Monitoring the Zn ion storage of Prussian blue analog via in situ spectral imaging strategy

Aqueous zinc-ion batteries (ZIBs) are rapidly developing, and powerful in situ monitoring methods can play a key role in their evolution, particularly for gaining a deeper understanding of the ion storage process in cathodes. To enhance the capabilities of in situ monitoring methods in the energy storage field, we apply an in situ optical recording technique combined with a multispectral imaging (MSI) reconstruction algorithm to study the charge storage process of ZIBs based on Prussian blue analog cathodes. The method can reconstruct time-domain spectra (TDS) based on optical reflectance at multiple wavelengths during online charging/discharging periods. Although the optical variation of the cathode is small, the reconstructed reflectance and real-time state of charge show excellent linearity with correlation coefficients all higher than 98%. Delicate peak shifts in TDS corresponding to phase variations in the cathodes can also be detected. Above all indicates great potential of the MSI strategy for accelerating the evolution of ZIBs and other batteries in the future.