Step 1. Open /Applications > Utilities > Disk Utility
ThinkPad-X220 macOS 10.12.6  Installation Document
ThinkPad-X220 macOS 10.12.6  Installation Document

Step 2. Open /Applications > Utilities > Terminal and then enter the following commands to creat Install macOS Sierra (disk2s1)

sudo su;
open /Volumes/linyongfeng\ HD/Library/Utilities/Install.macOS.10.12.6.MAS.dmg;
/Volumes/Install.macOS.10.12.6.MAS/Install\ macOS\ Sierra.app/Contents/Resources/createinstallmedia --volume /Volumes/USB --applicationpath /Volumes/Install.macOS.10.12.6.MAS/Install\ macOS\ Sierra.app --no interaction;

Step 3. After Done and then copy the necessary files into Install macOS Sierra (disk2s1)

cp /Volumes/linyongfeng\ HD/Library/Applications/ThinkPad\ x220\ macOS\ Sierra\ Utility\ and\ Kext\ pack.zip /Volumes/Install\ macOS\ Sierra;
cp -r /Volumes/linyongfeng\ HD/Library/Desktop\ Pictures /Volumes/Install\ macOS\ Sierra/;
cp -r /Volumes/linyongfeng\ HD/Library/Applications /Volumes/Install\ macOS\ Sierra/;
cp -r /Volumes/linyongfeng\ HD/Library/Utilities /Volumes/Install\ macOS\ Sierra/;

Step 4. Unzip the ThinkPad X220 macOS Sierra Utility and Kext Pack (ThinkPad x220 macOS Sierra Utility and Kext pack.zip) , Mount EFI on Install macOS Sierra (disk2s1) and copy the entire EFI folder from the Utility and Kext Pack to the EFI partition of Install macOS Sierra (disk2s1), replacing the existing folder if present

mkdir /Volumes/EFI;
mount -t msdos /dev/disk2s0 /Volumes/EFI/;
unzip -o /Volumes/Install\ macOS\ Sierra/ThinkPad\ x220\ macOS\ Sierra\ Utility\ and\ Kext\ pack.zip -d /tmp;
cp -r /Volumes/Install\ macOS\ Sierra/ThinkPad\ x220\ macOS\ Sierra\ Utility\ and\ Kext\ pack/EFI /Volumes/EFI/;
rm /Volumes/EFI/EFI/.DS_Store; ls -a /Volumes/EFI/EFI/;
diskutil unmount /Volumes/EFI/;
rmdir /Volumes/EFI/;