Highly flexible supercapacitors (SCs) have attracted significant attention in modern electronics. However, it has been found that flexible, metal sulfide-based electrodes usually suffer from corrosion, instability and low conductivity, which significantly limits their large scale application. Herein, we report on an electrode comprised of highly stable, free-standing carbon fiber/trinickel disulphide covered with polyaniline (CF/Ni₃S₂@PANI). This electrode was prepared and then employed in a high-performance of flexible asymmetric SCs (FASC). The coating layer of polyaniline served as both a protector and conducting shell for the Ni₃S₂ due to the nature of the highly stable N-Ni bonds that formed between the polyaniline and Ni₃S₂. In addition, the lightweight carbon fiber support served as both a current collector and flexible support. The prepared CF/Ni₃S₂@PANI electrode exhibited a significantly enhanced specific capacity (715.3 F·g⁻¹ at 1 A·g⁻¹) compared with the carbon fiber/Ni₃S₂ electrode (318 F·g⁻¹ at 1 A·g⁻¹). More importantly, the assembled FASC device delivered an impressive energy density of 35.7 Wh·kg⁻¹ at a power density of 850 W·kg⁻¹. The FASC device benefited from the interconnected flexible microstructure and the stable bond bridges, so that it could be bent into various angles without noticeably impairing its performance. This effective protective strategy may further inspire the design and manufacture of metallic oxide or sulfide electrode with ultrahigh-stability interbond bridges for high-performance flexible supercapacitors.