The global transition to renewable energy and electrified transport depends on scalable, affordable, and secure battery storage technologies. Lithium-ion batteries (LIBs) currently dominate this sector due to their high energy density, long cycle life, and mature manufacturing infrastructure. However, increasing demand for lithium, cobalt, and nickel has exposed major supply chain vulnerabilities, including geographic concentration, refining bottlenecks, price volatility, environmental impacts, and social concerns associated with critical metal extraction. This study aims to critically compare lithium- and sodium-based battery technologies by examining their electrochemical fundamentals, critical material requirements, supply chain risks, environmental footprints, technical limitations, commercial readiness, and application-specific suitability. The study finds that sodium-ion batteries (SIBs) offer important strategic advantages due to the abundance and wide distribution of sodium, reduced dependence on cobalt and nickel, compatibility with aluminium current collectors on both electrodes, and potential cost and sustainability benefits in stationary and low-cost mobility applications. Key technical findings show that SIBs still face lower gravimetric and volumetric energy density, slower ion transport, hard carbon initial Coulombic efficiency losses, cathode phase instability, and electrolyte/interface challenges. Nevertheless, recent advances in hard carbon anodes, layered oxide cathodes, polyanionic frameworks, Prussian blue analogues, and electrolyte engineering are narrowing the performance gap. All in all, LIBs and SIBs are best understood as complementary technologies: LIBs will remain dominant in high-energy mobile applications, while SIBs are strategically positioned for grid storage, backup power, and micromobility, supporting a more resilient and diversified energy storage future.