Optical clocks and frequency standards are the most precise measurement devices available today. However, further improvements are needed to extend applications in communication, in navigation and in fundamental metrology. This project will investigate laser-cooled trapped ions as a reference for a next generation of optical clocks of highest accuracy. While most precise optical clocks with trapped ions are based on single ions, this project will investigate large ensembles of ions in a Coulomb-coupled solid-like state, known as Coulomb crystals (CCs). The multi-ion approach used in this project will provide higher signal-to-noise for clocks of improved stability, enable the investigation of small frequency shifts caused by collisions with neutral particles or interactions between the ions, and the opportunity to study new systems which may show improved uncertainty.