What is the ruling of Islam and the right of the wife if she requests a divorce due to a sexual inadequacy of 20% that the husband does not wish to divorce over?

If the husband is sexually weak, and his wife requests a divorce for this reason, it is sunnah for him to grant her request. The wife has the right to seek separation (divorce or khul') if she is harmed by remaining with him and fears neglecting Allah's rights. There is no blame on the husband for requesting financial compensation (such as deferred mahr) in exchange for granting her a divorce, as Allah the Almighty says: ﴿But if you fear that they will not uphold the limits of Allah, then there is no blame upon either of them for what she gives to free herself.﴾ It is sunnah for the husband to grant the wife's request for khul', based on the hadith of Thabit ibn Qays and his wife.