From coordination polymers to anode-less sodium batteries: optimizing structural and electrochemical parameters for enhanced cycling stability

Abstract The growing demand for sustainable and high-performance energy storage systems has intensified research into cost-effective alternatives to lithium-ion batteries. Sodium-ion batteries (SIBs) represent a promising option due to the abundance and low cost of sodium, although its larger ionic radius and mass limits the achievable energy density. To overcome this limitation, the development of anode-less architecture offers a viable strategy to improve energy density by reducing cell weight and simplifying electrodes design. However, issues such as non-uniform sodium deposition, dendrite formation, and instability of the solid-electrolyte interphase remain major challenges for long-term operation. In this work, we conducted a systematic study to elucidate the influence of metal-center selection, ligand modification, electrolyte formulation, current density, and electrode porosity on sodium plating and stripping behavior. Coordination polymers were investigated as low-cost and scalable sodiophilic current collectors, capable of promoting uniform sodium nucleation and growth. Among the synthesized materials, Zn-based polymers exhibited the most stable electrochemical performance, attributed to the strong sodiophilic nature of zinc, and annealing-induced ligand modification further enhanced Lewis’s acid-base interactions with sodium, drastically improving interface stability. When tested in full cells with Prussian blue cathodes, the optimized configuration demonstrated excellent cycling stability and nearly 100% coulombic efficiency over 1000 cycles, highlighting the high potential of this approach for next-generation, high-efficiency SIBs.