Just bought a quirky x220 slice battery. Looks exactly like a 19+, but says 20+. Works completely fine with 1% wear. Does anyone know what it might be? : r/thinkpad
Re-Celling an Extended Slice Battery - Thinkpads Forum
Compatible for Lenovo ThinkPad Slice Battery Compatible with ThinkPad X220 X220s X220i Tablet 65Wh 42T4967 : Electronics - Amazon.com
Amazon.com: Compatible for Lenovo ThinkPad Slice Battery Compatible with ThinkPad X220 X220s X220i Tablet 65Wh 42T4967 : Electronics
Amazon.com: Lenovo 0A36307 ThinkPad 9 Cell Extended Life Battery 44++ for Lenovo ThinkPad X220, X230 Models Only. (Caution: Not for X220 Tablet, X230 Tablet Models) : Electronics
I put the Lenovo ThinkPad X220's 24-hour battery claim to the test | Windows Experience Blog