With today's rapidly increasing demand for lithium-ion batteries (LIBs) for emerging applications, such as electric vehicles (EVs) and large-scale grid storage, it begs the question of how sustainable batteries really are. Proponents of increasing electrification of our modern society often tout the environmental benefits of using battery energy storage over traditional fossil fuels, citing direct reductions in greenhouse gas emissions, especially when paired with renewable energy generation. Unfortunately, these often leave out considerations for the “dark side” of LIBs that few manufacturers in the battery industry have addressed: how to deal with batteries at their end of life. As the world accelerates toward displacing conventional vehicles with EVs, methods of handling large volumes of spent LIBs when these devices reach their end of life have not been fully developed. This potentially results in the accumulation of battery waste that will ultimately undo the environmental benefits batteries originally sought to achieve.