The development of artificial intelligence is rapidly evolving from functional, task-oriented systems to collaborative partners who can interpret and react to situations in a human context. This study investigates the undeniable fusion of emotional computing (or affective computing) and affective interfaces as two foundational aspects essential for attaining human-AI collaboration. It is proposed that for AI to go beyond acting as a tool and move to being a teammate, it must have the capacity to perceive, interpret, and respond to human emotional states. This paper reviews the technologies that constitute emotional computing, namely multimodal affect recognition, such as text, voice, face, and physiological signals, and affective generation, and examines the design principles for affective interfaces that can enable this emotional intelligence to manifest as natural, intuitive, and trustworthy interactions. In closing, the architectural diagrams for implementing these attributes into collaborative AI systems are discussed, along with compelling use cases from diverse areas such as healthcare, education, and creative industries. Major ethical and privacy concerns are also examined. The findings emphasize that developing emotional intelligence in AI represents not merely an incremental advancement but a transformative evolution enabling humans and machines to work together seamlessly, efficiently, and symbiotically.