Stay unplugged even longer with ThinkPad Battery 19+. This rechargeable six-cell slim external battery uses Lithium-Ion (Li-Ion) technology and easily attaches to your X220. The ThinkPad Battery 19+ features: Supports X220 ThinkPads Lithium-Ion (Li-Ion) technology Six cell, rechargeable system battery, 64Wh Allows direct charge from AC adapter (65W, 90W, 135W) No external battery charger needed Hot pluggable Standard system battery specifications Over-discharge protection