Born in Cesena in 1923, he later moved to Bologna, and studied at the Scuola del Nudo under the guidance of Virgilio Guidi. He moved first to Turin and then to Rome where he frequented the artists of the “Portonaccio” and “Arte Sociale” groups. His painting proposed poor figures and environments which gradually became less and less figurative and realist. Cappelli started from the 1960s towards a painting that, while maintaining the theme of a degraded and marginalized humanity, replaces rural subjects with themes of life and metropolitan realities set in poor interiors or in the gloomy and oppressive Milanese suburbs, which he depicts through new formal syntheses, with an expressionist imprint.