Power Up Arduino

Hey, so, I want to power up my arduino circuit using Li-ion batteries charged by a solar panel. I need some advice on what DC-DC Boost Convertor to buy so I can take my voltage up to 7V(for the VIN input) Right now I’m using Lm2596 but it can only lower voltage.
Input voltage is 3,5-3,6V.

Photo :

Here is one I made for someone:

found via a google search for “fritzing part solar cell charger” as I remember making it but not what it was called. There are probably more as well.