Did some sniffing and found your answer
"Once the cell assembly is complete the cell must be put through at least one precisely controlled charge / discharge cycle to activate the working materials, transforming them into their useable form. Instead of the normal constant current - constant voltage charging curve, the charging process begins with a low voltage which builds up gradually. This is called the Formation Process."
Full text here:
http://www.mpoweruk.com/battery_manufacturing.htm
Also the Wiki page:
http://en.wikipedia.org/wiki/Lithium_polymer