Optical semitransparent silver nanostructured layer electrode toward semitransparent lithium ion batteries

Silver nanoparticles (AgNPs) layers have been grown by spray-pyrolysis technique by using different spray pyrolysis deposition times (tsp). AgNPs with ca. 80 nm mean diameter have been obtained for the lower tsp value, whereas as the spray-pyrolysis time value is increased, the Ag NPs diameters increased, reaching a AgNPs mean diameter of 190 nm for the highest tsp assayed value. X-ray diffraction patterns of the AgNPs layers samples exhibited a pure polycrystalline cubic silver phase, irrespective of the different tsp values. An optical visible light transmittance maximum of 60% at 550 nm has been observed for samples grown at tsp = 5 s and 10 s. For higher tsp values this optical transmittance decreases. A semitransparent lithium ion battery (tsp = 5 s) has been obtained, exhibiting an optical transmittance of about 49% at λ = 554 nm. Electrochemical measurements showed that the amount of lithium that reacted with the AgNPs layer was around 6 lithium/mol. By cycling a transparent Li/Ag-ITO single cell, good capacity retention was observed for the first ten cycles for which a high value of capacity is delivered: 706 A h kg−1.When assembling this electrode in a full semitransparent battery, the electrochemical processes resulted to be reversible and the transparency preserved.