Solder this neat little square to the pins on the back of your Pico, plug in a suitable lithium-ion/polymer battery and tada - a LiPo Pico! The inbuilt charging circuit means you can recharge the attached battery by supplying power to the Pico via USB, and it includes protection against overdischarge and overcurrent. There's a power button to stop the SHIM from providing battery power when it's not needed and turn your project on and off, as well as two LED indicators - a white one that shows when the shim is providing power and a red one to tell you when the battery is being charged.