Increasing global population, global warming and depletion of fossil fuels have resulted in a growing need for better energy storage. Lithium-ion batteries are promising devices for this purpose, but have safety issues due to the presence of a liquid electrolyte. We can overcome these by replacing this liquid with a solid-state lithium electrolyte with the same structure as the mineral garnet. These are inert, unreactive oxide materials that will act as a heat sink to inhibit dangerous runaway reactions that can occur in batteries. Neutrons are uniquely able to identify the complex mixture of materials that arise as these garnets are formed from heating reaction mixtures. By examining these reactions we will be able to determine the cause of any instability in the garnet phase and so move towards safer, higher performance battery materials.