Best fit in Lenovo notebooks with ThinkPad X220i battery:

• Lenovo ThinkPad X220i Series Notebook Battery
• Not compatible with ThinkPad X220 Tablets

Compatible Battery Part numbers on Lenovo ThinkPad X220i Notebook:

• 0A36283
• FRU P/N 42T4865
• ASM P/N 424866
• 0A36281 etc,.

Lenovo batteries maintain

Do not modify or disassemble the ThinkPad X220i battery without professional help and knowledge.
Do not incinerate, or short-circuit the rechargeable battery pack (put battery with metal objects)
Do not expose laptop battery to heat more than 212°F(100°C), which may cause an exposure.
Do not place battery in device for a long period of time if device is not being used. Remove the battery when you store your computer for an extended period of time.
Do remember discharge then recharge the notebook battery for every few weeks during storage.
Do keep the Lenovo ThinkPad X220i battery away from children.

Extend Lenovo ThinkPad X220i battery life

The length of laptop running time may vary a lot, It depends on the running applications and the external devices connected to your laptop. Battery operating time (the time the battery can hold a charge) will decrease over time. When you travel with your laptop, you would want longer battery life. Here are some basic tips may help you.
1. Dim laptop screen - Adjust your screen brightness(Most laptops come with the ability to dim your laptop screen); As the screen will take 30% also power of the battery, Try turning down the display brightness to the lowest level you can bear(don't no hurt your eyes).
2. Cut down on unnecessary programs - Cut unnecessary auto running programs when boot up ,cut background programs like Itunes, Desktop Search, etc., Shut down everything that isn’t crucial when you’re on battery. You'd better save the basic firewall software when you are online.
3. Unplug unnecessary devices - USB devices (like mouse, keyboard, other widget chargers), PC cards, DVD drivers, Bluetooth and WiFi will extract your laptop battery power a lot. Remove all of this if applicable. Also check for other built-in components that you could disable to conserve more battery power.
4. Use power saving. Remember that standby mode still uses battery power a lot when you left , But use hibernate instead  will save more if your laptop supports this function .