Improving the energy density of Li-ion batteries is critical to meet the requirements of electric vehicles and energy storage systems. In this work, LiFePO₄ active material was combined with single-walled carbon nanotubes as the conductive additive to develop high-energy-density cathodes for rechargeable Li-ion batteries. The effect of the morphology of the active material particles on the cathodes’ electrochemical characteristics was investigated. Although providing higher packing density of electrodes, spherical LiFePO₄ microparticles had poorer contact with an aluminum current collector and showed lower rate capability than plate-shaped LiFePO₄ nanoparticles. A carbon-coated current collector helped enhance the interfacial contact with spherical LiFePO₄ particles and was instrumental in combining high electrode packing density (1.8 g cm⁻³) with excellent rate capability (100 mAh g⁻¹ at 10C). The weight percentages of carbon nanotubes and polyvinylidene fluoride binder in the electrodes were optimized for electrical conductivity, rate capability, adhesion strength, and cyclic stability. The electrodes that were formulated with 0.25 wt.% of carbon nanotubes and 1.75 wt.% of the binder demonstrated the best overall performance. The optimized electrode composition was used to formulate thick free-standing electrodes with high energy and power densities, achieving the areal capacity of 5.9 mAh cm⁻² at 1C rate.

The need for an alternative to lithium-ion batteries motivates the development of sodium-ion batteries, specifically focusing on biomass-derived hard carbon (HC) as anode material. However, the compositional variability in biomass leads to a lack of correlation between the microstructure and properties of HC. In this study, we used four simple carbohydrates present in all biomass-derived precursors as model objects to establish a reliable relationship between pretreatment temperature, the carbonization mechanism, defectiveness, and the electrochemical characteristics of HCs. The statistical analysis of Raman spectra from 25 HC samples enabled us not only to determine the degree of defectiveness in HCs but also, for the first time, to compare materials based on their inhomogeneity—that is, the variation in defectiveness within each HC material. The initial Coulombic efficiency of hard carbons was improved by 40%, reaching 89%, through the simultaneous reduction of surface area, defectiveness, and inhomogeneity. Additionally, the full cell with the HC and Na₃V₂(PO₄)₃/С cathode material demonstrated 80% capacity retention after 300 cycles.