Patent ID: 8801810

Claim:
A method of preparing a lithium ion cell, the method comprising: (a) receiving a negative electrode comprising silicon as a negative electrode electrochemically active material for releasing lithium ions during discharge of the lithium ion cell; (b) receiving a positive electrode containing a positive electrode electrochemically active material for taking up lithium ions during discharge of the lithium ion cell; (c) receiving a separator for electronically isolating the negative electrode and the positive electrode in the lithium ion cell; (d) preparing the lithium ion cell by arranging the positive electrode, the negative electrode, and the separator together with an electrolyte for transporting lithium ions between the positive electrode and the negative electrode during cycling of the lithium ion cell; and (e) forming the lithium ion cell by (i) charging the lithium ion cell to at least about 20% of the theoretical capacity of the negative electrode electrochemically active material, (ii) holding the lithium ion cell in a charged state for at least about 0.5 hours, and (iii) discharging the lithium ion cell, whereby holding the lithium ion cell in the charged state in (ii) provides improved Coulombic efficiency in one or more subsequent cycles.