This article reflects on the evolution of lithium-ion battery cathode chemistry, highlighting the fundamental research that has driven the development of high-energy density electrode materials. The emergence and dominance of lithium-ion batteries are attributed to their higher energy density compared to other rechargeable battery systems. The review focuses on three major categories of oxide cathodes: layered, spinel, and polyanion families, which were discovered in the 1980s by John Goodenough's group at the University of Oxford and the University of Texas at Austin. These cathodes have significantly increased the operating voltage and energy density of lithium-ion batteries, enabling their widespread use in portable electronics, electric vehicles, and renewable energy storage. The article also discusses the advantages and disadvantages of each cathode class, emphasizing the need for further research to address challenges such as cost, sustainability, and performance stability. Finally, it outlines future directions, including the exploration of lithium-rich layered oxides and conversion-reaction cathodes like sulfur and oxygen, while acknowledging the ongoing efforts to improve the practical viability of these materials.This article reflects on the evolution of lithium-ion battery cathode chemistry, highlighting the fundamental research that has driven the development of high-energy density electrode materials. The emergence and dominance of lithium-ion batteries are attributed to their higher energy density compared to other rechargeable battery systems. The review focuses on three major categories of oxide cathodes: layered, spinel, and polyanion families, which were discovered in the 1980s by John Goodenough's group at the University of Oxford and the University of Texas at Austin. These cathodes have significantly increased the operating voltage and energy density of lithium-ion batteries, enabling their widespread use in portable electronics, electric vehicles, and renewable energy storage. The article also discusses the advantages and disadvantages of each cathode class, emphasizing the need for further research to address challenges such as cost, sustainability, and performance stability. Finally, it outlines future directions, including the exploration of lithium-rich layered oxides and conversion-reaction cathodes like sulfur and oxygen, while acknowledging the ongoing efforts to improve the practical viability of these materials.