Your smartphone is already capable of capturing decent video. In order to record better quality audio, you should consider investing in a decent microphone. The Q Mic can help. It is a smart microphone with omni, directional, and ASMR modes. You can change mode with a single dial.
The microphone doesn’t require a battery to operate. You can easily rotate it 360 degrees. The Q Mic is compatible with all devices that have a 3.5mm jack. Expected to ship in December. You can find out more here.