Lightning supports 5 Gb/s when running USB 3. However, there are AFAIK no cables that support USB 3 - you need to use an adapter that exposes a USB 3 port like

Lightning supports 5 Gb/s when running USB 3. However, there are AFAIK no cables that support USB 3 - you need to use an adapter that exposes a USB 3 port like Apple's camera adapter kit. Likewise, there is no requirement that a USB-C cable (or port) support Superspeed USB. Most charging cables for example only support USB 2 speeds for cost reasons.