Search for: All records

Abstract All‐solid‐state sodium ion batteries (AS³iBs) are highly sought after for stationary energy storage systems due to their suitable safety and stability over a wide temperature range. Hard carbon (HC), which is low cost, exhibits a low redox potential, and a high capacity, is integral to achieve a practical large‐scale sodium‐ion battery. However, the energy density of the battery utilizing this anode material is hampered by its low initial Coulombic efficiency (ICE). Herein, two strategies, namely i) additional pyrolysis and ii) presodiation by thermal decomposition of NaBH₄, are explored to improve the ICE of pristine HC. Raman spectroscopy, X‐ray photoelectron spectroscopy, and electrochemical characterizations elucidate that the thermal treatment increases the C_sp2content in the HC structure, while the presodiation supplies the sodium to occupy the intrinsic irreversible sites. Consequently, presodiated HC exhibits an outstanding ICE (>99%) compared to the thermally treated (90%) or pristine HC (83%) in half‐cell configurations. More importantly, AS³iB using presodiated HC and NaCrO₂as the anode and cathode, respectively, exhibits a high ICE of 92% and an initial discharge energy density of . 

Abstract Lithium/fluorinated graphite (Li/CF_x) primary batteries show great promise for applications in a wide range of energy storage systems due to their high energy density (>2100 Wh kg^–1) and low self‐discharge rate (<0.5% per year at 25 °C). While the electrochemical performance of the CF_xcathode is indeed promising, the discharge reaction mechanism is not thoroughly understood to date. In this article, a multiscale investigation of the CF_xdischarge mechanism is performed using a novel cathode structure to minimize the carbon and fluorine additives for precise cathode characterizations. Titration gas chromatography, X‐ray diffraction, Raman spectroscopy, X‐ray photoelectron spectroscopy, scanning electron microscopy, cross‐sectional focused ion beam, high‐resolution transmission electron microscopy, and scanning transmission electron microscopy with electron energy loss spectroscopy are utilized to investigate this system. Results show no metallic lithium deposition or intercalation during the discharge reaction. Crystalline lithium fluoride particles uniformly distributed with <10 nm sizes into the CF_xlayers, and carbon with lower sp²content similar to the hard‐carbon structure are the products during discharge. This work deepens the understanding of CF_xas a high energy density cathode material and highlights the need for future investigations on primary battery materials to advance performance.