Synergistic graphene/in-situ carbon 3D network architecture unlocks high-power and durable LiMn0.5Fe0.5PO4 cathodes

Lithium manganese iron phosphate (LMFP) is a promising cathode material for medium-to-high power lithium-ion batteries owing to its high operating voltage, excellent safety, and low cost. However, its practical application is hindered by intrinsically poor ion/electronic conductivity. Herein, a three-dimensional (3D) conductive network was constructed via a microwave-hydrothermal method through the synergistic graphene-in-situ carbon modification, thereby optimizing the electron/ion conduction kinetics of LMFP. This integrated strategy enhanced reversible Li + insertion/extraction, suppressed interfacial side reactions, and maintained crystal integrity during prolonged cycling. The composite with 0.5 wt% graphene (0.5G-LMFP) exhibited an initial coulombic efficiency (CE) of 99.16%, which is attributed to the 3D conducive network and a dense carbon coating. At 1C, it retained 86.9% of capacity after 1000 cycles while achieving a steady-state CE of 99.98% (ΔCE < 0.005%). Kinetic analyses further confirmed a higher pseudocapacitive contribution, enhanced Li + diffusion, and 50.3% lower charge transfer resistance (R ct = 90.3 Ω) compared to mere carbon coating LMFP. This work demonstrates that the synergistic modification with graphene and an in-situ carbon coating effectively optimizes interfacial stability and charge transfer efficiency of LMFP, providing a feasible route toward high-performance LMFP cathodes.