Nyquist plot fitting results and the calculated corresponding D_Na+ values for pristine CuS and 0.8CuS:0.2g-C₃N₄ composite anodes for SIB.

Electrode	R s (Ω)	R cf (Ω)	R ct (Ω)	σ (Ω s−0.5)	D Na+ (cm2 s−1)
CuS (as prepared)	6.6135	27.3062	218.1103	3.87	1.02 × 10−13
CuS (after 100 cycles)	10.7270	18.4956	31.0023	12.57	0.97 × 10−12
0.8CuS:0.2g-C3N4 (as prepared)	4.7282	22.7626	168.3922	2.59	2.27 × 10−13
0.8CuS:0.2g-C3N4 (after 100 cycles)	3.2610	12.0883	16.7219	9.85	1.58 × 10−12