After receiving her Ph.D., Takeuchi worked as a postdoctoral fellow at the University of North Carolina at Chapel Hill. This experience provided valuable research experience.

One of Takeuchi's earliest and most impactful contributions was the invention of the lithium/silver vanadium oxide (Li/SVO) battery. This battery offered significantly longer life and higher energy density compared to existing batteries, revolutionizing the field of implantable medical devices, particularly cardiac defibrillators. Her invention dramatically reduced the frequency of battery replacement surgeries, improving patient outcomes and quality of life.

Takeuchi began her career at Wilson Greatbatch Ltd., a leading manufacturer of batteries for implantable medical devices. Here she developed and perfected her Lithium/Silver Vanadium Oxide battery.

Takeuchi transitioned to academia, joining the faculty at the University at Buffalo. Her research focused on developing new and improved energy storage technologies, including batteries, supercapacitors, and fuel cells. She mentored numerous students and postdocs, shaping the next generation of electrochemical engineers.

Takeuchi served as the Chief Scientist of the Energy Storage Division at Brookhaven National Laboratory. She focused on fundamental research and development in electrochemical energy storage, particularly for applications such as electric vehicles and grid-scale energy storage.

Takeuchi joined Stony Brook University as a Distinguished Professor. Here she continued to research and teach materials science.