As global energy priorities shift toward sustainable alternatives, the need for innovative energy storage solutions becomes increasingly crucial. In this landscape, solid-state batteries (SSBs) emerge as a leading contender, offering a significant upgrade over conventional lithium-ion batteries in terms of energy density, safety, and lifespan. This review provides a thorough exploration of SSBs, with a focus on both traditional and emerging cathode materials like lithium cobalt oxide (LiCoO2), lithium manganese oxide (LiMn2O4), lithium iron phosphate (LiFePO4), as well as novel sulfides and oxides. The compatibility of these materials with solid electrolytes and their respective benefits and limitations are extensively discussed. The review delves into the structural optimization of cathode materials, covering strategies such as nanostructuring, surface coatings, and composite formulations. These are critical in addressing issues like conductivity limitations and structural vulnerabilities. We also scrutinize the essential roles of electrical and thermal properties in maintaining battery safety and performance. To conclude, our analysis highlights the revolutionary role of SSBs in the future of energy storage. While substantial advancements have been made, the path forward presents numerous challenges and research opportunities. This review not only acknowledges these challenges, but also points out the need for scalable manufacturing approaches and a deeper understanding of electrode–electrolyte interactions. It aims to steer the scientific community toward addressing these challenges and advancing the field of SSBs, thereby contributing significantly to the development of environmentally friendly energy solutions.