High Performance Reported for Polyoxometalate Li-S Batteries

Reported high performance for polyoxometalate Li-S batteries

A recent article published in the journal Materials Today Nano discusses the development of modified Keggin and Dawson-like polyoxometalates (POMs) to improve performance of Li-S batteries.

​​​​​​​

​​​​​​​Study: Efficient polysulfide adsorption and polyoxometalate catalysis contributing to high performance Li-S batteries. Image Credit: RESTOCK images/Shutterstock.com

Although lithium-sulfur (Li-S) batteries are promising energy storage systems, they still suffer from some drawbacks, including migration of soluble lithium polysulfide (LiPS) intermediates, large volume change, and low sulfur conductivity.

Li-S batteries as energy storage systems

Increasing energy demand requires high energy storage technology. Li-S batteries have high energy density and high specific capacity, making them popular energy storage systems. Additionally, the cost-effectiveness and low toxicity of elemental sulfur make it an environmentally friendly cathode material, making Li-S batteries a next-generation energy storage system. However, soluble lithium polysulfides (LiPS; Li2SX, x = 4-8) causes the “shuttle effect”, leading to low Coulomb efficiency and poor cycle stability. For this purpose, the construction of the functional interlayer is necessary to improve the performance of the Li-S battery.

POMs are anionic metal oxide aggregates with good stability, redox property and diversity. Therefore, POMs are widely used in electrochemistry, catalysis and energy systems. K3[H3AgIPW11O39].12H2O (Silver substituted Keggin) served as the Lewis acid and base catalyst for the Li-S battery. Silver ions (Ag(I)) in silver-substituted Keggin are used as Lewis acid centers to enhance attachment of sulfur (S) moieties.

(NH4)6VtenO28 The (NVO) clusters immobilize the LiPS by attraction of the oxygen (O) atoms of the NVO by the Li cations of the LiPS or by the interaction of the vanadium atoms of the NVO with the sulfur anions of the LiPS. However, the application of POM as a Li-S battery interlayer for shuttle inhibition is rarely reported, and the mechanism behind the inhibition remains unclear.

Dividers for Li-S batteries

In the present study, the team designed three types of Li-S batteries with Keggin or Dawson type POMs as interlayers. They observed that cells with H3[PW12O40]. xH2O (P.W.12) interlayer had higher LiPS binding energy and represented better cycle performance than K6[P2W18O62].2 p.m.2O (P2O18) spacer. The adsorption capacity of (NH4)6[P2Mo18O62].11H2O (P2month18) to LiPS is greater than P2O18. Cells containing P2month18 as an interlayer had better electrochemical performance. TP12 exhibited catalytic function on LiPS, thus favoring Li2S/LiPS conversion.

search results

Scanning electron microscope (SEM) images of PW12 reveal the uniform surface of this interlayer without any agglomeration, suggesting that PW12 has sufficient dispersion on the separator. The middle layer showed no visible cracks during the bending process, suggesting its strength and structural flexibility, and the middle layer was 5 micrometers thick.

The elementary cartography of the PW12 the middle layer showed a uniform distribution of phosphorous (P), W, O, and carbon (C) elements, and Fourier transform infrared (FTIR) spectroscopy of bare PW12 showed peaks of P–O uptakeaW–Ovs–W, W=ODW–OD–W at 1081.8, 983.5. 889.0 and 804.1 reverse centimeters, respectively.

X-ray photoelectron spectroscopy (XPS) revealed the chemical bonding and elemental composition of the prepared PW12 spacer. The peak position of 134.6 electron volts in the XPS spectra aligns with the binding energy of P 2p. Additionally, the peaks at 36.2 and 38.3 electronvolts were attributed to W 4f7/2 and W 4f5/2respectively, and those at 532.6 and 531.3 electron volts in the O 1s spectra correspond to the OO species adsorbed on the surface of the Keggin structure.

Electrolyte drained on polypropylene (PP) and PW separator12 spacer helped in the contact angle tests, and the results showed that the contact angle of PW12 was lower than the PP separator. This test confirmed that PW-rich voids12 interlayer increases the wettability of the electrolyte, which facilitates lithium-ion mobility.

Subsequently, the evaluation of the electrochemical performance of Li-S batteries containing POMs interlayers and a zinc oxide C(ZnO)/S cathode revealed that the PW12 the middle layer had a higher capacitance of 1607.8 milliampere hours per gram and the lowest bias voltage (ΔE) of 165.9 millivolts than P2O18 and P2month18. These experimental results indicated the increased catalytic activity and rapid reaction kinetics of PW12.

The cyclic voltammetric curves of PW12-the cell containing 0.1 millivolt per second cyclic voltammetry showed two reduction peaks at 2.28 and 2.05 volts, indicating the reduction of S to Li2SX (4 ≤ x ≤ 8), followed by conversion to solid-state Li2S2/li2S electrochemically. Additionally, the peak at 2.39 volts indicates oxidation of Li2S2/Li2S to Li2SX and S

Conclusion

In summary, the researchers designed PW12P2O18and P2month18 spacers containing Li-S and PW batteries12 exhibited strong chemical interactions, efficient catalytic activity for LiPS and low redox potentials, showing the best electrochemical performance. Additionally, P.W.12 had an exceptional reversible capacity of 1032.7 milliampere hours per gram after 100 cycles.

The adsorption capacity of P2month18 at LiPSs is greater than P2O18. However, the cell with a P2O18 spacer displays superior electrochemical performance. This work demonstrated the effectiveness of POMs as interlayer materials for Li-S batteries.

Reference

Song, J., Jiang, Y., Yizhong Lu, Wang, M., Linlin Fan, YC, Liu, H. and Gao, G. (2022). Efficient polysulfide adsorption and polyoxometalate catalysis contributing to high performance Li-S batteries. Nano materials today. https://www.sciencedirect.com/science/article/pii/S2588842022000591

Disclaimer: The views expressed herein are those of the author expressed privately and do not necessarily represent the views of AZoM.com Limited T/A AZoNetwork, the owner and operator of this website. This disclaimer forms part of the Terms and conditions of using this website.

#Reported #high #performance #polyoxometalate #LiS #batteries

Leave a Comment

Your email address will not be published. Required fields are marked *