Desk Fan

I had a spare 5V 8025 cooling fan, a fan motherboard, and a 21700 lithium battery (a single 18650 lithium battery can also be used, but only one can be placed at most), so I designed this fan. I prioritized practicality, therefore I didn't focus on aesthetics. This fan allows free adjustment of the airflow angle, it is compact and easy to carry outdoors, but the purpose of this design is for desktop use, not handheld, as I am a student and only use it at school. Since it needs to accommodate a single 21700 lithium battery, the space design is quite compact, minimizing the overall thickness as much as possible. Because I know nothing about air duct design, I simply designed a back cover. Would any experts be willing to help me design one I express my sincere gratitude here
Bill of Materials: charging fan motherboard (search with image on shopping apps, pictures are at the end), 8025 cooling fan (5V), one 21700 lithium battery (a single 18650 lithium battery can also be used, but only one can be placed at most), two PH2.0 male connectors, four M2*6mm countersunk screws, six M2*4 screws, 3D Printed accessories
Total cost is around 20RMB

Regarding battery life: I have only tested the first gear, which is the lowest setting, and it can last about 8 hours. For students, this battery life should be quite long, right (I use an EVE 21700 lithium battery bought from PDD, its nominal capacity is 5000mAh, specific battery life varies depending on the battery you use)