Copper ion-releasing $(IUDs)$ are more efficient than non-medicated methods. Why?

(N/A) Intra Uterine Devices $(IUDs)$ are effective and popular contraceptive methods inserted by doctors or expert nurses into the uterus through the vagina.
These devices are categorized into three types:
$1$. Non-medicated $IUDs$ (e.g.,Lippes loop).
$2$. Copper-releasing $IUDs$ (e.g.,$CuT, Cu7,$ Multiload $375$).
$3$. Hormone-releasing $IUDs$ (e.g.,Progestasert,$LNG-20$).
All $IUDs$ increase the phagocytosis of sperms within the uterus. However,copper-releasing $IUDs$ are more efficient because the $Cu$ ions released suppress sperm motility and the fertilising capacity of sperms,providing an additional mechanism of action beyond simple phagocytosis.