Is it permissible for a wife to seek divorce due to not being sexually satisfied by her husband, and has Islam set standards for a husband's sexual inadequacy?

Allah has obligated the husband to treat his wife with kindness, and this includes satisfying her and fulfilling her desires. Scholars have differed regarding the obligatory frequency of intercourse. The majority of them hold that intercourse is obligatory once per cycle of purity if the husband is able, citing the Almighty’s saying: "So when they have purified themselves, then come to them from where Allah has ordained for you." Ash-Shafi'i said that this is not obligatory for him. Ahmad said it should be estimated at four months. Al-Ghazali said that he should come to her once every four nights. Based on the foregoing, the husband must fortify his wife. If chastity is not achieved and the woman cannot endure, then she has the right to seek separation, for the Almighty’s saying: "Retention with kindness or release with excellence."