Realizing anode-free potassium-organic batteries via sacrificial potassium superoxide additives

• For the first time, potassium superoxide (KO 2 ) has been employed as a sacrificial cathode additive to provide an external supply of potassium ion (K + ) source, successfully addressing the issue of initial K + source scarcity in anode-free potassium-organic batteries. • The decomposition of KO 2 only releases K + and gaseous oxygen without any harmful solid residues. • The decomposition process of KO 2 relies on the migration and transfer of soluble superoxide anion, which is highlighted with fast reaction kinetics (overpotential below 190 mV) and high utilization (97.9% of the theoretical capacity) in the absence of additional conductive agents. • A low-cost and high-safety chemical synthesis route for KO 2 has been developed: high-purity KO 2 can be prepared in just 5 minutes at room temperature with an estimated only 1/3 cost compared to the commercial one. • The KO 2 -based cathode additive is highly compatible with the existing dry-room manufacturing, significantly lowering the threshold for the practical application of anode-free batteries. Equipped with an organic cathode and a bare anode current collector, the anode-free potassium-organic batteries present remarkable benefits in terms of reduced cost and elevated safety. However, it is challenging to realize such anode-free organic batteries, especially considering the complete absence of potassium ion (K + ) source preserved on both electrodes. Here, we have first introduced potassium superoxide (KO 2 ) as a preloaded sacrificial agent on an organic cathode, serving as an external K + supply in an initial anode-free potassium-organic cell architecture. It is shown that the unique solution-mediated decomposition mechanism of KO 2 endows its high compensation capacity of 368.9 mAh/g (97.9% of the theoretical value) and low decomposition overpotential of below 190 mV in the absence of additional conductive agents. Differential electrochemical mass spectrometry further confirms the single-electron transfer process for the KO 2 decomposition with minimal CO 2 evolution. A proposed chemical route for synthesizing high-purity KO 2 could further reduce its cost and enhance synthesis efficiency (typically in 5 minutes). The proof-of-concept of anode-free organic cell configuration is demonstrated with a decent lifespan (retaining 84.9 mAh/g after 300 cycles) and reversibility (average coulombic efficiency of 99.5%). The use of KO 2 -based cathode additives offers an effective route to address the initial K + deficiency and enhances the electrochemical performance of burgeoning potassium-organic batteries. “Clean” superoxide-based cathode additives. This study introduces potassium superoxide (KO 2 ) as a residue-free and sacrificial cathode additive to resolve the initial potassium ion (K + ) deficiency in anode-free potassium-organic batteries. Its unique solution-mediated decomposition mechanism enables efficient K + compensation with minimal overpotential and high capacity. A proposed chemical route for synthesizing high-purity KO 2 further reduces its cost and enhances safety. The development of superoxide-based cathode additives brings practical anode-free batteries closer to reality.