There is a story of Goddess Kali fighting with Ravana. What are the details of this encounter between the two?
The only place where Kali & Ravan have been shown expressedly in conflict is in the Adbhut Ramayan. However, we should remember that this Ravan is different from the one killed by Shri Raam in the Valmiki Ramayan.
According to this version, Sahsranana Ravan is an elder sibling of the Ravan who lives in Lanka and is destroyed by Sita much later. The text actually shows the fierce side of Sita who transforms into Kali to destroy the demon whom even Rama hasn't been able to defeat.
You can read Sargas 17-26 in Hindi by clicking on the hyperlink and I shall share the relevant portions here:
For non Hindi readers following is the gist of the above text:
Seeing Rama defeated, Sita laughed, and transformed into Bhadrakali. She decapitated Sahasranana Ravaņa’s thousand heads and destroyed his army. Other fierce goddesses or Matrikas appeared in the battlefield to sport with the heads of the Rakshasas.
Sage Valmiki has written 'Adhbut Ramayana' and the Goddess Sita taking the form of Goddess Kali is mentioned there. When Sri Rama killed Ravana, and the news was sent to Sri Sita, she laughed and said it took so many years for Sri Rama to kill ten headed Ravana. How many years will he take to kill his brother Sahastra Ravana (the thousand headed Ravana who was brother of ten headed Ravana). Sahastra Ravana was much more powerful than his ten headed brother Ravana. Thereafter Sri Sita took form of Mahakali and killed Sahastra Ravana. Sri Sita was incarnation of Goddess Lakshmi and she taking form of Kali clearly tells that all mothers are form of the same Adhya Shakti. The mother has three forms : the creator (Saraswati), the preserver (Lakshmi) and the destroyer (Kali). When she nurtures she is compassionate and when she kills she is wrathful. She is gunateeta (beyond gunas) that is beyond all three gunas (satva guna, raja guna and tamo guna) and at the same time takes form related to one guna when needed.