The output wattage of your charger is too low (especially if you use a computer/laptop usb port). Find one that does 2 Amps or more. My Samsung Charger that came with my Galaxy charges at 5.4 V at 2 Amps (10.8 W). It took 2 Hrs & 30 minutes to go from 10% -> 100%. The majority of the charge is done under 2 hours, as the last few minutes the current drops significantly to top off the batteries. That is the battery internal circuits doing this.
I also have a USB PD charger (my laptop power), and it charges a little over 1 Hr and 30 minutes.
The only way to charge faster is to bypass the usb and charge directly to the batteries main port. You can charge in 60-70 minutes this way with products from Amazon.
Amazon.com: Tineer 2-in-1 Parrot Anafi Battery Car Charger,3 Batteries and 2 USB Ports Parallel Charging Multi Battery Charger Station Hub for Parrot Anafi Drone Accessory: Gateway
www.amazon.com
As others stated, if you use this method, then make sure you charge with usb once every 5 or so charges.