The dimensions of nanoribbons have a significant impact on their material properties. In the fields of optoelectronics and spintronics, one-dimensional nanoribbons exhibit distinct advantages due to their low-dimensional and quantum restrictions. Novel structures can be formed by combining silicon and carbon at different stoichiometric ratios. Using density functional theory, we thoroughly explored the electronic structure properties of two kinds of silicon–carbon nanoribbons (penta-SiC2and g-SiC3nanoribbons) with different widths and edge conditions. Our study reveals that the electronic properties of penta-SiC2and g-SiC3nanoribbons are closely related to their width and orientation. Specifically, one type of penta-SiC2nanoribbons exhibits antiferromagnetic semiconductor characteristics, two types of penta-SiC2nanoribbons have moderate band gaps, and the band gap of armchair g-SiC3nanoribbons oscillates in three dimensions with the width of the nanoribbon. Notably, zigzag g-SiC3nanoribbons exhibit excellent conductivity, high theoretical capacity (1421 mA h g−1), moderate open circuit voltage (0.27 V), and low diffusion barriers (0.09 eV), making them a promising candidate for high storage capacity electrode material in lithium-ion batteries. Our analysis provides a theoretical basis for exploring the potential of these nanoribbons in electronic and optoelectronic devices as well as high-performance batteries.