High‐Capacity Sodium–Prussian Blue Rechargeable Battery through Chelation‐Induced Nano‐Porosity

Abstract

Across the different classes of sodium‐ion battery cathodes, Prussian Blue holds the greatest promise because of its high working potentials, abundance, low‐toxicity and ease of synthesis. However, its performance as a sodium‐ion battery cathode has generally been limited to less than 120 mAh g−1, which is inferior compared to commercial lithium‐based counterparts. Here, sodium–Prussian Blue rechargeable batteries with a remarkably high discharge specific capacity of 153 ± 6 mAh g−1 at 1C is reported. This is achieved through the employment of excess ascorbic acid during the colloidal preparation of Prussian Blue crystals, followed by a 200 °C heat‐vacuum drying process. The optical, structural and thermogravimetric investigations show that the chelation of ascorbic acid to the iron ions disrupts the growth of Prussian Blue, and lead to the formation of a useful nano‐porous crystal structure. This allows for deeper percolation of sodium ions into the Prussian Blue crystals, and successfully unlocked useful inner volumes that are otherwise unreachable, thereby leading to an outstanding 47% elevation in specific capacity. This development brings sodium‐based battery technology significantly closer to the incumbent lithium‐ion batteries, and marks an important early step towards its practical application in commercial devices.

In situ polyaniline coating of Prussian blue as cathode material for sodium-ion battery

“…The difference between Sample-A and Sample-O in rate performance indicates the advantage of AA, owing to the ion pathway created inside of the particle. This improvement is also reported in other studies [6]. Compared with the traditional synthesis method, our method noticeably improves the rate performance of the electrode Figure 2c shows that after 76 cycles, Sample-O achieved a specific capacity of 98.9 mAh g −1 , indicating that the cycle stability of Sample-A can be improved.…”

“…Compared with the traditional synthesis method, our method noticeably improves the rate performance of the electrode Figure 2c shows that after 76 cycles, Sample-O achieved a specific capacity of 98.9 mAh g −1 , indicating that the cycle stability of Sample-A can be improved. This phenomenon has been explained in other studies [6]. The electronic supplementary material, figure S12 summarized the difference of PB produced by this work and others work reported [7,[23][24][25][26][27][28][29][30][31].…”

“…The difference between figure 1a and electronic supplementary material, figure S1a in XRD patterns indicates that most of the PB phase in Sample-A and Sample-O are formed in the process of rapid precipitation. The peaks related to the AA of Sample-A-precursor are revealed by the Fourier transform infrared spectroscopy (FT-IR) result as shown in the electronic supplementary material, figure S1b [6]. The figure 1b shows the FT-IR result, revealing that all the samples have a strong peak at 2083 cm −1 , which corresponds to the C-N groups.…”

“…The XPS result shows that the AA can prevent Fe 2+ from being oxidized to Fe 3+ to some extent during the ball-milling process. The effect of AA as an additive in the conventional co-precipitation method was figured out in other literature [6]. Through the calculation according to the thermo-gravimetric analyses (TGA) curve (figure 1d) and ICP/elemental analysis (EA) result (electronic supplementary material, table S1), the formula of Sample-A is determined to be Na 1.515 Fe[Fe(CN) 6 ] 0.879 •2.7H 2 O.…”

“…Prussian blue (PB), with an open framework and stable structure, can meet the requirements of high power density and long cycle life as a cathode material of SIB [5]. However, PB synthesized via a traditional co-precipitation method is time-consuming and the resultants show a low electric conductivity and a low specific capacity at a high rate (20 C less than 100 mAh g −1 , 1 C = 170 mA g −1 ) [6,7]. These disadvantages limit the commercial application of PB.…”