With the rapid advancement of energy storage technologies, there is a growing demand for affordable, efficient, and environmentally benign battery systems. Sodium-ion batteries (SIBs) present a promising alternative to lithium-ion systems due to sodium’s high abundance and similar electrochemical properties. Particular attention is given to developing NASICON -sodium (Na) super ionic conductor, type cathode materials, especially Na3V2(PO4)3, which exhibits high thermal and structural stability. This study focuses on the sol–gel synthesis of Na₃V₂(PO₄)₃ using citric acid and ethylene glycol, as well as investigating the effect of annealing temperature (400–1000 °C) on its structural and electrochemical properties. Phase composition, morphology, textural characteristics, and electrochemical performance were systematically analyzed. Above 700 °C, a highly crystalline NASICON phase free of secondary impurities was formed, as confirmed by X-ray diffraction (XRD). Microstructural evolution revealed a transition from a loose amorphous structure to a dense granular morphology, accompanied by changes in specific surface area and porosity. The highest surface area (67.40 m²/g) was achieved at 700 °C, while increasing the temperature to 1000 °C caused pore collapse due to sintering. X-ray photoelectron spectroscopy (XPS) confirmed the predominant presence of V³⁺ ions and the formation of V⁴⁺ at the highest temperature. The optimal balance of high crystallinity, uniform elemental distribution, and stable texture was achieved at 900 °C. Electrochemical testing in a Na/NVP half-cell configuration delivered an initial capacity of 70 mAh/g, which decayed to 55 mAh/g by the 100th cycle, attributed to solid-electrolyte interphase (SEI) formation and irreversible Na⁺ trapping. These results demonstrate that the proposed approach yields high-quality Na₃V₂(PO₄)₃ cathode materials with promising potential for sodium-ion battery applications.

The depletion of global lithium reserves, coupled with the necessity for environmentally sustainable and economically accessible energy storage systems, has driven the development of sodium-ion batteries (SIBs) as a promising alternative to lithium-ion technologies. Among various anode materials for SIBs, hard carbon exhibits obvious advantages and significant commercial potential owing to its high energy density, low operating potential, and stable capacity retention during prolonged cycling. Biomass represents the most attractive source of non-graphitizable carbon from a practical standpoint, being readily available, renewable, and low-cost. However, the complex internal structure of biomass precursors creates significant challenges for precise control of microstructure and properties of the resulting hard carbon materials, requiring further research and optimization of synthesis methodologies. This work reports the synthesis of hard carbon from Sasa kurilensis via pyrolysis at 900 °C and investigates the effect of alkaline pretreatment on the structural and electrochemical characteristics of the anode material for SIBs. Sasa kurilensis is employed for the first time as a source for non-graphitizable carbon synthesis, whose unique natural vascular structure forms optimal hierarchical porosity for sodium-ion intercalation upon thermal treatment. The materials were characterized by X-ray diffraction, infrared and Raman spectroscopy, scanning electron microscopy, X-ray microtomography and low-temperature nitrogen adsorption–desorption. Electrochemical properties were evaluated by galvanostatic cycling in the potential range of 0.02–2 V at a current density of 25 mAhg⁻¹ in half-cells with sodium metal counter electrodes. The unmodified sample demonstrated a discharge capacity of 160 mAhg⁻¹ by the 6th cycle, with an initial capacity of 77 mAhg⁻¹. The alkaline-treated material exhibited lower discharge capacity (114 mAhg⁻¹) and initial Coulombic efficiency (40%) due to increased specific surface area, leading to excessive electrolyte decomposition.

Lithium-ion batteries require cathode materials with high capacity and cycling stability. Li₃V₂(PO₄)₃ (LVP) offers a theoretical capacity of 197 mAh/g but suffers from poor electronic conductivity. In this study, a Li₃V₂(PO₄)₃/carbon (LVP/C) composite was synthesized via a citric acid-assisted sol–gel method. The effects of pyrolysis temperature (700–1000 °C) and citric acid-to-salt ratio (1:1, 0.5:1, 0.25:1) were systematically investigated. The optimal composite was obtained at 900 °C with a 1:1 ratio. This material exhibited a well-crystallized monoclinic structure (space group P2₁/c) with unit cell volume of 890.61 ų. The amorphous carbon coating provided a specific surface area of 33.03 m²/g. Electrochemically, the optimal LVP/C_1:1 composite delivered an initial specific capacity of 114 mAh/g at C/10 rate—twice that of samples with lower carbon content. It also demonstrated 100% capacity retention after 25 cycles with favorable coulombic efficiency (67%) and reduced charge-transfer resistance. These results show that pyrolysis at 900 °C with a 1:1 citric acid-to-salt ratio provides an optimal balance between crystallinity, carbon coating uniformity, and electrochemical performance for high-performance LVP/C composite cathodes.