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Building aqueous K-ion batteries for energy storage


Aqueous K-ion batteries (AKIBs) are promising candidates for grid-scale energy storage due to their inherent safety and low cost. However, full AKIBs have not yet been reported due to the limited availability of suitable electrodes and electrolytes. Here we propose an AKIB system consisting of an Fe-substituted Mn-rich Prussian blue KxFeyMn1 − y[Fe(CN)6]w·zH2O cathode, an organic 3,4,9,10-perylenetetracarboxylic diimide anode and a 22 M KCF3SO3 water-in-salt electrolyte. The cathode achieves 70% capacity retention at 100 C and a lifespan of over 10,000 cycles due to the mitigation of phase transitions by Fe substitution. Meanwhile, the electrolyte can help decrease the dissolution of both electrodes owing to the lack of free water. The AKIB exhibits a high energy density of 80 Wh kg−1 and can operate well at rates of 0.1–20 C and over a wide temperature range (−20 to 60 °C). We believe that our demonstration could pave the way for practical applications of AKIBs for grid-scale energy storage.

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This work was supported by the National Natural Science Foundation of China (51725206 and 51421002), the National Key Technologies R&D Programme of China (2016YFB0901500), and the Strategic Priority Research Programme of the Chinese Academy of Sciences (XDA21070500), the Strategic Priority Research Programme of the Chinese Academy of Sciences (XDA21070500) and the Beijing Municipal Science and Technology Commission (Z181100004718008).

Author information

Y.-S.H. and Y.L. designed this work; L.J. synthesized the cathodes and carried out the electrochemical experiments and first-principles calculations; C.Z. performed the structural refinement, L.L. carried out the Raman test, J. Zhang and X.Y. performed the hXAS test; Q.Z. performed the transmission electron microscopy test, X.S. and J. Zhao performed the inductively coupled plasma test. L.J., Y.L. and Y.-S.H. wrote the paper; all of the authors participated in analysis of the experimental data and discussions of the results as well as preparing the paper.

Competing interests

The authors declare no competing interests.

Correspondence to Yaxiang Lu or Yong-Sheng Hu.

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  1. Supplementary Information

    Supplementary Figs. 1–14, Supplementary Note 1, Supplementary Tables 1–9 and supplementary references

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Further reading

Fig. 1: The structure and performance optimization of the designed PBA cathodes.
Fig. 2: Electrochemical performance of the optimal KFeMnHCF-3565 cathode.
Fig. 3: The structural evolution and charge compensation mechanism of the KMnHCF electrode.
Fig. 4: The structural evolution and charge compensation mechanism of the KFeMnHCF-3565 electrode.
Fig. 5: First-principles calculations.
Fig. 6: Performance of the WIS electrolyte and the PTCDI anode.
Fig. 7: Performance of the KFeMnHCF-3565//22 M KCF3SO3//PTCDI full battery.