Untapped potential and prospects for non-lithium closed static “electrode-free” electrochemical energy storage architectures

Electrochemical energy storage technologies are pivotal in modern living and play a key role in global decarbonization and sustainability. Some applications, such as land and aerial electric vehicles, demand high gravimetric and volumetric energy densities. Simply altering the chemistry may not meet the requirement of these applications. Electrode-free architectures are viewed as a potential solution to meet the techno-economic requirements of these applications. While lithium (Li)-based batteries have predominantly been demonstrated in academic research using electrode-free architectures, concerns over Li supply could pose challenges to the global energy transition. Academia, industry, and governments explore non-Li-based batteries to diversify away from a dependence on Li in the global economy and energy systems. This review showcases notable demonstrations of non-Li-based electrode-free batteries, encompassing not only sodium (Na) but also other redox couples such as potassium (K), magnesium (Mg), zinc (Zn), aluminum (Al), and manganese dioxide (MnO₂), while providing quantitative assessments of the enhancements in capacity and energy density. Additionally, this review offers insights and prospective paths for non-Li electrode-free battery architectures.