Hélène, Huo, Da, Davoisne, Carine, Celzard, Alain, Fierro, Vanessa, Saurel, Damien, El Marssi, Mimoun, Benyoussef, Manal, Meunier, Philippe, Janot, Raphaël
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.05.2023; Elsevier
• Subjects: Chemical Sciences; Hard carbon; In situ Raman spectroscopy; Material chemistry; Porosity; SAXS; Sodium-ion battery; Hard carbon; Sodium-ion battery; Porosity; In situ Raman spectroscopy; SAXS
• ISSN: 0008-6223; 1873-3891
• DOI: 10.1016/j.carbon.2023.03.055

Hard carbons are the most investigated materials as negative electrode for Na-ion batteries, although the exact mechanism of sodium storage remains under debate. This work is focused on the study of the sodiation mechanism of non-graphitizing carbons (NGC) prepared in a wide range of pyrolysis temperatures (1000 °C–2500 °C), thus covering the whole range from hard carbons (HC) to glassy carbons (GC). Structural and textural characterizations show that increasing the pyrolysis temperature leads to NGCs with a more ordered structure, containing fewer heteroatoms and structural defects, and particularly leads to a developed closed microporosity. In this work, in situ Raman spectroscopy at different excitation wavelengths is used to clarify the mechanism of electrochemical sodiation: it is revealed that the intercalation of Na+ between the graphene layers occurs mainly during the sloping part of the galvanostatic profile, whereas the plateau at low voltage (below 0.1 V vs. Na+/Na) can be associated with the filling of micropores with sodium. [Display omitted] •Hard and glassy carbons are synthesized at four different pyrolysis temperatures.•Materials characterizations are structural, textural and electrochemical.•Pyrolysis temperature dependence of structure, performance and Na storage mechanism.•Multi-wavelength Raman spectroscopy is used for structural and mechanistic studies.•In situ Raman spectroscopy shows intercalation-pore filling mechanism.