As a result, the structural integrity of the cathode material can be well preserved, and the ASIBs deliver initial discharge capacities of 157 mAh g cathode −1 and 125 mAh g cathode −1 at 0.5 A g −1 and 10 A g −1, respectively.ĭesign of the concentrated aqueous electrolyte solution Given the lattice expansion that occurs upon Na + extraction, the anion Fe(CN) 6 4– is introduced to coordinate with the dislocating or dislocated Mn to repair the Mn vacancies in situ and enhance surface chemical stability. We present an unconventional in situ remediation strategy by introducing a cation-trap agent Na 4Fe(CN) 6 into a concentrated electrolyte (17.6 m NaClO 4, m represents molality) to rapidly capture soluble Mn 2+. 2.65H 2O is first employed as a cathode material for ASIBs.In this work, Fe-substituted Prussian blue Na 1.58Fe 0.07Mn 0.97Fe(CN) 6 However, to the best of our knowledge, a high-energy and stable ASIB with an MnPB-based positive electrode has not yet been reported. recently proposed a cation substitution method that involved the conversion of Mn-based Prussian blue to Fe-substituted Prussian blue, which reduced Mn dissolution and promoted highly reversible potassium-storage properties 24. Since the structural deformations start at the electrode/electrolyte interface, stabilization of the surface structure plays a critical role in preventing Mn dissolution. Previous efforts to suppress Mn dissolution have mainly focused on partial atom doping/substitution in the active positive electrode materials 20, 21 or electrolyte optimization 22, 23, but none of these approaches have achieved satisfactory results. Thus, it is necessary to mitigate or inhibit the JT effect to address this severe challenge. The large volume changes (>10%) that occur during the phase transitions continuously trigger surface defects and subsequently lead to internal structural distortions, eventually resulting in the loss of electrochemical activity of the positive electrode due to Mn dissolution. Unfortunately, MnPB shows poor cycle stability due to the irreversible phase changes arising from Jahn-Teller (JT) distortion 18, 19. In particular, much attention has been paid to the Mn-based PBAs (MnPB) because of the high working potential of 3.5 V (vs Na +/Na) and environmental friendliness. Recently, some progress has been made in the development of PBAs 15, 16, for example, for applications in transparent battery devices 17. Among them, PBAs have received increasing interest for their ease of synthesis and easily adjustable properties 12, 13, 14. Various active positive electrode materials have been studied, primarily transition-metal oxides 6, 7, polyanionic compounds 8, 9, and Prussian blue analogs (PBAs) 10, 11. One of the biggest obstacles is the lack of a suitable cathode material that can maintain good structural integrity upon repeated and rapid Na + (de)insertion. It remains a substantial challenge to develop compatible electrodes and electrolytes capable of delivering adequate electrochemical energy storage performance. However, the narrow electrochemical stability window of aqueous electrolytes and the material dissolution caused by the high activity of water have restricted the specific energy and cycle stability of these batteries 5. Benefiting from their nonflammability and abundant resources, aqueous sodium-ion batteries (ASIBs) are regarded as promising candidates for grid energy storage 3, 4. Large-scale energy storage systems are essential for the integration of intermittent renewable energies, such as wind, solar and tidal power 1, 2. When the engineered aqueous electrolyte solution and the NaFeMnF-based positive electrode are tested in combination with a 3, 4, 9, 10-perylenetetracarboxylic diimide-based negative electrode in a coin cell configuration, a specific energy of 94 Wh kg –1 at 0.5 A g −1 (specific energy based on the active material mass of both electrodes) and a specific discharge capacity retention of 73.4% after 15000 cycles at 2 A g −1 are achieved.
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