USB Power Cable to Male Adapter Jack 5.5×2.1mm 5V to 8.4V

From the shop's description

Features When the standard USB input is 5V, the 5.5×2.1mm port output is 8.4V Using this cable, you can charge your 18650 lithium battery by USB wall charger. When charging, the red light is on, the green light is on when fully charged. Suitable for lithium batteries (lithium ion batteries, lithium polymer batteries) Specifications: Input: USB 5V 2a Output voltage: DC 8.4V Output current: 0.5A max Cable length: about 100cm Color: Black Input interface: standard USB 2.0 male Output interface: 5.5×2.1mm connector (inside the positive, outside the negative) Package included: 1 x USB to 5.5×2.1mm Male charging cable