There comes a time in the process of curing infertility when a couple decides that they have availed all options and they must move on with their lives.
Many husbands see divorce and then remarriage as the only alternative to have children.
Islamically though he has an option that could be far more beneficial to his first wife, himself, and his marriage to follow. The option of polygyny is one that is looked down upon in western society, but one that is permissible and in some cases encouraged in Islam. That is nearer to prevent you from doing injustice. From this ayat it is clear that Islam has allowed men to marry up to four wives. He does not need any specific reason to have multiple wives, but he can do so for whatever reason he may wish as long as he is just with them.