Wot he ^ said. There's a large number of chips made to do exactly this, inside products.
Phones do exactly this, and just about all Power Banks do this.
Some are more clever than others, so find out exactly what they do.
What charge current do you want for your battery?
What current can you get out of a USB connector. Does it depend whether it's USB A,B, C, Mini, micro...?
You'll have to look up the specifications of them all.
Variations - many will cut back the charge current
as the appropriate voltage is being reached then hold it at a very low level, and protect against short circuits, and against over-temperature, and give you a readout of the state of charge of the battery, and on and on.
Don't forget your materials - heat resistance, insulating, non flammable, etc etc.
Is this the AQA course? I thought they'd finished with it/called it something else.
Last time I saw that you had to go through a ton of considerations like costs, which consumers, ergonomics, size, environmental safety, size, "moral justification"(!), sustainablity and probably other stuff as well. Never mind about whether it'll make you a profit!!
Here's a couple I just happen to have on my desk. Both are broken so they're going into something else.
Sorry they're grotty pictures, it's a bit late. Let me know if you want them better. Both these are micro USB in, one has a phone-type battery, and the other a 18650.