A disordered Rubik's cube-inspired framework for sodium-ion batteries with ultralong cycle lifespan.

Sodium-ion batteries (SIBs) with fast-charge capability and long lifespan could be applied in various sustainable energy storage systems, from personal devices to grid storage. Multi-metallic hexacyanoferrate (HCF) nanoclusters offer tailorable and unique chemistries and crystal structures that hold great potential in a virtually unlimited compositional space, leading to unexpected properties and interesting novelty in a wide variety of applications such as cathode materials for SIBs. Inspired by the disordered Rubik's cube, here, we report that the high-entropy (HE) concept can lead to a very substantial improvement in the sodium storage properties of HCF. An example of HE-HCF with the formula of Na1.41Mn0.32Fe0.11Co0.28Ni0.32Cu0.32[Fe(CN)6]×2.89H2O has been synthesized as a proof of concept, which has achieved impressive cycling stability (~ 95% capacity retention after 10,000 cycles and 79.2% after 50,000 cycles) and an outstanding fast-charging capability up to 75 C. Remarkable air stability and all-climate performance are observed. Its quasi-zero-strain reaction mechanism and high sodium diffusion coefficient have been measured and analyzed by multiple in-situ techniques and density functional theory calculations. This strategy provides new insights into the development of advanced electrode materials and provides the opportunity to tune electrochemical performance by tailoring the atomic composition.