High Fe^(LS)(C)electrochemical activity of an iron hexacyanoferrate cathode boosts superior sodium ion storage

摘要

Sodium iron hexacyanoferrate(FeHCF)is one of the most promising cathode materials for sodium-ion batteries(SIBs)due to its low cost theoretical capacity.However,the low electrochemical activity of Fe^(LS)(C)in FeHCF drags down its practical capacity and potential plateau.Herein,FeHCF with high Fe^(LS)(C)electrochemical activity(C-FeHCF)is synthesized via a facile citric acid-assisted solvothermal method.As the cathode of SIBs,C-FeHCF shows superior cycling stability(ca.87.3%capacity retention for 1000 cycles at 10 C)and outstanding rate performance(ca.68.5%capacity retention at 50 C).Importantly,the contribution of Fe^(LS)(C)to the whole capacity was quantitatively analyzed via combining dQ/dV and discharge curve for the first time,and the index reaches 44.53%for C-FeHCF,close to the theoretical value.In-situ X-ray diffraction proves the structure stability of C-FeHCF during charge-discharge process,ensuring its superior cycling performance.Furthermore,the application feasibility of the C-FeHCF cathode in quasi-solid SIBs is also evaluated.The quasi-solid SIBs with the C-FeHCF cathode exhibit excellent electrochemical performance,delivering an initial discharge capacity of 106.5 mAh g^(−1) at 5 C and high capacity retention of 89.8%over 1200 cycles.This work opens new insights into the design and development of advanced cathode materials for SIBs and the beyond.