Before you screw everything shut:

: A 3.7V Lithium-Polymer (Li-Po) battery, typically with a capacity of 170mAh to 180mAh . You can find these on sites like AliExpress Precision Screwdriver Set : Specifically a small Phillips head. Soldering Iron

Replacing the battery in a Sony Walkman NWZ-B172F is a technical process because the battery is built-in and typically soldered to the internal circuit board. Sony officially recommends having this service performed by a Sony Service Center

Given the (many units become brittle) and the need for soldering , it is strongly recommended to: