Is it safe to import mobile battery from ali express or any kind of risk that baattery will deyained by coustom clearence?????
battery of phone probably wont be detained as long as it has a receipt showing its mobile battery..
AliExpress sellers usually send free shipments through China Air Mail. I don't know about China Air Mail but many other carriers including DHL, FEDEX etc don't carry batteries. Before placing order, you should contact seller and ask him about shipment method and specifically ask him if his preferred carrier will have no objection on handling batteries.
If that is not a problem, there should be no problem at customs end. Low value items normally come to your place without any customs problem.