A New Approach to Synthesize LiFePO4/C Cathode with Improved Compacted Density and Enhanced Electrochemical Performance

Abstract To achieve the synergistic improvement in compaction density and electrochemical performance of LiFePO4, an innovative ternary solid-state synthesis route using Li3PO4, FePO4, and Fe2O3 as precursors is proposed (LFP-P) and compared with that from the conventional route employing Li2CO3 and FePO4 (LFP-C). It was found that, compared with the conventional route, using Li3PO4 as the primary lithium source markedly reduces gas evolution during synthesis. The suppressed gas release promotes primary particle growth, lowers the porosity, and facilitates the formation of a more continuous and uniform carbon coating, thereby resulting in a denser particle structure. Benefiting from its reduced pore volume and compact surface carbon layer, LFP-P delivers powder and electrode compaction densities of 2.804 and 2.63 g·cm–3, respectively, while its electronic conductivity is enhanced by 2.02 times compared with that of LFP-C. In addition, the well-developed large particles in LFP-P improve the lattice ordering within the crystal structure and result in a longer Li–O bond length, thereby facilitating Li+ migration kinetics. Ultimately, LFP-P exhibits superior electrochemical performance, with an initial capacity of 161.82 mA h·g–1 @ 0.1 C, a capacity retention of 98.2% after 500 cycles @ 0.5 C, and a rate capacity of 137.46 mA h·g–1 @ 5 C. These findings indicate that the Li3PO4-based approach can optimize both the particle packing structure and lattice structure, thereby achieving a synergistic enhancement of high compaction density and excellent electrochemical performance for LFP cathodes.