'Beyond Li-ion technology'-a status review

Li-ion battery is currently considered to be the most proven technology for energy storage systems when it comes to the overall combination of energy, power, cyclability and cost. However, there are continuous expectations for cost reduction in large-scale applications, especially in electric vehicles and grids, alongside growing concerns over safety, availability of natural resources for lithium, and environmental remediation. Therefore, industry and academia have consequently shifted their focus towards 'beyond Li-ion technologies'. In this respect, other non-Li-based alkali-ion/polyvalent-ion batteries, non-Li-based all solid-state batteries, fluoride-ion/ammonium-ion batteries, redox-flow batteries, sand batteries and hydrogen fuel cells etc. are becoming potential cost-effective alternatives. While there has been notable swift advancement across various materials, chemistries, architectures, and applications in this field, a comprehensive overview encompassing high-energy 'beyond Li-ion' technologies, along with considerations of commercial viability, is currently lacking. Therefore, in this review article, a rationalized approach is adopted to identify notable 'post-Li' candidates. Their pros and cons are comprehensively presented by discussing the fundamental principles in terms of material characteristics, relevant chemistries, and architectural developments that make a good high-energy 'beyond Li' storage system. Furthermore, a concise summary outlining the primary challenges of each system is provided, alongside the potential strategies being implemented to mitigate these issues. Additionally, the extent to which these strategies have positively influenced the performance of these 'post-Li' technologies is discussed.