Synergistic conductive network in LMFP/NCM composite cathodes: accelerating lithium-ion diffusion and lowering resistivity via carbon additive engineering

This study systematically investigates the modulation mechanisms of three conductive agents—carbon black (CB), CB-graphene-carbon nanotubes (THC: ternary carbon hybrid), and CB-carbon nanotubes (CC) —on the electrochemical performance of LMFP/NCM composites. EIS results show that the CC-modified electrode (LMFP/NCM-CC) exhibits the lowest total interfacial impedance (12.23 Ω), with its RSEI (3.40 Ω) and Rct (8.83 Ω) reduced by 82.5% and 50.3% respectively compared to CB. This advantage originates from a 3D continuous network co-constructed by carbon nanotubes and CB: nanotube frameworks buffer phase-transition stress to maintain electronic pathway integrity; ordered channels reduce Li⁺ diffusion tortuosity (verified by GITT); in-situ dense SEI films inhibit side reactions. Within the 3.6–4.1 V high-voltage range, CB demonstrates the lowest lithium-ion diffusion coefficient. After 100 cycles at 1 C, CC achieves the highest capacity retention rate (81%), surpassing TCH (69.3%) and CB (70.3%). After 50 cycles at 3 C rate, the LMFP/NCM-CC composite exhibits a capacity retention of 89.5% and delivers a discharge specific capacity of 138.9 mAh/g at the 50th cycle, demonstrating excellent rate capability and cycling stability.